Executive summary

What happened

On 11 March 2020, a Cessna 404 aircraft, registered VH-OZO, was being operated by Air Connect Australia to conduct a passenger charter flight from Cairns to Lockhart River, Queensland. On board were the pilot and 4 passengers, and the flight was being conducted under the instrument flight rules (IFR).

Consistent with the forecast, there were areas of cloud and rain that significantly reduced visibility at Lockhart River Airport. On descent, the pilot obtained the latest weather information from the airport’s automated weather information system (AWIS) and soon after commenced an area navigation (RNAV) global satellite system (GNSS) instrument approach to runway 30.

The pilot conducted the first approach consistent with the recommended (3°) constant descent profile, and the aircraft kept descending through the minimum descent altitude (MDA) of 730 ft and passed the missed approach point (MAPt). At about 400 ft, the pilot commenced a missed approach.

After conducting the missed approach, the pilot immediately commenced a second RNAV GNSS approach to runway 30. 

The occurrence

Overview

On 11 March 2020, a Cessna 404 aircraft, registered VH-OZO, was being operated by Air Connect Australia to conduct a passenger charter flight from Cairns to Lockhart River, Queensland. On board were the pilot and 4 passengers. The flight was being conducted under the instrument flight rules (IFR).[1]

Consistent with the forecast, there were areas of cloud and rain that significantly reduced visibility at Lockhart River Airport. After arriving at Lockhart River, the pilot commenced an area navigation (RNAV) global satellite system (GNSS) instrument approach to runway 30. The aircraft descended to an altitude of about 400 ft before the pilot conducted a missed approach. The pilot immediately commenced a second RNAV GNSS approach to runway 30, and during the descent the aircraft collided with terrain.

Planned flight

The passengers were contracted to carry out work at the local school at Lockhart River. The client arranged with the operator for the aircraft to depart Cairns at 0730 Eastern Standard Time[2] on 11 March 2020, wait on the ground at Lockhart River for about 5 hours, then depart at 1430 with the same passengers for the return flight. The operator assigned the pilot who regularly conducted the operator’s charter flights.

For the arrival at Lockhart River, the forecast weather was for light winds and rain and low cloud with periods of visibility reducing to 3 km in rain. There was also a 30% probability of thunderstorms. The pilot had submitted a flight notification, which specified IFR and capability for an RNAV instrument approach. The aircraft had sufficient fuel to conduct an approach at Lockhart River and return to Cairns and hold at Cairns for 1 hour if required.

Flight to Lockhart River

The aircraft departed Cairns at 0719 and tracked for the first planned waypoint on climb to its cruise level of 10,000 ft above mean sea level. Based on the forecast winds, the estimated time of arrival at Lockhart River was 0852. As the flight progressed, the pilot amended the estimated time of arrival to 0904. The aircraft’s track during the flight is shown in Figure 1.

Figure 1: VH-OZO recorded flight path from Cairns to Lockhart River, Queensland

Source: Google Earth overlaid with OzRunways data, annotated by the ATSB

At 0836, the pilot advised air traffic control that the aircraft was approaching top of descent, then tracking direct for the runway 30 RNAV GNSS instrument approach at Lockhart River, and the pilot requested traffic information. The controller responded there was no reported IFR traffic. At 0840, the pilot reported leaving 10,000 ft on descent and, at 0842, the controller advised the pilot of the very high frequency (VHF) and high frequency (HF) radio frequencies applicable to the rest of the flight. That was the controller’s last contact with the pilot and no further routine interactions with the controller were expected.[3]

During descent, the pilot transmitted on the common traffic advisory frequency (CTAF) for Lockhart River to activate the runway lighting for a period of 30 minutes. At 0852, the aerodrome frequency response unit (AFRU) broadcast ‘Lockhart River CTAF, runway lights are on’.

At about this time, the pilot very likely obtained weather information from the automated weather information service (AWIS) via VHF radio. Notes taken by the pilot indicated the wind was calm, visibility was at least 10 km, there was broken cloud[4] at 1,800 ft, broken cloud at 3,500 ft and overcast cloud at 5,300 ft, and the QNH was 1,008 hPa (see Automated weather information service).

At about 0857, the aircraft levelled off at 5,500 ft. At this time the aircraft was heading to waypoint LHREB, one of 3 initial approach fixes (IAFs) for the RNAV GNSS instrument approach to runway 30 (Figure 2). The weather information indicated that the conditions were better than the landing minima (which were a cloud ceiling of 730 ft and visibility 4,200 m).[5]

Figure 2: Lockhart River RNAV GNSS runway 30 approach chart

Source: Airservices Australia, annotated by the ATSB

First approach at Lockhart River

Figure 3 depicts the aircraft’s recorded flight track for the first approach and missed approach at Lockhart River. The altitudes described throughout the report are truncated to the nearest 100 ft. [6]

At 0859:38, the aircraft passed abeam LHREB, commenced descent from 5,400 ft and turned left to track to the runway in accordance with the RNAV GNSS procedure. At 0901:25, the pilot made a radio broadcast on the CTAF, advising the aircraft was 10 NM[7] to the south-east of the aerodrome, inbound to runway 30 and on descent passing 4,000 ft. Shortly afterwards, the aircraft passed the intermediate fix (IF) LHREI at 4,000 ft.  

Figure 3: Flight track of VH-OZO during first RNAV GNSS approach at Lockhart River Airport with times, feature labels, and approach parameters superimposed

Source: Google Earth overlaid with OzRunways data, annotated by the ATSB

At about 0903, one of the passengers sent a text message that contained an image of conditions outside the aircraft (Figure 4). At that time, the aircraft was over halfway between LHREI and the final approach fix (FAF) LHREF, at an altitude between 3,100 and 2,500 ft. The photograph had been taken through a passenger window on the right side of the aircraft cabin and, although there was significant cloud in the vicinity, some terrain/coastline was visible near the intersection of the wing’s leading edge and the engine cowl.

Figure 4: Image recorded by a passenger looking forward over the right engine and sent via text message at 0903

Source: Supplied, lower section of image cropped by the ATSB

The aircraft continued the descent on the approach track and passed LHREF on descent through 2,300 ft. At 0904:27, the pilot broadcast on the CTAF that the aircraft was at 5 NM and on final (approach) to runway 30.

The minimum descent altitude (MDA) was 730 ft.[8] The aircraft arrived at the missed approach point (MAPt) LHREM at 0906:17 on descent through about 600 ft. The descent continued to about 400 ft then, about 1,000 m from the runway, the aircraft started to climb. The aircraft was passing 600 ft as it crossed the runway threshold in the early stages of a missed approach. In accordance with the missed approach procedure, the aircraft was turned slightly right to track towards the turning fly-over waypoint LHREH.

At 0907:22, the pilot broadcast on the CTAF that they were conducting a missed approach for runway 30, tracking to the west then turning back to the east and climbing towards 3,500 ft (as specified for the missed approach procedure). After passing LHREH at 0907:43 on climb through 1,200 ft, the aircraft turned right to track east as prescribed by the approach chart.

At 0909, the pilot contacted Flightwatch[9] on HF and advised:

[VH-OZO] conducting a missed approach runway three zero [30] at Lockhart River, and we’ll be joining the approach on runway three zero [30], ops normal time two three three zero [2330]

The middle part of this radio transmission, as recorded by Airservices Australia, was unclear, which is not uncommon for HF radio communication.

Second approach at Lockhart River

The aircraft continued the climb to 3,800 ft before descending to level out at 3,500 ft, heading towards the closest IAF, LHREA. At 0912:51, the AFRU recorded runway lights on, consistent with the pilot reactivating the runway lights for another 30-minute period. About 2.0 NM prior to reaching LHREA, at 0913:53, the aircraft commenced a right turn towards the IF, and initially was right of the inbound track to LHREI (Figure 5).

Figure 5: Flight track of VH-OZO during second RNAV GNSS approach at Lockhart River Airport with times, feature labels, and approach parameters superimposed

Source: Google Earth overlaid with OzRunways data, annotated by the ATSB

At about 0914, while the aircraft was tracking towards LHREI on a south-westerly heading at 3,500 ft, an image was uploaded to social media by one of the passengers (Figure 6). The camera was oriented to the west, which was in the general direction of Lockhart River. An associated message indicated very low visibility and that the pilot was circling while waiting for a break in the weather. Another passenger sent a text message at 0914 stating that the first attempt at landing was unsuccessful, the runway was not visible and there was heavy rain. 

Figure 6: Image recorded by a passenger looking over the right wing and uploaded to social media at 0914

Source: Supplied

At about 0914:43, when about 2.7 NM from LHREI, the aircraft started descending from 3,500 ft. At this time, the aircraft was tracking towards the initial approach track between LHREA and LHREI (Figure 5).        

At 0915:50, the pilot made another inbound broadcast on the CTAF advising:

ten miles [10 NM] to the south-east on descent passing three thousand eight hundred [3,800 ft] correction two thousand eight hundred [2,800 ft], straight-in approach runway three zero [30], circuit area two one [time 0921].

The recorded height was about 2,800 ft at this time.

The aircraft continued descending and passed over LHREI and turned right to fly parallel to the intermediate approach track at about 2,800 ft. According to the recommended flight profile for a 3° approach (Figure 2), the aircraft should have descended from 3,500 ft at about 4.2 NM from the FAF (9.2 NM from the MAPt). At this point, the aircraft was at about 2,500 ft.

The descent continued at a similar gradient to the first approach although at about 1,000 ft lower than that approach. About halfway between LHREI and LHREF, the aircraft descended below the intermediate segment minimum safe altitude of 1,800 ft and continued to descend on the same descent profile.

When the aircraft passed LHREF at 0918:23, it was on descent through about 1,100 ft (below the 3° approach profile height of 2,160 ft). The aircraft was right of the final approach track and, shortly after passing LHREF, the aircraft started turning back towards the final approach track.

From LHREF to LHREM, the altitude limitation was the MDA of 730 ft and, at 09:18:55, the aircraft was approaching 700 ft. The aircraft then descended below the MDA and, soon after, the aircraft’s flight path crossed the final approach track (on a ground track about 20° left of the final approach track).

Collision with terrain

The aircraft’s track and descent continued until it impacted a sand dune on the coastline at about 0919:41. The pilot and 4 passengers were fatally injured, and the aircraft was destroyed. Due to the impact forces, the accident was not survivable.

Context

Pilot information

Qualifications and experience

The pilot held a commercial pilot licence (aeroplane) with an instrument rating and multi-engine aeroplane endorsement. They had recorded a total of 3,220 hours before the accident flight.

The pilot obtained the multi-engine endorsement in June 2014 (on a Cessna 310 aircraft), and had accrued 1,177 hours on multi-engine aircraft, including 399 hours on the Cessna 404 aircraft type. In June 2014, the pilot also obtained their initial (multi-engine) instrument rating, and their total instrument time was recorded as 148 hours.

The pilot operated as a commercial pilot in remote locations for about 5 years. Up until March 2016, they operated single-engine aircraft. In March 2016 they received training and were found competent on the Piper PA31 aeroplane type. Between March 2016 and February 2018, the pilot conducted flights for a charter company that operated Cessna 310 and Piper PA-31 aircraft, usually under visual flight rules (VFR[10]) with occasional instrument flights. They were approved by the Civil Aviation Safety Authority (CASA) as chief pilot of this operator in December 2016.

From October 2018, the pilot was employed by Air Connect Australia on a casual basis. Prior to joining the operator, the pilot’s recorded total flying time was 2,800 hours. The pilot completed induction then conducted a flight for type-specific training in a Cessna 421 from an independent CASA-approved flight examiner that the operator frequently used for proficiency checks. This flight was about 1.6 hours and the examiner recalled that the pilot managed the transition to the 400-series Cessna without any problems. Other than the pressurisation system in the Cessna 421, the examiner considered it was operationally equivalent to the unpressurised Cessna 404.[11]

Following this type-specific training, the chief pilot of Air Connect Australia supervised the pilot on 4 flight sectors in VH-OZO and conducted an operator proficiency check (OPC) over 2 further sectors on 29 October 2018. The chief pilot noted that the pilot’s planning was satisfactory, and operation of the aircraft was above standard.

From November 2018 to the accident flight, the pilot was based in Cairns and conducted most of the operator’s charter flights, normally in VH-OZO. In December 2019, the chief pilot organised for the pilot to undertake some supervised flying at night with an instructor in a Piper PA-44 Seminole in order for the pilot to maintain night recency. The operator rarely conducted night flights.

In the 90 days prior to the accident (11 March 2020), the pilot had conducted 59 flights (60 flight hours), all in VH-OZO. This included 4.5 hours recorded instrument flying time. In the last 30 days, the pilot had conducted 12 flights (13.5 flight hours), including 1.0 hour recorded instrument flying time. The most recent flights were on 18 February 2020.

Since joining the operator in late 2018, the pilot had logged 69 RNAV GNSS approaches to various aerodromes. These included 21 RNAV GNSS approaches in the previous 6 months, 12 in the previous 90 days, and 2 in the previous 30 days (with the last on 18 February 2020). Only one of the approaches in the previous 6 months was conducted to some extent in instrument meteorological conditions (IMC),[12] and this approach resulted in a missed approach (see Prior missed approach during an RNAV GNSS approach (22 January 2020).

Lockhart River experience

Since the start of 2019, the pilot had flown into Lockhart River 8 times, 6 of which were logged as RNAV GNSS approaches, with the most recent being on 14 October 2019.

The recorded data for previous RNAV GNSS approaches into Lockhart River were reviewed by the ATSB, with the details provided in Table 1. A review of recorded weather information indicated that none of these previous approaches at Lockhart River were conducted in IMC. For the 17 January 2019 approach, there may have been reduced visibility in the early part of the approach.[13]

Table 1: Pilot’s prior flights to Lockhart River 2019–2020

Proficiency checks and flight reviews

The pilot conducted initial instrument flight training in 2014. During training it was noted that the pilot needed to scan faster, improve situation awareness and improve radio phraseology. On one simulator training exercise it was noted the pilot was too high on the RNAV GNSS MDA and minimum altitudes.

The pilot did not pass their first attempt at attaining an instrument flight rating (in a Cessna 310) on 2 June 2014 for not maintaining altitude within +100 ft and -0 ft at the MDA, not using accepted navigation procedures, not being within half-scale deflection of glideslope, and not demonstrating sound command judgement. On the next day, 3 June 2014, the pilot passed on their second attempt.

Under Civil Aviation Safety Regulation (CASR) 61.650, pilots need to have completed an instrument proficiency check (IPC) in the previous 12 months to fly a multi-engine aircraft under the instrument flight rules (IFR). The IPC must also be done in a multi-engine aircraft of the same category.

The pilot undertook 6 IPCs with 3 different independent CASA-approved flight examiners between 2016 and 2019. These are detailed in Table 2.

Table 2: Pilot instrument proficiency checks 2016–2019

The pilot’s last 3 IPCs were conducted on 4 August 2018, 5 August 2018 and 7 August 2019, all with the same CASA-approved flight examiner (who also conducted the IPC in March 2016).

On 4 August 2018, the pilot did not pass the IPC due to misreading the altimeter. The flight examiner recalled that they were on descent to the minima on a circling approach and, when the aircraft was at 1,000 ft above the MDA, the pilot asked whether they were visual. It then became apparent that the pilot had misread the altimeter by 1,000 ft (that is, they thought the aircraft was 1,000 ft lower than it was). The pilot successfully passed the check the following day.

The pilot’s most recent IPC was conducted on 7 August 2019 and was valid until 7 August 2020. The flight examiner who conducted this check was selected by the pilot; it was not the flight examiner regularly used by the operator (and who was familiar with the Air Connect Australia operations manual and could also conduct OPCs).

For each of the IPCs in 2018 and 2019, the pilot conducted a training flight with an instructor prior to the test flight, using the same Cessna 310 aircraft as in the test flights. The instructor commented that the pilot flew significantly better in 2019. Between the 2 checks in 2018 and 2019, the Cessna 310 aircraft was fitted with a GPS/navigational system and electronic flight instruments comprising an attitude display indicator (ADI) and a horizontal situation indicator (HSI). The ADI displayed aircraft attitude information, together with a secondary display of air data information (airspeed, altitude and vertical speed). The ADI and HSI each provided course and advisory vertical guidance during RNAV GNSS approaches.[14]

As already noted, the pilot undertook an operator proficiency check (OPC) on 29 October 2018 before commencing line operations with Air Connect Australia. This was the last OPC carried out on the pilot (see also Operator proficiency checks).

Between February and June 2018, prior to joining the operator, the pilot undertook training with an airline in a multi-crew environment and high-performing (turboprop) aircraft. Although the pilot obtained high marks in theory and written tests, they did not obtain satisfactory ratings during 3 proficiency assessments in a simulator (with remedial training given after each of the first 2 assessments). A common identified problem was instrument approaches, with issues identified including inefficient instrument scan, fixation (on some parameters), speed control, workload management, insufficient situational awareness and ineffective profile management. The ATSB notes that the training and checking environment at the airline was different to the pilot’s previous experience and the operational environment at Air Connect Australia.

Observations of the pilot’s approach to safety

The chief pilot (and managing director) of Air Connect Australia described the pilot as being a good pilot who would not have gone into an approach if they thought the weather was going to be poor, and that there was never any pressure to fly in poor weather. The pilot was trusted to make safety decisions, which would be supported by the chief pilot. This was consistent with the recollection of a previous pilot who flew with the operator, who reported that there was never any operational pressure (from the operator’s key personnel).

Another pilot stated that the pilot of the accident flight had ‘good stick and rudder skills’ and that everything was done ‘by the book’. It was also reported that the pilot had not expressed any concerns about the operator, including its approach to safety.

Former colleagues from when the pilot was chief pilot at a previous operator described the pilot as smart, diligent, and methodical with good knowledge of the rules and regulations. They reported that the pilot did not take shortcuts or unnecessary risks and had good hand-flying skills.

With reference to instrument approaches, one pilot advised that they had many conversations with the pilot of the accident flight regarding aircraft accident reports and safety, and the pilot of the accident flight had stated that they would conduct instrument approaches using the published constant-descent profile and would not intentionally deviate below published segment minimum safe altitudes in order to get visual early in an approach.

During January 2020, the pilot spent a week conducting a series of charter flights between Aurukun and Weipa, Queensland, in VH-OZO with the same group of passengers (see also Prior missed approach during an RNAV GNSS approach (22 January 2020)). Their perception was that the pilot was a good, competent pilot who was diligent, professional, and responsible and that they never felt unsafe. They also advised that they observed the pilot reviewing forecast and actual weather conditions regularly and that the pilot would delay flights due to weather conditions if necessary. Some of the passengers reported observing the pilot make weather-based decisions and did not display any indications of external pressure to fly in poor weather. One of the passengers reported that the pilot had said they would only ever make 2 attempts at landing and, after that, would return to the departure aerodrome or divert to an alternate.

Recent history

The pilot had recently returned from annual leave, with their last flights before leave conducted on 18 February 2020. The 3 days prior to the accident flight were reported to be uneventful. It was described that the pilot ate and exercised regularly and had been sleeping well with a standard time to sleep about 2230 and wake time about 0700–0730. The night before the accident flight, the pilot went to bed at about 2230 and woke at about 0530. There was nothing of note from the pilot’s recent history to suggest they were experiencing a level of fatigue known to affect performance.

The pilot was notified about the 11 March 2020 flight a few days in advance. It was reported that the pilot had been in a good mood in the days prior to the flight and was looking forward to flying again. On the day before the flight, the pilot went to Cairns Airport and started the aircraft’s engines to re-familiarise themselves and ensure everything was ready for the next day’s flight.

Medical information

The pilot’s Class 1 Aviation Medical Certificate was renewed on 14 February 2020 and was valid until 14 February 2021. There were no indications of any significant medical problems in the pilot’s aviation medical records. There was no evidence to suggest the pilot had any current or ongoing medical issues at the time of the accident.

A post-mortem examination was conducted by a forensic pathologist on behalf of the Queensland Coroner. The pathologist found that there was ‘No obvious natural disease to contribute to the cause of death within limits of examination …’. Forensic toxicology screening returned negative results (that is, no alcohol or substances were detected). The sample was unsuitable for analysis for carbon monoxide.

Aircraft information

General information

The Cessna 404 Titan is an unpressurised, low-wing, twin piston-engine aircraft with retractable landing gear. The maximum take-off weight (MTOW) is 3,810 kg, and the aircraft was certified to be flown by a single pilot.

VH-OZO was manufactured by the Cessna Aircraft Company in 1980. It was reported that the aircraft was first operated in Australia before being transferred to Papua New Guinea and registered as P2-ALG. In December 2009, a CASA Certificate of Airworthiness was issued, and the aircraft was registered as VH-OZO. At that time, the aircraft’s total time in service was 28,193 hours.

Seating

The type certificate data sheet for the Cessna 404 stated the aircraft type had 11 total seats (2 pilot seats and 9 passenger seats). In 1980, VH-OZO was configured with a modified seating configuration with 13 seats (2 pilot seats and 11 passenger seats).[15]

During an audit of Air Connect Australia in June 2017, CASA identified that the Airplane Flight Manual stated a maximum of 9 passenger seats aft of the pilot seats but there was 11 on the aircraft. In its initial audit response, the operator stated that the seating change was approved many years ago and it was attempting to find supporting documentation. In a subsequent response, the operator stated that it had previously operated and would continue to operate with a maximum of 9 passengers. It noted that the extra seating would remain in the aircraft as it formed part of the aircraft’s current weight and balance data.

During the investigation, the chief pilot confirmed that the operator never operated the aircraft with more than 9 passengers and normally operated with significantly less than 9 passengers.

Photos taken during the accident flight indicated that no passengers were seated in the front right seat next to the pilot.

Aircraft instruments and systems

On arrival into Australia, the aircraft was fitted with aerial geophysical survey equipment and was operated in that configuration until the equipment was removed in March 2012. Concurrently, the aircraft were modified in accordance with an engineering order to install new types of avionics and integrate those with existing units. The post-modification avionics, including existing equipment, consisted of:

• Garmin GMA 340 audio panel
• dual Garmin GNS 430W GPS/Nav/Com units
• dual Garmin GI-106A GPS/VOR/LOC course deviation indicators (CDIs)
• Garmin GTX327 transponder
• Bendix/King KR87 automatic direction finder (ADF) and Bendix/King KI-227 ADF indicator
• Collins HF radio
• Cessna 400B Navomatic autopilot
• Bendix weather radar (monochrome display).

These units were still installed at the time of the accident except for the transponder, which had been replaced by an automatic dependent surveillance-broadcast (ADS-B) compliant unit in April 2017.

VH-OZO was not fitted with a terrain avoidance and warning system (TAWS), nor was it required to be under legislation in place in Australia at the time of the accident. Further information is provided in Terrain avoidance and warning systems.

An assigned altitude indicator was fitted to the aircraft, which was designed to be used as a reminder of the designated altitude. Altitudes could be manually set by means of individual thumb wheels and no aural or visual alerts were provided when reaching or leaving the set altitude. The aircraft did not have an altitude alerting system, nor was it required for the type of aircraft and operation.[16]

The 400B autopilot was one of the standard equipment options for the Cessna 404 type. It could provide pitch and roll control with heading and altitude hold (on command). A navigation function provided the autopilot with inputs from an associated CDI (the GI-106A), which in this case received data from the number‑1 GNS 430W.

For an RNAV GNSS approach, a pilot could ‘couple’ the autopilot for lateral navigation and manage vertical navigation by adjusting the autopilot pitch wheel to achieve the intended rate of descent. For a level segment, the pilot could select altitude hold on reaching the intended altitude. Several pilots who had flown VH-OZO advised that they routinely hand flew instrument approaches due to autopilot constraints.

The aircraft was fitted with the instrumentation required for operations under the IFR. These flight instruments were conventional analogue indicators and reflected the original specifications for the aircraft. The second artificial horizon/attitude indicator and altimeter were located on the right side of the co-pilot panel (far side of the instrument panel relative to the pilot) (Figure 7).

Figure 7: VH-OZO instrument panel

Source: Supplied, annotated by the ATSB

A closer view of the instrument panel is depicted in Figure 8. It had the standard 6 flight instruments directly in front of the pilot’s seat on the left. These include the attitude indicator, which depicts the aircraft’s basic roll and pitch attitude, and the primary performance instruments – altimeter, airspeed indicator and vertical speed indicator (VSI). Below those were 2 (GI-106A CDI) instruments[17] that provided course deviation indication provided either by the GNS 430’s digitally-tuned VOR/localiser and glideslope receiver or GPS input to conduct an RNAV GNSS approach. One CDI instrument was coupled to the aircraft’s number-1 GNS 430W GPS unit and the other to the number-2 GPS unit.

The basis of cockpit design is to have the primary instruments within a small arc of the pilot’s forward line of sight. Navigation systems such as the GPS units may be located next to the primary instruments, as was the case in VH-OZO. While conducting an RNAV GNSS approach, it is imperative that the pilot includes the GPS units in the scan.

Figure 8: Instrument panel of VH-OZO

Source: Supplied, annotated by the ATSB

Altimeters

VH-OZO was equipped with two 3-pointer altimeters (Figure 9), including one directly in front of the pilot. They had a 100-ft pointer (long and narrow), 1,000-ft pointer (short and wide) and 10,000-ft pointer (long and thin with a triangle at the end). The diagonal hashing indicated when below 10,000 ft and was gradually covered above that height.

These types of 3-pointer altimeters are very common in general aviation aircraft, including small aeroplanes used for passenger transport activities. Research has shown that such altimeters can be associated with misreading errors, including misreading the altitude by 1,000 ft, although accidents known to be associated with such errors seem relatively rare. Accordingly, such altimeters (and some other altimeter designs) are no longer allowed to be used on air transport certificated aircraft. Further information about requirements and guidance regarding altimeters is provided in Appendix A – Research and guidance regarding design of altimeters.

The aircraft was not fitted with a radio altimeter, nor was it required for the type of aircraft and operation.

Figure 9: Example of the 3-pointer type of altimeter fitted in VH-OZO

This altimeter shows an altitude of 1,210 ft (10,000 ft pointer indicating 0, 1,000 ft pointer indication 1,000 ft and 100 ft pointer indicating 210 ft.

Source: avioelectronica.com

GNS 430W overview

The Garmin GNS 430W is a panel-mounted unit that provides GPS navigation, instrument landing system or VHF omnidirectional radio range navigation, and VHF radio communication. It was approved for IFR operations, including RNAV GNSS approaches, and was used in conjunction with a CDI.

Although the ‘W’ designated wide area augmentation system capabilities[18] that facilitated GPS approaches with vertical guidance, Australia did not have the associated satellite-based augmentation system to enable this functionality at the time of the accident. As such, the GNS 430W was approved to provide distance and track information only for RNAV GNSS non-precision approaches.

Information was displayed to the pilot on an 8.4 cm by 4.6 cm (240 by 128 pixel) high-contrast colour LCD. A pilot could select the pages and menus to display relevant information during various flight stages. Those included the default navigation page and additional pages including:

• a 2-dimensional representation of terrain relative to the aircraft position
• information for vertical navigation of the aircraft
• a moving map display
• information about the status of the GPS satellite constellation
• information relevant for the navigation and communication functions of the unit.

When used for an RNAV GNSS approach, the navigation page would display a graphic CDI together with the active leg of the approach and 6 user-selectable data fields.[19] After passing the waypoint it was tracking to, the unit would automatically sequence to the next waypoint.

When approaching a waypoint such as an initial approach fix (IAF), if a turn was required, the unit would display the recommended flight path (turn) to intercept the next track segment. The unit would also display a flashing message about 10 seconds prior to the start of the recommended turn, alerting the pilot that a turn was required and the track to intercept.

To use the unit for RNAV GNSS approaches, it was a requirement that the NavData card[20] was valid and the approach procedure was loaded from the database. The operator subscribed to the Jeppesen NavData service that provided monthly updates. It was reported that the pilot updated the NavData card using a laptop computer in the 24 hours prior to the flight. There were no changes in the update that would have been relevant to the accident flight.

The terrain, obstacle and airport terrain database was loaded on a terrain data card. The operator did not subscribe to an update service for terrain/obstacle data. Obstacle data was updated on a 56-day cycle and updates to the terrain database were released on an ‘as-needed’ basis. There was no requirement to have current obstacle or terrain databases to use the GNS 430W for flight under the IFR and/or during an RNAV GNSS approach. A June 2018 photograph of VH‑OZO’s GNS 430W receivers indicated the obstacle database installed at that time was dated October 2011.[21]

Fault detection and exclusion was incorporated into the GNS 430W software to detect satellite failure and exclude failed satellites from usage.

In addition to their experience with VH-OZO, the pilot of the accident flight had experience using GNS 430 units during their time flying Cessna 310 and PA-31 aircraft with a previous operator, which included units with a terrain awareness function.

Garmin TERRAIN function

Garmin TERRAIN was a non-certified[22] terrain awareness system, provided as a standard feature of 400W-series units, to increase pilot situation awareness and help reduce the risk of controlled flight into terrain (CFIT). The functions required a valid 3D GPS position and a valid terrain and obstacle database. Terrain and obstacle information was advisory only and was not equivalent to warnings provided by TAWS. The Garmin 400W Series Pilot’s Guide & Reference manual stated:

CAUTION: The Terrain feature is for supplemental awareness only. The pilot/crew is responsible for all terrain and obstacle avoidance using information not provided by the 400W-series Terrain feature.

When the GNS 430’s terrain page was selected, it presented a 2-dimensional colour-coded display of terrain tiles and obstacles from its database, relative to the aircraft’s current position/altitude. Red (warning) indicated terrain/obstacles above and up to 100 ft below the aircraft’s current altitude, yellow (caution) between 100 ft and 1,000 ft below the current altitude, and black more than 1,000 ft below the current altitude. The terrain page would not normally be selected when conducting an RNAV GNSS approach.

Terrain advisory and alert messages were provided when flight conditions met specific parameters. The advisories/alerts comprised a visual annunciation in the lower left corner of the unit’s LCD display, accompanied by a larger pop-up advisory/alert on the current display page (except the page displaying terrain). To clear the pop-up advisory/alert, the pilot would either acknowledge the message to return to the selected page or acknowledge the advisory/alert and display the terrain page. The system did not provide auditory alerts.

A pilot could use an ’inhibit mode’ to deactivate the terrain advisory/alert message system and pop-up messages would not be generated. The terrain page was still selectable and would display colour-coded terrain and obstacle information relative to the aircraft’s position. Once inhibited, the terrain annunciator field displayed a ‘TER INHIB’ annunciation and the terrain alert system remained deactivated until reselected. The GNS 400W-Series manual stated that the terrain inhibit mode could be used when the advisories/alerts were deemed unnecessary by the pilot. The manual also stated:

Flying VFR into an area where unique terrain exists could cause the system to annunciate a nuisance alert. Pilots should use discretion when inhibiting the TERRAIN system and always remember to enable the system when appropriate.

According to the GNS 400W-Series manual, the terrain system issued a premature descent alert (PDA) when the aircraft was significantly below the normal approach path to a runway. The manual indicated that this alert would activate depending on the aircraft’s height above terrain and distance from the runway threshold (for example, it would be triggered if the aircraft was about 400 ft above terrain when 10 NM from the runway threshold, 350 ft at 5 NM, 320 ft at 4 NM, and 280 ft at 3 NM). PDA alerts were not provided when the aircraft was within 0.5 NM of the runway or less than 125 ft above terrain within 1.0 NM of the runway.

Based on this information and the recorded data for the accident flight (Recorded flight data), provided that the terrain advisory/alert function was enabled, a yellow and black ‘TERRAIN’ annunciation would be generated in the lower left corner of the LCD display, accompanied by a yellow and black ‘TOO LOW – TERRAIN’ PDA pop-up alert (Figure 10), about 15 seconds prior to the terrain collision.

Figure 10: Premature descent alert on the GNS 430W display

Source: Garmin GNS 400W Series Pilot’s Guide & Reference

The terrain system also provided forward-looking terrain avoidance (FLTA) alerts. Provided the terrain system was enabled, a FLTA terrain alert was generated when the predicted or present aircraft altitude above terrain or obstacles was below the minimum clearance value for that phase of flight. During an approach, the clearance value was 150 ft during level flight and 100 ft when descending.[23] The terrain/obstacle advisory alert comprised a yellow and black ‘TERRAIN’ annunciation in the lower left corner of the LCD display, accompanied by a yellow and black ‘TERRAIN ADVISORY’ or ‘CAUTION OBSTACLE’ pop-up message. The pop-up advisory alert would be displayed on all selectable pages (except the terrain page) and remained visible until the message was cleared/acknowledged by the pilot, or the minimum clearance value was no longer infringed.

If the minimum clearance value for terrain/obstacles remained, a terrain/obstacle ahead alert would be generated. The alert consisted of a flashing yellow and black ‘TERRAIN’ annunciation in the lower left of the LCD panel display and a flashing yellow and black ‘TERRAIN AHEAD’ or ‘OBSTACLE AHEAD’ pop-up alert. The pop-up alert would be displayed on all selectable pages, except the terrain page and remained visible until the message was cleared/acknowledged by the pilot, or the minimum clearance value was no longer infringed.

The GNS 400W-Series manual did not specify the warning period for FLTA alerts. However, an earlier version of the 430/430A-Series manual indicated the ‘TERRAIN ADVISORY’ or ‘OBSTACLE ADVISORY’ pop-up terrain alert would be displayed when approximately 60 seconds from potential impact and the ‘TERRAIN AHEAD’ or ‘OBSTACLE AHEAD’ flashing pop-up terrain alert when 30 seconds from potential impact.

On the accident flight, the descent rate when the aircraft reached 5 NM from the runway threshold (or 3.6 NM from the MAPt) is unclear (see Recorded flight data). However, soon after, the descent rate was about 1,200 ft/min and the predicted flight path would have resulted in an FLTA alert to be generated. Therefore, if the terrain awareness/alert system was enabled, an FLTA alert should have been generated about 30 seconds (or longer) prior to the collision.

Air Connect Australia did not have any operational guidance or procedures regarding the use of the terrain awareness function on the GNS 430W units. The chief pilot reported that, when they were the pilot flying VH-OZO, they would generally leave the function turned on, even though it could be annoying in some locations. However, they did not regularly fly the aircraft and had not conducted the most recent flights in the aircraft.

The ATSB spoke to several pilots who were familiar with GNS 430 units with a terrain awareness function. Some advised that the terrain awareness function would often be inhibited, whereas others would use the function on one 430 unit and inhibit it on the second 430 unit. None of the pilots were aware of operators having specific procedures and guidance for using the terrain function.

Pilots stated that the main reason for the terrain awareness function to be inhibited was the perception that it could issue nuisance alerts, with some of these pilots clarifying that this would only occur (or be a valid concern) when conducting visual approaches at non-licenced aerodromes. One pilot advised that they had heard of some pilots in one operator being concerned about using the terrain function if the terrain/obstacle database was not current. However, 2 experienced flight examiners advised that, in their experience, these databases were commonly not current on aircraft they encountered in their roles and that having a current database was not critical; the advantages of the terrain awareness function were more significant than any potential problem with a terrain/obstacle database not being current.

There was no information available regarding what the pilot of the accident flight normally did with the terrain awareness function when flying VH-OZO. Based on the available information, the ATSB could not establish if the terrain awareness function was enabled or inhibited during the accident sequence, or to what extent the pilot had previously encountered terrain alerts when conducting operations in the aircraft.

Configurations and speeds

The flap settings on the Cessna 404 included ‘UP’, ‘T.O. & APPR’ (take-off/approach) and ‘LAND’ (landing). The take-off/approach setting was often referred to as ‘approach flap’ and sometimes called ‘10° flap’.[24]  

According to the Cessna 404 Pilot’s Operating Handbook (POH), which included the Airplane Flight Manual approved by the US Federal Aviation Administration, the maximum landing gear extension speed (and operating speed) was 182 kt, the maximum speed to select approach flap was 182 kt, and the maximum speed to select landing flap was 152 kt.

The POH specified a recommended minimum approach speed (or V_ref[25]) at 50 ft of 91 kt (all engines operating, landing flaps, weight 8,100 lb or 3,6764 kg). For all aircraft weights of 7,500 lb (3,402 kg) and lower, the POH stated approach airspeeds (at 50 ft) of 88 kt. Consistent with the POH, the operator’s operations manual provided values for V_APP[26](approach speed) of 91 kt at 8,100 lb and 88 kt at 7,500 lb and lower weights.

The POH stated the minimum control speed (V_MCA) with approach flap selected was 78 kt. In addition, the one-engine inoperative best rate-of-climb speed for the aircraft type was 102 kt (flap in the take-off/approach position and gear up) and 109 kt (flap and gear up).

Aircraft maintenance

The aircraft logbook statement specified that VH-OZO was to be maintained in accordance with the system of maintenance developed by the aircraft owner and approved by CASA. The key elements of the system were:

• daily inspection in accordance with the Cessna 404 POH
• engine and airframe inspections every 100 +/- 10 hours in accordance with the Cessna 404 progressive care program (Operations 1 and 2 plus 3 and 4 completed within 12-month period)
• electrical and instrument inspections every 220 hours or 12 months in accordance with system of maintenance schedules
• IFR avionics inspections every 220 hours or 12 months in accordance with system of maintenance schedules
• special inspections, supplemental inspection documents, and corrosion prevention control program as required
• altimeter and pitot-static system inspection and test every 24 months
• maintenance release issue for a period of up to 220 hours or 12 months, whichever occurred first. 

Scheduled engine and airframe maintenance was carried out by the CASA-approved maintenance organisation associated with the aircraft owner. While the aircraft was based in Cairns, electrical, instrument, and radio maintenance as well as unscheduled maintenance was contracted to licensed aircraft maintenance engineers.

The most recent maintenance was the scheduled 100-hour inspection based on Operations 3 and 4 of the Cessna 404 progressive care program. That was completed on 16 February 2020 at 31,066 hours total time. A maintenance release was issued with the next scheduled maintenance being the oil/filter change after 50 hours operation and compass swing in July 2020. 

Other key maintenance was:

• 19 January 2020 at 31,050 hours: inspection of the electrical, instrument and IFR avionic systems certified as satisfactory
• 29 January 2019 at 30,750 hours: inspection and test of the pitot-static system and check of altimeters certified as satisfactory.

The current maintenance release was not found at the accident site. Operator records showed that the aircraft had been operated for 3.8 hours between maintenance release issue and the accident flight. The operator and aircraft owner both advised that no aircraft defects had been reported.

The ATSB identified that the vacuum pumps had been in service for a relatively long period and internal wear had not been inspected at the recent 100-hour inspection. Also, there was no record of testing or replacement of the vacuum manifold in the previous 10 years. Although these aspects increased the likelihood of a vacuum system failure, there was no evidence that the vacuum-powered instruments were adversely affected. Further information regarding the maintenance and serviceability of the vacuum system (associated with the attitude indicators and directional gyro) is provided in Appendix B – Vacuum system analysis.

Terrain avoidance and warning systems

General description

A terrain avoidance and warning system (TAWS) provides visual and aural alerting including a look-ahead terrain function. The aircraft’s height above terrain can be based on GPS or radio altitude information. TAWS is a generic term that also includes a ground proximity warning system (GPWS) with a forward-looking terrain avoidance function.

A TAWS is an important tool to help minimise the risk of controlled flight into terrain (CFIT). It provides an independent and unambiguous warning of proximity to the ground or obstacles, regardless of any navigational uncertainty or error such as mis-setting or misreading the altimeter.

Multiple levels or classes of TAWS are defined and internationally recognised. Class B TAWS (TAWS B) includes a minimum of the following alerts:

• reduced required terrain clearance
• imminent terrain impact
• premature descent
• excessive rates of descent
• negative climb rate or altitude loss after take-off
• descent of the aeroplane to 500 ft above the terrain or nearest runway elevation (voice callout ‘Five hundred’) during a non-precision approach.

Class B+ TAWS also has a terrain awareness display that shows surrounding terrain/obstacles relative to the aircraft. Class A TAWS (TAWS A) has all the requirements of Class B+ TAWS, plus 3 additional alerts. Both Class A and class B TAWS have a forward-looking terrain avoidance function.

To maximise its effectiveness, an aircraft operator should have standard operating procedures for the use of a TAWS and for actions to take in response to TAWS alerts.

Australian requirements

Civil Aviation Order (CAO) 20.18 (Aircraft equipment — basic operational requirements), which was in force at the time of the accident, stated that for Australian aircraft:

9.1C A turbine-engined aeroplane that:

(a) has a maximum take-off weight [MTOW] of more than 15 000 kg or is carrying 10 or more passengers; and

(b) is engaged in RPT [regular passenger transport], or charter, operations;

must not be operated under the I.F.R. unless it is fitted with

(c) an approved ground proximity warning system that has a predictive terrain hazard warning function…

(e) if the aeroplane has a maximum take-off weight of 5 700 kg or less, but is carrying 10 or more passengers – a TAWS-B+ system.

In effect, this meant that turbine-engine aeroplanes being used to conduct passenger transport operations under the IFR were required to have a TAWS if the aeroplane was carrying 10 or more passengers or it was a larger air transport aeroplane.[27] There was no requirement for a piston-engine aeroplane (such as VH-OZO) to be fitted with a TAWS.

International requirements for turbine-engine aeroplanes

The Australian TAWS requirements for turbine-engine aeroplanes were consistent with the standards included in International Civil Aviation Organization (ICAO) Annex 6 (Operation of Aircraft) Part I (International Commercial Air Transport – Aeroplanes), which included a standard[28] for all turbine-engine aeroplanes with a MTOW of more than 5,700 kg or authorised to carry 10 or more passengers to have a TAWS. In addition to Australia, this standard had been adopted by comparable countries, including the United States, Canada, New Zealand and Europe.

In 1996, the US National Transport Safety Board (NTSB) issued a recommendation to the US Federal Aviation Administration (FAA) to require that all turbojet-powered airplanes equipped with 6 or more passenger seats have an operating GPWS installed. In 1999 it also recommended that all turbine-powered aeroplanes of the same size be fitted with a TAWS. 

In response, the FAA commissioned a report that examined 44 CFIT accidents that occurred between 1985 and 1994 in the US involving turbine-powered aeroplanes with 6 to 10 passenger seats. Of the 44 aeroplanes, 11 were powered by turbojets and 33 were powered by turboprops. None were fitted with a GPWS system. Computer modelling techniques used to analyse the data showed that, had GPWS been fitted, 33 accidents could have been prevented; had enhanced GPWS been fitted, 42 accidents could have been prevented.

Accordingly, the FAA introduced a requirement for all turbine-powered aeroplanes with 6 or more passenger seats to be fitted with a TAWS B (in Federal Aviation Regulations 91.223 and 135.154). The requirement commenced in March 2002 for new aircraft and March 2005 for older aircraft.

The FAA did not propose to introduce the same requirement for piston-engine (or reciprocating-engine) aeroplanes. In its final rule summary in 2000, the FAA stated:

The General Aviation Manufacturers Association (GAMA) is against requiring TAWS on reciprocating-powered [piston-engine] airplanes because the costs would be high (e.g., “TAWS equipment would cost more than the hull value of the aircraft”), and the panel space for installing TAWS with a situational display is not available in these airplanes.

The FAA did not receive any comments that would justify undertaking a new rulemaking project to mandate TAWS for reciprocating-powered airplanes.

However, regarding the issue of panel space, the FAA knows of at least one manufacturer who has developed a complete TAWS unit that was designed to replace an existing panel instrument.

Following the US introduction, from November 2006, ICAO Annex 6 Part I included a recommendation that turbine-engine aeroplanes with an MTOW of 5,700 kg or less and authorised to carry 6–9 passengers should be equipped with a TAWS. This recommended practice was introduced as a regulatory requirement in other countries, including New Zealand (from 2007 for air transport operations under the IFR), Canada (from 2014 for operations other than day VFR flights), and in Europe (for such aeroplanes with an individual certificate of airworthiness issued after 1 January 2019).[29]

International requirements for piston-engine aeroplanes

Applicable from January 2007, ICAO Annex 6 Part I included a standard for TAWS B to be fitted to piston-engine aeroplanes with a MTOW greater than 5,700 kg or authorised to carry 10 or more passengers.

Subsequently, TAWS requirements were introduced in Canada (from 2014 for air transport operations other than day VFR flights), New Zealand (from 2007 for air transport operations under the IFR) and Europe (from 2012 for air transport operations) for piston-engine aeroplanes. No such requirements for piston-engine aeroplanes were introduced in the United States.

Canada also introduced the same requirement for piston-engine aeroplanes with a passenger seating capacity of 6–9 conducting air transport operations other than day VFR flights from 2014. As far as could be determined, no other countries had introduced a TAWS requirement for piston-engine aeroplanes with a passenger seating capacity less than 10.

In its notice of amendments about TAWS requirements in 2012, Transport Canada indicated that the cost for installing a TAWS B on small aeroplanes conducting air taxi (charter) operations in aircraft with a passenger seating capacity of less than 10 was about Can$23,000. It also noted that the expected benefits of TAWS (in terms of reduced fatalities, serious injuries and accidents due to CFITs) were significantly higher than the costs.[30]

Considerations of changes in Australia

In March 2006, the ATSB issued safety recommendation R20060008:

The Australian Transport Safety Bureau recommends that the Civil Aviation Safety Authority review the requirements for Terrain Awareness Warning Systems for Australian registered turbine-powered aircraft below 5,700 kgs, against international standards such as ICAO Annex 6 and regulations such as FAR 91.223, with the aim of reducing the potential for CFIT accidents.

CASA accepted the recommendation and stated that it would examine the capital/installation costs and benefits. This work was initiated as part of CASA’s notice of proposed rule making (NPRM) 0808OS (Passenger transport services and international cargo operations – Small aeroplanes) published in February 2009. The proposed requirements included that small aeroplanes (regardless of engine type) conducting passenger transport operations carrying 6 or more passengers under the IFR to be fitted with a TAWS B. In terms of benefits and costs, the NPRM stated:

The costs and benefits of mandating TAWS B equipment for IFR aeroplanes carrying 6 to 9 passengers has been assessed by CASA. Equipment and fitment costs are forecast to be approximately $23,000 per aeroplane. Options to offset these additional costs are under consideration by the Government. Benefits are expected to flow to the industry from increased public confidence with this equipment fit to small aeroplanes in which passenger operations are conducted, as the overall accident rate is expected to reduce.

Accordingly, the ATSB recommendation was closed.

Subsequently, CASA released a consultation draft of Civil Aviation Safety Regulation (CASR) Part 135 (Australian air transport operations—smaller aeroplanes) in 2012. This contained a requirement for a TAWS for aeroplanes conducting passenger transport operations with a maximum operational passenger seat configuration (MOPSC)[31] of 6 or more. The proposed requirement’s applicability had expanded to include all flights (not just IFR flights) and was based on the passenger seat capacity rather the actual number of passengers carried on a flight.

Following further consultation, the 2012 proposal was amended to a MOPSC of 10 or more. In the summary of proposed change for CASR Part 135 (published in August 2018), CASA stated:

CASA had originally proposed the fitment of a minimum of TAWS-Class B for aeroplanes with a MOPSC greater than 5 which aligned with the Federal Aviation Administration of the USA (FAA) and Transport Canada rules however this was changed after discussion with the Aviation Safety Advisory Panel Technical Working Group.

In the 2018 explanatory statement in for the introduction of CASR Part 135, CASA outlined the options it considered (in its regulatory impact statement) regarding the implementation of TAWS. It noted that the estimated cost of installing a TAWS was about $21,000 (including about $12,000 for the system and additional costs for installation and training). One option (named option 2) was to only require a TAWS for all aeroplanes with a MOPSC of 10 or more or a MTOW greater than 5,700 kg. It was determined that this would affect 18 aeroplanes (in addition to those that already had or required a TAWS). Another option (option 3) was to require a TAWS for all aeroplanes with a MOPSC of 6–9 as well. In terms of option 3, the statement noted:

The types of aircraft that are within this category include, the piston powered AeroCommander 680, Beech 95 and Cessna 421 and the turbine powered aeroplanes that include the Cessna 208, Fairchild SA 226 and Pilatus PC 12. CASA estimates that there are approximately 323 of these types of aircraft. Based on 323 aircraft within the six to nine seat range and the 18 aircraft with MTOW>5700kg of option 2 this would result in an estimated cost impact of $7.2m for 341 aircraft... [as well as $0.72m annually]

The statement noted that initially CASA had proposed option 3 to industry but, following initial consultation, it did not pursue this option. Feedback associated with the initial consultation on TAWS (and other proposed regulatory changes) included that charter businesses were operating in a difficult marketplace with many not being profitable.

As a result of this regulatory reform process, the Australian requirements for TAWS changed from December 2021, such that piston-engine aeroplanes with a MOPSC of 10 or more conducting air transport operations were required to have a TAWS, with the applicable date being December 2021 or December 2022 dependent on various factors (see Safety issues and actions).

For VH-OZO and its seating configuration at the time of the accident, CASA advised the MOPSC was 12.^[32]As such, if the operator had continued operating the aircraft for passenger transport flights with that seating configuration, the aeroplane would have been required to have a TAWS by December 2022 and, from December 2024, the operator would have had to operate the aeroplane under CASR Part 121 (and conduct all flights with 2 pilots under the IFR, as well as meet additional requirements compared to Part 135). Alternatively, the aeroplane would not have been required to have a TAWS or be operated under Part 121 if some seats were removed such that the MOPSC was 9 or less.^[33]

Aerodrome information

Lockhart River Airport had one sealed runway (12/30), which was 1,500 m long and 30 m wide. It was not serviced by an air traffic control (ATC) tower and it was outside of ATC radar coverage. The airport had a common traffic advisory frequency (CTAF), which was used by pilots to advise intentions and arrange separation with other traffic.  

The elevation of the runway was 76 ft at the threshold for runway 30 and 48 ft at the threshold for runway 12. The runway was equipped with low-intensity runway lights, and there was no visual approach slope guidance.

At the time of the accident there were 3 instrument approaches available at the airport:

• NDB approach to runway 30
• RNAV GNSS approach to runway 12
• RNAV GNSS instrument approach to runway 30 (Figure 2).

The airport was located on a coastal plain 4.5 km west of the Lockhart River township. The Great Dividing Range was nearby with the terrain rising to over 800 ft to the south-west and west within about 8 km of the airport.

Lockhart River was known to experience low cloud and poor visibility conditions. The average (mean) rainfall at Lockhart River is 2,058 mm. In the month of March, the average rainfall is 446 mm and 19.5 days have rainfall of more than 1 mm.

The ATSB interviewed several pilots with experience conducting RNAV GNSS approaches, including some who had conducted multiple approaches at Lockhart River due to poor visibility conditions. The pilots had several suggestions for reducing workload for a second approach, including holding or diverting to Coen or Weipa to wait for weather to pass.

Meteorological information

Weather forecasts - overview

The Bureau of Meteorology produced aviation forecasts, observations, warnings and advisories. As the official provider of the Aeronautical Information Service, Airservices Australia delivered the bureau’s aviation meteorological products to pilots through National Aeronautical Information Processing System (NAIPS).

For the flight from Cairns to Lockhart River, the meteorological forecast information consisted of aerodrome forecasts (TAFs), graphical area forecasts (GAFs), grid point wind and temperature charts (GPWTs) and any warnings (such as SIGMETs[34]). These could be supplemented by aerodrome weather reports (METARs), ground-based weather radar imagery, and satellite imagery.

According to the weather forecasts, the pilot would have expected mostly visual meteorological conditions (VMC)[35] during the day at Cairns with some periods of rain showers and low cloud. For the arrival at Lockhart River, the forecast weather was predominantly VMC but there were overlapping periods of rain and low cloud with 30% probability of thunderstorms.

Aerodrome forecasts

A TAF for Lockhart River was issued at 0449 EST[36] and was valid from 0600 to 1800. The expected weather conditions were:

• From 0600 to 1000: wind variable at 3 kt with visibility 10 km or greater. Light rain showers and cloud scattered at 1,000 ft.[37]
• Between 0600 and 1000: TEMPO[38] - visibility reduced to 3,000 m with rain and broken cloud at 500 ft.
• From 0600 to 0800: 30% probability of fog with visibility reduced to 500 ft and broken cloud at 100 ft.
• From 1000 to 1800: wind from the north-east at 5 kt with visibility 10 km or greater. Light rain showers with scattered cloud at 1,000 ft.
• Between 1000 and 1800: TEMPO - visibility reduced to 3,000 m with rain showers and broken cloud at 800 ft.
• For the whole forecast period, 0600 to 1800: 30% probability TEMPO - winds gusting 25 to 35 kt and visibility reduced to 1,000 m due to thunderstorms and rain. This was associated with broken cloud at 500 ft and scattered cumulonimbus cloud with the base at 1,000 ft.

Based on this forecast a pilot arriving at Lockhart River was required to plan for 60 minutes holding or diversion to an alternate aerodrome. The aircraft had more than sufficient fuel for that purpose (see Fuel calculations).

An amended TAF for Lockhart River was issued at 0925 (5 minutes after the accident) and was valid from 0900 to 1800. The expected weather conditions were:

• From 0900 to 1300: wind variable at 3 kt with visibility 10 km or greater. Light rain showers with cloud scattered at 1,000 ft and broken at 2,000 ft.
• For whole forecast period, 0900 to 1800: TEMPO – winds gusting from 20 to 35 kt and visibility reduced to 1,000 m due to thunderstorms and rain. This was associated with broken cloud at 500 ft and scattered cumulonimbus cloud with the base at 1,500 ft.

Graphical area forecasts

A GAF was issued at 0835 and was valid from 0900 to 1500 and applicable from surface to 10,000 ft. This covered the Queensland-North region, which was divided into 6 areas for this forecast. Most of the flight including the arrival at Lockhart River was within one area that was forecast to have the following conditions:

• Broken stratus 1,000 ft to 2,000 ft with broken cumulus/stratocumulus above that. Visibility reduced to 6,000 m in widespread rain.
• Isolated towering cumulus from 2,000 ft, broken stratus from 800 to 2,000 ft, and broken cumulus/stratocumulus from 2,000 ft. Visibility reduced to 2,000 m in scattered rain showers.
• Isolated cumulonimbus from 2,000 ft and broken status between 500 ft and 1,000 ft. Visibility reduced to 500 m in isolated thunderstorm rain showers.

A GPWT forecast was issued at 0538 and was valid to 1000. Lockhart River was located near the intersection of 4 data boxes and therefore roughly equidistant from 4 forecast locations. Taking 2,000 ft as a reference height for the approaches and coastal data as more relevant, the wind was forecast to be from the north-west at 9 kt increasing to 21 kt north of Lockhart River.

There were no significant weather warnings applicable to the flight.

Weather conditions - overview

The Bureau of Meteorology provided an overview to the ATSB of the actual weather conditions at Lockhart River on the day of the accident. It stated that a developing monsoon trough extended across Cape York Peninsula crossing the coast near Weipa and Lockhart River. A tropical low was embedded in the trough and was near Weipa at 1000, moving slowly eastward. The monsoon trough and low were causing scattered to widespread rain and isolated thunderstorms over much of Cape York Peninsula.

The surface winds at Lockhart River Airport were generally light and variable. Automatic weather sensors detected rain and heavy rain reducing visibility to 800 m and scattered to broken layers of cloud as low as 1,100 ft above ground level.

Aerodrome weather reports for Lockhart River

The METARs for Lockhart River were automatically generated every 30 minutes for routine reports and were issued as a special report (SPECI) at other times when one or more elements met specified criteria for degradation and improvement. For the period from 0830 to 0929 on 11 March 2020, the reports included:

• 0830: nil wind, visibility[39] 10 km or greater with rain and scattered cloud from 3,000 ft. Temperature and dewpoint were both 25 °C. Rainfall in the previous 10 minutes was 0.4 mm.
• 0900: nil wind, visibility 10 km or greater with rain and broken cloud at 2,000 ft, 3,500 ft, and 4,100 ft. Temperature and dewpoint were both 25 °C. Rainfall in the previous 10 minutes was 0.4 mm.
• SPECI 0910: nil wind, visibility 10 km or greater with rain and broken cloud at 1,800 ft and 3,400 ft then overcast at 4,200 ft. Temperature and dewpoint were 26 and 25 °C respectively. Rainfall in the previous 10 minutes was 0.4 mm.
• SPECI 0913: nil wind, visibility 3,800 m with rain and broken cloud at 1,800 ft and 3,400 ft, overcast at 4,200 ft. Temperature and dewpoint were 26 and 25 °C respectively. Rainfall in the previous 10 minutes was 2.2 mm.
• SPECI 0929: wind westerly at 5 kt, visibility 8,000 m with heavy rain and scattered cloud at 1,200 ft, broken cloud at 1,900 ft, and broken cloud at 3,600 ft. Temperature and dewpoint were both 25 °C. Rainfall in the previous 10 minutes was 0.4 mm and rainfall since 0900 was 3.8 mm.

The QNH remained at 1,008 hPa during this period.

Automatic weather station

The Bureau of Meteorology (BoM) provided data from the Lockhart River Airport automatic weather station (AWS) recorded at 1-minute intervals. Table 3 details 1-minute rainfall, 30-minute cloud and 10-minute visibility data for the period encompassing the aircraft’s first approach prior to the final approach fix (FAF) at 0904 to the accident at 0920. The last column in the table indicates the 1-minute visibility associated with the telephone message for the aerodrome’s automated weather information service (see following section section). More detailed information from the Lockhart River AWS for the period 0850 to 0930 is provided in Appendix C – Detailed 1-minute weather data Lockhart River 0850–0930.

Table 3: Extract of 1-minute weather data from Lockhart River Airport AWS

The first shaded area indicates when the aircraft was at the MAPt on the first approach and the second shaded area indicates the time of the accident on the second approach. The 1-minute visibility data was that recorded to be broadcast by the AWIS by telephone. The times have been displaced by 1 minute (back) to align with the 1-minute rainfall data provided by BoM. The cloud data was averaged over the previous 30 minutes (see description in report text).

Source: Bureau of Meteorology

The cloud information was derived using a sky condition algorithm. This involved taking a sample (using a ceilometer at the aerodrome) at least every 30 seconds and averaging the data over a 30-minute period, with samples taken in the last 10 minutes provided double weighting.[40] Although this algorithm provided more stable estimates of cloud than each sample, the reported cloud for any given minute did not necessarily reflect the cloud level at that specific point in time.[41]

The visibility meter estimated atmospheric visibility based on the continuous sampling of a single point, providing a measurement of the prevailing visibility at the sensor. However, it sampled a relatively small volume of air in the immediate vicinity of the instrument and, unlike a human observer, was not capable of estimating visibility in different directions or over longer distances. One-minute data was based on the last 60 seconds of sensor output, as an average based on a processing algorithm. The 10-minute data recorded each minute was the average value over the previous 10 minutes.

A number of factors can affect the accuracy of the reported visibility, including:

• discrete air masses, such as a shower of rain or a bank of fog, will not be identified unless the sensor is engulfed, and if the phenomenon is not of uniform density the visibility will be misreported
• stationary localised patches of fog will remain undetected if the sensor is clear of fog, or if the sensor is within the patch of fog the reported visibility may be less than actual.

The temperature and dewpoint were about 25 °C for the duration with the relative humidity at 99% (increasing to 100% from 0917).

The reported wind speeds and directions were the mean values at 10 m above ground level, averaged over the last 1-minute period. The recorded wind was 0 kt until 0914, with speeds of 3–4 kt from the west, between 0916 and 0921.

Automated weather information service

Lockhart River was equipped with an automated weather information service (AWIS) that transmitted AWS data in text-to-speech format on a discrete VHF frequency. A new AWIS message was generated every minute in a similar format to the METAR reports. To produce the reports from the AWS 1-minute data, some averaging and rounding of the information occurred. The broadcasts were not recorded.

In addition, AWIS data at Lockhart River could also be accessed by telephone. A different phone message based on the AWS data was produced every minute and this was recorded. However, the AWIS information available by telephone was processed differently to the AWIS information available by VHF, and therefore there could be slight differences in the information produced at the same time.

During the flight, the pilot recorded the following data in the space allocated for arrival weather information in the flight plan/log:

• calm (nil wind)
• 10 km (visibility)
• B1800 (broken cloud at 1,800 ft)
• B3500 (broken cloud at 3,500 ft)
• OV 5300 (overcast cloud at 5,300 ft)
• 1008 (QNH 1,008 hPa)
• 25 (temperature 25 °C).

This information closely matched the recorded AWS 1-minute data at 0854, which stated (with expected transmitted message in brackets):

• wind 0 kt at 023° (wind calm)
• visibility 10 km (visibility one zero)
• (present weather – rain)
• cloud 4 oktas[42] at 1,800 ft (cloud broken one thousand eight hundred)
• cloud 5 oktas at 3,500 ft (broken three thousand five hundred)
• cloud 7 oktas at 5,300 ft (broken five thousand three hundred)
• temperature 25.4 °C (temperature two five)
• dewpoint 25.2 °C (dewpoint two five)
• QNH 1,008.5 hPa (QNH one zero zero eight hectopascals)
• rainfall last 10 minutes 0.4 mm (rainfall last ten minutes zero decimal four millimetres). 

The pilot’s recorded weather information was also broadly consistent with the recorded AWIS messages available by phone for the period 0853­–0855. It did not closely match any of the other recorded AWS 1-minute data or the recorded AWIS messages available by phone during 0840–0920. Accordingly, it is very likely that the pilot wrote down the AWIS data accessed by VHF radio at about 0854. It could not be determined whether the pilot additionally accessed the AWIS data prior to this time and/or after this time.

The AWIS broadcasted the most recent 1-minute visibility data measured by the AWS (see Table 3, last column). This data indicated visibility below the landing minima (4,200 m) at the AWS site between 0911 and 0915, and at 0917.

BoM operated a network of weather watch radars around Australia that detected water droplets in the atmosphere. Information from the weather radar was displayed on a map, with different colours depicting the approximate rainfall/precipitation intensity.

The nearest weather radar was at Weipa, approximately 150 km west of Lockhart River. Coverage in the vicinity of Lockhart River was affected by the distance from the radar and terrain, reducing the radar’s ability to detect low-level showers. However, precipitation at higher altitudes would still produce radar echoes.

Figure 11 provides an indication of the weather around Lockhart River at 0918 on the morning of the accident (during the second approach), with Figure 12 displaying an extract of radar images from the time of the first approach and the time of the accident. The weather radar depicted areas of moderate precipitation in the vicinity of Lockhart River. In addition, an analysis of a sequential series of images showed precipitation moving through the area at a speed of about 30 kt (55 km/h) from the north-west.

The minute-by-minute data from the AWS around the time of the accident (see Automatic weather station and Table 3) recorded no significant surface wind. However, there was a short period of rainfall between 0910 and 0916, including moderate to heavy rainfall between 0912 and 0914. If this rainfall persisted and continued moving in a direction/speed consistent with the observed radar returns, it would have been in the vicinity of the accident site about the time of the accident.

Figure 11: Weipa radar image at 0918 EST (about 2 minutes prior to the accident) showing weather in Lockhart River area (circled, approximate radius 25 NM/46 km)

Source: Bureau of Meteorology, annotated by the ATSB

Figure 12: Extract of Weipa radar images at 0906 (time of the first approach) and 0918 EST showing rain rate on the approach path to runway 30 at Lockhart River Airport

Source: Bureau of Meteorology, annotated by the ATSB

Local weather observations

Two pilots were operating aircraft in the Lockhart River area before and after the accident. The first pilot, operating before the accident, tracked to Lockhart River from the south and conducted the RNAV GNSS runway 30 approach, landing at 0810. There were intermittent rain showers in the area and the pilot advised that the end of the runway was visible while descending through 1,000 ft. The pilot remained on the ground at Lockhart River until later in the day and heard an aircraft (VH-OZO) fly over at high engine power. They recalled that, at that time, there was scattered low cloud at 500–1,000 ft with reduced visibility in rain showers.

The following pilot, operating after the accident, tracked to Lockhart River from the south-west and diverted 15 NM to the right of track due to weather. On arrival, the pilot conducted the Lockhart River RNAV GNSS runway 30 approach and landed at 0953. The pilot reported that there was rain in the area and, although the conditions allowed visual navigation after the final approach fix (FAF) while descending through 1,500 ft, the runway was not visible until later in the approach.

A person who was near the airport at the time of the accident described the conditions as an unusual morning with mist coming from the rainforest, and that there was about 5 to 10 minutes of heavy rain at about the time the aircraft would have been in the area. At that time, there was low-lying cloud (north-west of the airport) and no wind.

Fishermen who were in the area at the time reported that, at about the time of the second approach, there was a ‘wall’ of heavy rain that came across from the north-west.

Instrument approach

Overview

An instrument approach is a published procedure that allows for safe navigation of an aircraft operating in instrument meteorological conditions (IMC) to descend from the lowest safe altitude to a specified position (missed approach point - MAPt) near the aerodrome. If the conditions are suitable, the approach can be continued to land. If the conditions are not suitable, the pilot must conduct a missed approach in accordance with the procedure.

There are 2 general categories of instrument approach:

• 2-dimensional (2D) – lateral/tracking guidance only, also known as non-precision approaches or LNAV (lateral navigation)
• 3-dimensional (3D) – lateral/tracking and vertical guidance, including precision approaches such as an instrument landing system (ILS) approach and a (non-precision) approach with vertical guidance (APV).

Both categories of instrument approaches were only conducted utilising ground-based navigation aids until RNAV GNSS[43] approaches were available in Australia from 1998.

An RNAV GNSS approach is a 2D instrument approach that utilises an on-board GPS receiver (or flight management system - FMS) to generate lateral/tracking guidance and distance information. These approaches are pre-programmed in a GPS/navigation system’s database. Other types of non-precision approaches use ground-based aids such as a non-directional beacon (NDB) or a VHF omni directional radio range (VOR).

The transition in Australia from navigation reliant on ground-based navaids to performance-based navigation is continuing. As part of that process, Airservices Australia has been implementing barometric vertical navigation (Baro-VNAV) APV approaches since 2016. These 3D approaches are restricted to runways with a validated (LNAV/VNAV RNP APCH) procedure and aircraft with the applicable avionics, typically an FMS. Although these approaches were available at Lockhart River from 3 December 2020, VH-OZO was not Baro-VNAV capable.[44]

RNAV GNSS approach design

RNAV GNSS approaches in Australia have a Y-pattern, runway-aligned design. The Lockhart River runway 30 RNAV GNSS approach uses this typical layout, as shown in Figure 13.

Figure 13: Extract from Lockhart River RNAV GNSS runway 30 approach chart showing layout of waypoints

Source: Airservices Australia, annotated by the ATSB

The approaches have 3 initial approach fixes (IAFs, in this case, LHREA, LHREB and LHREC), followed by an intermediate fix (IF, LHREI), final approach fix (FAF, LHREF) and missed approach point (MAPt, LHREM).

The segment between an IAF and the IF is the initial approach segment, the segment between the IF and the FAF is the intermediate approach segment, and the segment between the FAF and the MAPt is the final approach segment. Each segment is typically 5 NM.

The intermediate approach track is normally aligned with the final approach track. One of the IAF waypoints is also aligned with the intermediate/final approach track (in this case, LHREB) and the other IAFs are located 70° off the intermediate/final approach track (LHREAS and LHREC). A pilot can commence an approach by flying to one of the 3 IAFs within the capture region for that waypoint. The capture region is a 140° arc for the IAF on the intermediate/final approach track and a 180° arc for the IAFs not on the intermediate/final approach track (with the extreme points parallel to the intermediate/final approach track).

Instrument approach waypoints can either be fly-by waypoints (which require turn anticipation to allow tangential interception of the next segment) or flyover waypoints (at which the turn is initiated). For RNAV GNSS approaches, the IAFs, IF and FAF are fly-by waypoints and the MAPt is a flyover waypoint.

The approaches are recommended to be flown using a continuous descent angle.

The recommended profile published on approach charts consists of an initial approach altitude which then joins a constant descent to 50 ft above the runway threshold. The approach path angle of the descent is normally (and ideally) 3°. Depending on the approach, the initial approach altitude joins the constant descent profile at about the FAF or earlier.

For example, the approach chart for the Lockhart River runway 30 approach (Figure 14) had an initial approach altitude of 3,500 ft leading to an approach path angle of 3°, which commenced 0.8 NM after the IF (4.2 NM prior to the FAF and 9.2 NM prior to the MAPt).

Figure 14: Excerpt from Lockhart River RNAV (GNSS) runway 30 approach chart showing recommended vertical profile and segment minima safe altitudes

The full approach chart is provided in Figure 2.

Source: Airservices Australia, annotated by the ATSB   

Each segment of an RNAV GNSS approach has one or more specified segment minimum safe altitudes, depicted by shading on the chart’s profile diagram and the relevant altitude with a solid line underneath. For example, between the IF and the FAF on the runway 30 approach, the segment minimum safe altitude was 1,800 ft. The last segment minimum safe altitude, in the final approach segment, is the minimum descent altitude (MDA).

During an instrument approach, a pilot is able to descend below the recommended descent profile, but they are not allowed to descend below a segment minimum safe altitude, except for the MDA if certain conditions are met (as discussed below).[45] However, as stated in the Civil Aviation Advisory Publication (CAAP) 178-1(2) (Non-precision approaches (NPA) & approaches with vertical guidance (APV)):

While some pilots in the past have flown NPAs as a series of descending steps conforming to the minimum published altitudes, (a technique colloquially referred to as the ‘dive and drive’), CASA recommends a constant angle descent in a stabilised configuration. Many Controlled Flight into Terrain (CFIT) accidents have been attributed to the ‘dive and drive’ technique, due to human errors such as early descent before a step or failing to arrest descent. In addition, the aircraft’s descent is more difficult to manage due to changes in airspeed, rate of descent and configuration.

If the recommended descent profile starts prior to the FAF, the RNAV GNSS approach chart includes an advisory crossing altitude (or procedure height) at the FAF (and if required the IF) to assist pilots with maintaining the recommended descent profile (for example, 2,160 ft at the FAF in Figure 14). In addition, a pilot is provided with a distance/altitude scale on the approach chart that provides guidance for the recommended descent profile (see top of Figure 14). The distance specified is the distance to the next waypoint.

Approach waypoint naming convention

The waypoints documented on an RNAV GNSS approach chart are identified by a unique identifier comprising the airport identifier (in this case LHR), compass quadrant from which the approach is flown (E - east), and position on the approach (A, B, C, I, F, M or H).

During the investigation, some flight examiners stated that pilots occasionally misidentified waypoints (due to their similar names) and believed that they were on a different segment of the approach than they actually were. One flight examiner noted that this was more likely to occur when coming straight in via the IAF ‘B’ rather than when coming via one of the other 2 IAFs. This flight examiner also noted that one operator they worked with had introduced call-out requirement for pilots to annunciate that they were tracking from one waypoint to another in order to minimise this risk.

Conducting an approach

Before conducting the approach, the pilot must ensure they are qualified for RNAV GNSS approaches and satisfy the recent experience requirements. The aircraft must be equipped with an approved GPS receiver with a valid aeronautical database. It is also essential that the availability of receiver autonomous integrity monitoring (RAIM) is checked pre-flight and before entering the approach.[46]

To conduct the approach, the pilot selects the specific approach and IAF in the GPS unit (or FMS) and tracks towards the applicable IAF within the capture region. Prior to passing the IAF, a pilot must set the QNH to either the actual aerodrome QNH (from an approved source such as AWIS) or the aerodrome/area forecast QNH.

As the approach proceeds, the GPS (or FMS) will automatically sequence through the waypoints, displaying the next waypoint and distance to that waypoint. The pilot maintains the track with reference to the associated course deviation indicator (CDI).  

To maintain the recommended descent profile (without electronic vertical guidance), pilots are required to:

• establish a 3° descent by managing the descent rate proportional to the groundspeed (through engine power and pitch angle)
• with reference to the altimeter, monitor the aircraft’s altitude - relative to the distance from the next waypoint with reference to the table on the approach chart and/or when passing waypoints with advisory altitudes     
• adjust the descent rate and/or groundspeed as required to correct the profile
• level at the MDA and continue tracking to the MAPt unless the conditions are suitable for continuation of the approach.

The height of the MDA above the aerodrome elevation and the required visibility (in km) to complete the approach were included as bracketed figures after the MDA. If the minima label boxes on the approach chart were shaded, the MDA could be reduced by 100 ft when the actual aerodrome QNH was set. For example, for the accident flight, the pilot had noted the actual QNH so the 830 ft MDA could be reduced to 730 ft (Figure 15). At the lower MDA, the aircraft would be 653 ft above the aerodrome elevation and the minimum required visibility was 4.2 km. Practically, if the visibility was at the minima value, the pilot would see the runway threshold before the MAPt and, if the aircraft was on the recommended profile, by the MDA.

Figure 15: Excerpt from Lockhart River RNAV GNSS runway 30 approach chart showing minima table

The full approach chart is provided in Figure 2.

Source: Airservices Australia

The Aeronautical Information Publication (AIP) outlined several instructions or methods for pilots regarding the conduct of instrument approaches, in addition to those specified by an operator’s operations manual. CAO 20.91 (Instructions and directions for performance-based navigation, Instrument 2014) also applied to the operation of Australian aircraft using performance-based navigation (which included RNAV approaches during IFR flight), providing instructions/directions to operators and pilots conducting those operations. Relevant CAO and AIP requirements, instructions and methods are outlined in subsequent sections below.

Descent below the minimum descent altitude

After passing the FAF, a pilot is permitted to descend to the MDA (provided the aircraft is within navigational tolerances). Further descent below the MDA must not be made without the required visual reference. There may be different MDAs specified for a straight-in or circling approach. Descent below the straight-in approach MDA could only be conducted (AIP ENR 1.5, 1.8.2)[47] when:

• visual reference can be maintained;
• all elements of the meteorological minima are equal to or greater than those published for the aircraft performance category…; and
• the aircraft is continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal flight manoeuvres that will allow touchdown to occur within the touchdown zone of the runway of intended landing.

The AIP also stated that, if visual reference is not established at or before reaching the MAPt, a missed approach must be executed (ENR 1.5, 1.10.1).

The competencies and standards required for an initial instrument rating and IPCs were specified in the CASR Part 61 Manual of Standards (MOS). For a 2D approach, the required tolerance was within +100 ft at the MDA but not below it.

Lateral tolerances

The AIP stated that instrument approach procedures were based on specific navigation aids, ‘with the applicable navigation tolerances associated with the aids being used in the development of the procedure’s obstacle protection surfaces.’ For an RNAV GNSS approach, CAO 20.91 stated that the lateral tracking tolerances were 1.0 NM (1,852 m) for the initial, intermediate and missed approach segments (terminal area operations) and 0.3 NM (556 m) for the final approach segment.

Navigational equipment could be designed so that full-scale deflection on the CDI represented the required navigation performance (RNP) lateral tracking tolerance during that phase of flight. For an RNAV GNSS approach, this would typically be represented as a lateral 1 NM displacement being represented as a full-scale CDI deflection during the initial segment and most of the intermediate segment, then transitioning from about 2 NM (3,704 m) prior to the FAF to a 0.3 NM displacement being full-scale deflection about 1 NM after reaching the FAF (Figure 16).

The GNS 400W-series manual indicated that the CDI full-scale deflection varied during the final approach segment.[48] When conducting an RNAV GNSS approach using a GNS 400W-series unit, the full-scale deflection was 350 ft (0.06 NM or 107 m) at the MAPt, diverging back to the FAF at an angle of either 2° to the final approach track, or an angle such to achieve 0.3 NM full-scale deflection at the FAF, whichever was less (Figure 16).[49] For 5 NM final approach segments, the angular 2° would always be less than the lateral 0.3 NM CDI full-scale deflection at the FAF.

Figure 16: Conventional transition from RNP 1.0 to RNP 0.3 NM during final approach segment (represented by full-scale CDI deflection) compared to the full-scale CDI deflection provided by the GNS 400W-series GPS

Source: ATSB, derived from information contained in ICAO Doc 8168 Procedures for Air Navigation Services-Aircraft Operations, Vol II − Construction of Visual and Instrument Flight Procedures and the Garmin GNS 400W-Series Pilot’s Guide & Reference manual.

For the 5 NM final approach segment for the runway 30 approach at Lockhart River, an angular 2° to the final approach track displaced 350 ft (107 m) at the MAPt equated to 0.23 NM (430 m) at the FAF. The transition from 1.0 NM full-scale deflection during the intermediate segment to the 2° automatic rescaling full-scale deflection for the final approach segment commenced 2 NM prior to reaching the FAF and was completed by the FAF. In other words, during the final approach segment, GNS 400W series units presented CDI full-scale defection that was less than the lateral tracking limit specified in CAO 20.91 for the final approach segment. This difference was relatively minor at the FAF (0.3 NM versus 0.23 NM) but increased significantly as the aircraft got closer to the MAPt.

When using the GNS 400-series units, if the CDI exceeded a full-scale deflection, a green arrow and distance was displayed on the default navigation page’s CDI, indicating the direction (left or right) and distance the aircraft was displaced (in NM) from the required track.

For a straight-in, area navigation-based approach (such as the RNAV GNSS approach to runway 30 at Lockhart River), the AIP (ENR 1.5, 1.21) stated that an aircraft was required to:

…pass the waypoint, and when established on the specified track, descend to not below the specified altitude….

Note: “Established” means being within half full scale deflection for the ILS, VOR and GNSS... [50]

The AIP (ENR 1.5, 1.10.1) also stated that a missed approach had to be conducted if:

…during the final segment of an instrument approach, the aircraft is not maintained within the applicable navigation tolerance for the aid in use…

CAO 20.91, Appendix 6, contained operating standards for conducting an RNAV GNSS approach, which included the requirement to commence a missed approach if the cross-track error/deviation equalled or was reasonably likely to equal the RNP for that segment of the approach (that is, 1.0 NM for the initial and intermediate segments and 0.3 NM during the final approach segment).

In other words, to comply with the AIP, after passing the FAF, the aircraft needed to be established within half full-scale deflection before descending below the previous segment’s MSA. If the aircraft was established within half full-scale deflection, the descent could continue to an altitude not below the segment minimum safe altitude, which in this case was the MDA.[51] In addition, to comply with CAO 20.91, a pilot was required to conduct a missed approach if the aircraft was laterally displaced 0.3 NM or more from the final approach track.

CASA advised the ATSB that there was, in the aviation community, a commonly held misconception that half full-scale deflection was the required tracking tolerance limit. This was potentially related to a number of factors, such as:

• CAO 20.91 included a note that stated ‘So far as practicable, the cross-track error/deviation for normal operations should be limited to 0.5 NM (½ x RNP) for the initial segment, the intermediate segment and a missed approach, and to 0.15 NM (½ x RNP) for the final approach segment. Brief deviations are acceptable during and immediately after turns where accurate cross-track information is not provided during the turn.’ This reference to half the RNP was providing a target level of safety rather than a minimum acceptable level of safety.
• The CASR Part 61 MOS required tolerance when assessing a pilot’s competency for a 2D approach was within half full-scale deflection.
• CAAP 179A-1(1) (Navigation using the Global Navigation Satellite Systems (GNSS)), issued in 2006, stated (erroneously) that for an RNAV GNSS approach that ‘The tracking tolerance is half of full-scale deflection regardless of the CDI scale’.[52]

CASA advised that operators could choose to specify a more restrictive lateral tracking requirement than that stated in CAO 20.91. If an operator specified a more restrictive limit (such as half RNP or half full-scale deflection), and included that in its operations manual, then that limit would be the applicable limit for that operator.

As discussed in Operator’s stabilised approach criteria, the operator of VH-OZO specified in its operations manual that a missed approach was required if an aircraft on an RNAV approach was not within ‘half scale deflection’ at the FAF. The ATSB is aware through its investigations that a number of other operators also specified a similar requirement for initiation of a missed approach.

Handling speeds

The AIP (ENR 1.5, 1.16) stipulated handling airspeeds for aircraft during instrument approaches based on the aircraft’s performance category. Aircraft performance categories were based on an indicated airspeed at the runway threshold (V_AT).[53]

The Cessna 404 V_AT was 91 kt. Therefore, the performance category for the Cessna 404 was category B, which applied to aircraft with a V_AT  of 91­–120 kt.

The relevant handling speeds for instrument approaches for category B aircraft were:

• 120 to 180 kt for the initial and intermediate approach segments
• 85 to 130 kt for the final approach segments
• maximum 150 kt for the missed approach.

A note in the AIP stated that a pilot was permitted to reduce the speed below the minimum in the initial/intermediate segments ‘to enable the final approach speed to be achieved prior to the commencement of the final segment’. In other words, for a category B aircraft, a pilot could operate below 120 kt prior to reaching the FAF but they could not operate above 180 kt.

The AIP handling speeds are broad speed bands used for purposes such as ensuring aircraft remain within the design tolerances for instrument approach procedures. Operators should provide more specific guidance regarding the appropriate speeds to use during instrument approaches for their aircraft types (see Flight profiles).

The AIP also stated that the descent rate after the FAF ‘should not normally exceed’ 1,000 ft/min.

Instrument flying and workload

Single pilot IFR operations are widely regarded to be among the most difficult and/or involve the highest workload. As stated by the US Aircraft Owners and Pilots Association (AOPA) in 2006:

No type of flying requires greater skill or longer periods of concentration than [single-pilot IFR] SPIFR…

Very simply, the problem is pilot workload, aggravated by the need for multi-tasking. A single IFR pilot also serves as navigator, radio operator, systems manager, onboard meteorologist, record keeper, and sometimes, flight attendant. En route flight in benign weather is usually not too stressful, but add high-density traffic in poor weather conditions or a significant equipment malfunction, and overload may not be far away.

In instrument flight, the pilot maintains an awareness of the aircraft’s spatial position by reference to instruments rather than outside visual references. The fundamental skills of instrument flight are instrument scanning and instrument interpretation. Instrument scanning is ‘the continuous and logical observation of instruments for attitude and performance information’ (FAA 2012).

In any phase of flight or manoeuvre, there are primary instruments that give the most pertinent information and supporting instruments that assist in their continued correct interpretation. For example, even when the aircraft is established in a constant-rate descent, and trimmed to remove control pressure on the yoke, it is necessary for the pilot to continuously check relevant instruments and make appropriate control adjustments to maintain aircraft performance and control. 

With proficiency, a pilot scans at an appropriate rate and is able to interpret the instruments to maintain an accurate mental picture of what is happening. An ineffective scan, such as fixation on one instrument or the omission of another, or misinterpretation of the displayed information, can result in a pilot having an incorrect mental model of the aircraft’s position or flight path.

More generally, workload is described by Wickens and others (2013) as follows:

Mental workload characterizes the demands of tasks imposed on the limited information processing capacity of the brain in much the same way that physical workload characterises the energy demands upon the muscles. In any resource-limited system, the most relevant measure of demand is specified relative to the supply of available resources...

People experience workload differently, based on their individual capabilities and the local conditions at the time such as training and experience in the situation at hand and the operational demands during that phase of flight (Orlady and Orlady 1999). When workload gets too high for the available resources task shedding occurs (Wickens and others 2013).

Dismukes and others (2007) discussed task shedding in this context, explaining that a pilot may move from a proactive assessment of the situation, commonly referred to in aviation as ‘being ahead of the aircraft’, to a reactive situation, where the pilot is responding to events as they occur without an overall strategy to manage the situation (that is, being behind the aircraft). Wickens and others (2013) further explained that task shedding can result in some tasks being shed altogether, and others being shed in a non-optimal manner. In addition, tasks such as internal and external communication are often shed during periods of high workload.

Holmes and others (2003) stated that distractions and high workload can result in a pilot scanning fewer instruments and checking them less frequently. High workload can also lead to a reduction in the number of information sources that an individual will search, as well as the frequency or amount of time these sources are checked (Staal 2004). Additionally, vigilance tasks, such as monitoring flight instruments, require sustained attention with the associated eye movements being fatiguing (Wickens and others 2013).

The United Kingdom Civil Aviation publication, Monitoring Matters, provided information regarding monitoring and stated:

… whilst you are ahead of the game, concentrating on the next event, keeping an eye on all the flight parameters, system modes etc, everything runs fairly smoothly. But as soon as something draws your attention away and you become out of the loop it becomes difficult to play catch up. 

Although it is possible to attend to more than one task using selective attention techniques, there is a limit to cognitive capacity. If tasks consume this capacity, that is when task shedding will occur. This publication further advised that under high workload, especially during approach and descent, attention capacity diminishes. This includes the ability to detect when the configuration of the aircraft is not correct, even when there is an aural or visual alert, particularly in the case of single-pilot operations as:          

…the processes and procedures will be equivalent to multi crew operation except there will only be one person in the cockpit and the systems may be less automated. Hence the need to monitor the flight profile, flight instruments, fuel state, engines, radios, etc. diligently. The instrument scan must be carried out very frequently, especially during departure and approach in order to monitor the aircraft state and planned profile.

In addition to being a complex skill to acquire, instrument flying skills needs to be maintained by frequent practice (Newman 2007). As stated by CASA in 2016 (Changes to instrument proficiency checks):

Conducting IFR operations is a relatively high risk activity and so requires dedicated knowledge and practical flight training… Skill-based qualifications, like the instrument rating, require the qualification holder to maintain their skills and operational knowledge. Skills and knowledge degrade over time. In the interests of safety, rules are put in place to ensure pilots are sufficiently competent conducting IFR operations.

Accordingly, there are requirements in place for pilots conducting IFR operations to regularly undertake proficiency checks (Proficiency checks and flight reviews) and have recent experience (Monitoring of pilot recency). In general, skill decay or skill degradation increases as the retention interval (or time since learning) increases, and it also increases depending on the quantity and quality of the initial and recurrent training and the amount of task exposure (Arthur and others 1998, Sanli and others 2018, Vlasblom and others 2020). Skill decay has various effects, such as preventing the development of further expertise and decreasing spare mental capacity. As noted by the European Aviation Safety Agency (2021):

Proficiency decay in only a few skills may lead to time management issues, reduced situation awareness, and the ability to keep ahead of the situation. In non-normal situations or emergencies, appropriate actions may not be taken due to one’s inability to analyse the situation as a result of the cognitive overload.

RNAV GNSS approach workload

There has been limited research that has compared different types of instrument approaches, and specifically looked at RNAV GNSS approaches. Research was conducted by the ATSB following a CFIT accident on an RNAV GNSS approach at Lockhart River in 2005 (Godley, 2006). The study found that, for pilots of smaller single-engine and twin-engine aircraft, pilot workload was perceived as being higher, and reported losses of situational awareness were more common, for RNAV GNSS approaches compared to other approach types except for NDB non-precision approaches.

In contrast, pilots of larger aircraft found that RNAV GNSS approaches were not as problematic, with the workload only being higher than ILS (precision) approaches. The different aircraft category responses were likely to have been due to high capacity aircraft having advanced automation capabilities and operating mostly in controlled airspace. Such aircraft were also more likely to have an FMS rather than a GPS unit.

The concern most respondents had regarding the design of RNAV GNSS approaches was that they did not use references for distance to the missed approach point on the approach chart and cockpit displays (in contrast to previous types of approaches). Other problems raised were short and irregular segment distances and multiple minimum segment altitude steps, that the RNAV GNSS approach chart was the most difficult chart to interpret, and that five letter long waypoint names differing only by the last letter can easily be misread. The most common incident reported with RNAV GNSS approaches was commencing the descent too early due to a misinterpretation of position.

It should be noted that at the time of this research, many GPS units displays only provided numerical data rather than a map view of the aircraft’s lateral position (such as with the GNS 430W). In addition, RNAV GNSS approaches have become more common and pilots have become more familiar with them, and the design of RNAV GNSS approach charts has improved.

Recorded flight data

General information

The aircraft was not fitted with a flight data recorder or cockpit voice recorder, nor was it required for the type of aircraft and operation.

The ATSB obtained data broadcast by the automatic dependent surveillance broadcast (ADS-B)[54] equipment fitted to the aircraft and GPS data from the pilot’s iPad with the OzRunways[55] application installed. The data included:

• timestamp
• latitude and longitude
• pressure altitude (from the ADS-B data) – rounded to the nearest 100 ft (for example, 498 ft would be rounded to 500 ft)
• GPS altitude (from OzRunways) – truncated to 100 ft (for example, 498 ft would be presented as 400 ft)
• groundspeed.

The lateral location (latitude and longitude) from OzRunways and ADS-B-based data were in close agreement. This indicated that the data from OzRunways was sufficiently reliable to show the aircraft’s lateral flight path.

The pressure altitude data from the ADS-B data was fairly consistently 100 ft higher than the OzRunways GPS height, which was partially due to the ADS-B data being rounded to the nearest 100 ft and the OzRunways data being truncated to the nearest 100 ft. In addition, the local QNH was 1,008.5 to 1,008.9 hPa during the period from 0900 to 0921, lower than the standard 1,013.25 hPa datum for pressure altitude. This would result in an altimeter set to the local QNH reading about 130–140 ft lower than the pressure altitude.[56] Thus, within the applicable errors, the altitudes from the 2 sources were consistent.

The OzRunways data points were provided at 5-second intervals, with some data points missing, and they covered the whole flight (including all of the 2 approaches), whereas the ADS-B data points were only available for parts of the approaches and/or were provided at less frequent intervals. As such, the OzRunways data is used in this report.

Figure 17 depicts the recorded data for the first and second approaches from the initial approach fix (IAF), through the intermediate fix (IF) and final approach fix (FAF) and to the missed approach point (MAPt). The top panel displays the aircraft’s altitude, the middle panel displays the lateral position, and the bottom panel displays the groundspeed. All distances on the horizontal axes are relative to the next waypoint, as would be displayed to the pilot on the GPS unit during the approach.

Figure 17: Recorded data for first and second approaches to Lockhart River

The upper panel shows altitude, the middle panel shows lateral deviation from the instrument approach path and the lower panel shows groundspeed. The purple bands on the groundspeed panel refer to the handling speeds (for indicated airspeed) specified in the Aeronautical Information Publication for a category B aircraft, such as the Cessna 404 (see Handling speeds).

Source: OzRunways data overlaid with Airservices approach information, annotated by the ATSB

Altitude during approaches

The top panel of Figure 17 shows the 3° approach path guidance (recommended descent profile) to the MAPt, which commenced from the initial approach altitude of 3,500 ft about 9.2 NM from the MAPt. As previously noted, the minimum descent altitude (MDA) was 730 ft unless the pilot had the required visibility. Key aspects regarding the recorded altitude data included:

• The first approach (in blue) was flown at or slightly above a 3° approach to the MAPt from significantly prior to the IAF until reaching 700 ft just prior to the MAPt. The average descent rate during the first approach from the IAF to the MAPt was about 720 ft/min.
• Although not indicated on the figure, the aircraft kept descending and reached a recorded altitude of 400 ft[57] at about 0.5 NM past the MAPt or 0.9 NM (1,700 m) before the runway threshold. It remained at that recorded altitude over 3 data points, or until it was 0.5 NM (900 m) from the runway threshold. The next 2 data points were not recorded, with the subsequent recorded data point indicating an altitude of 600 ft as the aircraft passed the runway threshold.
• ADS-B data was available for the latter part of the first approach, and this data indicated that the aircraft had still been descending when it reached the second of the 400-ft data points (0.7 NM or 1,300 m from the runway threshold), and had started climbing just before the third of the 400-ft data points (1,000 m from the threshold). The ADS-B data also provided recorded values of geometric altitude rate of change. This data indicated that just before and just after the MAPt the descent rate was about 900 ft/min, and at about the second 400-ft data point the descent rate was about 960 ft/min.
• The second approach (in red) was flown at about 3,500 ft prior to and after passing the IAF, with the aircraft starting to descend at about 0914:48 when about 2.7 NM from the IF. From about 1.6 NM prior the IF (at 0915:18 and an altitude of 3,300 ft), this descent was flown at about a 3° flight path, although about 1,000 ft below the recommended descent profile.
• The radio call commencing at 0915:50, when the pilot stated the position (10 NM) and altitude of the aircraft (3,800 ft then corrected to 2,800 ft), started about 0.4 NM prior to the IF. At 0915:58, about 0.2 NM prior to the IF, the aircraft was at a recorded height of 2,800 ft.
• For the second approach, the descent rate was about 700 ft/min during the descent from 3,300 ft to about 700 ft (at 0919:08 and 3.3 NM before the MAPt). From 700 ft until 100 ft, the descent rate was about 1,200 ft/min. Given this last part of the descent was over a 30-second period, it probably indicates an actual change rather than the effect of truncated data.
• During both approaches, there were several instances during descent where 2 data points in succession were at the same recorded altitude. There were also 2 occasions during the second approach where 3 data points in succession were at the same recorded altitude (at 700 ft and at 2,200 ft). Although this could indicate that the descent rate decreased to some extent at those altitudes, such patterns could also occur (at least in part) due to the data being truncated to the nearest 100 ft and the small amount of error associated with each GPS data point. A descent rate of about 700 ft/min would equate to about 60-ft difference every 5 seconds, whereas a descent rate of 600 ft/min would equate to about a 50-ft difference every 5 seconds.

Lateral position during approaches

Figure 17 depicts the lateral paths flown on the 2 approaches relative to the lateral track prescribed for the approach (shown as a dash-dot line). Dotted lines depict the full-scale CDI deflection on the Garmin GNS 430W and show the scale transitioning from 1 NM full-scale deflection during the intermediate approach segment to 0.23 NM full-scale deflection at the FAF, narrowing to 0.06 NM full-scale deflection at the MAPt. The aircraft’s position is based on GPS data; the actual CDI values displayed to the pilot were not recorded.

Key aspects regarding the lateral position data include:

• The flight paths for both approaches were consistent with the pilot hand-flying the aircraft, rather than the autopilot maintaining a programmed track.
• The first approach passed the IAF LHREB in the middle of the capture region for that waypoint. The whole approach was contained within half full-scale deflection of the CDI.
• For the second approach, the aircraft was just within the 180° capture region for the IAF LHREB when the pilot commenced the turn towards the IF LHREI (Figure 5). Prior to turning towards the initial approach track, the aircraft was on a track that was about 100° to the initial approach track.
• On the second approach, the turn onto the track between the IAF and the IF resulted in the aircraft initially being displaced full-scale CDI deflection to the right, which was corrected soon after. The aircraft was also turned slightly late at the IF and overshot the waypoint, before being corrected back to the intermediate approach track.
• About 3 NM before the FAF, the aircraft started deviating right of the intermediate approach track. About 2 NM before the FAF, the sensitivity of the CDI began increasing (as indicated by the dotted lines, see also Figure 17).
• When passing the FAF on the second approach, the aircraft was at about full-scale CDI deflection (0.23 NM to the right), and it continued deviating further right of the final approach track for 25 seconds before starting to return closer to the final approach track. The aircraft remained outside full-scale deflection in the final approach segment for about 55 seconds and outside half-full scale deflection for an additional 5 seconds. From about 17 to 32 seconds after passing the FAF, the aircraft’s deviation equalled or slightly exceeded 0.3 NM to the right of the final approach track (the lateral tracking tolerance specified in CAO 20.91 for the final approach track).
• The aircraft started to deviate left of the final approach track at about 2.5 NM prior to the MAPt and it continued left until the end of the recorded data. 

Groundspeed during approaches

Deriving an estimate of indicated airspeed from groundspeed involves considering several factors. In this case:

• The recorded wind at ground level indicated nil wind during the first approach and 3–4 kt from about 280° during the second approach. However, a review of wind and temperature forecast and analysis charts from multiple sources indicated that there would have been more wind at higher altitudes. Acknowledging that this was forecast and analysis data rather than recorded data, the ATSB estimated that there would have probably been about 10 kt headwind on the intermediate/final approach track at 2,300 ft and 5 kt at 1,000 ft. In addition, when the aircraft was heading towards the IAF on the second approach at 3,500 ft, and when the aircraft was heading from the IAF to the IF, there would have been a tailwind.
• Air pressure and temperature differences from a standard atmosphere meant that calibrated airspeed would have been lower than the true airspeed, with this difference increasing as the altitude increased. The difference was about 10 kt at 3,500 ft and 5 kt at 1,100 ft.
• The Cessna 404 Pilot’s Operating Handbook (POH) stated that the indicated airspeed at 140 kt was 1 kt higher than the calibrated airspeed with gear and flap up, 3 kt higher with gear down and flap selected to the take-off/approach position, and 5 kt higher with gear down and flap selected to the landing position. During the descent part of an approach, the operator’s flight profile stated the landing gear should be down and the flaps in the approach position (Flight profiles).[58]

Overall, the ATSB estimated that the indicated airspeed would have probably been close to (within 0 to +5 kt) of the recorded groundspeed during the 2 approaches while the aircraft was on or close to the intermediate/final approach track. For simplicity in this report, the groundspeed was considered to be equivalent to the indicated airspeed during these periods.

Key aspects of the recorded groundspeed (and estimated indicated airspeed) data for the 2 approaches include:

• The groundspeed (and estimated indicated airspeed) for the first approach was about 130–­140 kt for the whole approach between the IAF and the IF, and 130 kt at the FAF. It then increased to 140 kt before the aircraft reached 1,000 ft and then remained at about that speed as the aircraft passed through the MDA, passed the MAPt and passed the runway threshold.
• For the second approach, the groundspeed when the aircraft was heading toward the IAF was about 185 kt, but the indicated airspeed was about 160 kt. After making the turn towards the IF, the groundspeed was about 160 kt and the indicated airspeed was about 145 kt.
• Before commencing descent from 3,500 ft, at 0914:43, the groundspeed was about 150 kt and the indicated airspeed was about 135 kt. Soon after, there was a decrease in speed, which was probably associated with the pilot selecting approach flap and lowering the landing gear. The subsequent increase was probably associated with the aircraft’s descent.
• Between the IF and the FAF, the groundspeed (and estimated indicated airspeed) was about 135 kt. It increased to 140 kt soon after passing the FAF and, when the aircraft was 3 NM from the MAPt, the groundspeed increased to about 150 kt (associated with the aircraft’s increased descent rate).

Wreckage and impact information

The accident site was located on a sand bank adjacent to the beach, about 6.4 km (3.5 NM) south-east of the runway 30 threshold at Lockhart River Airport and 500 m to the south-west of the specified final approach track. This location was about 2.1 NM (3.9 km) from the missed approach point (MAPt).

The accident site was in line with the aircraft’s recorded track over the previous 3 data points. It was about 200 m beyond the last recorded data point (which had a recorded height of 100 ft), and its location indicated that the impact occurred less than 3 seconds after the last recorded data point.

The wreckage trail was spread over a distance of about 20 m from the initial impact point and the trail indicated that the aircraft was on a heading of about 280° (magnetic), with the impact point about 30 ft above mean sea level (Figure 18).

Figure 18: Overview of accident site

Source: ATSB

The ATSB’s on-site examination of the wreckage, damage to surrounding vegetation and ground markings indicated that at initial impact the aircraft was:

• upright and close to wings level
• at a flight path angle of about 5° nose down
• at relatively high speed.

An area of foliage around the aircraft displayed signs of chemical burn from avgas, indicating that the aircraft had a significant amount of fuel on board. There was no evidence of any structural or mechanical defects, but the examination was limited by the extensive damage.

The damage to the recovered propellor blades indicated significant rotational energy at impact consistent with both engines operating normally with substantial power.

The landing gear was extended at the time of impact. Other aircraft configuration information such as flap position, trim settings and switch selections could not be validated due to the impact damage.

The only components on the aircraft that may have recorded data were a digital fuel flow indicator/totaliser and a transponder, and the ATSB recovered these components. After consideration of the damage to these components and the potential value of any data, no further examination was undertaken.

Survivability aspects

Given the aircraft’s speed at impact (about 150 kt or 278 km/h) and the resultant impact forces (as evidenced by the nature of the wreckage), the accident was not considered survivable.

The aircraft was not fitted with a fixed emergency locator transmitter (ELT), nor was it required to be under the current regulations. A personal locator beacon (PLB) was in the pilot’s flight bag. Post-accident onsite examination noted it was within its expiry date and it passed a function test. PLBs do not have an inertial g-switch to automatically switch them on when an accident occurs, so the PLB did not activate during the accident sequence.

At 0934 and 0938, air traffic control (ATC) attempted to contact the pilot of VH-OZO after they had not cancelled or amended the SARTIME[59] of 0930. ATC also requested that the pilot of an inbound aircraft attempt to contact VH-OZO on the CTAF.

At 0939, an INCERFA was declared (which is a situation where uncertainty exists regarding the safety of an aircraft and its occupants) and soon after ATC transferred management of the situation to the Joint Rescue Coordination Centre (JRCC). At 1020, the JRCC advised ATC that it had declared a DETRESFA or distress phase (which is a situation where there is reasonable certainty that an aircraft and its occupants require immediate assistance). At 1251, the JRCC advised the ATSB that the wreckage at been located.

Organisational information

Air Connect Australia

Air Connect Australia was issued with an Air Operator’s Certificate (AOC) by the Civil Aviation Safety Authority (CASA) in March 2017 with an expiry date of 31 March 2020. It authorised the certificate holder to operate Cessna C310/340, C404, C402/421 and Raytheon Baron/Travelair twin piston-engine aeroplane types as well as single piston-engine aeroplane types with a MTOW not exceeding 5,700 kg on charter and aerial work operations.

At the time of the accident, CASA was assessing the operator’s application to renew the AOC, which was subsequently issued on 1 May 2020 with an expiry date of 30 September 2023.

From April 2017, the operator dry-leased VH-OZO from the aircraft owner, who was based in Western Australia. In this arrangement, the aircraft owner was responsible for the continuing airworthiness of the aircraft and the operator managed the operational aspects, such as fuel and flight crew.

Initially the operator’s personnel consisted of a chief pilot and the managing director, who was also the head of aircraft airworthiness and maintenance control. The chief pilot and managing director were the operator’s only line pilots. The chief pilot left in 2018, and the manager director became the chief pilot following an assessment by CASA.

In the 18 months prior to the accident, VH-OZO was the only aircraft operated and the operator employed one pilot (the pilot of the accident flight) additional to the chief pilot. As previously stated, the pilot of the accident flight conducted most of the operator’s flights.

Operator proficiency checks

To conduct IFR flights in a multi-engine aircraft, a pilot was required to complete an instrument proficiency check (IPC) every 12 months. The checks had to be conducted by a CASA-approved flight examiner. There were no additional requirements for proficiency checks for pilots conducting passenger charter operations under the IFR unless the operator had a check and training organisation as specified in Civil Aviation Regulation 217 (Training and checking organisation), which did not apply to operators such as Air Connect Australia.

CASR Part 135 (Australian air transport operations—smaller aeroplanes) was registered in December 2018 and commenced on 2 December 2021. It included a requirement for operators to conduct proficiency checks on pilots, with the requirements for such checks to be specified in the Manual of Standards (MOS). The draft Manual of Standards (MOS) for Part 135, publicly consulted in September 2018, included specific requirements for recurrent proficiency checks. For operators conducting IFR flights or flights at night, an operator proficiency check (OPCs) was required about 6 months after commencing unsupervised line operations for the operator and subsequently at intervals of 6 months. The MOS for Part 135 that came into effect in December 2021 had effectively the same requirements (with an OPC now called a ‘flight crew member proficiency check’).

Version 2 of the operator’s operations manual (February 2018) required an OPC to be conducted ‘every year’, with another section stating these needed to be completed ‘within the previous 12 months’. Version 3 of the manual (February 2020) required an OPC be conducted at the chief pilot’s discretion at periods not exceeding 24 months.[60] The manual stated that the OPC could be conducted by the chief pilot or a designated flight examiner.

The chief pilot noted that the flight examiner who regularly conducted IPCs for the operator (and was designated to conduct OPCs) would effectively conduct an OPC when they did an IPC. The change to every 24 months was done to provide more flexibility for scheduling checks.

In terms of the nature or content of the OPC, the operations manual stated that an OPC was required to be conducted

…on a flight encompassing all operations in which the pilot would normally be engaged. These flights will cover flight planning, refuelling, aircraft weight and balance, passenger briefing, forced landings and all emergency operations.

The manual also included an OPC form, which listed 23 items to be evaluated.

As previously discussed (Qualifications and experience), after the pilot of VH-OZO was cleared for line operations on 29 October 2018 (which included an OPC), the operator did not conduct any OPCs on the pilot. In addition, the chief pilot did not conduct any flights with the pilot after October 2018.

The pilot’s IPC in August 2019 was conducted with a flight examiner who was not familiar with the operator’s operations manual and therefore did not cover all aspects of an OPC, and the additional supervised training in December 2019 for night recency was done by an external provider and did not evaluate line operations.

Monitoring of pilot recency

CASR Part 61 outlined several different recency requirements. With relevance to the accident flight, these included a pilot not being able to:

• conduct a flight with passengers by day in a particular category of aircraft unless had conducted 3 take-offs and landings within the previous 90 days in that category of aircraft (CASR 61.395 (1))
• conduct a flight under the IFR unless had conducted at least 3 instrument approaches within the previous 90 days (CASR 61.870 (2))
• conduct a flight under the IFR in a particular category of aircraft unless had conducted at least 1 instrument approach in the previous 90 days in that category of aircraft (CASR 61.870 (3))
• conduct a 2D instrument approach unless had conducted at least one such approach in the previous 90 days (CASR 61.870 (4))
• conduct a flight under the IFR in a single-pilot operation unless had conducted at least one single-pilot flight under the IFR in the previous 6 months that had a duration of at least 1 hour and involved one instrument approach (CASR 61.875).

The CASA website stated:

We use recent experience requirements to maintain a pilots knowledge and skills when conducting instrument approach operations.

When conducting an approach to satisfy a recent experience, pilots should recognise the purpose of the approach is to maintain their competency to conduct such operations.

Simulating IMC, when safe to do so, will enhance the purpose of the approach. Conducting the approach provides some effective practice…

As previously noted, the pilot had been regularly logging the conduct of RNAV GNSS approaches (Qualifications and experience) as well as other types of instrument approaches. The pilot met all required recency requirements listed above.

The operator used the Aerotrack aviation management tool. The tool could be used to manage flight scheduling, fleet operations, and crew recency and rostering to meet regulatory requirements. It also created an online pilot logbook, as it tracked all flights conducted for the operator, and totalled recency requirements such as IFR flight time and instrument approaches.

The Aerotrack system correctly tracked all of the recency requirements except for CASR 61.875. The system tracked the total number of single-pilot IFR flight hours over a rolling 6-month period, calculated as a sum of all hours logged including partial hours (such as 0.5 hours).[61] However, it was not programmed to track if a single-pilot flight under the IFR (of at least 1 hour duration) was conducted.  

Regulatory oversight

In June 2017, CASA conducted a level-1 surveillance event on Air Connect Australia. CASA concluded that the operator was:

an overall compliant organisation with sufficiently equipped facilities and suitable qualified personnel conducting operations in accordance with its legislative authorisations and responsibilities.

The audit identified 5 non-compliance notices, including 3 relating to operations manual content regarding transponders, daily inspections and oil consumption records, and 2 relating to incomplete staff induction records for one pilot and the emergency proficiency checks for one pilot carried out by a person who was not the chief pilot. Other findings included 2 observations relating to job descriptions and one aircraft survey report finding. These findings were addressed by the operator.

In June 2018, CASA conducted a level-2 airworthiness and maintenance system surveillance activity relating to VH-OZO, prior to a flying operations inspector flying on the aircraft for the purpose of a chief pilot assessment. The surveillance report found there were no anomalies identified in either the technical documentation assessment or the physical inspection of the aircraft and the chief pilot assessment was then conducted.

In February 2020, CASA conducted a desk-top surveillance activity to determine if the AOC could be subsequently re-issued. The surveillance considered the organisation’s surveillance and compliance history, the management structure and operational oversight effectiveness. The review did not indicate any matter that would preclude a subsequent issue of the organisation’s AOC.

In May 2020, CASA conducted a post-accident regulatory and safety review. This review concluded that VH-OZO was correctly registered, certified for flight, maintained by qualified people, flown by a qualified person to a qualified aerodrome using a correctly validated approach. The review stated that past and current surveillance events had not detailed safety concerns with the operation of VH-OZO.

Operational information

Pre-flight planning and in-flight monitoring

Civil Aviation Regulation 239 (Planning of flight by pilot in command) stated:

Before beginning a flight, the pilot in command shall study all available information appropriate to the intended operation, and, in the cases of flights away from the vicinity of an aerodrome and all I.F.R. flights, shall make a careful study of:

a. current weather reports and forecasts for the route to be followed and at aerodromes to be used;

b. the airways facilities available on the route to be followed and the condition of those facilities;

c. the condition of aerodromes to be used and their suitability for the aircraft to be used; and

d. the air traffic control rules and procedure appertaining to the particular flight;

and the pilot shall plan the flight in relation to the information obtained.

AIP ENR 1.10 (Flight Planning) also stated these requirements. In addition, it stated a pilot was required to review NOTAMs[62] applicable to the flight.

At 1326 on the day before the accident flight, the pilot accessed a location briefing for Lockhart River from the National Aeronautical Information Processing System (NAIPS) via an electronic flight bag (EFB) application. This type of briefing typically displayed current forecasts, reports, and ‘notice to airmen’ (NOTAM) applicable to the nominated location.

Later that day, at 1830, the pilot requested grid point wind and temperature charts (GPWT) and a specific pre-flight information bulletin (SPFIB) from NAIPS via flight planning software. The SPFIB request was for Cairns to Lockhart River and return with the estimated time of departure nominated as 1930 the same day. This bulletin was valid until 1830 on the day of the accident.

A printout of the SPFIB found at the accident site showed aerodrome forecast (TAF) and weather reports (METAR) for Cairns. The weather for the next day (day of accident flight) at Cairns Airport was expected to be a visibility of 10 km or greater and showers of light rain with scattered cloud at 1,800 ft in the morning lifting to 2,500 ft. In addition, the forecast imposed a TEMPO for the next day to specify periods of visibility reduced to 2,000 m with showers of moderate rain and broken cloud at 1,000 ft.

On the printout of the SPFIB, a METAR for Lockhart River for 1800 (10 March 2020) showed light winds, visibility 10 km or greater and nil cloud detected. Since 0900 that morning, recorded rainfall was 1.8 mm.

No TAF was provided on the SPFIB for Lockhart River as the time of the request was outside the issue and validity period. There were no predicted outages of global positioning system/global navigation satellite system (GPS/GNSS) capability for Cairns or Lockhart River. NOTAM information included a change to Lockhart River runway distance and gradient data and no other notices with significance for the planned flight.

After the SPFIB was received, at 1942, the pilot submitted a flight notification for the planned departure from Cairns at 0730 the next morning to Lockhart River followed by a departure at 1430 for the return sector. Both sectors were planned under IFR with nominated capability for instrument approaches using GPS/GNSS equipment.

After the pilot requested the SPFIB and submitted the flight notification on the evening before the accident flight, there was no record of further requests for meteorological information from NAIPS. Such information was also available from the Bureau of Meteorology website and other sources without any user registration requirements. The ATSB was advised that the pilot was aware of the current weather forecasts for Lockhart River and Cairns on the morning before the flight.  

A damaged and partly illegible copy of the pilot’s flight plan/log was found at the accident site. This was a printout from flight planning software showing key navigational data and pilot notes on progress of the flight. There was no indication of any operational abnormalities.

Fuel calculations

On the morning of the flight, the pilot refuelled the aircraft with 650 L of avgas. A tabulated fuel plan showed 1,040 L on board at engine start at Cairns and expected fuel consumption of 285 L for the planned 94-minute flight to Lockhart River. The pilot had included provision for 45 minutes fixed reserve (124 L), 40 L variable reserve and 60 minutes holding (110 L) if required (consistent with the forecast TEMPO conditions in the TAF, see Aerodrome forecasts). If the variable reserve and holding allowance was consumed on the outbound sector (in addition to the calculated flight fuel), the remaining 605 L was sufficient to return to Cairns with allowance for 60-minutes holding on arrival.

In summary, the aircraft had sufficient fuel to conduct the flight from Cairns to Lockhart River and return, with additional fuel for holding on both sectors if required. The pilot was probably not intending to refuel at Lockhart River, although avgas was available if required.

Weight and balance

The pilot completed the operator’s passenger/cargo manifest form and calculated the aircraft’s weight and balance with reference to individual passenger weights and baggage. The take-off weight was recorded as 3,678 kg and nominal landing weight as 3,366 kg (7,421 lb). The aircraft’s maximum take-off weight was 3,810 kg and maximum landing weight was 3,674 kg. The graphical trimsheet showed the centre of gravity was within limits throughout the flight.

A copy of the operator’s in-flight monitoring form was found at the accident site. When the pilot completed the form in cruise at 10,000 ft, all of the recorded engine parameters for each engine were comparatively similar with no indication of any aircraft-related problems.

Communications during approaches

The AIP (ENR 1.1, 10.1) recommended radio calls at an uncontrolled aerodrome. These included:

• the pilot being inbound to an aerodrome (10 NM or earlier, commensurate with aeroplane performance and pilot workload, with an estimated time of arrival)
• during an instrument approach:
  • departing the FAF or established on the final approach segment (including details of position and intentions)
  • terminating the approach or commencing the missed approach (including details of position and intentions).

The Air Connect Australia operations manual stated the following for communications at non-towered aerodromes:

When operating within the vicinity of a non-controlled aerodrome, a known training area or authorised low flying area, Company pilots are to broadcast their intentions, listening out and communicate with any possible conflicting aircraft in accordance with the requirements of the AIP. 

Additionally, for straight-in approaches at non-towered aerodromes, the manual stated:

• Monitor / broadcast on CTAF shall be made by 10 NM and include aircraft type, position, callsign and include the intention to make a straight-in approach.
• Monitor / broadcast at 3 NM that the aircraft is established on the final approach.

During both of the approaches at Lockhart River, the pilot of VH-OZO made broadcasts when at 10 NM (that is, at about the IF). During the first approach, the pilot also made a broadcast at 5 NM (at the FAF) and during the missed approach. There was no call recorded when the aircraft was at 5 NM on the second approach.

Electronic flight bag and approach charts

During the flight, the pilot was using an iPad with an electronic flight bag (EFB) application (OzRunways) and was carrying a second iPad as a backup. The operator’s operations manual (section 2A1.3.2.2) stipulated that all EFB devices permitted for use were class 1 (portable electronic device) and functionality level 1, which meant that it could be one or more of the following:

1. held in the hand
2. mounted on an approved mount
3. attached to a stand-alone kneeboard secured to a flight crew member
4. connected to the aircraft power for battery re-charging
5. connected to an installed antenna intended for use with the EFB for situational awareness but not navigation.

Furthermore, unless secured in accordance with b or c above, the EFB was required to be stowed during take-off, landing, instrument approach and when flying less than 1,000 ft above terrain. It was also only to be used:

…as a source of navigational data e.g. Departure and Approach plates and airport information.

The operator did not have an approved mount for the iPad. Accordingly, the operator required paper approach charts to be used when conducting an instrument approach. The chief pilot stated that the pilot subscribed to the departure and arrival procedure charts published by Airservices Australia. There was a clamp on the control column where a paper approach chart could be placed (Figure 8). There were no paper approach charts identified at the accident site, although the flight plan/log was found. Due to the disruption of the wreckage, it could not be determined whether the pilot carried the paper charts on board.

A friend of the pilot stated that they had provided the pilot with a mounting device that could be used to mount an iPad on a control column. The pilot’s iPad EFB was on[63] during the approach, however there were differing reports about how the pilot used the iPad during previous flights and whether it was mounted on the control column, placed on their knee or placed on the vacant seat next to the pilot. Due to disruption of the aircraft in the accident, only the second (backup) iPad was found at the accident site.

Flight profiles

The operator’s operations manual included flight profiles to be used for various situations for the Cessna 404, and stated that the profiles were required to be used for all operations. The prescribed flight profile for an RNAV GNSS approach (and other straight-in instrument approaches) is shown in Figure 19.

The indicated airspeed was required to be below 180 kt at the IAF and at 130 kt (+ or - 5 kt) at the start of the descent after passing the IAF (with the landing gear down and approach flap selected). The airspeed was also required to be V_ref to V_ref +10 kt at the FAF. As noted in Configurations and speeds, the V_ref at maximum landing weight (8,100 lb) for the Cessna 404 was 91 kt and at weights 7,500 lb and below was 88 kt. In effect, the operator’s flight profile requirement to be at V_ref to V_ref + 10 kt at the FAF equated to an indicated airspeed of about 90–100 kt.

Figure 19: Flight profile for Cessna 404 RNAV GNSS approach

In another section titled ‘Final approach & threshold speeds’, the operations manual stated:

• The [pilot] shall conduct the final approach in accordance with the stabilised approach criteria… [see next section]
• CAT B: Speeds 91 – 120 kts. Initial / Intermediate 120 – 180 kts. Final app 85 – 130 kts. Visual circling 135 kts. Max speed for Missed Approach 150 kts.

These were the ‘handling speeds’ referred to the AIP for instrument approaches for a category B aircraft, such as the Cessna 404 (see Handling speeds). In effect, these speeds meant that the maximum allowed indicated airspeed after passing the IAF for the Cessna 404 was 180 kt and the maximum airspeed after passing the FAF was 130 kt.

The chief pilot recalled that the flight profiles were included in the operations manual by the previous chief pilot, who had based them on profiles used by another operator. The chief pilot stated that they advised the pilot of the accident flight to be at about 5,000 ft at the start of an approach (at the IAF) and then use a continuous descent to the runway from the IAF, and they demonstrated this to the pilot during their supervised flying in October 2018.

The chief pilot recalled that, when they flew the aircraft, they would select approach flap and landing gear early in the descent and be stabilised at a speed of 120 kt and a descent rate of 600 ft/min[64] well before the FAF. The chief pilot stated that the speed at the FAF should be about V_ref + 20 kt (which equates to about 110 kt) but that the 100 kt specified in the flight profile would be acceptable. They stated that 130 kt at the FAF was too fast.

The previous chief pilot also recalled that the operator’s flight profile was most likely obtained from another operator. They noted their recollection of speeds was limited given the time since they flew the aircraft, but they recalled that they would be at least at V_ref + 10 kt (that is, 100 kt) but not faster than 120 kt at the FAF, then slowing the aircraft down by 1,000 ft.

The flight examiner regularly used by the operator also worked with another operator of Cessna 404 aircraft (which was a different operator to that referred to by the previous chief pilot). The examiner stated that at the IF they would normally be at 130 kt with gear down and approach flap selected. The normal speed they used at the FAF was 110 kt (V_ref + 20 kt), and 100 kt would be a little slow at that point on the approach. The examiner advised that these speeds were also used by the other Cessna 404 operator.

In summary, the ATSB concluded that the operator’s published flight profile speed of 90–100 kt at the FAF was probably not the operator’s preferred speed during flight operations. Rather, it appeared that the preferred speed at the FAF was probably about 110 kt. However, the extent to which this was clearly communicated to the pilot of the accident flight could not be determined.

Stabilised approach criteria

Guidance regarding stabilised approach criteria

A stabilised approach is one in which all criteria specified in the operations manual are met, at or before the applicable height or reference point. The Flight Safety Foundation (FSF) has for many years recommended that operators have stabilised approach criteria. Detailed guidance was provided by the FSF in its approach and landing accident reduction (ALAR) briefing note 7.1 (Stabilized approach, 2000a). The recommended criteria were summarised in a list, as reproduced in Figure 20.

Figure 20: FSF recommended elements of a stabilised approach

Source: ALAR briefing note 7.1  (Flight Safety Foundation 2000a)

The FSF briefing note also stated:

The flight crew must “stay ahead of the aircraft” throughout the flight. This includes achieving desired flight parameters … during the descent, approach and landing. Any indication that a desired flight parameter will not be achieved should prompt immediate corrective action or the decision to go around.

The minimum stabilization height constitutes an approach gate on the final approach; a go-around must be initiated if:

• The required configuration and airspeed are not established, or the flight path is not stabilized when reaching the minimum stabilization height;
• The aircraft becomes unstabilized below the minimum stabilization height.

ICAO Annex 6 Part I applied to international commercial air transport operations in aeroplanes. Since 1998, it included a standard stating an operator’s operations manual had to include stabilised approach procedures.

ICAO document 8168 (Procedures for Air Navigation Services, Aircraft Operations, known as PANS-OPS) provided recommendations on procedures for flight crew. Since 2001, PANS-OPS included content on stabilised approaches and stabilised approach criteria. It stated:

Studies have shown that the risk of controlled flight into terrain (CFIT) is high on non-precision approaches. While the procedures themselves are not inherently unsafe, the use of the traditional step down descent technique for flying non-precision approaches is prone to error, and is therefore discouraged. Operators should reduce this risk by emphasizing training and standardization in vertical path control on non-precision approach procedures…

Operators should use the CDFA (continuous descent final approach) technique whenever possible as it adds to the safety of the approach operation by reducing pilot workload and by lessening the possibility of error in flying the approach…

This technique requires a continuous descent, flown either with vertical navigation (VNAV) guidance calculated by on-board equipment or based on manual calculation of the required rate of descent, without level-offs. The rate of descent is selected and adjusted to achieve a continuous descent to a point approximately 15 m (50 ft) above the landing runway threshold or the point where the flare manoeuvre should begin for the type of aircraft flown...

The guidance document also stated:

The primary safety consideration in the development of the stabilized approach procedure shall be maintenance of the intended flight path as depicted in the published approach procedure, without excessive manoeuvring.

PANS-OPS stated the types of information that should be included in stabilised approach criteria (such as speeds, minimum power settings, attitudes, crossing altitude deviation tolerances, aircraft configuration, maximum sink rate and competition of checklists and briefings). In addition, the document stated that an operator’s procedures should include, as a minimum:

a) that in instrument meteorological conditions (IMC), all flights shall be stabilized by no lower than 300 m (1 000 ft) height above threshold; and

b) that all flights of any nature shall be stabilized by no lower than 150 m (500 ft) height above threshold.

Although the FSF and ICAO guidance may be considered most applicable to larger air transport aircraft with multi-crew operations and turbine engines, similar guidance (with the same applicable heights of 1,000 ft for operations in IMC and 500 ft for operations in VMC) has also been widely recommended for operations in smaller aircraft (Appendix D – Guidance to industry regarding stabilised approaches). This guidance has emphasised the benefits of using a CDFA technique with stabilised approach criteria in terms of reducing workload and increasing the time to monitor, detect and react to problems.

In Australia, since 2014, the Civil Aviation Advisory Publication (CAAP) 215-1 (Guide to the preparation of operations manuals) stated that an operator’s manual should include stabilised approach criteria in its section on approach and landing procedures. Guidance regarding applicable heights or reference points for such criteria were not specified in the CAAP or other CASA guidance documents.[65]

CASA advised the ATSB that specific Australian guidance was not provided prior to 2021 since there was no direct legislative requirement for operators to use such criteria, and it was considered that there was readily available and significant global guidance on this topic available from a wide range of authoritative sources.

Operator’s stabilised approach criteria

The Air Connect Australia operations manual stated:

Stabilised Approach Criteria are as follows:

(a) All flights, other than training flights, must be stabilised by 300 feet above aerodrome elevation in both IMC and VMC.

(b) An approach is stabilised when the following criteria are met:

• The aircraft is on the correct flight path;
• Only small changes in heading and pitch are required to maintain the correct flight path;
• The aircraft is not more than V_ref + 20 kts and not less than V_ref indicated airspeed
• The aircraft is in the correct landing configuration;
• Sink rate is no greater than 1000 fpm [ft/min];[66] if an approach requires a sink rate greater than 1000 fpm, a special briefing should be conducted;
• Power setting is appropriate for the aircraft configuration and is not below the minimum power for approach as defined by the aircraft operating manual;
• All briefings and checklists have been conducted;
• Instrument approaches are stabilised by the final approach fix, if they also fulfil the tracking requirements – established within ‘half scale deflection’ for the ILS, VOR and GNSS, within + or – 5 degrees for the NBD; during a circling approach, wings should be level on final by 300 feet above aerodrome elevation;
• Unique approach procedures or abnormal conditions requiring a deviation from the above elements of a stabilized approach require a special briefing.

Missed Approach Procedure is as follows:

(a) Other than on training flights, an approach that is not stable below 300 feet aerodrome elevation in both IMC and VMC requires an immediate GO-AROUND. The procedure for a go around / missed approach is as follows:

• Should be flown as per the approach chart missed approach procedure, or as advised by ATC;
• The aircraft handling technique will be as per the relevant AFM for the appropriate aircraft…

The manual further stated:

If an approach does not meet the criteria for a stabilised approach…, the Pilot-in-Command shall conduct a missed approach.

To meet these stabilised approach criteria, the maximum indicated airspeed in a Cessna 404 needed to be V_ref + 20 kt or about 110 kt at 300 ft above aerodrome elevation.

The chief pilot advised the ATSB that the published applicable height of 300 ft was too low to be effective, as it was normally below the MDA. They believed approaches should be stabilised much earlier, ideally at height of about 1,000 ft or even earlier. The chief pilot also stated that all configuration changes should be done early in the approach, with only the selection of landing flap to be completed late in the approach at the pilot’s discretion. The flight examiner used by the operator noted that stabilised approach criteria for most piston twin-engine and single-engine aeroplanes needed to acknowledge that the last stage of flap (or landing flap) should generally not be selected until about 300 ft due to aircraft performance considerations.

The chief pilot also recalled that they had discussed the importance of being stabilised early in the approach to the pilot of the accident flight on multiple occasions, and they had stated the importance of conducting constant angle descents down to the MDA at 600 ft/min. The chief pilot also noted that they had emphasised to the pilot the importance of gradual reductions in power and therefore speed during approaches in order to minimise undesirable cylinder head temperatures, and use slow descent rates for passenger comfort. 

Additional information

During its investigation into the 2005 CFIT accident of a Metro aircraft at Lockhart River involving an operator that conducted passenger transport operations in Metro turboprop aircraft, the ATSB identified that that operator did not have stabilised approach criteria.[67] Of 5 other operators conducting operations in Metro aircraft, all had stabilised approach criteria, with 1 having an applicable height of 200 ft, 2 having an applicable height of 300 ft and 2 having an applicable height of 1,000 ft.

The ATSB also identified that an operator conducting passenger transport operations in a DHC-8 aircraft in 2012 had stabilised approach criteria based on an applicable height of 300 ft.[68] In addition, during another investigation commenced in 2021, the ATSB recently identified another operator of turboprop aircraft conducting passenger transport operations (charter) that had stabilised approach criteria with an applicable height of 300 ft. The ATSB has also identified that major airlines and some operators of single-pilot IFR operations in Australia have criteria based on 1,000 ft above ground level in IMC.

Prior missed approach during an RNAV GNSS approach (22 January 2020)

A review of the pilot’s logbook identified one other flight since the pilot joined the operator that involved 2 instrument approaches (and therefore a missed approach following an instrument approach). This occurred on a flight from Weipa to Aurukun, Queensland, on 22 January 2020, after which the pilot logged 2 RNAV GNSS approaches. Recorded data confirmed that the pilot conducted 2 approaches to runway 34 at Aurukun.

Analysis of the weather conditions and interviews with the passengers identified that there was a storm in the vicinity at the time, and interviews and recorded flight data indicated that the pilot was trying to avoid the weather. The passengers recalled observing the pilot using the onboard weather radar as well as an iPad with the weather on it to track the movement of the storm.

Passenger recollections regarding the weather during the first approach were varied; some recalled that they could not see the runway at times whereas others recalled the runway was still visible though restricted. The ground appeared to be visible most of the time. Images taken by a passenger during the first approach confirmed that there was significant cloud in the area though the ground could be seen to the left of the aircraft.

Review of the recorded flight data indicated that, on the first approach, the aircraft commenced descent on the recommended descent profile from about 1,600 ft, slightly below the initial approach altitude of 1,800 ft. The aircraft passed the FAF at an indicated airspeed of about 140 kt, and it was about 200–300 ft below the recommended descent profile when it passed the MDA at an indicated airspeed of about 145 kt. The aircraft descended to a recorded altitude of about 200–300 ft (at about 140 kt) before starting to climb.

The missed approach did not conform to the published missed approach procedure, with the aircraft flying to the right of the MAPt rather than maintaining the runway heading. However, the conditions may have been visual at this time. After the missed approach, the pilot circled for some time, remaining in VMC and waiting for the storm to pass, before conducting a second approach (about 31 minutes after the first approach). Images taken by a passenger during the second approach confirmed that the weather conditions were significantly better than on the first approach.

The exact reasons for the missed approach could not be determined (that is, whether it was due to reduced visibility of the runway or also due to the aircraft’s speed not meeting the operator’s stabilised approach criteria at 300 ft above aerodrome elevation).

Further details of these 2 approaches are provided in Appendix E – Aurukun incident flight – 22 January 2020.

Review of the pilot’s recent RNAV GNSS approaches

General aspects

The ATSB reviewed the available recorded data for the pilot’s flights in the previous 6 months for which the pilot had logged an RNAV GNSS approach (that is, 21 approaches). Recorded data was available for 16 of these approaches. Of these 16 approaches:

• 10 involved straight-in approaches to the runway
• 5 were flown to past the FAF and then a circling approach was flown from above the specified circling minima to the opposite (reciprocal) runway
• 1 was not an RNAV GNSS approach as it did not fly near the designated waypoints (and it was therefore not considered for further analysis).

Based on a review of available weather information, all 21 approaches were very likely conducted in VMC except for the first approach conducted at Aurukun on 22 January 2020 (which was potentially in IMC for a brief period). For those approaches conducted in VMC, the pilot was not specifically required to conduct an RNAV GNSS approach, except for the purpose of meeting recency requirements.

The published approach charts for all the approaches had 5 NM segments between the IAF and IF, IF and FAF, and FAF and MAPt. Most of the approaches were conducted at locations where the recommended descent profile commenced at about the FAF, except for one approach to runway 11 at Cooktown (where the recommended descent profile commenced at the IAF).

Vertical profiles

For most of the 15 RNAV GNSS approaches with recorded data available, the data showed the pilot typically descended to about 5,000–5,300 ft and then levelled out for a short period prior to the IAF. When passing the IAF, the pilot commenced a continuous descent to join the approach’s recommended descent profile on about a 3° approach.

The only exceptions to this method were the 2 approaches conducted at Aurukun on 22 January 2020 (when the pilot commenced descent on the approaches from close to the published initial approach altitude of 1,800 ft). As noted in Recorded flight data, the second approach at Lockhart River during the accident flight was also commenced at a lower altitude (that is, the published initial approach altitude of 3,500 ft) when the aircraft was between the IAF and the IF).

In general, the approaches were conducted close to the recommended descent profile. The only exception was the first approach at Aurukun on 22 January 2020, which reached the MDA about 200–300 ft below the recommended profile.

Lateral positions

The pilot generally entered each approach via the nearest of the 3 IAFs. In most cases, the aircraft passed the IAF from close to the middle of the capture region for that waypoint, or at least on a track that was less than 45° difference to the initial approach track. On one approach (at Cooktown), they entered from a similar position as the second approach at Lockhart River, although from about 65° right of the extended initial approach track to the IAF labelled ‘A’ (as opposed to about 100° at Lockhart River).

For all the straight-in runway approaches (except the second approach at Lockhart River), the aircraft remained close to the intermediate approach track and final approach track. In most cases, the aircraft also remained close to the initial approach track. The only exceptions were:

• the Cooktown approach (when the aircraft flew over the IAF then, while descending, deviated left of the initial approach track by 0.9 NM and remained left until close to the IF)
• the first approach at Aurukun on 22 January 2020 (when the pilot commenced the approach from slightly more than 1 NM west of the IAF and flew direct to the IF from that position, while remaining close to the initial approach altitude).

Indicated airspeeds

The ATSB reviewed the indicated airspeeds during the pilot’s 8 previous straight-in RNAV GNSS approaches to evaluate their consistency with the operator’s speed requirements and preferences, and these were compared with the 2 approaches at Lockhart River on the day of the accident (Figure 17). The 8 other approaches included the 2 approaches conducted at Aurukun on 22 January 2020 (Figure 25), and 6 other approaches that the pilot conducted from December 2019 to February 2020 and logged as RNAV GNSS approaches.

For the 10 approaches, the ATSB estimated the indicated airspeeds based on the recorded groundspeed, forecast and analysis wind charts and other relevant information. The actual wind speeds above the aerodrome on each occasion were not known, and as a result there could have been some differences between the estimated indicated speeds and the actual indicated airspeeds.

The results for key points on the approaches are shown in Table 4. In general terms:

• In all 10 cases, the approaches did not exceed (and were well below) the maximum AIP handling speed of 180 kt in the initial and intermediate approach segments.
• In all 10 cases, the approaches exceeded the operator’s preferred speed of 110 kt at the FAF. Most of the approaches were about 130–140 kt at the FAF, and 7 of the approaches appeared to exceed the maximum AIP handling speed of 130 kt at or after passing the FAF by 10 kt or more.
• In most cases, the approaches appeared to be close to the operator’s maximum stabilised approach speed of 110 kt at or approaching 300 ft. However, in 3 cases there was a significant exceedance. These included the first approach at Aurukun on 22 January 2020 (which was followed by a missed approach), and the 2 approaches at Lockhart River (with the first followed by a missed approach).

Table 4: Summary of estimated indicated airspeeds during the pilot’s recent RNAV GNSS approaches (in kt)[69]

The requirement at 300 ft above aerodrome elevation is from the operator’s stabilised approach criteria. The maximum requirements for the IF, FAF and 1,000 ft above aerodrome elevation are from the AIP handling speeds for a category B aircraft (also referred to in the operations manual). The operator preferred speed at the FAF is based on interviews. All speeds rounded to nearest 5 kt. Green shading indicates the speed was consistent with the requirement or preference (within 5 kt), orange shading indicates a small exceedance (within 10 kt), and red shading indicates a significant exceedance (15 kt or more).

¹Descent to just above 300 ft above aerodrome elevation (or just below that height) on this approach occurred after passing the MAPt.

In summary, the pilot was not conducting RNAV instrument approaches in the Cessna 404 in accordance with the operator’s preferred speed of 110 kt at the FAF. In some cases, the pilot appeared to be complying or was close to the AIP handling speed requirement to be at a maximum speed of 130 kt in the final approach segment, but in some cases they exceeded this requirement. The chief pilot advised that they were unaware that the pilot was conducting RNAV approaches with a speed that was significantly above 110 kt at the FAF.

Controlled flight into terrain

CFIT accident data

The ATSB research report CFIT: Australia in context 1996 to 2005 (ATSB, 2007), defined a controlled flight into terrain (CFIT) as an in-flight collision with terrain, water, or obstacles, in which:

• the aircraft is under the control of the pilot(s)
• there is no defect or unserviceability that would prevent normal operation of the aircraft
• the pilot(s) had little or no awareness of the impending collision.

In the 10-year reporting period for that research (1996–2005), there were 27 CFIT occurrences in Australia. Of these 27 occurrences:

• 25 were accidents, including 15 fatal accidents, resulting in a total of 47 fatalities.
• 19 involved aeroplanes (including 18 accidents and 12 fatal accidents) and 8 involved helicopters (including 7 accidents and 3 fatal accidents)
• 17 (63%) occurred during the approach phase, with 8 during a visual approach and 9 during an instrument approach
• 1 occurred during a low-capacity regular public transport flight (RPT), 8 during charter flights, 4 during aerial work flights and 14 during private/business flights.
• only one aircraft of the 27 occurrences was fitted with a TAWS – the Fairchild SA227-DC (Metro) aircraft involved in the low-capacity RPT CFIT accident at Lockhart River in May 2005.[70] This GPWS was not a predictive or enhanced TAWS, which became required for turbine aircraft like the Metro by the end of June 2005.

Of the 9 CFIT occurrences that occurred during an instrument approach:[71]

• all 9 were accidents, including 7 fatal accidents, resulting in a total of 31 fatalities
• all 9 involved aeroplanes
• 4 occurred during an RNAV GNSS approach, 2 during a GPS arrival and 3 during an NDB approach.
• 1 occurred during a low-capacity RPT flight, 3 during charter flights, 2 during aerial work flights and 3 during private/business flights.

Further details of some of these accidents are provided in Appendix F – R­elated occurrences.

A review of the ATSB database for the 15-year period 2006–2020 identified only 1 CFIT involving an aeroplane on an instrument approach (that is, VH-OZO at Lockhart River, resulting in 5 fatalities). There were also 5 other CFITs involving aeroplanes on visual approaches, which resulted in 2 accidents, including 1 fatal accident with 4 fatalities.

The International Air Transport Association (IATA) (2018) published a report on worldwide CFIT accidents from 2008 to 2017 involving aircraft with a MTOW of at least 5,700 kg (12,540 lb). During that period, there were 47 CFIT accidents, which accounted for 6% of total accidents. Most (42 or 89%) of the CFIT accidents involved fatalities, and CFIT was the second highest fatal accident category (after loss of control in-flight), accounting for 28% of all fatal accidents.

Of the 47 CFIT accidents, 24 (51%) occurred during the approach phase of flight, 7 (15%) during landing, and 4 (9%) during a go-around. Turbo-prop aircraft had a much higher CFIT rate (per million flights) than jet aircraft. Older generation aircraft were also involved in more CFIT accidents.

The IATA report found that the rate of CFIT accidents was significantly lower in the last 5 years (2013–17) compared to the first 5 years (2008–12). The report stated:

It is generally accepted that the reduction in CFIT accidents can be traced back to the introduction of Ground Proximity Warning System (GPWS), and Terrain Awareness Warning System (TAWS). Other improvements, may have also contributed directly or indirectly to the reduction of the likelihood of CFIT accidents, including aircraft design, replacing non-precision with precision approach procedures, pilot training, improved flight standards, Continuous Descent Final Approach (CDFA) technique, approach lightning, visual approach guidance and procedures, ground-based Minimum Safe Altitude Warning (MSAW) system, visual and instrument approach guidance and procedures.

In addition, the IATA report noted common contributing factors to CFIT accidents, including poor visibility or IMC (49%) and lack of visual reference (33%). Unstable approaches were cited in 10% of accidents. The report stated:

Unstable approaches increase the possibility of diverting a flight crew’s attention away from the approach procedure to regain better control of the airplane. Stabilized approach policies broadly concur in stating that a safe approach requires the flight path angle, configuration, and airspeed to be stabilized. Once one or more of these parameters are violated, the approach becomes unstable and the margin for a safe landing is decreased to a level requiring flight crew action; a go-around should be initiated.

Since the CDFA techniques contribute to a stabilized approach, the industry should also as soon as, and wherever, possible to develop procedures and train pilots to fly a stabilized CDFA…

The report also stated:

It is evident that most of the CFIT accidents result from a pilot’s breakdown in situational awareness (SA) instead of aircraft malfunction or a fire. In other words, these accidents are, for the most part, entirely preventable by the pilot. SA refers to the accurate perception by flight crew of the factors and conditions currently affecting the safe operation of the aircraft, and their vertical and/or horizontal position awareness in relation to the ground, water, or obstacles. The data shows that 49 percent of CFIT accidents had vertical, lateral or speed deviations as a contributing factor to CFIT accidents. One method to provide pilots with a greater level of safety through enhanced situational awareness and, more reliable warnings of possible terrain conflicts such as EGPWS that is equipped with accurate navigation systems like global positioning system (GPS) for both navigation and terrain surveillance.

Research conducted for the Netherlands Directorate-General of Civil Aviation, under the auspices of the Flight Safety Foundation, identified a fivefold increase in accident risk in commercial aircraft flying a non-precision approach compared with a precision approach (Enders and others, 1996).

Other research conducted into the human factors associated with CFIT accidents between 2007 and 2017 found that 24 out of 50 accidents reviewed (48%) occurred during the approach phase of flight (Kelly and Efthymiou, 2019). This research also found that ‘Breakdown of the Visual Scan’ occurred in 84% of accidents and that, in 42 of the analysed accident reports, a critical parameter such as altitude was ignored, and an unsafe situation occurred through ‘distraction’, ‘complacency’ or ‘lack of skill’.

Efforts to reduce CFIT accidents

In 1995 an international CFIT task force, whose major goal was to prevent CFIT accidents, completed its work after creating several unique products for the Flight Safety Foundation (FSF) including a CFIT Education and Training Aid. The training aid described GPWS (now known as TAWS) as ‘one of the major weapons in the growing arsenal of CFIT prevention methods.’ It further recommended every aircraft be fitted with such a system, as a GPWS warning ‘is normally the flight crew’s last opportunity to avoid CFIT’.

The training aid recommended standard operating procedures and/or guidance from the aircraft manufacturer that specified flight crew actions in the event of a terrain warning. In the absence of these, the aid provided a standard escape manoeuvre for flight crew to follow in the event of a terrain warning.

The CFIT task force identified 2 ‘basic causes’ of CFIT accidents – a lack of flight crew’s vertical position awareness and their lack of horizontal position awareness in relation to the ground, water, or obstacles. More than two-thirds of all CFIT accidents were the result of altitude error or lack of vertical situational awareness. To mitigate against this, the training aid emphasised the importance of flight crew training and discipline.

CFIT mitigation strategies

In 1994, the international CFIT task force also designed a CFIT checklist for the FSF, aimed at reducing CFIT accidents (Appendix G – Flight Safety Foundation CFIT Checklist). The checklist had 3 parts:

• Part I enabled a calculation of the CFIT risk factors for the planned destinations (including air traffic control capabilities and the types of approaches available) and risk multipliers (such as the type of operation and weather conditions). Some of the risk factors relevant to this accident included no ATC at the airport and a non-precision approach type. Risk multipliers included passenger-carrying charter operation, IMC, and a single-pilot flight crew.
• Part II of the checklist listed CFIT risk-reduction factors in 4 areas: company culture, flight standards, hazard awareness and training, and aircraft equipment. 
• Part III calculated the CFIT risk score by adding the destination CFIT risk factors (which are negative values) multiplied by the calculated risk multiplier to the risk-reduction factors.

The ATSB included copies of the FSF checklist in several of its accident reports, and also referred to the checklist in the research report CFIT: Australia in context 1996 to 2005 (ATSB, 2007).

In addition to the checklist, the FSF developed a CFIT Education and Training Aid in the 1990s, which included an example CFIT training program (albeit focussed on larger aircraft operations). It also developed a video training aid (for regional and business aircraft operators) and the ALAR Tool Kit, which included a number of briefing notes, such as the briefing note on stabilised approaches (see Guidance regarding stabilised approach criteria).

More recently, the FSF also developed a basic aviation risk standard (BARS) program that was designed to provide organisations that engaged contracted aircraft operators with a standard to assist in the risk-based management of aviation activities. It advised that the standard was suited to any organisation that used aircraft operators to provide contracted aviation support for its operations, particularly within remote and challenging environments. The program was used by several large mining/resource companies and other organisations. Participating aircraft operators could be audited against the standard.

The standard document stated:

All national and international regulations pertaining to aviation operations must be followed. This Standard is designed to supplement those requirements.

With regards to CFIT, the following risk controls were specified:

• 2 pilots for flights to be flown at night or ‘in IFR’
• multi-engine aircraft to be used for flights flown at night or ‘in IFR’
• aircraft operators to include type-specific stabilised approach requirements in their operations manual
• aircraft that fly under IFR or at night and on long-term contract to be fitted with an approved and serviceable Class A TAWS when an approved modification exists for the aircraft type (and the operator must have related procedures to be followed by the flight crew in the event of an alert).

The BARS implementation guide outlined guidance for stabilised approach criteria, based on the ALAR briefing note 7.1.

Operator’s CFIT risk mitigation

General aspects

At the time of the accident, Air Connect Australia was not required to have a safety management system (SMS). At the core of an SMS is a formal risk safety management process, which is used specifically to:

• identify hazards associated with an organisation’s operations
• analyse and assess the risks associated with those hazards
• implement control, to prevent future accidents, incidents or occurrences (CASA, 2018).

The operator advised it had an SMS incorporated into its operations manual, which included a requirement for 6-monthly safety meetings as well as a hazard, incident and accident report form. However, this did not include a detailed hazard identification and mitigation process. Without a documented hazard identification process, Air Connect Australia had not explicitly identified CFIT as a hazard nor detailed how it would mitigate the risk.

Based on the FSF CFIT checklist, the ATSB assessed that a single-pilot passenger transport operation involving non-precision approaches to airports without ATC and radar coverage (such as Lockhart River) in IMC carried a significant CFIT risk. Many of the risk-reduction factors listed in the checklist were specific to multi-crew operations and would not be appropriate or viable for a small operator conducting single-pilot operations such as Air Connect Australia. However, the checklist highlighted the CFIT risk for such an operation and provided some ways to mitigate the risk.

The ATSB further assessed Air Connect Australia and the aircraft (VH-OZO) against the suggested risk-reduction factors, as outlined in the following sections.

Section 1 – Company culture

The checklist items included aspects such as the operator placing safety before schedule and placing no negative conations on diversions or missed approaches. The chief pilot advised the ATSB that they often cancelled or postponed flights due to adverse weather. They also stated that they had frequent discussions with the pilot, and they were approachable and open to discussions with the pilot about any safety issues or concerns. Friends of the pilot were not aware of the pilot having any concerns about the chief pilot or the operator and confirmed that the pilot and chief pilot had frequent discussions about operational matters before flights.

Section 2 – Flight standards

The CFIT checklist did not specifically refer to stabilised approach criteria (which were introduced in later FSF guidance material). However, it listed a number of other items. Those potentially applicable to single-pilot operations included:

Reviewing approach or departure plates

Reviewing significant terrain along intended approach or departure course…

Briefing and observing MSA circles on approach charts as part of plate review

Checking crossing altitudes at IAF positions

Checking crossing altitudes at FAF and glideslope centering…

Use of 500-foot altitude call and other enhanced procedures for NPAs…

The operator’s operations manual stated, for all arrivals:

Before descending to an ALA [aircraft landing area], the Pilot-in-Command shall study available charts of the proposed ALA and surrounding area and make a note of hazards indicated on the charts.

The manual also required pilots to check the existing conditions in flight to determine their suitability for the approach and landing (including in terms of the MDA and required visibility on the approach charts). In addition, the manual included a requirement for crew to self-brief prior to the approach and also before landing:

Instrument Approaches – A self-briefing is to be carried out before every landing regarding the intentions of the Pilot-in-Command before / after the commitment point.

…

An emergency self-briefing is to be carried out before the landing regarding:

(a) the intentions of the Pilot-in-Command before / after the commitment point; and

(b) identifying missed approach track or heading.

As previously noted, the flight profile for a straight-in instrument approach also required a pilot to check the altimeter at the FAF. No other checks or altitude calls were explicitly stated.

Section 3 – Hazard awareness and training

The FSF checklist outlined various requirements for CFIT hazard awareness, including:

Your company’s pilots are reviewed annually about the following:

Flight standards operating procedures

Reasons for and examples of how the procedures can detect a CFIT “trap”

Recent and past CFIT incidents/accidents

Audiovisual aids to illustrate CFIT traps

Minimum altitude definitions…

The operator did not conduct formal hazard awareness training and there were no records of any training relating specifically to CFIT. There was no specific regulatory requirement for the operator to conduct such training.[72] 

The checklist also included items regarding incident reporting and investigation:

You have an incident/exceedance review and reporting program

Your organization investigates every instance in which minimum terrain clearance has been compromised

The company culture items also referred to fostering a culture where CFIT incidents could be reported. The chief pilot advised they had frequent discussions with the pilot and believed there was a high level of mutual trust, such that that if the pilot had a concern they would feel comfortable coming to talk to the chief pilot about it. However, the chief pilot was not aware of the circumstances associated with the missed approach at Aurukun in January 2020.

The chief pilot advised that the pilot used their own tablet device (iPad) and OzRunways subscription. As a result, the chief pilot did not have access to the recorded data.

Section 4 – Aircraft equipment

The CFIT checklist referred to GPWS, radio altimeter, various types of displays and autopilot functions. The checklist was not up-to-date and not targeted to the needs and potential current opportunities for small aircraft.

As previously noted, VH-OZO was not fitted with a TAWS or radio altimeter, nor were these mandated by the regulatory requirements at the time. The aircraft’s GPS units did not provide vertical guidance for RNAV GNSS approaches and the autopilot was not capable of maintaining a vertical profile without pilot input.

CFIT risk score

Based on the total CFIT risk factors for the destination and risk multipliers, then consideration of the available risk-reduction factors, the total CFIT risk score calculated for the operator was less than zero and indicated a significant CFIT risk. However, as already noted, other operators conducting single-pilot charter flights involving non-precision approaches in IMC to airports without ATC and radar coverage (such as Lockhart River) would also be exposed to a significant CFIT risk as assessed by this checklist.

Safety analysis

Introduction

After conducting an area navigation (RNAV) global navigation satellite system (GNSS) approach to runway 30 at Lockhart River and then a missed approach, the pilot of the Cessna 404 aircraft (VH-OZO) immediately commenced a second RNAV GNSS approach to runway 30. The aircraft’s descent gradient was similar to the first approach but significantly lower than the recommended profile in the approach chart. This descent continued until the aircraft collided with terrain 6.4 km short of the runway.

There was no evidence of any conditions or circumstances likely to induce a medical problem or incapacitation for the pilot, who had been in good health and was well rested. Also, based on the recorded flight data and impact information, the aircraft appeared to be in controlled flight up until the time of the impact. Accordingly, it is very unlikely that the pilot was incapacitated or impaired during the flight.

There was no evidence of any aircraft system or mechanical anomalies that would have influenced the accident. However, as a consequence of extensive aircraft damage, it was not possible to be conclusive about the aircraft’s serviceability.

Therefore, based on the available evidence, the accident was very likely the result of controlled flight into terrain (CFIT). That is, an airworthy aircraft under the control of the pilot was flown unintentionally into terrain, probably with no (or very limited) prior awareness by the pilot of the aircraft’s proximity to terrain.

As evidenced in this case, a CFIT accident generally results in significantly adverse consequences for the occupants of an aircraft, and thus operators conducting operations in instrument meteorological conditions (IMC) or degraded visual conditions need to have robust risk controls to minimise the risk of such accidents.

This analysis considers the weather and sequence of events, followed by the factors that likely influenced the pilot’s performance. It also discusses risk controls for CFIT relevant to this accident.

Weather conditions

The weather conditions at Lockhart River at the time of the 2 approaches were consistent with the forecast, with periods of reduced visibility due to rain and cloud. The conditions had been suitable for the pilot of one aircraft to land about 1 hour prior to the accident and allowed another to land about 30 minutes afterwards.

Although the pilot of VH-OZO had not obtained the latest weather forecast for Lockhart River on the morning prior to the flight using their National Aeronautical Information Processing System (NAIPS) account, they could have obtained the forecast from other sources and they were reportedly aware of the current weather information. In any case, the pilot had ensured the aircraft had sufficient fuel to hold, divert or return to Cairns if necessary.

The landing minima for the runway 30 approach at Lockhart River included a cloud ceiling (for broken cloud or worse) of 730 ft and a visibility of 4,200 m. On arrival at Lockhart River, the pilot listened to the automated weather information service (AWIS) via VHF radio, and received information that the reported conditions were above the landing minima (with 10 km visibility and broken cloud at 1,800 ft).

The conditions recorded by the airport’s automatic weather station (AWS) at the time of the first approach’s final segment (0904–0907) included a visibility of 10 km, some rainfall (0.2 mm at 0904) and nil wind. The visibility was measured in the immediate vicinity of the sensor and may not have reflected the conditions experienced by the pilot during the approach. The recorded cloud base was 1,800 ft, however the recorded values for cloud were averaged over the preceding 30-minute period, and the cloud conditions at any specific time may have been worse than recorded.

Based on a witness report, it appeared as though the conditions at times were probably worse than recorded, with periods of reduced visibility due to cloud and rain. Messages sent by 2 of the passengers at 0914 indicated there was low visibility and one stated there was heavy rain, however it was not clear whether these comments were related to the conditions during the first approach or were observations of the conditions closer to 0914, which was about 7 minutes after the aircraft passed the missed approach point (MAPt).

Therefore, although the AWS observations indicated the weather was above the landing minima, there were areas of reduced visibility in the vicinity of the airport and it was not possible to conclusively determine the actual conditions experienced by the pilot when they reached the MAPt during the first approach.

The recorded visibility deteriorated to 800 m at 0912 and was below the landing minima for most of the period 0911–0917. This aligned with recorded rainfall between 0910–0916, including moderate to heavy rain during 0912–0914. Weather radar images from the Bureau of Meteorology (BoM) also showed rain passing through the Lockhart River area during both approaches, with heavier rain during the second approach. The radar images were consistent with the weather observations by people in the area, including that a ‘wall’ of heavy rain passed through at about the time of the accident. Given the direction the radar returns were moving, it is likely the aircraft entered the rain during the second approach.

In summary, while the pilot was operating in the vicinity of Lockhart River Airport, there were areas of cloud and rain that significantly reduced visibility and increased the risk of CFIT. In particular, the aircraft probably entered areas of significantly reduced visibility during the second approach. As a result of the reduced visibility, the pilot would have been reliant on the aircraft’s flight instruments and GPS units during both approaches.

Conduct of the approaches

First approach and missed approach

On the first approach, the pilot levelled at about 5,000 ft prior to the initial approach fix (IAF), which in this case was LHREB, then established the aircraft on a 3° descent from the IAF. This was consistent with the pilot’s normal method and conformed to the operator’s recommendations and the guidance shown on the approach chart. The pilot conducted the approach consistent with the recommended (3°) constant descent profile, and the aircraft kept descending through the minimum descent altitude (MDA) of 730 ft and passed the missed approach point (MAPt).

There were no significant lateral deviations from the published track, and the indicated airspeed when passing the final approach fix (FAF) was about 130 kt. However, after the FAF, the airspeed increased to about 140 kt, which was sustained throughout the remaining descent. This was significantly in excess of the operator’s preferred airspeed for such approaches (about 110 kt at the FAF), and it also exceeded the applicable handling speed limit specified in the Aeronautical Information Publication (AIP) of 130 kt in the final approach segment.

After passing the MAPt, the aircraft’s recorded descent rate was 900 to 960 ft/min. When the aircraft reached about 400 ft, the pilot initiated a missed approach. The airspeed at that time significantly exceeded the operator’s stabilised approach criteria speed (that is, about 110 kt at 300 ft above aerodrome elevation).

The reason for the non-conforming airspeed on this approach could not be determined. It is possible that this was intentional, and the pilot was expediting the arrival in response to the visible weather. Alternatively, it could have been inadvertent and associated with a focus on other flying tasks in this phase, such as maintaining track (with reduced tolerances) and/or searching for visual cues such as the runway threshold in reduced visibility (see also Awareness of procedural requirements). Whatever the reason, the high airspeed would have made it difficult to configure the aircraft for a stabilised final approach and landing.  

Although the descent rate was just within the operator’s limit for a stabilised approach (that is, 1,000 ft/min), it was higher than the 600 ft/min that would be typical for this stage of a final approach. It was also higher than the 750 ft/min that would be commensurate with a 3° profile at 140 kt. Similar to the high airspeed, the reason for the relatively high descent rate could not be determined. It is possible that the pilot was attempting to maintain visual reference.     

As previously noted, the weather conditions when the aircraft reached the MAPt could not be determined. It is possible that the conditions were better than the landing minima at that point but then deteriorated as the approach continued and when the aircraft was at a lower altitude.

Irrespective of the conditions, this was not a stable approach due to the relatively high airspeed and a missed approach was necessary. Ultimately, the pilot commenced the missed approach when the aircraft reached about 400 ft. Whether the decision to conduct the missed approach at that time was based on the weather conditions, airspeed, descent rate or some combination of those factors could not be determined.

After initiating the missed approach, the pilot was required to select one of 4 options:

• immediately conduct another instrument approach
• hold in the area, monitor the weather at Lockhart River and, if suitable, conduct another instrument approach
• divert to a nearby airport, monitor the weather at Lockhart River and, if suitable, return for another approach 
• return to Cairns.

Having descended to 400 ft then overflown the airport during the missed approach, it is expected that the pilot had an appreciation of the low-level weather conditions. Then, during the missed approach, the aircraft tracked initially to the north-west, which was in the direction of weather that was moving towards Lockhart River. Given heavy rain was recorded at the airport about 5–7 minutes after the aircraft had been overhead, the boundary of this rain area may have been visible to the pilot. The rain should also have been displayed on the aircraft’s weather radar display and potentially also the iPad the pilot was using during the flight, although exactly what information was displayed to (or observed by) the pilot could not be determined.

As reported by a passenger in a text message at 0914, at some point during the missed approach or transition to the second approach, the aircraft was in or near heavy rain. Although the AWS between 0911 and 0917 was indicating below-minima weather at the airport, it is unlikely that the pilot had spare capacity to access the AWIS in that period.      

Given this context, the pilot may have considered there was a window of opportunity to conduct a second approach before there was heavy rain at the airport and, accordingly, they expedited the second approach.  

Second approach – vertical profile

The pilot tracked directly towards the IAF LHREA at 3,500 ft to commence the second approach. After passing the IAF, the aircraft remained at that altitude while heading to the IF. The pilot then commenced descent from 3,500 ft about 2.7 NM prior to the IF. From about 1.6 NM before the IF, the descent was flown at about a normal 3° flight path, although about 1,000 ft below the recommended descent profile. The aircraft descended through the intermediate segment minimum safe altitude of 1,800 ft and passed the FAF at about 1,100 ft. When the aircraft reached a recorded altitude of 700 ft, the descent rate increased from about 700 ft/min to about 1,200 ft/min until the collision with terrain.

The investigation considered 3 main scenarios to explain the vertical profile of the second approach. The first scenario is the pilot misunderstood their position along the approach (or misidentified the waypoints) and believed they were one segment (5 NM) further along the approach than they actually were. Figure 21 shows the vertical profile of the second approach (in red) and it also shows the vertical profile moved 5 NM to the left (in green), as if the pilot thought they were one segment further along the approach. With regard to this scenario:

• The scenario does not provide a good explanation of the recorded data as the aircraft remained about 600 ft above the recommended profile for an extended period and there was no indication of any attempt to correct such a perceived problem prior to reaching the perceived MAPt.
• The waypoint names on RNAV approaches are similar and there is some potential for confusion. However, in this case the pilot had significant cues to indicate their position along the approach, given they were turning at the IF (10 NM from the MAPt), and they had broadcasted they were at this position just prior to the turn. Although the absence of a subsequent broadcast by the pilot at the FAF (5 NM) could indicate a loss of awareness of the aircraft’s position at that time, it could also have been omitted because the pilot assessed it was unnecessary due to the lack of other aircraft in the vicinity, and/or the pilot was experiencing high workload.

Figure 21: Second approach to runway 30 (red), second approach displaced 5 NM (green) and second approached raised 1,000 ft (yellow)

The second scenario is the pilot believed they were 1,000 ft higher than they actually were during most of the descent. This scenario is shown on Figure 21 (in yellow). With regard to this scenario:

• The scenario closely matches the recommended descent profile in terms of commencing the 3° descent at about the right point for a constant descent and then continuing the descent past the IF and FAF.
• When the pilot commenced the descent from 3,500 ft, they were correcting the aircraft’s lateral position (right of the initial approach track) and would therefore have been experiencing a high workload. The potential to mis-read instruments (such as an altimeter) is significantly increased under high workload, and the ability to subsequently detect and correct such an error would also be reduced, given that high workload can lead to scanning information sources less frequently and also scanning them for shorter durations.
• Just prior to passing the IF, the pilot broadcasted that they were at ‘3,800 correction 2,800 ft’, and this correction was an accurate broadcast of the aircraft’s altitude at the time. This indicated an initial mis-reading of the altimeter, but it also indicated that the pilot had correctly read the altimeter at that time. However, this correction occurred at one point in time for the purpose of making the radio broadcast, and the pilot may not have fully assimilated the information for the purpose of monitoring their descent profile.
• The pilot should have been regularly checking the altimeter during the descent as part of their instrument scan, so for this scenario to be viable the pilot would need to mis-read the altimeter multiple times, or at least not detect a problem when scanning the altimeter after an initial error. This would seem unlikely over an extended period. However, as noted before, the pilot may have been scanning instruments less frequently and for shorter durations due to workload. They may also have been focussing more on the vertical speed indicator than the altimeter after commencing the descent.
• The aircraft was fitted with a 3-pointer altimeter, which are widely used in small aircraft. Research has shown that pilots can mis-read this type of altimeter, including mis-reading by 1,000 ft, although accidents known to be associated with such errors seem relatively rare.
• The scenario does not specifically explain why the descent rate increased in the last 30 seconds of the approach. However, the pilot was probably experiencing a very high workload at that time associated with correcting the aircraft’s lateral position (see Second approach - lateral position). The pilot may also have started increasing the amount of time they were looking outside the aircraft for visual cues, and/or their attention was diverted when entering heavy rain. In addition, heavy rain on a windshield is known to create refraction effects that can lead a pilot to perceive that the aircraft is too high, which can result in an unwarranted nose-down correction and flight below the desired flight path (Flight Safety Foundation 2000).[73] 

The third scenario is the pilot intentionally descended below the recommended descent profile and segment minimum safe altitude in order to maximise the chances of becoming visual before reaching the MAPt. For this type of scenario, it is unlikely a pilot would intentionally descend below the MDA before the MAPt unless there were some visual references. With regard to this scenario:

• There were no indications in the pilot’s recent RNAV GNSS approaches of descending this early on an approach or descending below segment minimum safe altitudes, although it is acknowledged that the pilot had limited experience with having to conduct a second approach in IMC. There was also no indication that the pilot took unnecessary risks in interviews with other pilots who had flown with the pilot.
• Lockhart River is a location widely known to be problematic in terms of the weather conditions and terrain. Although the pilot had flown to Lockhart River on several occasions, as far as could be determined they had not previously encountered IMC at this location before. Nevertheless, given the location’s reputation, it would be reasonable to expect that the pilot would be conducting approaches cautiously and therefore less likely to descend below altitude limits.
• If the pilot was intentionally descending early, it is not exactly clear why they would choose to conduct a 3° descent that was about 1,000 ft below the recommended descent profile. However, it is possible the pilot wanted to reach the MDA over water (to ensure more clearance from terrain) and had calculated that such a profile would enable the aircraft to be over water just after reaching the FAF.
• There was some indication in the recorded data that the aircraft’s descent rate may have briefly reduced near the MDA, with 3 successive data points recorded at 700 ft. This might be associated with an attempt to level out at about the MDA. Alternatively, the descent rate may have only briefly reduced from 700 ft/min to 500–600 ft/min due to the pilot’s workload and attention been focussed on the aircraft’s lateral position at that time, or due to the pilot’s attention being diverted when they entered heavy rain. It is also possible that the 3 data points at the same level were an artefact of the recorded data and there was no significant change in descent rate.
• If the pilot was attempting to level out at about 700 ft, it is unclear why the aircraft kept descending for over 30 seconds after reaching this altitude at a descent rate of 1,200 ft/min. It is possible the pilot did not retrim the aircraft after levelling out and then did not effectively monitor the altimeter due to other tasks, including looking outside to gain visual references.

In summary, following the missed approach, the pilot immediately conducted another approach to the same runway that was on a similar gradient to the recommended descent profile but displaced about 1,000 ft below that profile. While continuing on this descent profile, the aircraft descended below a segment minimum safe altitude and the minimum descent altitude, then kept descending until the collision with terrain about 6 km before the runway threshold.

Based on the available evidence, it is unlikely that the pilot thought they were one segment out on the approach and there was no specific evidence to indicate that the pilot had or would intentionally descend below the recommended descent profile and below a segment minimum safe altitude. Overall, mis-reading the altimeter by 1,000 ft appears to be the most likely scenario, although there was insufficient evidence to provide a definitive conclusion. Regardless of the exact scenario, it is evident from the continued descent that the pilot did not effectively monitor the aircraft’s altitude and descent rate for an extended period.

Second approach - lateral position

The aircraft was just within the capture region for the IAF LHREA when the pilot commenced the turn towards the IF, and it was then initially significantly to the right of the initial approach track. The pilot corrected the aircraft’s heading, but the aircraft was still more than half full-scale deflection on the course deviation indicator (CDI) at the time it started descending from 3,500 ft. The descent was paused soon after and then recommenced, before the IF, with the aircraft within the required half full-scale deflection in order to descend.

Before reaching the IF, the aircraft was close to the initial approach track. The pilot then turned slightly late at the IF and the aircraft was left of the intermediate approach track, reaching about half full-scale deflection on the CDI. The pilot promptly took corrective action, though the aircraft then started deviating to the right of the approach track about 3 NM prior to the FAF. However, the lateral deviation at that stage was less than half full-scale deflection.  

Nearing the FAF, the sensitivity of the CDI increased, and when the aircraft passed the FAF it was at about full-scale deflection on the CDI (as presented by the Garmin GNS 430W), and then it exceeded full-scale deflection for about 55 seconds (and was outside half-scale deflection for about 60 seconds). The aircraft’s change of track to the left during the final 30 seconds of the approach suggests the pilot had observed the CDI and attempted to correct the situation, but had then flown through the final approach track and, before a further correction back to the right could be conducted, the aircraft impacted terrain.

Given the aircraft was more than half full-scale deflection on the CDI when it reached the FAF, the pilot was required to conduct a missed approach in accordance with the operator’s stabilised approach procedures. It is acknowledged that the GNS 430W presented full-scale CDI deflection more restrictively than the required navigation performance (RNP) requirements specified in Civil Aviation Order (CAO) 20.91 (that is, 0.23 NM compared to the RNP of 0.3 NM at the FAF). Nevertheless, given that the aircraft’s position was at full-scale deflection (rather than half-scale deflection), this difference should not have affected the pilot’s decision.   

In addition, the aircraft was at 0.3 NM lateral displacement shortly after passing the FAF (for about 10 seconds). This would have been displayed to the pilot as more than full-scale CDI deflection, and the lateral displacement distance would also have been displayed on the graphical CDI on the default NAV page of the GNS 430W. Accordingly, the pilot was also required to conduct a missed approach in accordance with the CAO 20.91 requirements at that time.

Finally, with reference to the AIP, the pilot was also required to be within half full-scale deflection on the CDI after passing the FAF before continuing the descent below the previous segment minimum safe altitude (1,800 ft). This should have precluded further descent when passing the FAF (actual altitude 1,100 ft) or soon after (when the actual height was 800 ft and the perceived height may have been 1,800 ft).

It is possible the pilot may not have promptly detected the lateral deviation due to other workload, or they may not have fully realised the extent of the change in the sensitivity of the CDI near the FAF. Alternatively, it is possible that the lateral deviation was due, in part, to the pilot attempting to avoid the most adverse weather.

In summary, the pilot experienced some difficulty controlling the aircraft’s lateral position throughout the second approach. In particular, when passing the FAF and after passing the FAF, the aircraft reached or exceeded the required limits to conduct a missed approach, and a missed approach was not conducted. Regardless of the reason for the lateral deviations, by continuing the approach the pilot significantly increased their workload and the risk of collision with terrain/obstacles.

Second approach - indicated airspeed

The aircraft was at about 135 kt when it passed the FAF, before increasing to 140 kt soon after the FAF. It then increased to 150 kt towards the end of the flight, which was associated with the increased descent rate.

By exceeding the operator’s preferred speed of 110 kt at the FAF, the pilot significantly increased their workload and reduced the time available in the final approach segment to detect and identify other problems with the conduct of the approach (in terms of altitude, descent rate or lateral deviation). More specifically, if the airspeed had been about 110 kt at the FAF, and remained at or below that speed, the pilot would have had over 20 seconds more time prior to the collision to identify problems with the aircraft’s flight path (as well as additional time prior to reaching the FAF). A lower speed would also have made it easier to effectively correct the aircraft’s lateral position.

Unstable approach

Overall, at times during the conduct of the second approach, the pilot appeared to experience difficulty controlling the aircraft’s lateral position, and after passing the FAF they did not effectively control the aircraft’s altitude, descent rate, lateral position and airspeed. As already noted, the approach did not meet the operator’s stabilised approach criteria for lateral deviation at the FAF, and the pilot was required to conduct a missed approach at that point.

In addition, the second approach did not meet the stabilised approach criteria for airspeed (110 kt maximum) or descent rate (1,000 ft/min) at the operator’s applicable height of 300 ft above aerodrome elevation. At this point, the aircraft was travelling at about 150 kt and descending at 1,200 ft/min. However, given that the pilot may have believed the aircraft was 1,000 ft higher than it actually was during the approach, or may have thought they were in level flight near the MDA, they may have not yet considered these stabilised approach criteria.  

Factors influencing pilot performance

Introduction

As previously noted, there was no evidence to indicate that the pilot was incapacitated during the accident flight. There was also no evidence to indicate the pilot was experiencing fatigue. The investigation considered a range of other factors that could have influenced the pilot’s performance, including workload, instrument flying proficiency, awareness of procedural requirements, and operational, social or organisational pressures.

Workload and monitoring

Single-pilot operations under the instrument flight rules (IFR), conducting instrument approaches in poor visibility and hand flying an aircraft are all demanding tasks. A pilot needs to be regularly scanning and interpreting the flight instruments, GPS unit (or navigational display) and approach chart, and assimilating the information from multiple sources. As they near the MAPt, they also need to be looking outside to evaluate the visual conditions.

It could not be determined with certainty whether the pilot was using a paper approach chart clamped to the control column and/or was referring to an iPad with the approach chart displayed. Based on the evidence available, it was more likely the pilot was using an iPad, but it was not clear whether it was secured to the control column or if it was on the pilot’s knee. If they were routinely scanning an iPad that was not fixed to the control column, this would have increased the difficulty of the pilot’s scanning and exacerbated the inherent workload associated with the tasks.

Overall, the pilot’s workload on the second approach was elevated throughout the approach compared to the first approach (and other recent instrument approaches conducted by the pilot). Initially the workload was elevated because they joined the approach directly after conducting the missed approach and from just within the capture region of the IAF LHREA. This limited their time to prepare for the approach, and also required more manoeuvring than normal at the IAF.

After turning at the IAF, the pilot’s workload was further elevated by the need to correct the aircraft’s track while also reducing airspeed. As previously noted, it was during this period that the pilot decided to commence the descent from 3,500 ft, which also involved selecting the approach flap and lowering the landing gear soon after.

The pilot’s workload after turning at the IF was also elevated due to the turn being slightly late and then needing to correct the aircraft’s track. This workload would have been significantly elevated after passing the FAF, with the deviation from the final approach track needing more significant correction, as well as due to potentially starting to look more outside the aircraft to assess the visual conditions.

At some point the aircraft probably entered rain, and this would also have increased the pilot’s workload and the difficulty of their task. The presence of rain decreases contrast in the visual environment, making it more difficult to detect terrain features. This effect is exacerbated when approaching or flying over water. In addition, as already discussed, heavy rain on a windshield can lead to a perception of being too high. Light rain can also result in a pilot misperceiving their aircraft to be higher than it is, resulting in a tendency to pitch down (Gibb and others 2010, Flight Safety Foundation 2000b, Previc 2004).

A further factor potentially increasing the difficulty of the pilot’s task after passing the FAF was the increasing sensitivity of the Garmin GNS 430W’s CDI. At and just past the FAF, where a decision to conduct a missed approach should have been made, full-scale deflection on the 430W was not significantly different to the RNP. Towards the MAPt, the 430W was significantly more restrictive than the RNP. The pilot should have been familiar with the system, although the extent to which they fully appreciated the effect of the increasing sensitivity could not be determined.

As previously noted, the omission of the broadcast at 5 NM could be an indication of the pilot’s high workload at that time. In addition, the aircraft’s increased descent rate and speed in the final 30 seconds as the pilot was correcting the lateral deviation is also consistent with the effects of high workload, reducing the ability to monitor and effectively control multiple flight parameters at the same time.

As previously discussed, the pilot’s workload could have been reduced by conducting the approach at a lower airspeed prior to and after the FAF. In addition, there were other available options after conducting the missed approach, including taking more time prior to conducting the second approach and commencing it from another position (for example, tracking further away from the IAF and then approaching it from closer to the centre of its capture region). Alternatively, the pilot could have conducted a holding pattern and waited for the weather to pass before attempting the second approach.

Such options would have provided more time to prepare for the approach and minimise the potential for altitude, descent rate or lateral deviations or other workload problems. These options may also have provided the pilot more opportunity to use the autopilot to reduce their sustained workload prior to initiating the second approach. 

Instrument flying proficiency

Many pilots experience some difficulty with developing instrument flying skills and then consistently maintaining those skills. The pilot of the accident flight experienced some difficulties obtaining their initial instrument rating in 2014, and also experienced some difficulties in subsequent instrument proficiency checks (IPCs) in 2016 (underpinning knowledge) and 2017 (mis-reading the altimeter), before passing subsequent assessments. The pilot also experienced significant difficulties in conducting instrument approaches, including the management of multiple flight parameters at the same time, when being assessed in an airline simulator in early 2018, albeit in a much different environment to their previous operations.

The pilot’s last IPC was conducted in August 2019, 7 months prior to the accident, and no problems were noted. However, on that occasion, the Cessna 310 aircraft used for the check was fitted with a navigational system capable of providing vertical guidance for an RNAV GNSS approach. As far as could be determined, the pilot’s instrument flying skills using VH-OZO (a Cessna 404 with GNS 430 GPS units) or similar aircraft had not been observed by the chief pilot or a flight examiner pilot since they were cleared for line operations in October 2018.

Since their last IPC, the pilot had regularly logged RNAV GNSS approaches in VH-OZO and these approaches were generally flown accurately. However, these approaches were almost all conducted in VMC, which would have provided the pilot with cues to identify and correct problems with the aircraft’s position.

The pilot had only conducted one previous approach since the last IPC that potentially encountered IMC for a brief period, at Aurukun on 22 January 2020. This approach was not initiated in the pilot’s normal manner (with a descent from about 5,000 ft at the IAF). In addition, the aircraft reached the MDA 200–300 ft below the recommended descent profile and there were problems with speed control, with the speed after the FAF reaching 145 kt.

Overall, it was difficult to assess the pilot’s instrument flying skills at the time of the accident. Given the limited number of recent RNAV GNSS approaches in IMC or simulated IMC, it is conceivable that the pilot would have experienced significant workload in conducting an approach in IMC, particularly in circumstances where the approach required them to use a different method to normal. They would probably also have had limited ability to manage any additional problems or tasks that occurred during the conduct of an approach in IMC.   

Awareness of procedural requirements

The operator’s published flight profile for an RNAV GNSS approach required a Cessna 404 to be at an indicated airspeed of about 90–100 kt at the FAF. However, interviews with the operator’s relevant personnel suggested that the operator’s preferred speed was probably about 110 kt. Given that the one-engine inoperative best rate of climb speed for the aircraft type was 102 kt (flap in the take-off/approach position and gear up), 110 kt was a more appropriate speed at the FAF. The pilot’s approaches routinely exceeded the operator’s preferred speed by a significant margin, with speeds of 130–140 kt being common.

Although the pilot should have been familiar with the contents of the operations manual, it is unclear to what extent they were aware of the flight profile speed or the operator’s preferred speed, and, if they were aware, the extent to which they thought these were reasonable expectations. In other regards, the pilot appeared to be conducting RNAV GNSS approaches in a manner consistent with the chief pilot’s expectations, using a constant descent from about 5,000 ft at the IAF in order to maximise the potential for a stabilised approach.

Having held an instrument rating since 2014, and been subject to many IPCs since then, the pilot should have been aware of the requirement to be to be no faster than 130 kt after the FAF while conducting an RNAV GNSS approach. They should also have been aware of the operator’s requirement to be within half-scale deflection of CDI in the final approach segment.

There were no indications from interviews with various people who flew with the pilot to suggest that the pilot routinely or intentionally deviated from procedural requirements. Given many of the pilot’s previous instrument approaches were conducted in VMC, it is possible the pilot did not consider that some procedural requirements, such as keeping the speed below 130 kt, were essential during such approaches. The pilot may have then become familiar with using such speeds and, when actually conducting approaches in IMC, did not fully recognise the problem. Alternatively, as already discussed, these speed deviations on the approaches in IMC may have been unintentional and were symptoms of high workload and/or limited proficiency.

Operational, social and organisational pressures

Pilots conducting passenger charter flights can experience or perceive a range of social and organisational pressures that can influence the potential to conduct or continue flights in unsuitable conditions (Paletz and others 2009, Michalski and Bearman 2014). These can include not wanting to disappoint customers, reluctance to admit defeat or time-related pressures.

Although such pressures can exist in operational environments, the ATSB identified no evidence to indicate the pilot was subject to any pressure to conduct this flight, complete the flight as quickly as possible, or to deviate from procedural requirements. The chief pilot had previously cancelled flights due to poor weather, but the forecast conditions in this case did not necessitate that the flight be cancelled.

As previously noted, the pilot had ensured the aircraft had sufficient fuel to conduct holding after arrival at Lockhart River, and divert or return to Cairns. They had also conducted holding for an extended period after a missed approach on a previous flight to Aurukun while waiting for a storm to pass, without any apparent negative social or organisational consequences.

As noted above, it is possible that, following the missed approach during the accident flight, the pilot assessed that the weather conditions were worsening and they had limited time to conduct a second approach before a more extensive delay. It is also possible that the pilot was worried about some aspect of the aircraft’s serviceability and did not want to delay the flight further. However, as previously noted, there was no evidence available to indicate a problem with the aircraft’s serviceability.

The pilot had previously commented to a passenger that they would only ever attempt 2 approaches prior to diverting. To what extent this may have placed self-imposed pressure on the pilot on this occasion to continue the approach could not to be determined.

Summary

In summary, the pilot was probably experiencing a very high workload during periods of the second approach. In addition to the normal high workload associated with a single pilot hand flying an approach in IMC, the pilot’s workload was elevated due to conducting an immediate entry into the second approach, conducting the approach in a different manner to their normal method, the need to correct lateral tracking deviations throughout the approach, and higher than appropriate speeds in the final approach segment. The workload was potentially further exacerbated by the pilot having limited recent experience in conducting RNAV GNSS approaches in IMC.

There was no evidence to indicate any organisational or commercial pressures on the pilot to complete the flight, but the extent to which self-imposed pressures or incomplete knowledge of procedural requirements influenced the pilot’s performance could not be reliably determined.

Risk controls for minimising the likelihood of controlled flight into terrain

Introduction

CFIT accidents have been a significant problem over the years, although the rate of such accidents has been decreasing. In Australia, the number of CFIT accidents during instrument approaches decreased from 9 in the 10-year period 1996–2005 and only 1 in the subsequent 15 years (that is, the accident involving VH-OZO at Lockhart River).

This decrease can be attributed, at least in part, to improved instrument approach designs, the increased use of better equipment to display relevant lateral and vertical navigational information, the increased fitment of a terrain warning system (TAWS), and greater use of constant descent angle approaches. However, risk factors still remain, particularly for smaller operators.

Air Connect Australia was a very small operator, with effectively only 2 pilots and one conducting almost all of the operator’s flights. Nevertheless, it conducted passenger transport operations in an aircraft with up to 9 passengers, and multiple factors existed that indicated a significant CFIT risk. These factors included:

• single-pilot operations under the IFR
• many of the operator’s destination aerodromes were in uncontrolled airspace and outside radar coverage
• most of the destination aerodromes offered only non-precision approaches with limited runway lighting systems and without visual approach slope indicating systems
• some of the destination aerodromes (such as Lockhart River) were associated with frequent rainfall or adverse weather conditions.

Although the operator had started introducing a safety management system (SMS), it had not developed a formal hazard register and a formalised approach to addressing the risk of hazards such as CFIT. The operator had introduced various measures to manage CFIT risk, such as a flight profile and stabilised approach criteria. However, there were limitations with these and some of the operator’s other risk controls.

Design of the flight profile

The operator’s operations manual included a flight profile for RNAV GNSS and other straight-in runway approaches. Such a flight profile can be an effective way of summarising an operator’s requirements and expectations for pilots regarding how an approach should be conducted.

However, as previously noted, the stated speed on the profile at the FAF (V_ref to V_ref + 10 kt) was very conservative and unrealistic in most situations. In addition, it did not appear to reflect the expectations of the operator’s key personnel (which equated to V_ref + 20 kt or about 110 kt). The flight profile also did not include any requirements or expectations at the IF, which increased the potential for ambiguity.

Design of stabilised approach criteria

An essential and effective means of minimising the risk of CFIT accidents is for an operator to publish clear and relevant stabilised approach criteria, and then ensure that flight crew are aware of and comply with these criteria. Air Connect Australia’s stabilised approach criteria covered relevant parameters and factors, such as airspeed, configuration, descent rate, lateral tracking and briefings/checklists. The chief pilot also reportedly promoted the use of stabilised approaches to the pilot.

However, other than for lateral flight path deviations, the operator’s published criteria had an applicable height of 300 ft above aerodrome elevation for operations in both IMC and VMC. Such a height will have limited effectiveness for non-precision (or 2D) instrument approaches conducted in IMC, particularly given that the MDA for such approaches will often be above 300 ft. An applicable height of 1,000 ft above aerodrome elevation in IMC is widely recommended, including for operations in small aeroplanes. This will enable pilots to ensure that an approach is stable well before reaching the MAPt, reducing workload and maximising the time available to monitor the approach and identify and correct any problems.

The pilot of the accident flight generally appeared to be close to the stabilised approach speed of 110 kt at 300 ft in most of the instrument approaches examined by the ATSB, with 2 main exceptions being the first approach at Aurukun on 22 January and the first approach at Lockhart River, both of which resulted in missed approaches. Based on this information, the pilot appeared to be generally complying with the stabilised approach criteria. Therefore, had the operator specified an applicable height of 1,000 ft in IMC, it seems likely that the pilot would generally have been conducting approaches with a lower speed at this height.

However, it is not clear whether an applicable height of 1,000 ft would have influenced the pilot’s performance and changed the outcome of the second approach on the accident flight. As previously discussed, the exact reasons why the aircraft was descending below the recommended descent profile could not be determined. The pilot may have believed the aircraft was 1,000 ft higher than it was, and therefore thought the aircraft was still above 1,000 ft in the period immediately prior to the collision. Nevertheless, if they were effectively monitoring the flight instruments and complying with the criteria, they should have been slowing down well before reaching an altitude of 1,100 ft (the applicable height at Lockhart River given the aerodrome elevation).

An applicable stabilised approach height of 1,000 ft has been widely recommended by organisations such as the International Civil Aviation Organization (ICAO), the Flight Safety Foundation (FSF) and overseas regulators. However, as of the time of the accident, no formal guidance regarding the content of stabilised approach criteria had been published for Australian operators by the Civil Aviation Safety Authority (CASA). The ATSB has identified a number of Australian operators over the years conducting passenger transport operations under the IFR with applicable heights for all approaches of 300 ft. Accordingly, providing more specific formal guidance in Australia should reduce the likelihood that other operators will use such heights as the reference point for their criteria for all approaches.

It is acknowledged that operators need to tailor stabilised approach criteria to their specific aircraft and operations, and the use of 300 ft may be appropriate for some criteria on some types of approaches. In particular, circling approaches could involve a turn onto final approach at about 500 ft, and therefore cannot meet all stabilised approach criteria until about 300 ft (which is acknowledged in the FSF’s recommended criteria). In addition, it may not be appropriate to select full flap on many smaller aeroplanes until much lower than 1,000 ft on an approach (although other criteria could be met at a different height).

Nevertheless, with greater use of straight-in approaches, all operators should ensure the applicable heights for their stabilised approach criteria are consistent with contemporary guidance where possible for such approaches, particularly for operations in IMC.

Fitment of a terrain avoidance and warning systems

The use of a terrain avoidance and warning system (TAWS) has been shown to significantly reduce the risk of a CFIT. However, VH-OZO was not fitted with a TAWS, nor was one required to be fitted.

Given the aircraft’s descent profile on the second approach, if a TAWS had been fitted and been operational, it would have provided the pilot with both visual and aural alerts of the approaching terrain for an extended period. Accordingly, it is very likely that the accident would not have occurred.

The requirements for a TAWS have been increasing over time. However, the requirements in Australian have lagged behind those in comparable countries, and they were also not consistent with ICAO standards and recommended practices. In Australia there was a requirement for turbine-engine aeroplanes carrying 10 or more passengers on air transport flights under the IFR to be fitted with a TAWS, whereas the ICAO standard required aeroplanes authorised to carry 10 or more passengers to be fitted with a TAWS, regardless of the number of passengers carried on a flight. More importantly:

• There was no requirement for piston-engine aeroplanes conducting air transport operations to be fitted with a TAWS, even though this had been an ICAO standard since 2007 for such aeroplanes authorised to carry 10 or more passengers, and this standard had been adopted as a requirement in many comparable countries.
• There was no requirement for turbine-engine aeroplanes conducting air transport operations that were authorised to carry 6–9 passengers to be fitted with a TAWS, even though this had been an ICAO recommended practice since 2007, and this recommended practice had been adopted as a requirement in many comparable countries.

CASA had been consulting on applying TAWS requirements to more aircraft since 2008, and had proposed introducing a TAWS requirement for aeroplanes conducting air transport operations (turbine- and piston-engine) with a maximum operational passenger seat configuration (MOPSC) of 6 or more in 2012. However, following consultation with industry, this proposal was amended in 2018 to only require aeroplanes with a MOPSC of 10 or more to be fitted with a TAWS, with the application date being December 2021 or December 2022 depending on various factors.

VH-OZO had 12 seats that could be used by passengers and therefore it had a MOPSC of 12 when used for single-pilot operations. If it remained in that configuration, the operator would have had to have fitted a TAWS to the aircraft by December 2022 and, by December 2024, operated the aircraft under CASR Part 121 (which imposed additional requirements, including 2 pilots for all flights). Given that context, it is likely that an operator in this situation would have chosen to modify such an aircraft so that its MOPSC was 9 or less. Consequently, even if the changes to the TAWS requirements had been introduced in Australia earlier, they probably would not have resulted in an aircraft such as VH-OZO being fitted with a TAWS.

In terms of other comparable countries, only Canada has introduced a requirement for piston-engine aeroplanes with a passenger seating capacity of 6–9 seats to be fitted with a TAWS. However, it is noted that Canada generally experiences more adverse weather conditions than most areas of Australia.

In summary, there was no requirement for VH-OZO to be fitted with a TAWS, and piston-engine aeroplanes with a passenger seating capacity of 6–9 seats were not required to have a TAWS in most comparable countries. Accordingly, it would probably have been difficult to justify mandating that such aeroplanes be fitted with a TAWS in Australia.

Nevertheless, the lessons from the VH-OZO accident (and many previous accidents) are clear: all operators conducting passenger transport operations under the IFR in aircraft that do not currently have a TAWS should recognise the substantial benefits of a TAWS, and be actively seeking to install a TAWS in their aircraft to maximise the safety of their operations.

Use of the GNS 430W terrain awareness function

Although not developed to the same standard and with the same functionality as a TAWS, the Garmin GNS 430W units fitted to VH-OZO had a terrain awareness function that was capable of providing visual pop-up terrain alerts. If the function was selected on, then the system should have displayed a terrain alert to the pilot within the last 30 seconds of the flight (and potentially longer).

However, the terrain awareness function could be inhibited by a pilot, in which case no terrain alerts would be displayed. It could not be determined whether the function was selected or inhibited during the approaches at Lockhart River.

Given the pilot had significant experience using GPS units with a terrain awareness function, it would be expected that they were aware of the function and had seen terrain alerts in the past. However, the investigation could not determine how the pilot normally used the function (that is, whether they normally had it selected on or inhibited).  

The Garmin 400W Series Pilot’s Guide & Reference manual explicitly stated that the system’s terrain awareness function was to be used for supplemental awareness only and was not to be relied upon for terrain avoidance. Nevertheless, although not as effective as a TAWS, the terrain awareness function could still be a valuable tool during instrument approaches in IMC if an operator (and its pilots) had clearly-defined procedures, training and guidance on how to effectively and safely use the function.

For example, an operator could require its pilots to confirm that the function was selected on as part of the descent checklist (particularly when conducting an instrument approach). However, the operator of VH-OZO did not have any explicit procedures or guidance, and this was similar to other operators who used the same type of equipment.

Vertical guidance information

At the time of the accident, the approaches available to the pilot at Lockhart River were RNAV GNSS approaches available for runways 12 and 30, and an NDB approach for runway 30. These were non-precision approaches that did not provide vertical guidance to pilots.

More advanced GPS/navigational systems than the GNS 430W, such as that fitted to the aircraft in which the pilot conducted their most recent IPC, can provide vertical guidance to aid in maintaining the correct vertical profile for a non-precision RNAV GNSS approach.  

Vertical guidance information (showing the aircraft’s vertical position during the approach) would have significantly assisted the pilot in maintaining awareness of the aircraft’s vertical position and would have provided a salient indication that the aircraft was dangerously low for an extended period. Having vertical guidance available would also have reduced the pilot’s workload, such as reducing the extent of the mental calculations required to ascertain the aircraft’s position versus altitude and any necessary corrections to the descent rate.

There was no requirement for VH-OZO to be fitted a GPS/navigational system that provided vertical guidance information. However, in the absence of a TAWS, such a system could have significantly reduced the risk of CFIT during instrument approaches.

Monitoring of line operations

The pilot generally conducted instrument approaches in a manner that was consistent with the chief pilot’s preferred method. However, the approaches were also conducted at speeds significantly higher than the operator’s preferred speed. Although they were having regular discussions with the pilot about their flights, the chief pilot had no awareness that this was occurring.

One means of identifying potential problems with the conduct of line operations is through regular proficiency checks. The pilot had not received an operator proficiency check (OPC) since being checked to line in October 2018, and the chief pilot (or the designated flight examiner who could conduct OPCs) had also not flown with the pilot since that time. The pilot had completed an IPC in August 2019, although with a flight examiner who was not familiar with the operator’s procedures and in a different aircraft, with different navigational equipment, than the operator used.   

At the time of the accident, there was no specific regulatory requirement for most charter operators to conduct OPCs on their pilots (though pilots conducting IFR operations still needed to undertake an IPC every 12 months). However, as of December 2021, such operators needed to conduct OPCs (or flight crew member proficiency checks) every 6 months.

It is acknowledged that OPCs will not necessarily identify all problems, and pilots may sometimes perform differently when being observed compared to when they are not being observed. However, such checks provide a valuable opportunity for identifying potential misunderstandings regarding the operator’s expectations about how key aspects of flight operations should be conducted.

Another option now readily available to small operators is the use of GPS-based flight data, either through an electronic flight bag application (EFB) or via other sources. Such data may only include some basic flight parameters, which is not as useful as a flight data recorder or other device specifically designed for monitoring flight operations. However, it could still assist with evaluating some aspects of flight operations, including the way instrument approaches are conducted.

Reviewing recorded GPS-based flight data would require a chief pilot or other designated person to be aware of the limitations of the data, and the process would be best done cooperatively with pilots. Nevertheless, the process would not require significant resources and, if done on a regular basis, could help identify potential misunderstandings regarding the operator’s expectations and also provide useful feedback and learning opportunities for pilots.

Hazard awareness training

As stated by the FSF, another useful mitigator for reducing the risk of CFITs is hazard awareness training. The operator had not developed any hazard awareness training material relating to CFIT, and it would be difficult for a small operator to develop a detailed and tailored training program. Nevertheless, various resources from the FSF could be selected and used to provide some guidance information to pilots, together with focussed discussions regarding flight profiles and stabilised approach criteria.

Summary

Ideally, in order to minimise the risk of CFIT, operators conducting passenger transport operations under the IFR would use aircraft fitted with a TAWS and/or have a GPS/navigational system that provides vertical guidance during a non-precision instrument approach. However, without such equipment being a regulatory requirement, it would be difficult for some operators to justify the cost, including in cases where they are leasing the aircraft from another organisation (as was the case with Air Connect Australia).

Nevertheless, there are other means available for such operators to minimise CFIT risk. In this case, the operator had included stabilised approach criteria and flight profiles in its operations manual, and it encouraged the use of stabilised approaches. However, there were problems with the applicable height for the criteria (that is, not 1,000 in IMC) and the flight profile for straight-in approaches did not fully reflect the operator’s requirements or preferences. The operator had also not developed clear procedures and guidance for the use of the terrain awareness function in the aircraft’s 430W GPS/navigational units, and had not conducted regular OPCs or other checks of line operations. Overall, improving these procedural controls would have reduced the operator’s CFIT risk and probably reduced the likelihood of this particular accident.

It is likely that many of these limitations will also exist in other small operators conducting passenger transport operations in small aircraft. Accordingly, this accident has provided many important lessons to such operators regarding ways they can minimise their CFIT risk during IFR operations. These are summarised in the Executive summary.

Findings

From the evidence available, the following findings are made with respect to the controlled flight into terrain involving a Cessna 404 aircraft, registered VH-OZO, which occurred near Lockhart River Airport, Queensland, on 11 March 2020.

Contributing factors

• While the pilot was operating in the vicinity of Lockhart River Airport, there were areas of cloud and rain that significantly reduced visibility and increased the risk of controlled flight into terrain. In particular, the aircraft probably entered areas of significantly reduced visibility during the second approach.
• After an area navigation (RNAV) global satellite system (GNSS) approach to runway 30 and missed approach, the pilot immediately conducted another approach to the same runway that was on a similar gradient to the recommended descent profile but displaced about 1,000 ft below that profile. While continuing on this descent profile, the aircraft descended below a segment minimum safe altitude and the minimum descent altitude, then kept descending until the collision with terrain about 6 km before the runway threshold.
• Although the exact reasons for the aircraft being significantly below the recommended descent profile and the continued descent below the minimum descent altitude could not be determined, it was evident that the pilot did not effectively monitor the aircraft’s altitude and descent rate for an extended period.
• When passing the final approach fix (FAF), the aircraft’s lateral position was at about full-scale deflection on the course deviation indicator (CDI), and it then exceeded full-scale deflection for an extended period. In accordance with the operator’s stabilised approach procedures, a missed approach should have been conducted if the aircraft exceeded half full-scale deflection at the FAF, however a missed approach was not conducted.
• The pilot was probably experiencing a very high workload during periods of the second approach. In addition to the normal high workload associated with a single pilot hand flying an approach in instrument meteorological conditions, the pilot’s workload was elevated due to conducting an immediate entry into the second approach, conducting the approach in a different manner to their normal method, the need to correct lateral tracking deviations throughout the approach, and higher than appropriate speeds in the final approach segment.
• The aircraft was not fitted with a terrain avoidance and warning system (TAWS). Such a system would have provided visual and aural alerts to the pilot of the approaching terrain for an extended period, reducing the risk of controlled flight into terrain.
• Although the aircraft was fitted with a GPS/navigational system suitable for an area navigation (RNAV) global satellite system (GNSS) approach and other non-precision approaches, it was not fitted with a system that provided vertical guidance information, which would have explicitly indicated that the aircraft was well below the recommended descent profile.
• Although the operator had specified a flight profile for a straight-in approaches and stabilised approach criteria in its operations manual, and encouraged the use of stabilised approaches, there were limitations with the design of these procedures. In addition, there were limitations with other risk controls for minimising the risk of controlled flight into terrain (CFIT), including no procedures or guidance for the use of the terrain awareness function on the aircraft’s GNS 430W GPS/navigational units and limited monitoring of the conduct of line operations. (Safety Issue)

Other factors that increased risk

• Although an applicable height of 1,000 ft for stabilised approach criteria in instrument meteorological conditions has been widely recommended by organisations such as the International Civil Aviation Organization for over 20 years, the Civil Aviation Safety Authority had not provided formal guidance information to Australian operators regarding the content of stabilised approach criteria. (Safety issue)
• The Australian requirements for installing a terrain avoidance and warning system (TAWS) were less than those of other comparable countries for some types of small aeroplanes conducting air transport operations, and the requirements were not consistent with International Civil Aviation Organization (ICAO) standards and recommended practices. More specifically, although there was a TAWS requirement in Australia for turbine-engine aeroplanes carrying 10 or more passengers under the instrument flight rules: 
  • There was no requirement for piston-engine aeroplanes to be fitted with a TAWS, even though this was an ICAO standard for such aeroplanes authorised to carry 10 or more passengers, and this standard had been adopted as a requirement in many comparable countries.
  • There was no requirement for turbine-engine aeroplanes authorised to carry 6–9 passengers to be fitted with a TAWS, even though this had been an ICAO recommended practice since 2007, and this recommended practice had been adopted as a requirement in many comparable countries. (Safety Issue)

Other findings

• The forecast weather at Lockhart River for the time of the aircraft’s arrival required the pilot to plan for 60 minutes holding or diversion to an alternate aerodrome. The aircraft had sufficient fuel for that purpose; and the aircraft had sufficient fuel to conduct the flight from Cairns to Lockhart River and return, with additional fuel for holding on both sectors if required.
• There was no evidence of any organisational or commercial pressure to conduct the flight to Lockhart River or to complete the flight once to commenced.
• Based on the available evidence, it is very unlikely that the pilot was incapacitated or impaired during the flight.
• There was no evidence of any aircraft system or mechanical anomalies that would have directly influenced the accident. However, as a consequence of extensive aircraft damage, it was not possible to be conclusive about the aircraft’s serviceability.
• The aircraft was fitted with Garmin GNS 430W GPS/navigational units that could be configured to provide visual (but not aural) terrain alerts. However, it could not be determined whether the terrain awareness function was selected on during the accident flight.

Safety issues and actions

Operator’s risk controls to mitigate CFIT risk

Safety issue number: AO-2020-017-SI-01

Safety issue description: Although the operator had specified a flight profile for a straight-in approaches and stabilised approach criteria in its operations manual, and encouraged the use of stabilised approaches, there were limitations with the design of these procedures. In addition, there were limitations with other risk controls for minimising the risk of controlled flight into terrain (CFIT), including no procedures or guidance for the use of the terrain awareness function on the aircraft’s GNS 430W GPS/navigational units, and limited monitoring of the conduct of line operations.

Regulatory requirements for TAWS

Safety issue number: AO-2020-017-SI-02

Safety issue description: The Australian requirements for installing a terrain avoidance and warning system (TAWS) were less than those of other comparable countries for some types of small aeroplanes conducting air transport operations, and the requirements were not consistent with International Civil Aviation Organization (ICAO) standards and recommended practices. More specifically, although there was a TAWS requirement in Australia for turbine-engine aeroplanes carrying 10 or more passengers under the instrument flight rules:

• There was no requirement for piston-engine aeroplanes to be fitted with a TAWS, even though this was an ICAO standard for such aeroplanes authorised to carry 10 or more passengers, and this standard had been adopted as a requirement in many comparable countries.
• There was no requirement for turbine-engine aeroplanes authorised to carry 6–9 passengers to be fitted with a TAWS, even though this had been an ICAO recommended practice since 2007, and this recommended practice had been adopted as a requirement in many comparable countries.

Regulatory guidance for stabilised approach criteria

Safety issue number: AO-2020-017-SI-03

Safety issue description: Although an applicable height of 1,000 ft for stabilised approach criteria in instrument meteorological conditions has been widely recommended by organisations such as the International Civil Aviation Organization for over 20 years, the Civil Aviation Safety Authority had not provided formal guidance information to Australian operators regarding the content of stabilised approach criteria.

Safety action not associated with an identified safety issue

Additional safety action by Aerotrack

The owner of Aerotrack has made a change to the tool to ensure compliance with Civil Aviation Safety Regulation 61.875. As a result, only instrument flight rules (IFR) flights with over 1 hour IFR flight time were included in the calculation of recency, and decimals were not included in the calculation.

Additional safety action regarding instrument approach types

A barometric vertical navigation (Baro-VNAV) approach with vertical guidance (APVs) enables a suitably-equipped aircraft’s systems to compute and display a vertical guidance path. Accordingly, they are a 3D instrument approach. Airservices Australia has been implementing Baro-VNAV APV approaches since 2016. After the accident (in December 2020), a Baro-VNAV approach was implemented at Lockhart River (and several other airports in Australia). However, this type of approach requires the aircraft to have a flight management system and VH-OZO was not equipped to conduct a Baro-VNAV approach.

Additional safety action regarding recurrent proficiency checks

On 2 December 2021, CASR Part 135 (Australian air transport operations – smaller aeroplanes) commenced. Air transport operations included passenger transport operations, regardless of whether they were scheduled or charter operations.

It included a requirement for operators to conduct proficiency checks on pilots, with the requirements for such checks to be specified in the Manual of Standards (MOS). The MOS for Part 135 defined a flight crew member proficiency check as:

… an assessment, conducted by an aeroplane’s operator in accordance with the operator’s exposition, of whether a person is competent to safely carry out the person’s duties as a flight crew member in the aeroplane, which relates to the matters mentioned in subsection 12.05(2).

Standard 12.08 stated:

(3) The flight crew member must successfully undertake the operator’s flight crew member proficiency check, for the relevant type or class of aeroplane, as follows:

(a) for a flight crew member only conducting a flight under the VFR by day — subject to subsections (4) and (5), initially 6 months after first commencing unsupervised line operations for the operator, and then at intervals of 1 year after the previous proficiency check;

(b) otherwise — subject to subsections (4) and (5), initially 6 months after first commencing unsupervised line operations for the operator, and then at intervals of 6 months after the previous proficiency check.

For the 1-year requirement, the check could be done within 90 days of the required date and for the 6-months requirement the check could be done within 30 days of the required date.

The matters specified in 12.05(2) were:

(a) training in the duties and responsibilities for the flight crew member’s position;

(b) training in the standard operating procedures for the type or class of aeroplane used for the flight;

(c) training in the normal, non-normal and emergency procedures for an aeroplane of that type or class;

(d) training in any flight procedures or manoeuvres, conducted in an aeroplane of that type or class, for which the operator holds an approval under regulation 91.045, or 135.020, of CASR;

Note: Examples of approvals issued under regulation 91.045, or 135.020, of CASR include approvals to conduct low visibility operations and flights using certain PBN navigation specifications.

(e) training in the procedures for any other operations conducted by the operator in an aeroplane of that type or class that the flight crew member has not previously experienced, for example, precision runway monitor operations or land and hold short operations.

Glossary

ADS-B              Automatic dependent surveillance-broadcast

AFRU               Aerodrome frequency response unit

AGL                  Above ground level

AIP                   Aviation information publication

AOC                 Air operator’s certificate

APV                 Approach with vertical guidance

ATC                  Air traffic control

AWIS                Automated weather information service

AWS                 Automatic weather station

BARS               Basic aviation risk standard (a Flight Safety Foundation program)

BoM                 Bureau of Meteorology

CASA               Civil Aviation Safety Authority

CASR               Civil Aviation Safety Regulations

CDI                   Course deviation indicator

CFIT                 Controlled flight into terrain

CTAF                Common traffic advisory frequency

DETRESFA       Distress phase

EFB                  Electronic flight bag

EST                  Eastern Standard Time

ETA                  Estimated time of arrival

FAF                  Final approach fix

FLTA                Forward looking terrain avoidance (a function of the Garmin GNS 430W unit)

FMS                 Flight management system

FSF                  Flight Safety Foundation

GAF                 Graphical area forecast

GNSS               Global navigation satellite system

GPS                 Global positioning system

GPWS              Ground proximity warning system

GPWT               Grid point wind and temperature chart

HF                    High frequency

IAF                   Initial approach fix

ICAO                International Civil Aviation Organization

IF                     Intermediate fix

IFR                   Instrument flight rules

ILS                   Instrument landing system

IMC                  Instrument meteorological conditions

INCERFA          Uncertainty phase

IPC                   Instrument proficiency check

JRCC                Joint Rescue Coordination Centre

LCD                  Liquid crystal display

LNAV                Lateral navigation

MAPt                Missed approach point

MDA                 Minimum descent altitude

METAR             Meteorological aerodrome report

MOPSC            Maximum operational passenger seat configuration

NAIPS              National Aeronautical information Processing System

NM                   Nautical miles

NOTAM             Notice to airmen

NPRM               Notice of proposed rule making

OPC                 Operator proficiency check

PDA                 Premature descent alert (a function of the Garmin GNS 430W unit)

PLB                  Personal locator beacon

POH                 Pilot’s operating handbook

QNH                 That pressure setting which, when placed on the pressure setting sub‑scale of a sensitive altimeter of an aircraft located at the reference point of an aerodrome, will cause the altimeter to indicate the vertical displacement of the reference point above mean sea level.

RAIM                Receiver autonomous integrity monitoring

RNAV               Area navigation

RNP                 Required navigation performance

SIGMET            Significant meteorological information

SMS                 Safety management system

SPFIB               Specific pre-flight information bulletin

TAF                  Aerodrome forecast

TAWS               Terrain avoidance and warning system

VFR                  Visual flight rules

VHF                  Very high frequency

VMC                 Visual meteorological conditions

VNAV               Vertical navigation

V_ref                   Reference landing speed

VSI                   Vertical speed indicator

Sources and submissions

Sources of information

The sources of information during the investigation included the:

• operator/chief pilot of Air Connect Australia
• aircraft owner and maintainer for VH-OZO
• GPS unit manufacturer (Garmin)
• Civil Aviation Safety Authority
• Queensland Police Service
• Airservices Australia
• Bureau of Meteorology
• OzRunways flight data.

References

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Federal Aviation Administration (2012) Instrument flying handbook, FAA-H-8083-15B

Flight Safety Foundation 2000a ‘ALAR briefing note 7.1 – Stabilized approach’, Flight Safety Digest, August-November 2000.

Flight Safety Foundation 2000b ‘ALAR briefing note 5.3 – Visual illusions’, Flight Safety Digest, August-November 2000.

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International Air Transport Association (IATA) (2018) Controlled flight into terrain accident analysis report 2008–2017 data, Montreal, Canada

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Mitchell TR (1972) Altimetry display study Part 1 – Summary report, Report No. FAA-RD-72-46 I, prepared by The Mitre Corporation for the US Department of Transportation, Federal Aviation Administration.

Orlady HW & Orlady LM (1999) Human factors in multi crew operations, Ashgate, Aldershot, UK.

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Staal MA (2004) Stress, cognition, and human performance: A literature review and conceptual framework, National Aeronautics and Space Administration Technical Memorandum NASA/TM-2004-212824.

Vlasblom JID, Pennings HJM, Van der Pal J and Oprins EAPB (2020) ‘Competence retention in safety-critical professions: A systematic literature review’, Educational Research Review, 30:10.1016.

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Submissions

Under section 26 of the Transport Safety Investigation Act 2003, the ATSB may provide a draft report, on a confidential basis, to any person whom the ATSB considers appropriate. That section allows a person receiving a draft report to make submissions to the ATSB about the draft report.

A draft of this report was provided to the following directly involved parties:

• the aircraft operator
• the aircraft owner/maintainer
• the Civil Aviation Safety Authority
• Airservices Australia
• Bureau of Meteorology
• Aerotrack
• United States National Transportation Safety Board
• the aircraft manufacturer
• Garmin.

Submissions were received from:

• the aircraft operator
• the Civil Aviation Safety Authority
• Bureau of Meteorology
• Garmin.

The submissions were reviewed and, where considered appropriate, the text of the report was amended accordingly.

Appendices

Appendix A – Research and guidance regarding design of altimeters

Civil Aviation Order (CAO) 20.18 (Aircraft equipment — basic operational requirements) required that aeroplanes engaged in passenger charter operations under the instrument flight rules (IFR) be equipped with 2 sensitive pressure altimeters. As already noted in Aircraft instruments, VH‑OZO was fitted with two 3-pointer altimeters that met this requirement.

A series of research studies have compared the effectiveness different types of altimeter display. In summarising the research from 1960 to 1972 for the United States Federal Aviation Administration (FAA), Shrager (1972) concluded:

3. Comparative laboratory, simulator, and flight tests of 3P [3-pointer], DP [drum-pointer], CP counter-pointer], and CDP [counter drum pointer] altimeter displays[76] indicate that the least preferred was the 3P and the most desirable was the CDP by subject opinion. This order of ranking is most pronounced when the subjects used were pilots as opposed to nonpilots. The subjective display preference was further accentuated when random dynamic changes in altitude and secondary tasks were introduced into the experiment.

4. The 3P display required the longest time to interpret and produced the largest number of errors among all the production-type displays evaluated. The misreading errors included both those of l,000- and 10,000-foot altitudes. The experimental test results have been supported by significant actual flight experiences on the part of both the military and commercial aviation.[77]

5. A majority of the air carriers and the military have or are converting to displays other than the 3P. The principal display selected has been the CDP.

6. The most prevalent type of altimeter display in general aviation is the 3P. The 10,000-foot error of the 3P display has not been supported by significant actual flight experience by general aviation. However, the 1,000-foot error is a problem in the 3P display.

As part of a related research program, Hoekstra and others (1972) reviewed civil and military accidents during 1964–1970. They noted that problems with misreading an altimeter were cited in a small number of accident investigation reports. For the examples provided, where the type of altimeter was stated or otherwise known, the majority involved 3-pointer altimeters. This study also conducted a survey of various organisations. Its conclusions included:

1. Official investigations have cited altimetry as a causal factor in approximately 1% of all accidents; considering accidents of unknown causes and those where altimetry could possibly have been a factor, it is estimated that altimetry contributes to a maximum of 3% of all accidents. This estimate includes mechanical malfunctions and human errors.

2. Ten to twenty percent of all accidents are "altitude-related" as they involve altitude displacement for some reason.

3. "Altitude-related" accidents occur more frequently in conditions where it is difficult to see the terrain, i.e., at night and in restricted visibility.

4. The majority of "altitude-related" accidents occur during the landing approach. Most are without benefit of vertical guidance from any source other than the altimeter and pilot visual contact with the terrain.

5. Although a few accidents occurred in landing approaches where precision aids were used, they were characterized by a deviation from the glide path after the pilot gained visual contact.

6. Survey comments indicated that the three-pointer altimeter is susceptible to frequent misreading by 1,000 or 10,000 feet, but the number of accidents known to have been caused or possibly could have been caused, by this type of misreading was small. However, several incidents of misreading were reported.

7. Small improvements in the accident rate could be achieved by improving altimetry display, static/pitot systems and setting procedures, but greater improvement would result from the provision of more precision aids and visual warning systems in the ground environment.

A report summarising the FAA research program (Mitchell 1972) concluded that retrofitting of aircraft was not justified. However, it recommended that an advisory circular should be distributed, suggesting that all 3-pointer and drum-pointer altimeters be replaced with counter-drum pointer altimeters where feasible, and that counter-drum pointer altimeters should be required for all yet-to-be-constructed transport category aircraft and more expensive general aviation aircraft.

In 1991, the Flight Safety Foundation launched a campaign to reduce the number of controlled flight into terrain (CFIT) accidents and, together with other organisations, it formed a task force. As part of its work, the FSF CFIT task force made 8 recommendations to the International Civil Aviation Organization (ICAO), including a warning against the use of 3-pointer and drum-pointer altimeters.

ICAO Annex 6 (Operation of Aircraft) Part I (International Commercial Air Transport – Aeroplanes) paragraph 6.9.1 required that aeroplanes operated in accordance with IFR (for commercial air transport) be equipped with 2 sensitive pressure altimeters. Since 1998, it also required that these altimeters have ‘counter drum-pointer or equivalent presentation’. A note under this requirement stated that 3-pointer or drum-pointer altimeters did not satisfy this requirement.[78]

All modern transport aircraft are equipped with vertical altimeter displays or, for some older transport aircraft, counter-drum pointer altimeters. However, 3-pointer altimeters are still very common in general aviation aircraft, including small aeroplanes used for passenger transport activities.

Several experienced pilots interviewed by the ATSB during the investigation reported that misreading a 3-pointer altimeter is more commonly seen in pilots undergoing initial instrument training.

Appendix B – Vacuum system analysis

System overview

VH-OZO had 2 artificial horizon (attitude indicator) instruments and one directional gyro instrument that were powered through hoses connected to a common manifold with 2 sources of power from a vacuum pump on each engine, controlled by in-line regulators. An analogue suction indicator (vacuum gauge) located on the lower left pilot-side instrument panel showed the pilot the net amount of suction at the manifold and ‘dolls eye’ indicators showed if each vacuum pump was operating or not.  

Maintenance history

Both artificial horizon instruments and directional gyro instrument as well as vacuum regulators were not subject to service life or maintenance requirements, other than regulator garter filter changes that were being carried out. According to a service bulletin issued by the manufacturer of the vacuum pumps, the vanes could be inspected through a wear indicator port and it recommended the pump be replaced at the wear limit.  

The left vacuum pump had been in service for about 1,076 hours and the right for about 911 hours, which exceeded the life of the previous pumps (711 hours and 880 hours respectively). The previous pumps were replaced due to failing in service rather than due to wear. Inspection of pump wear through a port was not carried out consistently by the aircraft maintainer and it is unlikely it was conducted at the previous periodic inspection.

The ATSB identified that the vacuum system manifold had not been tested in the previous 5 years or replaced in the previous 10 years, as specified by the component manufacturer. This was due to an oversight in the maintenance tracking system that was subsequently rectified. A search of the aircraft logbooks did not identify any recorded replacement of the manifold and markings that might indicate component life were indistinct. 

Pilots and engineers can carry out an informal test of the manifold by alternating the engine that is started (and/or shut down) first and verifying that either vacuum pump by itself can maintain adequate supply. This was not noted at the recent 100-hour inspection and it is not known if the pilot routinely monitored the operation of each vacuum pump at engine start or shutdown. Damage sustained in the accident prevented functional testing and examination of the internal condition of the manifold.           

Although the vacuum manifold was outside its specified service life and its condition could not be verified, if there was an age-related defect there was no effect on aircraft operation unless one of the vacuum pumps failed.

Post-accident inspection

Both vacuum pumps were recovered from the aircraft after the accident and examined.

The right vacuum pump showed evidence of casing deformation and damage consistent with a heavy impact sustained during the accident sequence. When the right vacuum pump was removed from the engine the drive shaft was observed to have sheared. An accurate wear measurement could not be ascertained due to internal damage within the unit. Inspection of the internal components indicated that the pump vanes were intact, and the carbon block had fractured. The support pin had also failed in overload. Inspection of the frangible drive shaft showed damage indicative of overload. Further examination of the frangible shaft fracture surface under a microscope did not identify any features indicative of surface-to-surface rotation contact that may be possible when the engine is running and the pump is seized. Post-accident examination concluded that it was highly likely the pump failed due to the impact with terrain. 

The left vacuum pump showed no sign of external damage and the drive shaft was intact. The pump did not show any signs of accident damage. An accurate wear measurement could not be conducted because the pump did not have an inspection port. Inspection of the internal components indicated that the pump vanes and carbon block were intact. The pump internal components were rotated and observed to work as designed. There were no pre- or post-impact defects identified within the left vacuum pump that would make it incapable of supplying pressure as required.

The left artificial horizon instrument and directional guidance instrument were recovered from the aircraft after the accident, disassembled and examined. The left artificial horizon instrument was significantly damaged, however detailed examination of the components did not identify any pre-impact defects. Rotational scoring was noted between the rotor, the casing and the end cap with metal transfer evident (Figure 22). This indicates that the rotor was rotating with significant speed, highly likely produced by suction from the vacuum pump(s), when the aircraft impacted with terrain.

Figure 22: Left artificial horizon internal components showing rotational contact damage

Source: ATSB

The directional gyro instrument was significantly damaged, with detailed examination producing no identified pre-impact defects with the components that were available for inspection. There was evidence of rotational scoring on the rotor case end and the rotor end. There was no scoring evidence in the rotor case. The rotational scoring indicates that the directional gyro was rotating at significant speed, highly likely produced by suction from the vacuum pump(s), when the aircraft impacted with terrain.

Appendix C – Detailed 1-minute weather data Lockhart River 0850–0930

Appendix D – Guidance to industry regarding stabilised approaches

Overview

This appendix provides examples of guidance provided regarding stabilised approach criteria for flight operations in addition to that provided by the Flight Safety Foundation.

Transport Canada guidance

Transport Canada’s Advisory Circular AC700-028 (Vertical path control on non-precision approaches, issued 2013) was applicable to all flight crew and types of operations. It was issued in 2013, at the same time that NAV CANADA introduced non-precision approach (NPA) charts with constant descent angles. In terms of stabilised approaches, the AC stated:

Many air operators require their crews to use a stabilized approach technique which is entirely different from that envisaged in the original NPA procedure design. A stabilized approach is calculated to achieve a constant rate of descent at an approximate 3° flight path angle; with stable airspeed, power setting, and attitude; and with the aircraft configured for landing. The safety benefits derived from a stabilized final approach have been recognized by many organizations including ICAO, the Federal Aviation Administration, and Transport Canada Civil Aviation (TCCA). Those air operators not already doing so are encouraged to incorporate stabilized approach criteria into their Standard Operating Procedures (SOPs) and training syllabi.

With regard to reference points for stabilised approach criteria, the AC stated:

Stabilized approach criteria should be defined for all approaches and may include:

1. that flights shall be stabilized by no lower than 1,000 feet (ft.) above the threshold when in instrument meteorological conditions (IMC);
2. that all flights shall be stabilized by no lower than 500 ft. above the threshold;
3. that the flight remain stabilized until landing
4. that if an approach is not stabilized in accordance with these requirements, or has become destabilized afterwards, a go-around is required.[79]

The AC also provided detailed comments regarding step-down versus constant descent angle approach techniques. It noted that step-down techniques were inherently unstable and resulted in higher workload. They also resulted in inconsistent rates of descent and at times high rates of descent, and also extended periods with the aircraft flown at minimum safe altitudes. In contrast, constant descent angle approaches were inherently stable and associated with lighter workload.

In 2015, Transport Canada also issued a Civil Aviation Safety Alert 2015-04 (Stabilized approach) for all commercial air operators (including airline, commuter, air taxi and aerial work). It reiterated the key points of the AC, and noted that:

Rushed and unstabilized approaches remain a significant factor in Controlled Flight Into Terrain (CFIT) and other Approach-and-Landing Accidents (ALA). The safety benefits derived from a stabilized final approach have been recognized by many organizations including ICAO, the FAA, EASA and TCCA. These benefits include:

• Increased flight crew situational awareness;
• More time and attention for monitoring ATC communications, weather conditions and systems operation;
• More time and attention for flight path and energy monitoring;
• Defined flight parameter deviation limits and minimum stabilization heights to support the decision to land or to go-around; and,
• Landing performance consistent with expected performance values.

It also stated:

Stabilized approach criteria should be defined for all approaches and should include that:

• Approaches be stabilized by no lower than 1,000 feet (ft) above aerodrome elevation (AAE) when in instrument meteorological conditions (IMC);
• All approaches be stabilized by no lower than 500 ft AAE in visual meteorological conditions (VMC);
• A call be made upon reaching 1000 ft AAE in IMC or 500 ft AAE in VMC as to whether the approach is stabilized or not;
• The approach remain stabilized until landing;
• If an approach is not stabilized in accordance with these requirements, or has become destabilized afterwards, a go-around is required.

Federal Aviation Administration guidance

The United States Federal Aviation Administration issued guidance for general aviation pilots regarding CFIT in Advisory Circular AC 61-134 (General aviation controlled flight into terrain awareness), issued in 2003. The background section stated:

According to FAA information, general aviation CFIT accidents account for 17 percent of all general aviation fatalities. More than half of these CFIT accidents occurred during IMC…

Because a single-piloted, small GA aircraft is vulnerable to the same CFIT risks as a crewed aircraft but with only one pilot to perform all of the flight and decision-making duties, that pilot must be better prepared to avoid a CFIT type accident…

Under a section regarding GA operations in IMC on an IFR flight, the AC stated:

These operations also pose special risks. Whether it is failure to follow safe takeoff and departure techniques, recommended en route procedures ― which includes loss of situational awareness ― or failure to maneuver safely to a landing, IFR operations can be dangerous for those not prepared to operate or not current and proficient in the IMC and IFR environments. Many of these accidents result in fatalities. Techniques or suggestions for avoiding some of these IFR risk factors include…

s. The importance of flying a stabilized approach. A common definition of a stabilized approach is maintaining a stable speed, descent rate, vertical flightpath, and configuration throughout the final segment of the approach. Although originally designed for turbojet aircraft, a stabilized approach is also recommended for propeller-driven aircraft. The idea is to reduce pilot workload and aircraft configuration changes during the critical final approach segment of an approach. The goal is to have the aircraft in the proper landing configuration, at the proper approach speed, and on the proper flightpath before descending below the minimum stabilized approach height. The following are recommended minimum stabilized approach heights.

(1) 500 feet above the airport elevation during VFR weather conditions.

(2) MDA or 500 feet above airport elevation, whichever is lower, for a circling approach.

(3) 1,000 feet above the airport or touch down zone elevation during IMC.

In 2011, the United States Federal Aviation Administration (FAA) issued AC 120-108 (Continuous descent final approach), providing guidance for operators on the continuous descent final approach technique for NPAs. The AC was intended for airline and air taxi operators, though it noted the guidance was beneficial to all operators. The background section stated:

Controlled flight into terrain (CFIT) is a primary cause of worldwide commercial aviation fatal accidents. Unstabilized approaches are a key contributor to CFIT events. Present NPAs are designed with and without stepdown fixes in the final approach segment. Stepdowns flown without a constant descent will require multiple thrust, pitch, and altitude adjustments inside the final approach fix (FAF). These adjustments increase pilot workload and potential errors during a critical phase of flight. NPAs designed without stepdown fixes in the final segment allow pilots to immediately descend to the MDA after crossing the FAF. In both cases, the aircraft remains at the MDA until descending for the runway or reaching the missed approach point (MAP). This practice, commonly referred to as “dive and drive,” can result in extended level flight as low as 250 feet above the ground in instrument meteorological conditions (IMC) and shallow or steep final approaches.

In terms of stabilised approaches, the AC 120-08 stated:

A stabilized approach is a key feature to a safe approach and landing. Operators are encouraged by the FAA and the International Civil Aviation Organization (ICAO) to use the stabilized approach concept to help eliminate CFIT. The stabilized approach concept is characterized by maintaining a stable approach speed, descent rate, vertical flightpath, and configuration to the landing touchdown point. Depart the FAF configured for landing and on the proper approach speed, power setting, and flightpath before descending below the minimum stabilized approach height; e.g., 1,000 feet above the airport elevation and at a rate of descent no greater than 1,000 feet per minute (fpm), unless specifically briefed. (Refer to AC120-71.)

The FAA also issued guidance regarding stabilised approaches in AC 91-79A (Mitigating the risks of a runway overrun upon landing), issued in 2014 and last updated in 2018. The intended audience was all pilots, flight crew and operators. The AC stated in part:

Stabilized on Profile. The airplane should be stabilized on profile before descending through the 1,000-ft window or through the 500 ft above touchdown zone elevation (TDZE) window in visual meteorological conditions (VMC). Configuration, trim, speed, and glidepath should be at or near the optimum parameters early in the approach to avoid distractions and conflicts as the airplane nears the threshold window. The electronic or visual glidepath or an optimum glidepath angle of 3 degrees should be established and maintained…

Indicated Airspeed. Indicated airspeed should be not more than VREF + 5 or the POH published approach airspeed, with appropriate adjustments for wind or other factors, and never less than V_REF or the appropriate airspeed in order to avoid the loss of aircraft control.

United States Aircraft Owners and Pilots Association

The United States Aircraft Owners and Pilots Association (AOPA) stated in a 2000 article (The stabilized approach):

Most of us don’t have to worry about the vagaries of turbine aircraft and their response to power and speed changes on approach. But there are plenty of good reasons to fly stabilized approaches regardless of whether you fly a Cessna Skyhawk or Golden Eagle, Beech King Air or Piper Super Cub. Here are a few:

• It reduces workload…
• It gives us more opportunity to see the big picture…
• It slows the aircraft down earlier, allowing more time to think…
• It allows more time to react...
• It makes it easier to fly the VOR, ILS, or ADF needles...
• It allows the pilot more opportunity to detect changes in the wind on approach…
• It reduces the variables and thus reduces our required reactions to these changes. When you have the airspeed nailed early, you have one less variable to worry about, freeing you to focus on other things. If we can set the power and mostly forget it, we don't have to constantly change power in response to our configuration and speed changes.
• It creates the time to finish your before-landing checklist and to really look around the airplane for other things you might have missed or neglected when rushed...
• It makes the approach—and thus the landing spot—predictable because you do it the same every time.

Notice that time is the major benefit when we fly a stabilized approach. Time allows us to more easily perceive changes and then make corrections to course, altitude, or airplane management.

Most airlines set the stabilized approach point at 500 feet in visual conditions and 1,000 feet when the weather is IMC. These 500- and 1,000-foot target points might be a good starting place when establishing your own stabilized approach minimums. You might also want to use 1,000 feet for night approaches and landings because the fewer visual cues at night reduce your ability to perceive differences and changes.

Appendix E – Aurukun incident flight – 22 January 2020

Introduction

On 22 January 2020, on a flight from Weipa to Aurukun, the pilot conducted 2 RNAV (GNSS) approaches to runway 34 at Aurukun in VH-OZO, with the first approach followed by a missed approach.

An extract of the relevant Airservices Australia approach chart is depicted in Figure 23. As indicated in the chart, the recommended initial approach altitude was 1,800 ft, with the recommended 3° approach profile to the runway threshold commencing just prior to the final approach fix (FAF). The minimum descent altitude (MDA) for a pilot with an actual QNH was 450 ft.

The ATSB analysed OzRunways GPS data from the 2 approaches and the missed approach (Figure 24). The data was recorded at 5-second intervals. Recorded altitude, lateral position and groundspeed data for the 2 approaches from the initial approach fix (IAF) to the missed approach point (MAPt) is shown in Figure 25.

The recorded altitudes were slightly below the recommended approach profile during the 2 approaches. Aurukun Airport has an elevation of about 30 ft above sea level, and one of the passengers recalled observing the altimeter reading 50–100 ft when the aircraft was on the ground after landing. This indicated the QNH set on the altimeter may not have accurately reflected the actual QNH when the aircraft landed,[80] and the altimeter may have been slightly overreading during the approaches. In addition, the recorded altitude data was truncated to the nearest 100 ft.

Figure 23: Extract of the Aurukun RNAV (GNSS) RWY 34 approach

Source: Airservices Australia, annotated by the ATSB

Figure 24: VH-OZO recorded data 22 January 2020 at Aurukun, Queensland

Source: Google Earth overlaid with OzRunways data, annotated by the ATSB

First approach

The data showed that the aircraft approached from the north and about 1,100 ft and overflew the runway 34 threshold before continuing to track south. After passing about 3 NM west of the initial approach fix (IAF) AURSB at 1,500 ft, the aircraft turned 180° then passed 1 NM to the west of the IAF and then tracked direct towards the intermediate fix (IF) AURSI at 1,500 ft. About 1 NM prior to AURSI, the aircraft climbed to 1,700 ft and passed over the IF.

The aircraft was at 1,600 ft when it reached the FAF AURSF, and it then commenced the descent on about a 3° profile (Figure 25). The aircraft was about 200–300 ft below the recommended 3° descent profile when it reached the MDA, about 1.8 NM prior to the MAPt AURSM. The minimum recorded altitude the aircraft descended to (1 data point) was 200 ft when 1.2 NM prior to the MAPt, and it was at a recorded altitude of 200–300 ft over 4 data points (15–20 seconds) prior to reaching the MAPt.

Figure 25: Recorded data for 2 RNAV approaches to Aurukun 22 January 2020

Source: ATSB

The descent rate from the FAF (recorded height 1,600 ft) until the aircraft reached 900 ft was about 650 ft/min, and the descent rate for the remainder of the descent was about 1,050 ft/min.

A review of wind and temperature forecast and analysis charts from multiple sources and other information indicated that the indicated airspeeds would have been about 5 kt higher than the recorded groundspeeds during the 2 approaches while the aircraft was on or near the intermediate/final approach track. Therefore, on the first approach the indicated airspeed was about 140 kt when the aircraft passed the FAF, about 145 kt when the aircraft passed through the MDA and about 140 kt when the aircraft reached a height of 300 ft above aerodrome elevation.

Missed approach

A missed approach was commenced prior to the MAPt, with the aircraft climbing and passing 0.2 NM to the right of the MAPt. The aircraft passed over the Aurukun township at an altitude of about 800 ft, then turned left and heading south, climbing to 1,900 ft.

The published missed approach commenced at AURSM and required the aircraft to maintain runway direction for 3 NM before turning left to heading 170° and climbing to 1,700 ft. Based on witness reports, it is possible that the pilot was avoiding a nearby thunderstorm during the missed approach and/or was in visual conditions at the time.

The exact reasons for the missed approach could not be determined (that is, whether it was due only to reduced visibility of the runway at the time or also due to the aircraft’s speed not meeting the operator’s stabilised approach criteria at 300 ft above aerodrome elevation).

Second approach

The aircraft then headed south to about 8 NM south-south west of AURSB, before turning back to the IAF and then doing a holding pattern before again approaching the IAF. The pilot then commenced a second RNAV approach about 31 minutes after the first approach from an altitude of about 1,900 ft. The aircraft was close to the published descent profile throughout the approach and also within the required lateral tolerances.  

Given the indicated airspeeds were about 5 kt higher than the recorded groundspeeds, the indicated airspeeds were 135 kt at the FAF and 105 kt at 300 ft above aerodrome elevation. Overall, the approach appeared to comply with the operator’s stabilised approach criteria.

Appendix F – R­elated occurrences

Collision with Terrain involving Fairchild Metro 23 aircraft, VH-TFU, 11 km north-west of Lockhart River Airport, Queensland, on 7 May 2005

On 7 May 2005, a Fairchild Aircraft Inc. SA227-DC Metro 23 turbo-prop aircraft, registered VH-TFU, with 2 pilots and 13 passengers, was being operated on an instrument flight rules (IFR) regular public transport service from Bamaga to Cairns, with an intermediate stop at Lockhart River, Queensland. At 1143:39 local time, the aircraft impacted terrain 11 km north-west of the Lockhart River Airport. At the time of the accident, the crew was conducting an area navigation global navigation satellite system (RNAV GNSS) non-precision approach to runway 12. The occupants were fatally injured and the aircraft was destroyed.

The accident was almost certainly the result of a controlled flight into terrain. Weather conditions in the Lockhart River area were poor and necessitated the conduct of an instrument approach procedure for an intended landing at the aerodrome. The cloud base was probably between 500 ft and 1,000 ft above mean sea level and the terrain to the west of the aerodrome, beneath the runway 12 RNAV GNSS approach, was probably obscured by cloud.

The investigated identified a significant number of contributing factors and other safety factors associated with the crew’s performance, local conditions, the operator’s procedures and regulatory oversight. With relevance to the findings of the 2020 accident involving VH-OZO, these included the aircraft descending below the segment minimum safe altitude for the aircraft’s position on the approach (after passing the final approach fix) and the speeds and descent rate exceeding those appropriate for a stabilised approach. The operator’s procedures did not provide clear guidance on approach speeds, when to select aircraft configuration changes during an approach and clear criteria for a stabilised approach. There were also problems with the operator’s processes for supervising the standard of flight operations, and the operator did not have a structured process for managing safety-related risks.

The aircraft was fitted with a ground proximity warning system (GPWS), but there would have been insufficient time for the crew to effectively respond to the GPWS alert and warnings that were probably annunciated during the final 5 seconds prior to impact with terrain. The aircraft was not fitted with a terrain avoidance and warning system (TAWS).

The GPS unit fitted to the aircraft (Garmin GPS 155XL) also had several limitations compared with more recent models available at the time. These included the limited usefulness of the moving map display because of the vertical size of the screen size, the lack of an option to display a distance to the missed approach point (MAPt) throughout the approach, and the lack of any form of vertical advisory guidance.

Additional CFIT investigations in Australia

The ATSB has investigated a number of other CFIT accidents in Australia, all involving aircraft that were not fitted with a TAWS. These included the following occurrences.

ATSB occurrence 200105769

On 10 December 2001, a Raytheon Beech 200C Super King Air was being operated under the IFR to Mt Gambier, South Australia, on an aeromedical flight with the pilot and a medical crew member on board. At approximately 2333 local time, the pilot reported to air traffic control that they were in the circuit at Mt Gambier and would report after landing. At approximately 2336, the aircraft impacted the ground at a position 3.1 NM from the threshold of the runway. The pilot was fatally injured and the medical crew member sustained serious injuries.

Dark night conditions existed in the area. The available evidence indicated that the pilot was conducting a GPS arrival procedure.

ATSB occurrence 200302172

On 15 May 2003, a Raytheon Beech 200C Super King Air was being operated under the IFR to Coffs Harbour, New South Wales, on an aeromedical flight with a pilot, 2 medical crew and a patient on board. The pilot conducted a missed approach from a low height and the aircraft impacted the sea, or a reef, approximately 3.2 NM north of the airport at about 0833 local time. During the missed approach, the aircraft narrowly avoided a breakwater and an adjacent restaurant. During the subsequent landing the aircraft was substantially damaged.

The pilot was conducting a GPS non-precision approach. Instrument meteorological conditions (IMC) existed at the time, including heavy rain and restricted visibility.

ATSB occurrence 200402797

On 28 July 2004, a Piper PA-31T Cheyenne, with one pilot and 5 passengers, was being operated on a private IFR flight from Bankstown, New South Wales, to Benalla, Victoria. The aircraft collided with terrain 18 NM south-east of Benalla. All occupants were fatally injured and the aircraft was destroyed.

IMC existed at the time and the pilot had reported commencing a GPS non-precision approach to Benalla.

ATSB occurrence 200503265

On 28 July 2004, a Piper PA31-350 Navajo Chieftain was being operated under the IFR to Mount Hotham, Victoria on a passenger charter flight with the pilot and 2 passengers on board. The aircraft collided with terrain 5 km south-east of the aerodrome and to the left of the extended centreline of runway. All occupants were fatally injured and the aircraft was destroyed.

IMC existed at the time and the pilot had reported commencing an RNAV GNSS approach.

Appendix G – Flight Safety Foundation CFIT Checklist

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2022 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

On 9 February 2020, a Qantas Boeing 787-9 was conducting a flight from London Heathrow Airport, Greater London, United Kingdom to Perth Airport, Australia. During rotation, the pilots received a tail strike caution message and returned for landing at London Heathrow Airport. 

The United Kingdom Air Accident Investigation Branch (AAIB) is conducting an investigation into this occurrence. As Australia is the State of Registration of the aircraft, the AAIB has requested an Accredited Representative from the Australian Transport Safety Bureau (ATSB) be appointed.

To facilitate this request, the ATSB initiated an external investigation under the provisions of the Transport Safety Investigation Act 2003.

The UK AAIB is responsible for and will administer the release of the final investigation report into this incident.

Any enquiries relating to the investigation should be directed to the AAIB at: www.aaib.gov.uk 

Safety summary

What happened

At about 0438 local time on 29 February 2020, in darkness and clear visibility, the inbound fishing vessel Sandgroper collided with the outbound self-discharging bulk carrier Accolade II, off the entrance to Port Adelaide, South Australia. The collision occurred within port limits shortly after Accolade II had exited the Port Adelaide channel and resulted in significant structural damage to Sandgroper and minor damage to Accolade II. There were no injuries reported on either vessel.

What the ATSB found

The ATSB found that a proper lookout using all available means was not being maintained on board either vessel in the time leading up to the collision. Consequently, neither vessel was aware of the risk of the collision posed by the other until shortly before the collision when it was too late to take effective avoiding action.

Accolade II’s bridge team did not have a complete appreciation of the traffic situation and of the risk of collision outside the port channel before the ship exited the channel. In particular, effective use was not made of radar and a dedicated look-out was not posted in darkness.

Sandgroper’s skipper initially sighted Accolade II while the ship was still in the channel. However, a proper look-out was not subsequently maintained using all available means, including radar and radio. As a result, Sandgroper's skipper was not aware that Accolade II had exited the port channel and a close quarters situation with the ship was developing. While Sandgroper was not equipped with, nor required to be equipped with, an automatic identification system (AIS) transceiver, had one been fitted, it would have improved the vessel's detectability. That in turn would have increased the chances that the vessel was detected by Accolade II’s bridge team in sufficient time to avoid collision.

What has been done as a result

Following this incident Sandgroper was fitted with an AIS transceiver.

Accolade II’s managers (Inco Ships) advised that a navigational audit of the ship’s operations was conducted, which resulted in several recommendations to improve the ship’s bridge resource management practices.

Safety message

The safety of fishers and people in small boats continues to be of concern to the ATSB as collisions between trading ships and small vessels on the Australian coast continue to occur. Safety investigations into such collisions have consistently shown that the keeping of a proper lookout by all available means, including radar, radio and AIS, in accordance with the collision regulations could have prevented most of these collisions.

The occurrence

At about 1100 Central Daylight-saving Time^[1] on 28 February, Sandgroper (Figure 1) departed its fishing grounds off Kangaroo Island, South Australia and began making its way back to North Arm Marina in Port Adelaide. The vessel was crewed by a skipper and two uncertificated crew (deckhands). The crew had been fishing at sea for the previous week when a hydraulic equipment malfunction resulted in the decision to return to port.

Figure 1: Sandgroper

Source: Ashworth Maritime Services

At 0226 on the morning of 29 February, Sandgroper was about 13 nautical miles (miles)^[2] south‑west of Port Adelaide’s southern breakwater (Figure 2), on a heading^[3] of about 020°, with steering in autopilot mode and a speed of about 5-6 knots. The skipper was on watch in the wheelhouse with the deckhands resting. At about 0300, the skipper handed over the watch to one of the deckhands in order to get some rest. The skipper instructed the deckhand to follow the course plotted on the chart plotter and to wake them if there were any concerns or when arriving at a nominated point marked on the chart plotter near Port Adelaide’s port limits. The skipper then lay down to rest on the wheelhouse bunk, aft of the conning position. Both the vessel’s very high frequency (VHF) radio units were set to maintain a listening watch on VHF channel 16.^[4]

Meanwhile, Accolade II was alongside at Adelaide Brighton Cement’s K-Berth in Port Adelaide Inner Harbour. The ship was engaged in discharging a cargo of limestone loaded earlier that day at Klein Point, South Australia.

Figure 2: Section of chart Aus 781 showing key locations and vessel tracks

Source: Australian Hydrographic Office, annotated by the ATSB using electronically recorded data

At about 0230, Accolade II’s first engineer woke the chief mate and provided 1-hours’ notice for the ship’s planned departure at 0330 for Klein Point. The chief mate went up to the ship’s navigation bridge (bridge) to complete the bridge pre-departure checklist. The checklist included checking that the ship’s radar^[5] was on, testing that the ship’s whistle was operational and testing engine and steering gear controls. The checks also included confirming that one VHF radio was set to the port’s working channel (VHF channel 12), and that the ship’s planned departure time of 0330 was reported to the Flinders Ports Communications Tower (communications tower).^[6]

At 0255, the chief mate woke the chief integrated rating (IR)^[7] and shortly after, the master. By about 0310, the master had made his way to the bridge where he met the chief mate who was on his way down to deal with cargo paperwork and read the ship’s draughts. At 0320, cargo discharge was completed, and the ship’s departure draught recorded as 3.77 m forward and 4.97 m aft.

At 0327, the master contacted the communications tower on VHF radio and reported that the ship was departing its berth. The ship’s forward mooring station were manned by the chief mate and an IR while the aft mooring station was manned by the chief IR and another IR. By 0329, all mooring lines were cast off and, by 0339, the ship had completed its swing to the north and commenced its outbound passage to Klein Point through the Port Adelaide Inner and Outer Harbours. The crew at the mooring stations were stood down and the chief IR went up to the bridge to assume helmsman duties. The chief mate went back to the accommodation to finalise cargo-related paperwork while the other IRs attended to routine post-departure tasks on deck.

At about the time Accolade II was casting off, Sandgroper was about 6.8 miles south-west of Port Adelaide’s southern breakwater. The fishing vessel was on autopilot, still on a heading of about 020° and a speed of about 5-6 knots, with a deckhand on watch and the skipper resting.

By 0356, Accolade II was passing the reporting point at beacon number 39 in the Port Adelaide River at a speed of about 8.9 knots. The master reported passing beacon number 39 to the communications tower on VHF channel 12 and continued the ship’s passage with the helmsman steering.

At about 0415, Sandgroper’s deckhand sighted a red light off the port bow and, shortly after, woke the skipper. The deckhand handed over the watch including reporting the sighting of the red light on the vessel’s port bow. The deckhand then left the wheelhouse to rest while the skipper made a coffee.

At about 0420, Sandgroper entered Port Adelaide’s port limits. The weather at the time was fine, with light winds, calm seas, good visibility and no moon. The skipper checked the reported red light and assessed it to be the port sidelight of an outbound ship in the channel. He then identified the ship on the radar display, which was set on a range scale of 3 miles. The skipper assumed the ship would stay in the channel, and at about 0426 or very shortly after, altered Sandgroper’s course to starboard to stay out of the channel and avoid giving the impression of heading for the channel and thereby impeding the ship’s progress. The skipper then reduced the radar display range scale from 3 miles to 0.125 miles as the vessel progressed towards the port’s breakwater.

At about 0428, as Accolade II was approaching Port Adelaide’s southern breakwater, the chief mate arrived on the ship’s bridge. At about 0433, the ship’s course was altered to port and it exited the channel between beacons number 13 and 15 at a speed of about 9.1 knots. The master contacted the communications tower and reported that the ship was ‘…departing at beacon 13.’ The master then instructed the helmsman to change the ship’s steering from manual to autopilot. The helmsman changed the steering to autopilot and turned off two of the ship’s four steering motors, which was the usual practice for the sea passage.

Meanwhile, the chief mate increased the range scale of Accolade II’s radar display from 0.75 miles to 3 miles and selected the ‘Off Center’ function to provide for the maximum view on the display ahead of the ship. Accolade II’s radar immediately detected Sandgroper. The fishing vessel’s radar echo immediately began to paint on the ship’s radar display about 1.2 miles off Accolade II’s starboard bow, but the chief mate did not notice it.

At about 0434, the chief mate used the radar to select and display the automatic identification system (AIS)^[8] target data of two vessels off the ship’s port bow. At about the same time, the master dismissed the helmsman who then left the bridge with a radio. At about 0435, the chief mate answered a call on the bridge telephone. The call lasted about a minute before the chief mate went back to familiarising himself with the navigational situation and adjusting bridge equipment, such as dimming lights, in preparation for taking over the watch from the master.

The collision

Just after 0436, the chief mate, who was standing by the steering console on the ship’s centreline, sighted a red light fine off the ship’s starboard bow. The chief mate crossed to the starboard side of the bridge, got a pair of binoculars to better observe the sighted light and moved to the port side of the bridge to avoid a visual blind sector created by the ship’s bucket elevator on deck. Meanwhile, the master, who was also alerted to the red light, crossed to the port side of the bridge to get another pair of binoculars and returned to the centreline. Both officers then recalled seeing both red and green sidelights of the vessel. By this time, Sandgroper was about 0.5 miles from the ship.

Just over a minute later, at 0437, Accolade II’s radar range scale was reduced from 3 to 1.5 miles. By this time, Sandgroper had closed to about 0.25 miles and the master instructed the chief mate to ‘…go more south…’. The chief mate switched over to manual steering and applied 15° of port rudder helm as the master repeated his instructions to go further south. The master went out on to the starboard bridge wing and their instructions to ‘...go more south…’ became increasingly urgent. The chief mate then applied full port rudder as the ship slowly began turning to port at a speed of about 9.4 knots. The chief mate also attempted to sound the ship’s whistle without success.

Meanwhile, on board Sandgroper, the skipper unexpectedly saw Accolade II’s green sidelight at very close range. The skipper quickly put the vessel’s propulsion full astern, but this had little effect. Shortly after 0438, Sandgroper collided with Accolade II’s starboard side, just forward of midships (Figure 3).

Figure 3: Sections of charts Aus 130 and Aus 138 showing sequence of the collision

Source: Australian Hydrographic Office, annotated by the ATSB using electronically recorded data

At about 0439, the master tried unsuccessfully to call Sandgroper on VHF channel 12. Meanwhile, the chief mate recalled the IR to the ship’s bridge and handed over the helm. The chief mate then issued helm orders to steady the ship’s heading to avoid close quarters situations with the two vessels on the ship’s port side. At about 0440, the master reported the collision to the port’s communications tower.

Shortly after, Sandgroper’s skipper called Accolade II on VHF channel 16. The masters of the two vessels then switched over to VHF channel 13 and exchanged details, confirmed that there were no injuries to anyone on either vessel and that neither vessel required assistance. Accolade II’s master then reported the collision to the ship manager by phone and, having assessed there was no significant damage, resumed the ship’s passage to Klein Point.

Sandgroper’s skipper telephoned the vessel’s manager to report the collision and was advised to resume its passage. By about 0830 that morning, Sandgroper was safely alongside at North Arm Marina.

Sandgroper sustained significant structural damage to the starboard bow (Figure 4) with some minor damage to the vessel’s port side as well. Additionally, Sandgroper’s anchor was lost from the vessel’s bow and was found lodged in Accolade II’s deck railings.

Figure 4: Damage to Sandgroper

Source: Australian Maritime Safety Authority and Inco Ships

Accolade II sustained relatively minor damage to deck structures and railings on the ship’s starboard side as a result of the collision (Figure 5).

Figure 5: Damage to Accolade II

Source: Inco Ships

__________

1. Central Daylight-saving Time (CDT): Coordinated Universal Time (UTC) + 10.5 hours.
2. A nautical mile is 1,852 m.
3. The direction of the bow of a vessel expressed in degrees, either magnetic or true. Sandgroper’s headings in this report are in degrees by magnetic compass while Accolade II’s headings are in degrees by gyro compass.
4. VHF channel 16 (156.800 MHz) is the international distress, safety and calling frequency. All VHF-equipped vessels are required to maintain a continuous listening watch on this frequency at sea.).
5. Accolade II was appropriately equipped with a single radar in accordance with the provisions of the relevant SOLAS regulations in force at that time of its construction
6. The Flinders Ports Communications Tower’s call sign was ‘Adelaide Outer Harbour’.
7. Integrated ratings are qualified to perform the duties of both an able seaman and an engine rating.
8. The automatic identification system (AIS) is a very high frequency (VHF) radio broadcasting system which enables AIS equipped vessels and shore-based stations to send and receive identifying information. See the section titled Automatic identification system for further information.

Context

Accolade II

Accolade II is a 108 m, self-unloading bulk carrier of 6,310 gross tonnage, built in 1982 by Carrington Slipways, Newcastle, New South Wales. The ship was owned by Adelaide Brighton Cement and, at the time of the collision, was managed and operated by Inco Ships. Accolade II was designed and built for the carriage of limestone from quarries at Klein Point, South Australia, across the Gulf St. Vincent, to Adelaide Brighton Cement’s facilities at Birkenhead, situated within Port Adelaide’s inner harbour.

Equipment and machinery

Accolade II was a Regulated Australian Vessel (RAV). RAVs are commercial vessels which operate (or can be operated) outside the Australian exclusive economic zone. RAVs are subject to the Navigation Act 2012 and are generally required to comply with the requirements of international conventions as given effect by the Australian Maritime Safety Authority’s (AMSA) marine orders.^[9]Accolade II was equipped with the navigational and safety equipment required by the International Convention for the Safety of Life at Sea (SOLAS)^[10] for a ship of its size and age.

The ship’s navigation equipment included a single radar, automatic identification system (AIS), gyrocompass, differential GPS and a bridge navigational watch alarm system.^[11]Accolade II was also fitted with a Japan Radio Company (JRC) JCY 1850 simplified voyage data recorder (VDR).^[12] The ship’s primary means of navigation was paper charts although it was also fitted with a chart plotter.^[13]

The ship’s propulsion was provided by twin Fuji Diesel 6LG32X dual-fuel propulsion engines that used compressed natural gas as their main fuel, although they could also be operated with marine gas oil.

Radar

Accolade II was equipped with a single JRC JMA-5312-6 X‑Band^[14] radar with automatic radar plotting aid (ARPA) and automatic target acquisition capability as well as data input from the AIS and GPS units.

SOLAS regulations prescribed radar carriage requirements for ships based on their gross tonnage. Most modern merchant ships of Accolade II’s size were required to be equipped with two radars. However, Accolade II was subject to the provisions of SOLAS regulations that were in force at that time of its construction, which only required that ships of 1,600 gross tonnage and upwards be fitted with a single, type-approved radar. The regulations allowed for ships constructed before 1 July 2002 to be fitted with equipment which fulfilled the requirements prescribed in the relevant regulations in force prior to 2002.

Crew

Accolade II was manned and operated by a crew of nine in compliance with the ship’s AMSA‑issued minimum safe manning document. The ship’s complement included two deck watchkeeping officers—a master and a chief mate—as well as three integrated ratings, a chief engineer, two first engineers and a cook. The ship’s crews operated on a 3-week roster and most personnel had been assigned to the ship for several years. Crew changes were staggered so that different crew began their 3-week duty periods at different stages of the 3-week roster period.

The master had about 32 years of seagoing experience and held an Australian master’s (unlimited) certificate of competency. The master had worked exclusively on Accolade II for the previous 6.5 years and had joined the ship 16 days before the collision. The master’s usual rank on board was as chief mate (with over 10 years’ experience in the rank) but he had acted in the role of master several times in the past, usually for about a week at a time. In this instance, he was acting in the role of master for the last week of his 3-week roster period. The master also held a marine pilotage exemption certificate (PEC) for Port Adelaide. The PEC was endorsed for night navigation and allowed the master to navigate Accolade II in the waters of Port Adelaide’s Inner and Outer harbours at any time without the need to take on a pilot.

The chief mate had about 15 years of seagoing experience, held a Philippines master’s (unlimited) certificate of competency and the equivalent Australian certificate of recognition. The chief mate had about 8 years’ experience in the rank, had worked exclusively on Accolade II for the previous 5 years and had joined the ship 2 days before the collision. The chief mate did not hold a PEC for Port Adelaide.

Operations

Accolade II generally conducted a daily return voyage between Port Adelaide and Klein Point.

The ship’s operations routinely involved a departure from Port Adelaide in the early hours of the morning with the exact time of departure varying depending on when cargo discharge was completed. The chief mate was usually woken about an hour before completion of cargo discharge/departure with the master usually woken about half-an-hour before departure. The chief mate assisted with unmooring operations, following which the master piloted the ship out of the harbour.

On exiting the channel, the chief mate usually took over the watch for the 4-hour sea voyage to Klein Point. The master returned to the bridge when the ship was approaching Klein Point and berthed the ship with the chief mate’s assistance. Once alongside, the chief mate was stood down while the master managed cargo loading operations, which usually took about 4 hours.

The chief mate was recalled for departure and then kept the sea watch for the passage back to Port Adelaide. The master returned to the bridge and took over the watch just before the ship entered the Port Adelaide channel (near beacon number 13). The chief mate then assisted with bringing the ship alongside and with mooring operations. Once alongside, both the master and chief mate stood down while the ship’s cargo was discharged, which usually took about 8 hours.

Sandgroper

Sandgroper is a steel-hulled trawler built in 1978 in Johnsonville, Victoria. The vessel was owned by Pescatore Di Mare and, at the time of the collision, managed and operated by Southern Fisheries Group. The vessel operated out of the Government-owned North Arm Marina, a commercial fishing harbour located in a narrow channel off the Port Adelaide river, south of Torrens Island.

At the time of the collision, Sandgroper was a class 3B domestic commercial vessel (DCV) and was equipped with navigational and safety equipment required for an ‘existing’ class 3B DCV.^[15]

The trawler’s wheelhouse was equipped with a Furuno 1942 Mark-2 radar, GPS, echo sounder and two VHF radios, both with dual watch capability. Sandgroper was not equipped with AIS or VDR, nor was it required to be (see the section titled Automatic identification system). Additionally, the trawler was equipped with a vessel monitoring system (VMS)^[16] required by the Australian Fisheries Management Authority (AFMA).

Sandgroper was crewed and operated by a crew of three – a skipper and two uncertificated crew – in compliance with the applicable conditions in the vessel’s AMSA-issued Certificate of Operation. The skipper had over 28 years’ seagoing experience and held an Australian master’s (<24 m, near coastal) certificate of competency as well as a marine engine driver’s (Grade 3, near coastal) certificate of competency. The skipper had operated out of Port Adelaide for more than 20 years.

International regulations for preventing collisions at sea

The look-out

The International Regulations for Preventing Collisions at Sea, 1972, as amended (COLREGs) provide internationally‑agreed rules and measures to prevent collisions. The COLREGs generally apply to all vessels at sea, including fishing vessels. The COLREGs include requirements for keeping a look-out, assessing risk of collision with other vessels as well as the conduct and responsibilities of vessels in preventing collisions.

With respect to keeping a lookout, Rule 5 of the COLREGs (Look-out), states:

Every vessel shall at all times maintain a proper look-out by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions so as to make a full appraisal of the situation and of the risk of collision.

The rules required that a lookout be kept not only by sight and hearing, but by all available means including radar, AIS, and information from other sources such as port radio broadcasts and ship‑to‑ship or ship‑to‑shore calls.

The ‘prevailing circumstances and conditions’ include various factors that should be considered when keeping an effective lookout. While not explicitly identified in the rule on the look-out, many of these factors were identifiable elsewhere within the COLREGS. For example, Rule 6 (Safe speed) listed several factors that were also relevant to the keeping of a lookout. Factors relevant to keeping an effective lookout include the:

• state of visibility and time of day (day, night or twilight)
• background lights (shore lights or back scatter from own lights)
• expected traffic in the area (open sea, coastal passage, port or harbour)
• traffic density, including concentrations of fishing and other vessels
• characteristics, efficiency and limitations of radar (including its range and any interference)
• constraints imposed by the radar range scale in use.

Other relevant factors include the availability, type, capability, and limitations of the AIS units of the vessels involved, available local knowledge and information, and the availability of traffic information via radio (ship‑to‑ship calls, all ship broadcasts and schedules). A number of the factors listed above are interrelated. For example, the use of radar significantly enhances keeping a lookout, particularly during darkness or when visibility is restricted by fog, rain or other conditions.

The COLREGs made specific mention of the proper use of radar equipment to obtain early warning of the risk of collision. The regulations also warned against making assumptions based on scanty information. The keeping of a proper lookout enables the risk of collision to be assessed in sufficient time for early and appropriate action to be taken.

Navigation lights

The COLREGs also described the requirements for vessels to exhibit specific lights (navigation lights) from sunset to sunrise. These lights were generally dependent on vessel length with some additional lights required depending on the type/purpose of the vessel or under certain circumstances and conditions.

Accolade II was required to display a white masthead light forward, a second masthead light abaft of, and higher than the forward one (mandatory for vessels 50 m or more in length), sidelights, and a stern light.

Sandgroper was not engaged in fishing at the time of the collision and therefore was required to display a single masthead light, sidelights and a sternlight.

At the time of the incident, both Accolade II and Sandgroper were probably displaying the required navigation lights for power-driven vessels of their size while underway. Additionally, neither vessel was displaying other lights, such as working lights or deck lights, that could obscure or be mistaken for regulation navigation lights or otherwise be an impediment to sighting and identifying navigation lights.

Signals to attract attention

The COLREGs required that vessels carry equipment to make sound signals for manoeuvring and warning purposes as well as to attract attention. Depending on size, a vessel may be required to carry a whistle, a bell and/or a gong.^[17]

Accolade II was equipped with a pneumatic whistle fitted on the main mast. The whistle could be operated from six different locations, including from buttons on the bridge and bridge wings. Accolade II’s chief mate reported that when he attempted to sound the ship’s whistle to attract Sandgroper’s attention before the collision, he probably did not hold the button down long enough for it to sound. Accolade II was also equipped with an Aldis lamp^[18] that was not used to attract attention because of the lack of available time.

Sandgroper was equipped with a manually operated horn. However, no attempt was made to use it, probably due to the rapid sequence and unexpected nature of the collision.

Accolade II’s look-out

Accolade II’s safety management system (SMS) included procedures for the navigation and operation of the ship. The procedures stated that the collision regulations as well as other international and local regulations relating to safe navigation were to be strictly complied with. They also noted that the primary reference documents for the operation of the ship at sea included:

• the COLREGs
• Standards of Training, Certification and Watchkeeping for Seafarers (STCW) Code^[19]
• AMSA’s Marine Order 28 (Operations standards and procedures)^[20]
• Master’s standing orders
• Bridge Procedures Guide^[21]

Together, these documents and publications, referenced in Accolade II’s procedures, comprehensively dealt with the subject of watchkeeping and the look-out.

The STCW Code provided mandatory watchkeeping standards applicable to ‘seagoing ships’ and required that a proper lookout be maintained at all times in compliance with the COLREGs. The Code required that the lookout be able to give full attention to lookout duties and not be assigned or undertake any duties which could interfere with that task. It also clarified that the duties of a lookout and helmsperson on a ship are separate. While the Code permitted the watchkeeping officer to be the sole lookout in daylight (in good conditions), it implied that a separate, dedicated lookout was to be posted in darkness.

Accolade II’s master’s standing orders made it clear that during the hours of darkness, the minimum manning requirement for the bridge was a qualified watchkeeping officer and one integrated rating (IR) as a lookout. The orders also clarified that the lookout should not be assigned any other tasks, although they could be absent from the bridge for brief periods to perform tasks such as a fire and safety round.

The Bridge Procedures Guide is a publication that aims to reflect best practice on subjects such as passage planning and watchkeeping, including on the subject of the look-out, and is widely used internationally to support shipboard safety management systems. The guide and its content are consistent with the requirements of COLREGs and the STCW Code.

On the morning of the collision, when Accolade II departed the berth at about 0339, the ship’s bridge was manned by a watchkeeping officer (the master) and a helmsman (an IR). The pilot‑exempt master (with the helmsman steering) navigated the ship in darkness within the confines of the Port Adelaide River for about 50 minutes before the chief mate joined them on the bridge at about 0428. As such, for the duration of the ship’s passage within the harbour in darkness, there was no separate, dedicated look-out posted as required.

Once on the bridge, the chief mate performed a number of tasks to become familiar with the navigational situation in preparation for taking over the watch. While the chief mate was pre‑occupied with these tasks, the IR (helmsman) was dismissed from the bridge instead of being retained as a dedicated look-out.

Events and conditions on board Accolade II

On departure from the berth, Accolade II’s radar display was centred, north-up and in relative motion mode on a 0.75 nautical mile (mile) range scale. A variable range marker (VRM) was turned on and set to a range of 1.005 miles, but no electronic bearing line (EBL) was turned on. The radar’s heading input was sourced from the gyrocompass while speed input was from the GPS. The radar’s functionality allowed the ship’s passage plan waypoints to be input to display the ship’s planned track, but this was not used. Target vectors were set to ‘True’ for a duration of 3 minutes.^[22] The ‘Trails’ function was off. This function displays the recent history (or past track) of a target as an echo trail or afterglow, making it conspicuous while distinguishing it from inconsistent echoes, such as from sea clutter or from stationary targets such as beacons (depending on whether true motion trails or relative motion trails have been selected).^[23].

During the bridge pre-departure checks, the cursor was moved to the right of the display, over the AIS information menu item (Figure 6). The cursor’s position and other radar settings remained unchanged for Accolade II’s passage through Port Adelaide River and channel.

Figure 6: Set-up of Accolade II's radar as it exited the channel at 0433

The radar display was centred on a 0.75 mile range scale and that Sandgroper’s radar echo was not visible with these settings.

Source: Accolade II’s VDR, annotated by the ATSB 

Table 1 and Figure 7 below provide a brief sequence of the events leading up to the collision referenced against relevant radar and audio data from the ship’s VDR.^[24]

Table 1: Sequence of events referenced against Accolade II's VDR radar and audio data

Figure 7: Section of chart Aus 138 showing events leading up to collision

Note that Sandgroper’s actual track between 0426 and 0434:02 is an approximate track as there was no positional data available for the vessel between these times

Source: Australian Hydrographic Office, annotated by the ATSB using electronically recorded data

Sandgroper first appeared on Accolade II’s radar display at about 0433 (Figure 8). However, no one on the bridge detected the fishing vessel until about 3 minutes later when the chief mate sighted its port sidelight. In those 3 minutes, the chief mate was pre-occupied with tasks such as adjusting radar settings, acquiring AIS icons of vessels on the radar, dimming lights and getting accustomed to the darkness in preparation to take over the watch.

About 1 minute of the chief mate’s time was taken up attending to a phone call. Meanwhile, the master recalled concentrating on navigating the ship clear of the channel and beacons (rather than checking outside the channel for traffic, either visually or using the radar). The master may have been experiencing a degree of cognitive tunnelling, which is an inattentional blindness where one becomes overly focused on some variable other than the present environment (Mack and Rock, 1998; Most, 2010).

Figure 8: Sandgroper's first appearance on Accolade II's radar at 0434:02

The radar image at 0434:02 shows that as soon as the range scale was increased from 0.75 miles to 3 miles and the ‘Off Center’ view was selected, Sandgroper’s radar echo immediately became visible on the radar display.

Source: Accolade II’s VDR, annotated by the ATSB 

Additionally, the repetitive nature of the ship’s voyage may have induced a sense of complacency in the ship’s officers. One behavioural definition of complacency is trending behavioural variation that eventually exceeds safety boundaries (Hyten and Ludwig, 2017). This variation can be influenced by habituation. The master and chief officer had both worked on Accolade II for several years, executing the same voyage almost daily, to the point where it became a highly practiced activity.

Highly practised activities become automatic and require less attention than new or slightly practiced activities. Automatic processes occur without intention, taking place without effort. When a person is using automated processing (sometimes referred to as being on autopilot), they are sometimes ‘out of the loop’. It is recognised that to have good situational awareness, a monitoring operator needs to be ‘in the loop’, in order to notice anomalies.

Figure 9: Accolade II's radar display immediately before collision at 0438:02

Source: Accolade II’s VDR, annotated by the ATSB

Bucket elevator

The cargo system on board Accolade II comprised a single hold, two longitudinal scraper conveyors, a transverse scraper conveyor, a shuttle belt conveyor and a bucket elevator. The bucket elevator was located on the starboard side, just forward of midships. The 2 m wide elevator extended about 8.5 m above the ship’s main deck. This created a visual blind sector across the view of the sea surface as seen from the ship’s bridge (Figure 10).

SOLAS regulations required that any blind sector caused by cargo gear outside of the wheelhouse forward of the beam that obstructs the view of the sea surface as seen from the conning position, should not exceed 10°. Additionally, SOLAS stated that each individual blind sector obstructing the view of the sea surface from the conning position, forward of the bow to 10° on either side, should not exceed 5°.

Figure 10: Views from different positions on Accolade II's bridge

Source: Inco Ships, annotated by the ATSB

Figure 11: Bucket elevator visual blind sectors

Source: Inco Ships, annotated by the ATSB

The bucket elevator had been documented in several of the ship’s annual navigational audits as a known visual obstruction. As such, the blind sector created by the elevator was a known factor that the ship’s crew were aware of and one they routinely allowed for.

While Sandgroper might have been temporarily visually obscured by the bucket elevator, it did not pose a significant impediment to detecting the vessel if an effective visual lookout had been kept. The blind sector would only have affected observers near the starboard extremities of the ship’s bridge with visibility for observers elsewhere on the bridge unaffected. In any case, the bucket elevator had no effect on the performance of the ship’s radar.^[25]

Sandgroper’s look-out

Sandgroper’s SMS included procedures on passage planning and watchkeeping which stated that the COLREGs were to be complied with at all times.

Sandgroper’s skipper was alerted to the presence of Accolade II by the deckhand’s sighting of the ship’s red sidelight. The skipper assessed that the ship was in, and would remain within, the channel. Due to that expectation, the potential for collision with the ship was probably not anticipated. Sandgroper’s skipper may have been experiencing an expectation bias in expecting Accolade II to continue down the channel. Expectation bias can occur when an individual's expectations about an outcome influence the perception of one's own or others’ behaviour (Williams and others 2012).

The skipper reported that following the course alteration and reduction of the radar range scale (from 3 miles to 0.125 miles), no vessels were sighted either visually or on radar until the collision. At the reduced radar range scale, the skipper would only have been able to see radar echoes within about 230 m around the vessel. The skipper also reported that the presence of lights on the shoreline made it difficult to visually distinguish Accolade II’s navigation lights.

Sandgroper was within port limits when Accolade II’s master broadcast the message to the communications tower that the ship was exiting the channel at beacon number 13. Sandgroper’s skipper did not hear this VHF broadcast as a listening watch on channel 12 was not being maintained. Although the vessel was equipped with two VHF radio units, a listening watch was being maintained only on VHF channel 16 as was the skipper’s usual practice. The port rules did not require fishing vessels to report to the communications tower and the skipper could not recall any past communications or interaction with the tower.

Automatic identification system

The automatic identification system (AIS) is a maritime communications device that uses the VHF radio frequency band to transfer data, including a vessel’s course, speed and other dynamic and static data. The system enables AIS-equipped vessels and shore-based AIS stations to send and/or receive identification information that, in addition to the AIS unit, can be displayed on an electronic chart and compatible radar. The information received can be used to assist the watchkeeper in making a full appraisal of the situation and of the risk of collision.

The Australian Maritime Safety Authority (AMSA) is responsible for the safety of domestic commercial vessels (DCVs). Under the National Law,^[26] the National Standard for Commercial Vessels (NSCV) set out the standards for vessel survey, construction, equipment, design, operation, and crew competencies for DCVs.

The NSCV required that class 3B vessels carry an AIS Class B receiver/transmitter unit. However, ‘grandfathering’ arrangements allowed older DCVs (built before July 2013) to continue to operate under the requirements that existed before the introduction of the National Law and NSCV. As an ‘existing vessel’ built in 1978, Sandgroper was not required to have an AIS unit fitted to comply with survey requirements, and an AIS unit was not fitted on the vessel at the time of the collision.

Use of AIS for collision avoidance

The use of AIS can enhance situational awareness and can assist in target tracking. AMSA considers the use of AIS to transmit accurate data and to locate targets as a way to keep a proper lookout. AMSA also encouraged operators to help improve the detectability of their vessels by transmitting AIS data.^[27] However, it is also important to note the use of AIS cannot replace the need for a visual lookout. Additionally, AIS target tracking data should be treated with caution for collision avoidance for which radar plotting data and compass bearings of targets remain the primary assessment tools.^[28]

Fatigue

Fatigue has been defined as decreased capability to perform mental or physical work, produced as a function of inadequate sleep, circadian disruption, or time on task (Brown, 1994). Factors that contribute to fatigue-impaired work performance include:

• the duration of a duty period
• inadequate sleep
• circadian effects
• the type or nature of the task being undertaken (workload)
• the work environment.

Fatigue can have a range of effects on human performance, such as decreased short-term memory, slowed reaction time, decreased work efficiency, reduced motivational drive, increased variability in work performance, and increased errors of omission (Battelle Memorial Institute, 1998).

An AMSA safety awareness bulletin^[29] summarised fatigue among seafarers as follows:

The nature of vessel operations means seafarers are exposed to conditions which lead to fatigue. Insufficient sleep, night work, irregular and long working hours, monotonous tasks, high work demands are all frequently present in seafaring jobs. These are the primary factors that lead to fatigue. The need to manage the risk of fatigue - both at the individual and management level - is critical.

The ATSB has also highlighted the issue of fatigue through previous investigation findings and specific publications, including for the fishing vessel sector.^[30]

Accolade II

The crew on board Accolade II were required to comply with the rest hour requirements of the STCW Code (as given effect by AMSA’s Marine Order 28). The ship’s SMS included a procedure that defined fatigue, provided guidance on recognising the signs of fatigue and reflected the rest hour requirements of the STCW Code.

The SMS also required crew to record their daily hours of work and rest on board. The rest hour records for Accolade II’s master and chief mate showed that their rest hours complied with the minimum rest hour requirements of the STCW Code. While self-assessment of fatigue is not a reliable indicator of alertness, both reported feeling very alert and well rested.

The sleep environment on the ship was reportedly comfortable and hence suitable for achieving restorative rest. A review of the ship’s voyage reports for January and February 2020 showed at least two instances in each month when the ship’s sailing was delayed to ensure compliance with rest hour requirements. The reports also showed no voyage on 27 February 2020 (2 days before the collision), with the day marked as a ‘Reset day’.

FAST analysis

A roster analysis of the master and chief mate’s work and rest times was conducted using the Fatigue Avoidance Scheduling Tool (FAST) bio-mathematical model to assess fatigue/alertness, and the effect on performance.

The FAST analysis showed that while there may have been a slightly higher fatigue risk for the chief mate, overall, the analysis did not appear to show that levels of fatigue likely to influence performance were present for either the chief mate or the master. The accuracy of the analysis was influenced by the nature of the ship’s fatigue management system. The recorded hours of rest indicated rest opportunity and not the exact hours of sleep, which had to be estimated.

Sandgroper

As a DCV, Sandgroper and its crew were not subject to the minimum rest hour requirements of the STCW Code. There were no prescribed minimum hours of rest and no requirement to record hours of rest. However, AMSA’s Marine Order 504^[31] required that ‘the risk of fatigue of the master and crew’ be considered, among other factors, when determining the number of crew required to safely carry out a vessel’s operations. The AMSA website also provided guidance on managing crew fatigue on DCVs including practical information on the causes, effects and management of fatigue and its risks. Owners and masters were advised to take all practicable steps to ensure the safety of the vessel and crew, and that the crew were to be involved in the management of fatigue and the risks to safety.

Sandgroper’s SMS included some basic information on managing crew fatigue and required the skipper to manage crew fatigue. Guidance for crew stated they were to try and achieve 7–9 hours of sleep in every 24 hours.

Sandgroper’s AFMA fishing logs showed that the crew usually shot their fishing gear from about 0230-0430 and hauled the gear between 0930-1330 with rest opportunity obtained in between these times. This meant there was a total of about 18 hours of rest opportunity in every 24-hour period.

On the night before the collision, the skipper reported resting from about 1700–2300 followed by taking the watch until about 0300. The skipper then handed the watch to the deckhand and slept for about an hour until woken shortly after 0415.

Sandgroper’s skipper self-reported feeling ‘…well rested as far as a fisherman gets rest’ and alert. The skipper reported consuming at least one cup of coffee after waking that morning.

FAST analysis

The accuracy of the FAST analysis for Sandgroper’s skipper was influenced by the absence of recorded hours of work and rest, and no reliable record of sleep obtained in the days preceding the collision. The analysis was conducted based on estimates of sleep obtained and the AFMA fishing logs. Overall, the analysis did not appear to show that levels of fatigue likely to influence performance were present for the skipper.

Summary

Based on the available evidence, it was considered unlikely that levels of fatigue likely to influence performance were experienced by either vessel’s crew. However, there were several relevant risk factors present that were conducive to an environment in which fatigue could develop or that could have increased the chances of crew being fatigued.

Port Adelaide

Port Adelaide is the main port of South Australia handling a range of cargo including grains and seeds, limestone, containers, dry and wet bulk, vehicles, and general cargo. The port was owned and operated by Flinders Ports which was formed in 2001 when the Flinders Ports consortium successfully acquired seven ports that were privatised by the South Australian Government.

Port Adelaide port rules

Flinders Ports’ published rules for Port Adelaide that were intended to inform commercial users of the port of their responsibilities for the safe navigation of vessels within the port. The rules did not specifically define a ‘commercial user’ but, according to Flinders Ports, it did not include fishing and recreational vessels.

The rules documented three entry and exit points for the channel—at the entrance beacon, beacon number 5 and beacon number 9—depending on the vessel’s draught. Fishing vessels and recreational vessels could enter/exit the channel at any point. While Accolade II’s entry/exit point between beacons 13 and 15 was not among those listed, the ship was allowed the liberty of entering/exiting the channel at this location owing to its long history of operating in the port and its generally shallow draught.

At the time of the collision, Port Adelaide was not authorised as a Vessel Traffic Service (VTS) Authority. A VTS is established to improve the safety and efficiency of vessel traffic and to protect the environment. Ports may apply to establish a VTS when the volume of traffic or degree of risk justifies the service. Port Adelaide operated a communications tower (Flinders Ports Communications Tower) that kept a 24/7 listening watch on VHF channels 16 and 12. Channel 12 was used for ship/shore operations, information, transit advice and ship-to-ship traffic.

Flinders Ports rules required all pilots, masters and exempt masters to communicate with the tower at designated reporting points on channel 12. The rules also stated that vessels should monitor VHF channel 12 at all times in port limits for information.

Flinders Ports clarified to the ATSB that the port’s reporting requirements and the requirement to monitor the port’s working channel (channel 12) within port limits only applied to commercial vessels. As such, fishing vessels and recreational vessels were not required to report nor were the rules regarding a listening watch on channel 12 applicable to them.

Port Adelaide VTS

On 4 December 2020, about 8 months after the collision, Port Adelaide was authorised as a VTS authority with a new call sign of ‘Adelaide VTS’. Adelaide VTS was authorised to provide services, including a traffic organisation service (TOS). The TOS is a service to prevent the development of dangerous marine traffic situations and to provide for the safe and efficient movement of vessel traffic within the declared VTS area.

Adelaide VTS required all vessels over 150 gross tonnage (or where there was no gross tonnage, vessels 35 m or greater in length) to participate in the VTS. The rules required all commercial vessels to comply with VTS reporting requirements and Adelaide VTS can request any other vessel in the coverage area to participate. However, fishing and recreational vessels were generally not required to report.

While VTS rules stated that all vessels were to maintain a listening watch on VHF channels 12 when within or approaching Port Adelaide port limits, Flinders Ports advised that the rule only applies to commercial vessels. However, all vessels, including fishing and recreational vessels were encouraged to monitor the channel through the port’s safety outreach programs to educate and inform the public. The South Australian Department of Planning, Transport and Infrastructure (DPTI) also published a recreational boating safety handbook and boating safety advice, which included material on radio communication and listed channel 12 as among the channels usually used for port communications.

Rules in other ports

Local rules covering operations within port waters vary depending primarily on the port’s specific risk profile and resources. The applicability of the various rules also varies from port to port but are usually applied on the basis of factors such as vessel type, length or tonnage. Consequently, in each port, certain rules apply to vessels meeting certain defined criteria and not to others as the following examples show.

The Port of Fremantle, Western Australia, required all vessels 35 m or greater in length and all commercial vessels, regardless of length, to participate in the VTS when operating in the coverage area. It required all vessels navigating within port limits or at an anchorage within the port to maintain a continuous listening watch on the port’s working channel.

The Port of Melbourne, Victoria, required all vessels 50 m or greater in length to report at designated points/times and maintaining a continuous listening watch on the VTS working frequency. Non-recreational vessels less than 50 m in length (including fishing vessels) were required to watch the VTS working frequency and to report to VTS if 35 m or greater in length. Recreational vessels less than 50 m in length and equipped with VHF radio were required to watch the VTS working frequency when operating in port waters.

The ports of Weipa and Cairns in Queensland required all vessels, whether commercial or recreational, to maintain a listening watch on channel 16 and, if equipped, channel 12 while within the ports’ pilotage areas. Additionally, all ships greater than 24 m in length had to obtain approval from VTS before entering, leaving or manoeuvring within the pilotage area and all ships between 10 and 24 m in length were required to advise VTS before entering, leaving or manoeuvring within the port’s pilotage area.

The Port of Darwin, Northern Territory, although not serviced by a VTS, required all vessels of 20 m or greater in length, vessels carrying more than 12 passengers and certain other vessels to participate in the port’s traffic organisation service. Other vessels were encouraged to participate voluntarily.

As evident from the examples above, port rules and their applicability vary depending on various factors and there was nothing unusual in the content or applicability of Port Adelaide’s rules.

Similar occurrences

Over the last 30 years, at least 68 collisions between trading ships and small vessels have been reported to the ATSB or its predecessor. Of these, at least 40 have been investigated. The failure to keep a proper and effective lookout and/or take early and effective avoiding action in accordance with the COLREGs were recurrent contributing factors that could have prevented most of these collisions.

Collisions between large trading ships and small vessels, particularly fishing vessels, continue to occur off the Australian coast. In these collisions, a fishing vessel, being significantly smaller than a ship, almost always comes off worse and sometimes with severe consequences. For example, the 2000 collision between Star Sea Bridge and the fishing vessel Sue M, off Evans Head, New South Wales, and the 2003 collision between Asian Nova and the fishing vessel Sassenach off Townsville, Queensland, both resulted in the loss of life and of the vessels themselves.

While the measures in place to prevent such collisions might appear straightforward, the recurrence of similar contributing factors indicates that further effort is required from operators and crews to implement these measures. In addition to its safety investigation reports into collisions, the ATSB has published a number of safety bulletins to highlight collision risks and educate all seafarers. These documents and other safety information about marine safety issues are available on the ATSB website.

__________

9. Marine Orders, also described as regulatory instruments or legislative regulations, are legal instruments made by AMSA pursuant to powers under Commonwealth legislation.
10. The International Convention for the safety of Life at Sea, 1974, as amended.
11. A mandatory system, the bridge navigational watch alarm system (BNWAS) automatically alerts the master or another qualified officer if the officer of the watch becomes incapable of performing the officer of the watch’s duties for any reason such as falling asleep or becoming otherwise incapacitated.
12. A voyage data recorder is designed to collect and store data from various shipboard systems in compliance with SOLAS requirements. A simplified voyage data recorder is similar to a voyage data recorder but does not store the same level of detailed data.
13. A device used in marine navigation that integrates GPS data with an electronic navigational chart. It displays the electronic chart along with the position, heading and speed of the ship.
14. An x-band radar operates at a frequency of about 10 GHz and its fine resolution makes it useful for collision avoidance.
15. An ‘existing’ vessel is essentially one that was constructed or, for construction of which design approval was lodged or approved, before 1 July 2013. For a more detailed definition of an ‘existing’ vessel, see Section 22 of Marine Order 503 (Certificates of survey — national law) 2018.
16. The vessel monitoring system (VMS) includes cameras and other equipment to monitor the position, course and speed of a vessel.
17. A whistle means any signalling appliance capable of producing the required signals and is generally used by vessels to make manoeuvring and warning signals and to attract attention. The bell and gong are used to warn of vessels at anchor and vessels aground.
18. A hand-held electrically operated signal lamp.
19. International Maritime Organisation, The International Convention on Standards of Training, Certification and Watchkeeping for Seafarers 1978, as amended, IMO, London.
20. Marine Order 28 (Operations standards and procedures) 2015 provides for the safe navigation and operation of vessels by giving effect to provisions of the STCW Convention and STCW Code.
21. International Chamber of Shipping 2016, Bridge Procedures Guide, Marisec Publications, London
22. A true vector represents the predicted true motion of a target for a specified period of time, showing course and speed with reference to the ground or sea. The direction of a true target vector indicates the true course of the target and its vector length is proportional to the target’s speed.
23. Relative motion trails depict the trails of a target relative to the own ship and therefore, if the own ship is moving, the system plots trails of fixed targets as well as moving targets. True motion trails depict the absolute motion trails of a target irrespective of the own ship’s position and therefore, do not depict trails for fixed targets.
24. The VDR saved radar images every 15 seconds. Therefore, times for some of the events or radar user-actions in this report could have occurred up to 14 seconds earlier than described.
25. The ship did have a radar blind sector radar however this was located aft of the ship, mostly likely caused by the ship’s main mast.
26. In 2013, the National System for Domestic Commercial Vessel Safety was introduced in Australia under the Marine Safety (Domestic Commercial Vessel) National Law Act 2012 (National Law).
27. Australian Maritime Safety Authority, 2020, Marine Notice 6/2020 Reducing the risk of collisions at sea, Canberra, Australia.
28. Maritime and Coastguard Agency, 2016, Marine Guidance Note (MGN) 324 (M+F), Navigation: Watchkeeping Safety – Use of VHF Radio and AIS, Southampton, United Kingdom.
29. Australian Maritime Safety Authority, 2017, Maritime Safety Awareness Bulletin, Issue 5, March 2017, Canberra, Australia.
30. Australian Transport Safety Bureau, 2004, Safety Bulletin 04 – Fatigue and fishing crews, Canberra, Australia.
31. Australian Maritime Safety Authority, 2018, Marine Order 504 (Certificates of operation and operation requirements — national law) 2018, Canberra.

Safety analysis

Introduction

At about 0438 local time on 29 February 2020, in darkness and clear visibility, the inbound fishing vessel Sandgroper collided with the outbound self-discharging bulk carrier Accolade II, within port limits, about 1.5 NM south-west of the entrance to Port Adelaide, South Australia. The collision resulted in significant structural damage to Sandgroper and minor damage to Accolade II. Neither vessel identified that a risk of collision existed with the other until it was too late for effective avoiding action to be taken.

Look-out

Accolade II

In the time leading up to the collision, both the master and chief mate were occupied with tasks demanding much of their attention. The master was focused on navigating clear of the shipping channel while the chief mate was busy with various activities, including preparation to take over from the master. There was no dedicated look-out who could devote their full attention to sighting and reporting targets, including Sandgroper. As a consequence, the master and chief mate only sighted the fishing vessel moments before the collision.

Accolade II’s radar offered an additional means of detecting Sandgroper at an early stage. However, the radar’s initially small display range scale setting did not allow for an appreciation of the situation outside the channel before the ship exited it. Further, when the scale was eventually adjusted to one more conducive to detecting Sandgroper’s presence, the chief mate focussed on the automatic identification system (AIS) icons of two other vessels displayed on the radar display at the expense of Sandgroper’s radar echo. In addition, useful radar tools such as the trails function, which could have made Sandgroper’s radar echo more conspicuous and increased the chances of the vessel being detected were not used.

In summary, Sandgroper was not detected by anyone on board Accolade II until it was too late for effective avoiding action to be taken. Had better use been made of the radar or a dedicated lookout been posted as required, it would have increased the chances of detecting Sandgroper early and allowed more time to take action to avoid collision.

Sandgroper

Sandgroper’s skipper sighted Accolade II early when it was in the channel and assumed, not unreasonably, that it would remain in the channel. On that basis, the skipper altered Sandgroper’s course to keep clear of the ship. However, the skipper then paid little attention to the ship and its movement probably due to expectation bias that the ship would follow the channel. Further, the radar range scale was reduced to the minimum and an effective visual lookout by sight was also not maintained.

While there was no explicit requirement for fishing vessels to monitor Port Adelaide’s VHF radio working channel, Sandgroper was equipped to do so. Had the skipper monitored the working channel, it might have provided forewarning that Accolade II was exiting the channel at beacon number 13 (contrary to the skipper’s assumption), and to the developing close-quarters situation.

Sandgroper’s radar and VHF radio were both available means that could have enhanced the skipper’s look-out and allowed for an improved appreciation of the situation. However, neither was used effectively to maintain a proper look-out. Consequently, Sandgroper’s skipper was not aware of the risk of collision until collision was imminent and it was too late for effective avoiding action.

Automatic identification system

Sandgroper was not fitted with an automatic identification system (AIS) transceiver unit, nor was it required to be. Had an AIS unit been fitted, it would almost certainly have improved the detectability of the fishing vessel and made it more conspicuous on Accolade II’s radar and chart plotter. The evidence in this case shows that Accolade II’s chief mate readily acquired and monitored the AIS icons of two other vessels on the radar display but not Sandgroper’s radar echo, which should have been of immediate concern.

In addition, the fitting of an AIS unit with a display on board Sandgroper would have given its skipper the means to detect Accolade II’s AIS-transmitted data thereby enhancing situational awareness and augmented the keeping of a proper look-out.

Findings

From the evidence available, the following findings are made with respect to the collision between Accolade II and Sandgroper, off Port Adelaide, South Australia, on 29 February 2020.

Contributing factors

• A proper lookout by all available means was not maintained on board Accolade II. In particular, radar was not used effectively, and the dedicated lookout required in darkness was not posted. Consequently, Accolade II's watchkeepers were not aware of Sandgroper's presence or of the risk of collision until shortly before the collision when it was too late to take effective action.
• After initially sighting Accolade II, Sandgroper’s skipper did not maintain a proper lookout or assess the risk of collision using all available means, in particular the radar and radio. As a result, the skipper only saw the ship when collision was imminent and unavoidable.

Other factors that increased risk

• Sandgroper did not have an automatic identification system (AIS) transceiver fitted, nor was one required to be fitted. An AIS transceiver would have improved the vessel's detectability and enhanced the ability of its crew to keep a proper look-out.

Other findings

• Accolade II’s bucket elevator did not pose a significant impediment to the ability of the ship’s watchkeepers to detect Sandgroper.

Safety actions

Safety action not associated with an identified safety issue

Additional safety action by Southern Fisheries Group

Southern Fisheries Group advised the ATSB of the following safety action taken in response to the collision:

• Sandgroper was fitted with an automatic identification system
• Skippers and crews were provided with education on Port Adelaide River traffic
• All crew are now required to be on watch when approaching port.

Additional safety action by Inco Ships

Accolade II’s managers (Inco Ships) advised the ATSB that, following the collision, a navigational audit was undertaken to assess the performance and effectiveness of the ship’s bridge team and bridge resource management. Inco Ships advised that the audit resulted in several recommendations to improve Accolade II’s bridge resource management practices.

Sources and submissions

Sources of information

The sources of information during the investigation included:

• the master and chief mate of Accolade II
• the skipper and deckhand of Sandgroper
• Inco Ships
• Adelaide Brighton Cement
• Southern Fisheries Group
• Australian Maritime Safety Authority
• Australian Fisheries Management Authority
• Flinders Ports
• Ashworth Maritime Services
• Lloyd’s Register.

References

Australian Maritime Safety Authority, 2017, Maritime Safety Awareness Bulletin, Issue 5, March 2017, Canberra, Australia.

Australian Maritime Safety Authority, 2018, Marine Order 504 (Certificates of operation and operation requirements — national law) 2018, Canberra.

Australian Maritime Safety Authority, 2020, Marine Notice 06/2020 Reducing the risk of collisions at sea, Canberra, Australia.

Australian Transport Safety Bureau, 2004, Safety Bulletin 04 – Fatigue and fishing crews, Canberra, Australia.

Battelle Memorial Institute. An Overview of the Scientific Literature Concerning Fatigue, Sleep, and the Circadian Cycle, 1998. (Report prepared for the Office of the Chief Scientific and Technical Advisor for Human Factors, Federal Aviation Administration, USA.).

Brown, I. D. (1994). Driver fatigue. Human Factors, 36(2), 298-314.

Hyten, C., & Ludwig, T. D. (2017). Complacency in process safety: A behavior analysis toward prevention strategies. Journal of Organizational Behavior Management, 37(3-4), 240–260.

International Maritime Organisation, Standards of Training, Certification and Watchkeeping for Seafarers (STCW) Code, 1995, as amended, IMO, London.

International Maritime Organization, 2020, The International Convention for the Safety of Life at Sea (SOLAS) 1974 as amended, IMO, London.

Mack A & Rock I 1998, Inattentional blindness, MIT Press Cambridge MA.

Maritime and Coastguard Agency, 2016, Marine Guidance Note (MGN) 324 (M+F), Navigation: Watchkeeping Safety – Use of VHF Radio and AIS, Southampton, United Kingdom.

Most SB 2010, What's "inattentional" about inattentional blindness?, Consciousness and Cognition, vol. 19, pp.1102-1104.

Williams JB, Popp, D, Kobak KA & Detke MJ 2012, The power of expectation bias, European Psychiatry, vol. 27, pp.1

Submissions

Under section 26 of the Transport Safety Investigation Act 2003, the ATSB may provide a draft report, on a confidential basis, to any person whom the ATSB considers appropriate. That section allows a person receiving a draft report to make submissions to the ATSB about the draft report.

A draft of this report was provided to the following directly involved parties:

• the master, chief mate, owner and manager of Accolade II
• the master, deckhand and manager of Sandgroper
• Australian Maritime Safety Authority (AMSA)
• Flinders Ports.

Submissions were received from AMSA and Accolade II’s managers (Inco Ships). The submissions were reviewed and, where considered appropriate, the text of the report was amended accordingly.

Glossary

Purpose of safety investigations & publishing information

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2021 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

Safety summary

What happened

On 4 February 2020, an Airbus Helicopters AS 350 B3 was being operated in support of New South Wales National Parks and Wildlife Service activities. Winching of personnel and equipment was being conducted when the operating crewman detected a technical issue with the load cable of the hoist system fitted to the helicopter. The outer strands of the cable toward its termination into the hook assembly had loosened in respect of the inner core.

During a subsequent hoist operation to restore the cable integrity, the cable fractured at the hook assembly while under load, releasing the weight bag and hook assembly to the ground. There was no damage to the helicopter or injuries to personnel.

What the ATSB found

The ATSB found that variations in the operator’s stowage practices over an extended period of winching operations led to inadequate compression of the hook assembly and subsequent wear to the load cable. The wear damage was due to vibration and movement of the hook assembly during periods of helicopter operation. This led to a significant reduction in the cross-sectional area of the cable, fatigue and fracture of the strands and an associated reduction in cable strength.

It is likely that specific post-flight inspection requirements for the Breeze Eastern rescue hoist required in the Civil Aviation Safety Authority (CASA) Airworthiness Directive AD/SUPP/10 were not being adequately completed by the operator. The inspections were targeted at minimising wear damage to the load cable by ensuring correct stowage of the hook assembly at the end of each flight.

Finally, the operator’s method of cycle counting during operation of the rescue hoist led to an accumulation of cycles that significantly exceeded the helicopter manufacturer’s recommended life-limit. That exceedance probably compounded the level of wear damage sustained to the load cable. 

What has been done as a result

The New South Wales National Parks and Wildlife Service (ParkAir) implemented a range of pro‑active safety actions since the occurrence, including:

• In July 2020, ParkAir provided Breeze-Eastern Flight Line maintenance training for all staff including pilots, maintainers and rescue hoist crewman.
• A measurement gauge is now used by crewman to determine whether the hoist has adequate compression in accordance with the pre- and post-flight requirements listed within CASA Airworthiness Directive AD/SUPP/10.
• In January 2021, a revision of the ParkAir Flight Manual Supplement was accomplished to ensure cable inspection procedures requirements are now completed in accordance with CASA Airworthiness Directive AD/SUPP/10.
• ParkAir have adopted the more conservative Airbus Helicopters method for hoist cycle counting and all hoist cables now have a 500 cycle life-limit.

Additionally, as a direct result of this occurrence and the release of ATSB’s Safety Advisory Notice SAN-2020-013-001, the following pro-active safety advice was released by organisations responsible for the design, manufacture, and regulation of helicopter rescue hoist systems:

• Breeze-Eastern Service Information Letter (SIL 14 Maintenance) Breeze-Eastern Rescue Hoist Maintenance & Flight Line Inspections for BL-29700 Series, release date 6 April 2020
• CASA Airworthiness Bulletin (AWB) 25-034 Helicopter Rescue Hoist Wire Rope – Wear, Fatigue and Failure, release date 22 April 2020
• Airbus Helicopters Safety Information Notice (SIN) 3507-S-25 Fatigue failure of a BREEZE 450 Lbs hoist cable, release date 4 June 2020
• European Aviation Safety Agency (EASA) Safety Information Bulletin (SIB) 2020-11 Helicopter Rescue Hoist Cable Failure, release date 11 June 2020.

Safety message

The ATSB advises all helicopter operators and flight crew involved in rescue hoist operations to review their current operational practices to ensure hoist operation and hook stowage are in accordance with the manufacturers’ published procedures.

In addition, it is recommended that the pre- and post-flight inspection requirements of the hook and cable assembly, along with any recurring scheduled maintenance of the hoist system are closely reviewed, to ensure that they are completed in accordance with the manufacturers’ instructions. Improper stowage of the hoist hook assembly can lead to excessive movement and accelerated wear of the cable, which if undetected, could have a fatal outcome.

Should any load cable exhibit an increased frequency of outer strand loosening requiring a condition operation, operators should be particularly mindful to check for narrowing or ‘necking’ of the cable at the ball end within the swivel hook assembly. This can signify that the cable has become damaged due to extreme wear and may no longer be safe to use.

Summary video

The occurrence

An Airbus Helicopters AS 350 B3, registered VH-UAH, was being operated by the New South Wales (NSW) National Parks and Wildlife Service (NPWS) Flight Operations Unit (ParkAir) in support of bushfire operations during the 2019/20 summer period. The helicopter had been repositioned from the ParkAir aviation base at Bankstown Airport to a NPWS depot at Bulga, NSW to provide aerial support to fire crews at the Springvalley fire-grounds, within the Blue Mountains National Park. During that period, the helicopter was operated by a single pilot and a crewman operated the rescue hoist.

On 2 February 2020, the crewman assigned to VH-UAH was exchanged with another ParkAir crewman who had mobilised to Bulga. At duty handover, the departing crewman identified that the rescue hoist was operating without issue, however the load cable was starting to exhibit loose wires and would need monitoring. Over the next two days of operation about 30 winches of personnel and equipment was conducted. During that period the replacement crewman identified that the condition of the load cable from the hoist was continuing to deteriorate.

The outer wire strands of the load cable toward its termination into the swivel hook had loosened in relation to the inner core. Such loosening can develop during repeated short-length cable deployment and retrieval cycles. The crewman reported that, in an attempt to rectify the looseness, the outer wires of the cable were massaged and manipulated as it was reeled in and wound onto the hoist drum during operation. Despite that, the looseness was unable to be rectified.

On 4 February 2020, at the conclusion of the daily operations and on return to the Bulga depot, the crewman recommended to the ParkAir senior pilot that a conditioning operation be accomplished. Cable conditioning was a specific procedure intended to tension the cable and realign the wires to restore the cable integrity. It was agreed that it would be completed the following day prior to the conduct of any further winching sorties.

On the morning of 5 February 2020, following a pre-flight inspection of the rescue hoist, the crewman and senior pilot commenced the conditioning operation. A 160 kg weighted bag was attached to the swivel hook and the helicopter was lifted into a low hover and flown to an open field adjacent the NPWS Bulga depot. The bag was suspended about 5 m above the ground and the helicopter lifted into a vertical climb at an equivalent rate as the cable was reeled out from the rescue hoist. This continued until the maximum reel out extension limits of the hoist system were reached, after which the cable was reeled in. At the conclusion of that first conditioning run the crewman identified that the cable had further degraded.

The conduct of an additional conditioning operation was agreed and during that operation while under tension and close to maximum reel out, the cable failed, releasing the weighted bag and swivel hook to the ground.

The crewman advised the pilot that the cable had failed and that the hook and bag had fallen. The pilot’s only reported perception of an anomaly was a slight tilt of the helicopter from the centre‑of‑gravity redistribution when the bag fell. Both crew members returned to the depot and recovered the bag and swivel hook for subsequent examination. There were no injuries to personnel or additional damage to the helicopter. A portion of the fractured cable and the general fitment of the rescue hoist to the AS350 helicopter is shown at Figure 1.

ParkAir immediate actions

Following the cable failure, the Chief Pilot and Senior Pilot distributed an internal notification to ParkAir staff advising of the occurrence. As an immediate measure, ParkAir contacted the hoist manufacturer and arranged for it to be examined. All further ParkAir winching operations were suspended until each system was inspected and had their cables replaced (with the exception of a single hoist that remained in service due to the recent fitment of a new load cable).

Figure 1: A NPWS ParkAir AS350 helicopter (left) displaying general fitment of the rescue hoist, and a close-up of the fractured cable (right)

The fractured cable was found protruding from the swivel hook assembly.
Source: National Parks and Wildlife Service

Context

Operational overview

The New South Wales (NSW) National Parks and Wildlife Service (NPWS) Flight Operations Unit (ParkAir) utilised a fleet of four AS350 B3 helicopters to support field operations that included fire management, personnel insertion duties, feral animal and pest species control. Each ParkAir helicopter could be equipped with an electric-powered recue hoist. A fifth hoist, also operated by ParkAir, was used as back-up in case of an unserviceability. The hoists were used for aerial winching of personnel and equipment into confined areas.

Aircraft information

VH-UAH was an Airbus Helicopters AS350-B3 light utility helicopter manufactured in 2014. It was powered by a single turbine engine and depending on its internal cabin configuration, could transport up to six people. The helicopter had been fitted with a hoist that was attached to an externally mounted mechanical arm on the left side of the helicopter, adjacent to the rear cabin (Figure 1). The arm pivoted outward during use and also allowed the hoist to be stowed against the fuselage during forward flight.

Hoist information

Manufactured by Breeze-Eastern, the rescue hoist was a model HS-29700 and provided a means for the lowering and raising of a single person or equipment to and from the helicopter (Figure 2). The hoist was remotely operated by the crewmember using a controller and the pilot was also able to control the system if necessary.

The hoist was an approved modification for the helicopter. The instructions for continued airworthiness for the hoist were contained in the:

• Breeze-Eastern Flight Line and Operations Manual^[1]
• Airbus Helicopters AS350B3 Master Servicing Manual.^[2]

The HS-29700 hoist has an allowable lifting limit of 204 kg and contains a rotating drum onto which is spooled 50 m of useable wire cable that terminates with a swivel hook and bumper assembly. The cable speed can be varied^[3] during operation and limit switches within the system automatically trigger to slow the hoist speed as the cable approaches the full-out, or full-in position. The bumper assembly near the swivel hook consists of a crushable rubber block and conical spring that is intended to compress as the cable is reeled in and the full-in limit switch is activated, stopping the hoist. Compression of the spring and bumper assembly is a design feature by the hoist manufacturer to ensure that the swivel hook is adequately homed after being reeled in.

The Breeze-Eastern maintenance manual contained the hoist operating instructions and guidance for continued airworthiness. The manual advised that when reeling in, the cable should be guided by hand, at full pendant thumbwheel deflection to the full in position. The manual provided the following cautionary statement:

WARNING: WHEN NOT IN USE, THE HOOK MUST BE HOMED COMPLETELY IN THE FULL IN POSITION TO AVOID FATIGUE OF THE CABLE NEAR THE BALL END DUE TO VIBRATION.

Hoist cable

The load cable was specified to be manufactured from 0.156-inch diameter corrosion‑resistant stainless steel into a 19-strand by 7-wire configured arrangement comprising an inner core and outer layer (Figure 2). To resist rotation during use, the outer strands were woven in the opposite direction to the inner core. A stainless-steel fitting with a spherical ball-end was swaged onto the termination of the cable to enable secure fitment of the swivel hook and bump stop assembly.

Cycle counting

The Breeze-Eastern hoist was designed with a mechanical counter that recorded each revolution of the drum. The number on the counter was required to be recorded in the hoist logbooks and a calculation provided the total number of hoist cycles accrued during each recurring maintenance period.

Breeze-Eastern used a method whereby the difference on the cycle counter between successive maintenance periods was divided by 264. One complete hoist cycle was equivalent to a full reel-out and then a full reel-in of the cable. This was equivalent to 264 revolutions of the drum being logged by the counter. The method was specific to Breeze-Eastern and did not consider the actual number of winch operations that had been completed. Breeze-Eastern recommended a 1,500‑cycle life-limit for their hoist cables. The following cautionary note was contained within the Breeze-Eastern hoist manual:

1500 hoist cycle recommended replacement criteria is under ideal laboratory conditions, and may not be representative of actual operating conditions, or usage.

Figure 2: Breeze-Eastern HS-29700 rescue hoist and cross-section of the load cable showing its 19 strand x 7 wire configuration

Source: Breeze-Eastern, annotated by ATSB

Recent maintenance

All significant inspections, including recurring maintenance, were conducted by ParkAir’s maintenance provider for the hoist. Records showed that the occurrence rescue hoist (serial number 203) was bought and first introduced into service by ParkAir in December 2011. Over the subsequent 9 years of operation, the hoist was installed onto various AS350 helicopters within the ParkAir fleet until being rotated onto VH-UAH in July 2019 where it remained in service. The hoist logbook contained cycle counter entries confirming that ParkAir had been using the Breeze‑Eastern method for recording usage of their rescue hoists.

The last recorded maintenance activity contained in the hoist logbooks was on 3 December 2019 at approximately 600 hoist cycles and indicated the accomplishment of a 3-month and 6-month repetitive inspection in accordance with the Breeze-Eastern HS-29700 maintenance manual. Along with various checks of the system for functionality, an inspection of the swivel hook assembly was indicated as complete with no recorded defects. The load cable had accrued 617 hoist cycles at the time of the cable failure.

Technical examination

Hoist cable from ParkAir AS350 B3 helicopter, VH-UAH

The rescue hoist and the fractured load cable were sent to the ATSB technical facilities in Canberra for further analysis, with senior personnel from ParkAir in attendance during the preliminary examination.

The construction of the cable confirmed it to be of the configuration and type specified by Breeze‑Eastern for the BL-29700 hoist. Measurements confirmed the cable to be of the correct diameter with a 19-strand by 7-wire arrangement. The specifications^[4] required the load cable to be manufactured from an austenitic stainless steel with a minimum breaking strength of 980 kg.

The load cable fractured approximately 10 mm from the swaged ball end fitting that terminated into the swivel hook assembly (Figure 3). The diameter of the remnant cable stub had drawn down with ‘necking’ of the cable cross-section evident. Measurements also identified that the inner core had retracted between 50 to 60 mm from the outer layer. Those outer strands had splayed which was typical of an overload cable failure, while the inner core remained tightly gathered. A faint serial number was etched on the shank of the swaged fitting that was confirmed by Breeze-Eastern to match their own records for the hoist and that the cable had been an original fitment from 2011.

Close visual examination of the cable at the point of fracture in the ‘necked’ region identified that many of the wires were grooved and scalloped (Figure 4). There was no evidence of foreign debris, external abrasion, corrosion, kinking or nicks that might otherwise explain the failure. Remnant lubricant was identified between the wires and on the swaged ball end fitting.

A scanning electron microscope (SEM) was utilised to further analyse the failed cable at much higher magnifications. The SEM examination confirmed that the severe scalloping was due to a wear mechanism of the cable near the point of fracture. The wear had progressed to an extreme level with many of the wires having lost almost the entirety of their cross-section.

A mixed fracture mode was also identified with evidence that some wires had sustained fatigue cracking prior to failure (Figure 5). The general shape of the fatigue cracking was indicative that the cable had been exposed to cyclic bending loads. A portion of the wires had also failed in ductile overstress and these were likely what provided the remnant cable strength during the final conditioning operation.

Hoist cable from ParkAir AS350 B3 helicopter, VH-ZHG

An additional hoist cable was also supplied by ParkAir for comparative examination. That cable had been removed from another Breeze-Eastern BL-29700 rescue hoist as an immediate organisational response to the failure. The secondary hoist cable had accrued 535 hoist cycles. External inspection before destructive sectioning of that cable showed local ‘necking’ had also occurred in the same area as the failed cable approximately 10 mm from the swaged ball end fitting.

The ‘necking’ provided an indicator of the onset toward a serious defect, such as worn or broken internal wires and strands. The subtle changes in diameter associated with the ‘necking’ could also be felt when handling the cable during physical inspection. Magnified examination of the ‘necked’ region identified that wear grooves and scallops had occurred to the wires comprising the cable. The damage was similar in appearance to that from the failed cable off VH-UAH, though all strands remained intact. Figures 6 and 7 provide further detail on the severity of wear damage associated with ‘necking’ of the intact hoist cable.

Figure 3: Swivel hook and bumper assembly

The wire strands comprising the inner core of the cable had retracted approximately 50 mm to 60 mm from the outer strands.
Source: ATSB

Figure 4: Close-up of the remnant cable portion near the swaged ball end fitting showed narrowing or ‘necking’ and grooves in many of the wires from severe wear damage

Source: ATSB

Figure 5: SEM images of the fractured cable identified severely worn wires (left) and fatigue crack progression bands from bending fatigue (right)

Source: ATSB

Figure 6: Another ParkAir rescue hoist removed from service after the occurrence displayed narrowing of the cable at the ball end fitting.

The narrowing, or ‘necking’, could be detected during physical handling and close visual examination. The cable had accrued 535 hoist cycles throughout its service life.

Source: ATSB

Figure 7: Severe wear to the wires was evident from the intact cable at the point of narrowing near the swaged fitting

The cable strands in the ‘necked’ region were spread apart in order to identify the extent of wear damage.

Source: ATSB

Hoist cable inspection requirements

Airworthiness Directive AD/SUPP/10 Breeze‑Eastern hoists

Australian operators of Breeze-Eastern hoists were required to comply with Civil Aviation Safety Authority (CASA) Airworthiness Directive AD/SUPP/10.^[5] The AD noted that damage can occur to a particular area of the load cable that may evade detection during normal inspection, resulting in a serious compromise of cable integrity. The AD referenced Breeze-Eastern document CAB-100-30^[6] that introduced inspections intended to significantly improve the operational safety of the rescue hoist system. Specifically, operators of Breeze-Eastern hoists were required to conduct:

1. A one-time and recurring inspection of the of the hoist’s load cable in a specific area.

2. A pre-flight and post-flight inspection of the hook and bumper assembly during stowage.

During the one-time and recurring inspections, CAB-100-30 required maintenance personnel to partially disassemble the hook assembly to allow a close visual inspection of the cable at the ball end for evidence of necking down, loose or broken wires, and other damage. The hoist logbook indicated no defects were identified from that specific cable inspection, which had last been completed in December 2019 (at approximately 600 hoist cycles).

Pre- and post-flight inspections required from CAB-100-30 were intended to ensure proper stowage of the hook assembly ‑ firmly seated against the bump stop at the conclusion of the homing procedure. CAB-100-30 noted that assurance of adequate hook homing could be achieved by grasping it and rocking it fore and aft. Importantly, the advice from Breeze-Eastern within CAB-100-30 also indicated that during the post-flight inspection of the swivel hook, the degree of spring compression was required to be measured to verify proper homing of the hook, as identified in Figure 8.

Figure 8: Extract from Breeze-Eastern CAB 100-30 describing the inspection requirements 1) the load cable and 2) the hook and bumper spring compression measurement

Source: Breeze-Eastern

Organisation

ParkAir rescue hoist operation

While the rescue hoists within their operator’s fleet were primarily used for winching of personnel and equipment in response to operational requirements, another significant aspect of hoist usage involved hoist training/familiarisation exercises. The familiarisation training was mostly conducted at low heights with about 5 m of cable reeled out, leading to the accrual of hundreds of short-haul winches per year.

Hook homing

The Breeze-Eastern procedures for reeling up the load cable and homing of the hook assembly were defined in the hoist operations manual.^[7] At the conclusion of a winching operation, and while positioning the hook to the upper limit stop, Breeze-Eastern indicated that it was important to ensure that completion of that action was uninterrupted and provided the following advice:

Always guide the hook by hand as the cable is reeled in, at full pendant thumbwheel deflection, to the full in position. Ensure the spring in the bumper is compressed sufficiently to prevent the hook from moving when the helicopter is in flight.

ParkAir advised the ATSB that minor variations to the prescribed Breeze-Eastern hook homing procedure had probably developed over the years without correction. It was indicated that in certain instances intermittent control of the cable speed and gentle homing had been conducted to avoid damaging the rubber bumper attached to the hook assembly.

The operator advised that it was uncertain how this deviation in practise arose, however it may have been influenced by a lack of recent Breeze-Eastern Flight Line maintenance training on the hoist system. Such training had last been conducted by ParkAir staff approximately 7 years prior. ParkAir had expanded in that time and staff turnover may have led to the factory‑instructed lessons being diluted.

AD/SUPP/10 hoist inspections pre- and post-flight

The ATSB identified that there was no reference within the operator’s supplementary documentation to ensure the pre- and post-flight verification that the hook assembly was correctly homed. The safety concerns and corresponding checks raised by CASA within AD/SUPP/10 regarding adequate compression of the hook assembly were not mentioned within the documentation. The operator indicated that, although homing of the hook assembly was physically checked by the crewman at the end of each winching operation, a verification measurement for hook assembly compression, as per AD/SUPP/10 was not accomplished.

Airbus Helicopters hoist specific maintenance

Airbus Helicopters provided technical guidance in their Master Servicing Manual^[8]that specified the maintenance operations to be performed by the helicopter operator. Within section 25-63Equipment and Furnishings of the manual, Airbus Helicopters defined a hard life-limit of 500 hoist cycles on the load cable for the Breeze-Eastern BL-29700 hoist. Airbus Helicopters defined a hoist cycle as:

Hoisting cycles: HC (Hoist Cycle)

1 HC =

- In flight, one downward movement + one upward movement, whatever the length of cable and load involved.

- On the ground, one downward movement of 5 meters or more and one equivalent upward movement, whatever the load involved.   

Both the Airbus Helicopters definition of a hoist cycle, and their definition of load cable life-limit were notably different to the definition and limits specified by Breeze-Eastern. Airbus Helicopters indicated that the reason for the discrepancy was to align the hoist cycle definition to other hoists within the Airbus Helicopters fleet. It was also indicated that although the Airbus Helicopters life‑limit is significantly more restrictive than that defined by Breeze-Eastern, their limits were intended to provide a greater safety margin during operation.

Regulatory guidance on maintenance

During the course of the investigation, CASA advised the ATSB that regulatory information was available to operators regarding which publication should be consulted if there are two sources of conflicting information for maintaining continued airworthiness, such as that issued by Breeze‑Eastern and that issued by Airbus Helicopters. Civil Aviation Regulation (CAR) 50E Inconsistent requirements – resolution of inconsistencies, stated the order of priorities under these circumstances:

(4) The order of priority of requirements is as follows (starting with those of highest priority):

(a) requirements in these Regulations (except those requirements mentioned in the remaining provisions of this subregulation);

(b) requirements in instruments made under these Regulations;

(c) requirements in documents (including designs) approved by CASA or authorised persons under these Regulations;

(d) requirements in instructions issued by designers of modifications of aircraft;

(e) requirements in instructions issued by designers of modifications of aircraft components;

(f) requirements in instructions issued by aircraft manufacturers;

(g) requirements in instructions issued by aircraft component manufacturers;

(h) requirements in instructions issued by aircraft material manufacturers;

(j) requirements in documents that are approved maintenance data because of paragraph 2A(2)(e).

Using the above list of priority requirements, the hoist had been fitted to the helicopter under a separate engineering instruction 4(d), however that instruction advised that the Airbus Helicopters 4(f) and Breeze-Eastern 4(g) maintenance instructions should be followed. CASA indicated that in this instance, the life-limits listed in the Airbus Helicopters master servicing manual would take precedence and were therefore to be followed.

Other occurrences

A search of the Australian defect reporting system, managed by CASA, identified no specific examples of cable failure similar to the occurrence involving VH-UAH.

However, a similar report of cable ‘necking’ was identified on a rescue hoist fitted to an Agusta Westland AW139 helicopter. The necking was identified at the swaged terminal within the hook assembly of a Breeze-Eastern hoist by that operator in May 2020. The defect report indicated that the necking had been found after release of CASA AWB 25-034 Helicopter Rescue Hoist Wire Rope – Wear, Fatigue and Failure (released in response to the occurrence involving VH‑UAH). The cable had accrued 114 cycles and after identifying the necking it was replaced. Also mentioned in the defect report was an indication that the ‘necking’ was associated with many short hoist cycles accrued in training.

__________

1. Breeze-Eastern TD-01-002, Flight Line Operation and Maintenance Manual HS-29700 Series Rescue Hoist System]\ BUMPER STOWAGE INSPECTION, 8 December 1987.
2. Airbus Helicopters Master Servicing Manual AS350 B3
3. Line speed for the HS-29700 winch could be varied by the air crewman from 0 to 210 feet per minute by adjustment of the thumbwheel on the remote pendant.
4. US Department of Defence, MIL-DTL-83140A, ‘WIRE ROPE: STEEL, (STAINLESS STEEL) PREFORMED, NONROTATING, FOR AIRCRAFT RESCUE HOIST AND CARGO HANDLING (WINCHING)’, 9 July 2004
5. Civil Aviation Safety Authority Airworthiness Directive AD/SUPP/10 Breeze-Eastern Hoists, November 1998.
6. Breeze-Eastern Customer Advisory Bulletin CAB-100-30, RESCUE HOIST LOAD CABLE AND HOOK / BUMPER STOWAGE INSPECTION, 8 December 1987.
7. Breeze-Eastern Flight Line Operation and Maintenance Manual, HS-29700 Series Rescue Hoist System, 2008, p10.
8. Airbus Helicopters Master Servicing Manual AS350 B3

Safety analysis

Introduction

The following analysis discusses the factors surrounding the cable failure from a Breeze-Eastern rescue hoist fitted to an Airbus Helicopters AS 350 B3 helicopter, registered VH-UAH, which occurred near Bulga, New South Wales. The failure occurred while the helicopter crew were conducting a conditioning maintenance operation of the rescue hoist system to restore the integrity of the cable. Although no personnel were injured in this occurrence, the helicopter had previously been conducting live winching.

Wear damage and cable failure

The ATSB’s technical examination identified that severe wear damage had developed within the wire strands of the load cable. Additionally, the cable internal core had retracted from the externally wound strands indicating that the inner portion had probably fractured prior to the commencement of the conditioning operation. The failure occurred when the cable was loaded with a 160 kg weighted bag which was significantly less than the ultimate tensile load limit of the cable. In normal circumstances the cable should have withstood the imposed load. There was no evidence of corrosion, kinking, shock loading or any other such damage on the cable that might have otherwise contributed to the failure. Remnant lubricant was identified between the wire strands.

The identified wear led to a significant reduction in cross-sectional area and eventual overstress of the load cable. Some of the worn wires also showed indicators of progressive fracture consistent with the development of fatigue cracking, with the remainder displaying ductile overstress fracture.

Stowage practices and Airworthiness Directive AD/SUPP/10

Breeze-Eastern provided clear advice in the operating instructions for the rescue hoist that when homing the hook, it was important to ensure that the homing action was not interrupted, using full deflection of the controller. This ensured adequate compression of the bump spring and prevented the hook from moving during flight.

The operator commented to the ATSB that in certain instances, intermittent control of the cable speed and gentle homing of the hook had been conducted to avoid damaging the rubber bumper attached to the hook assembly. Although that stowage practice was intended to prevent component damage, it probably led to inadequate compression of the hook assembly that resulted in winch cable damage as the hook assembly vibrated and moved during helicopter operation. The observed wear in the failed cable and the cable off another ParkAir rescue hoist, found to be the result of vibratory movement, supported that conclusion.

In addition to variations in the homing practices, it is likely that specific post-flight inspection requirements for the Breeze Eastern rescue hoist listed in Airworthiness Directive AD/SUPP/10 were not being adequately completed by the operator. The inspections were targeted at verifying correct stowage of the hook assembly at the beginning and end of each flight.

Although the hook assemblies were physically checked for security at the end of each winching sortie, a specific instruction contained within AD/SUPP/10 identified the requirement to measure the degree of spring compression that in turn verified proper hook stowage. The operator’s inspection requirements for the rescue hoist did not contain any reference for a compression measurement to be accomplished.

Cycle counting

A significant difference was identified between the method that Breeze-Eastern and Airbus Helicopters used to define hoist cycles and life-limits for load cables. Breeze-Eastern recommended a 1,500-cycle life-limit while Airbus recommended a 500-cycle life-limit. Breeze‑Eastern utilised a mechanical counter within the mechanism of the winch to determine a full winch cycle, while Airbus identified a hoist cycle as a downward and upward movement of the cable in flight.

The winch had been installed onto the helicopter using an engineering instruction that deferred to both the Breeze-Eastern and Airbus Helicopters technical documentation for maintaining continuing airworthiness. In the event of conflicting sources of information, Civil Aviation Regulation (CAR) 50E Inconsistent requirements – resolution of inconsistencies provided the means to prioritise the relevant instruction. Under these circumstances, given the hierarchy of inspection orders contained within the regulations, the Airbus Helicopters maintenance instructions should have been followed. ParkAir’s use of the Breeze-Eastern method for cycle counting during operation led to an accumulation of load cycles that significantly exceeded the 500-cycle life-limit recommended by Airbus Helicopters.

The wear that occurred to the wires probably occurred over an extended period of in-service movement of the hook assembly, further compounded by the overall extended age and accumulated load cycles of the cable. The hoist cable had accrued 617 hoist cycles and was 9 years old. Based on the number of short-haul winches accrued each year, it is very likely the cable had been exposed to thousands of load cycles. Had the Airbus Helicopters cycle life‑limit been followed, the cable would have been removed from service prior to failure.

Findings

From the evidence available, the following findings are made with respect to the rescue hoist cable failure from an AS350 B3 helicopter that occurred on 5 February 2020.

Contributing factors

• While the helicopter crew were conducting a conditioning maintenance operation of the hoist system, the hoist cable fractured, which allowed the suspended load to fall to the ground.
• Wear damage from in-service movement of the hook assembly led to a significant reduction in cross-sectional area, fatigue and overstress fracture of the strands and an associated reduction in cable strength. The wear was probably compounded by the extended age of the cable and accumulated load cycles.
• Variations in hook stowage practices following winching operations led to inadequate compression of the hook assembly. This probably led to the winch cable becoming damaged due to wear as the hook assembly vibrated and moved during helicopter operation.
• It is likely that specific post-flight inspection requirements for the Breeze‑Eastern rescue hoist listed in Airworthiness Directive AD/SUPP/10 were not adequately completed by the operator. The inspections were targeted at ensuring correct stowage of the hook assembly at the end of each flight. (Safety issue)
• The operator’s method for cycle counting during operation of the rescue hoist led to an accumulation of cable load cycles that exceeded the 500-cycle life-limit recommended by Airbus Helicopters.

Safety issues and actions

Safety action not associated with an identified safety issue

Industry awareness of the rescue hoist cable failure

After being notified of the cable failure and on completing the technical examination of the hoist components, the ATSB advised the Civil Aviation Safety (CASA), Breeze-Eastern, the European Aviation Safety Agency (EASA), and Airbus Helicopters. Those organisations, along with the ATSB, released the following advisories to provide an alert to the broader helicopter industry.

Breeze-Eastern released Service Information Letter (SIL 14 Maintenance) Breeze-Eastern Rescue Hoist Maintenance & Flight Line Inspections for BL-29700 Series, on 6 April 2020. The SIL reminded operators, hoist maintainers and personnel of the critical importance of all listed inspections, including pre-and post-flight, contained in the BL-29700 hoist maintenance manual. The SIL reiterated the requirement to ensure proper compression of the spring from the bumper assembly, and the need for careful inspection of the cable in the immediate area of the swaged ball end fitting.

Proper hook homing inspections post flight must be done according to the flight line maintenance manual and other appropriate technical documents. Failure to complete these checks and verify that the hook is homed correctly post flight could cause a loosely stowed hook to vibrate during flight, creating stress on the wire rope cable.

The continual vibration of a helicopter and a loosely “homed” hook can result in a fatigue failure of the cable immediately above the ball end fitting.

CASA released Airworthiness Bulletin (AWB) 25-034 Helicopter Rescue Hoist Wire Rope – Wear, Fatigue and Failure, on 22 April 2020 to emphasise the care, attention and proficiency required to safely operate and maintain winch systems that lifted and lowered personnel and loads. Within the AWB CASA discussed the cable failure and recommended operators to:

Ensure inspections are completed methodically and thoroughly.

Always ensure the hook has been homed securely, as per approved data. This will prevent the hook causing premature cable fatigue.

Hoist system cycle counters cannot be used to replace physical and visual system inspections. These cycles are based on fatigue life determined in laboratories. Many hoist operations consist of much shorter deploy and retrieve cycles, than a counter may show. Additional inspections may be warranted.

ATSB released a Safety Advisory Notice (SAN) AO-2020-013-SAN-001 on 23 April 2020 that provided a preliminary summary of the cable failure. The SAN was distributed to all Australian operators permitted to conduct aerial work and conduct helicopter winching operations. The SAN advised:

For all helicopter operators and flight crew involved in rescue hoist operations to review their current operational practices to ensure hoist operation and hook stowage are in accordance with the hoist manufacturers’ published procedures.

For operators, flight crew and maintainers to closely review the pre- and post-flight inspection requirements of the hook and cable assembly, along with any recurring scheduled maintenance of the hoist system, to ensure that they are completed in accordance with the manufacturers’ instructions.

Airbus Helicopters released a Safety Information Notice (SIN) 3507-S-25 Fatigue failure of a BREEZE 450 Lbs hoist cable, on 4 June 2020 to all operators of AS350 and AS355 civilian helicopters fitted with the Breeze-Eastern BL-29700 winch. The notice provided a reminder that:

… after a hoisting mission, the hoist operator must position the hoist hook to the upper stop, while holding the control handle in the upward direction without interrupting the automatic stop of the hoist so that the compression phase of the hook assembly is not interrupted.

The notice also advised operators that maintenance of the hoist was to be completed using the Airbus Helicopters definition of a hoist cycle, whereby:

1 Hoist cycle (HC) =

In flight, one downward movement + one upward movement, whatever the length of the cable and load involved

On the ground, one downward movement of 5 meters or more and one equivalent upward movement, whatever the load involved.

EASA released Safety Information Bulletin (SIB) 2020-11 Helicopter Rescue Hoist Cable Failure on 11 June 2020 that informed European operators of the Breeze-Eastern 450 lb BL‑29700 series rescue hoist of the Australian occurrence. EASA recommended the following to all AS350 and AS355 helicopter operators:

…maintenance personnel should use the applicable Airbus Helicopters definition of a hoist cycle

…maintenance personnel and pilot(s), as applicable, should perform the pre-flight and post-flight inspection(s) as per applicable B-E CMM instructions

…pilots and on-board hoist operators should ensure a proper hoist stowing at the end of each hoist operation, by fully reeling it in to compress the hook bumper. Failure to follow this procedure could result in damage (due to wear and fatigue through vibration and aerodynamic loading) to the cable.

Compliance with AD SUPP 10

Safety issue number: AO-2020-013-SI-01

Safety issue description: It is likely that specific post-flight inspection requirements for the Breeze Eastern rescue hoist listed in Airworthiness Directive AD/SUPP/10 were not adequately completed by the operator. The inspections were targeted at ensuring correct stowage of the hook assembly at the end of each flight.

Glossary

AD                   Airworthiness Directive

ATSB               Australian Transport Safety Bureau

AWB                Airworthiness Bulletin

CAR                 Civil Aviation Regulation

CASA               Civil Aviation Safety Authority

CMM                Component maintenance manual

EASA               European Aviation Safety Agency

HC                   Hoist cycle

NPWS              National Parks and Wildlife Service

NSW                New South Wales

SAN                 Safety Advisory Notice

SEM                 Scanning electron microscope

SIB                   Safety Information Bulletin

SIL                   Service Information Letter

SIN                  Safety Information Notice

Sources and submissions

Sources of information

The sources of information during the investigation included:

• New South Wales National Parks and Wildlife Service Flight Operations Unit (ParkAir)
• Civil Aviation Safety Authority
• Breeze-Eastern
• Airbus Helicopters

Additional references

Breeze-Eastern Customer Advisory Bulletin CAB 100-51, Use and Maintenance of Wire Rope on Airborne Personnel Hoists, October 1994

Civil Aviation Safety Authority, Helicopter Personnel Winching, Airworthiness Article AAC 1-103 September 1998

Civil Aviation Safety Authority, Airworthiness Bulletin 25-003 Issue 1, Helicopter Personnel Winching - Human External Cargo (HEC) Operations, 25 April 2015

Helicopter Rescue Techniques, Civilian Public Safety and Military Helicopter Rescue Operations, United States Department of the Interior National Park Service, National SAR Academy (NSARA), First edition October 2013

Information on Helicopter Hoist Wire Rope, Failure Modes, and Rejection Criteria, Zephyr International IIc 2013

James Paul WALLIS, The importance of cable care, AirMed & Rescue Magazine, 4 June 2019

Kasim TURGAT et. al. Falls from height: a retrospective analysis, World Journal of Emergency Medicine, 2018 pp46-50

US Department of Defence, Wire Rope – Steel - Nonrotating for Aircraft Rescue Hoist, Military Specification MIL-W-83140 April 1969. Washington, DC

Submissions

Under section 26 of the Transport Safety Investigation Act 2003, the ATSB may provide a draft report, on a confidential basis, to any person whom the ATSB considers appropriate. That section allows a person receiving a draft report to make submissions to the ATSB about the draft report.

A draft of this report was provided to the following directly involved parties:

• New South Wales National Parks and Wildlife Service Flight Operations Unit (ParkAir)
• Civil Aviation Safety Authority
• European Aviation Safety Association
• United States National Transportation Safety Board
• Breeze-Eastern
• Airbus Helicopters
• Bureau d'Enquêtes et d'Analyses of France
• the helicopter owner
• the rescue hoist maintainer

Submissions were received from:

• Breeze-Eastern
• Civil Aviation Safety Authority

The submissions were reviewed and, where considered appropriate, the text of the report was amended accordingly.

Purpose of safety investigations & publishing information

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2021 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

Safety summary

What happened

Around midday on 19 February 2020 a Beech D95A Travel Air, registered VH-AEM, and a Piper PA44-180 Seminole, VH-JQF, collided mid-air approximately 8 km south of Mangalore Airport, Victoria. The Travel Air was approaching Mangalore Airport from the south, on descent to conduct a practice instrument approach, while the Seminole was southbound on climb from Mangalore to Essendon Airport.

Both aircraft were operating under the instrument flight rules (IFR) in non-controlled airspace. The pilots of each aircraft had been provided with traffic information about the other aircraft prior to the collision, in accordance with procedures. Both aircraft were fitted with dual radios. Other pilots monitoring the common traffic advisory frequency (CTAF) associated with Mangalore Airport reported hearing pilots from both aircraft broadcast but had no recollection of hearing them speaking directly to each other.

The two aircraft collided with no evasive manoeuvring identified in recorded flight data. All four pilots were fatally injured and both aircraft were destroyed.

What the ATSB found

This was the first mid‑air collision between two civil aircraft operating under the instrument flight rules and procedures that have been in place in Australia for decades.

The ATSB identified that, following receipt of verbal traffic information from the controller, the pilots did not successfully manoeuvre or establish direct communications on the CTAF to maintain separation, probably due to the collision risk not being recognised.

While it is probable that the aircraft were in instrument meteorological conditions at the time of the collision due to the presence of extensive cloud, the known limitations of the ‘see-and-avoid’ principle meant that the pilots were unlikely to have seen each other in sufficient time to prevent the collision even in clear weather conditions.

Additionally, following receipt of an alert indicating the developing proximity of the aircraft, the controller assessed it in accordance with the required procedure. However, after considering that the pilots were aware of each other’s presence and were required to ensure their own separation in non‑controlled airspace, the controller did not intervene further.

While the pilots were responsible for self-separation within the Mangalore CTAF area, they did not have access to radar or automatic dependent surveillance broadcast (ADS-B) information. As a result, the pilots were required to make timely decisions to avoid a collision without the best available information.

Finally, although not contributory to the accident, the ATSB identified that the wording of procedures relating to the conduct of practice instrument approaches at Mangalore Airport resulted in varied application and an increased risk of traffic conflicts.

What has been done as a result

Airservices Australia (Airservices) have proposed a change to the Civil Aviation Safety Authority (CASA) to introduce a surveillance flight information service (SFIS) around Mangalore Airport, designed to provide enhanced traffic information services to all aircraft operating in a 20 NM radius of the airport. The proposed service would require all aircraft to broadcast on the CTAF within the broadcast area, while providing a dedicated air traffic controller operating on the CTAF to provide a flight information service utilising surveillance.

By listening on the CTAF, the controller would be able to determine whether aircraft have arranged their own separation following receipt of traffic information and provide updated traffic information if required. A similar service was introduced around Ballina Airport in August 2021.

In September 2021, the CASA Office of Airspace Regulation (OAR) announced an aeronautical study into the airspace within a 25 NM area of Mangalore Airport, up to an altitude of 8,500 ft. The scope of this study involves:

• a review of traffic type and density over the previous 5 years
• an evaluation of the suitability and efficiency of the airspace
• a review of the equitability of access to the airspace, the appropriateness of the airspace classification and the suitability of the existing services and facilities provided by Airservices Australia.

As of February 2022, this aeronautical study has not been published.

The proposal for the introduction of an SFIS on the Mangalore CTAF is currently on hold pending completion of the OAR review. However, a dedicated controller is providing safety alerting on the Mangalore CTAF in the interim period. Communications on the CTAF are recorded by Airservices when the safety alerting service is operational. A further consultation has been raised by Airservices to lower the base of Class E airspace around Mangalore Airport. As of February 2022, that proposal was in review by Airservices following an industry consultation period.

In December 2021, the Department of Infrastructure announced a $30 million fund to provide rebates to general aviation aircraft operators to fund up to $5,000 or 50% of the cost of installing ADS-B transponder technology into their aircraft.

Safety message

While this accident involved aircraft operating under the IFR, irrespective of whether operating under the instrument or visual flight rules, pilots are responsible for separation from other aircraft in non‑controlled airspace.

As such, if made aware of traffic, either via advice from air traffic control (ATC), a received broadcast or any other means it is vitally important that the traffic is risk assessed and, if necessary, a plan established to assure separation. The following separation methods can be useful in maintaining a safe operating distance between aircraft:

• different operating altitudes
• ground feature reference (e.g. townships, lakes or linear features – rivers, roads)
• navigation or avionics reference (e.g. radial or GPS distance)
• ‘clock code’ reference – useful to assist aircraft sighting.

The ATSB also strongly encourages the fitment of ADS‑B transmitting, receiving and display devices as they significantly assist the identification and avoidance of conflicting traffic. The continuous positional information that ADS‑B provides can highlight a developing situation many minutes before it becomes hazardous – a significant improvement on both point‑in‑time radio traffic advice and ‘see‑and‑avoid’. The ATSB also notes that ADS‑B receivers, suitable for use on aircraft operating under both the instrument or visual flight rules, are currently available within Australia at low cost and can be used in aircraft without any additional regulatory approval or expense.

It is also important to recognise however that ADS‑B cannot be relied upon to display all nearby traffic so effective use of radio remains a primary defence in avoiding mid‑air collisions. In that context pilots need to make all required broadcasts detailed in the Aeronautical Information Publication, even if there is no known traffic, and respond to broadcasts if a potential traffic conflict is identified.

The ATSB publication A pilot’s guide to staying safe in the vicinity of non-towered aerodromes highlights some of the known challenges presented to pilots operating around these airfields.

Finally, in line with the key objective of ATC being the prevention of collisions, controllers should advise pilots if they become aware of a developing traffic conflict rather than assume that the pilots are already aware of it.

The occurrence

On 19 February 2020, at about 1055 Eastern Daylight-saving Time^[1], a Beech Travel Air D95A aircraft registered VH-AEM (AEM), departed Tyabb Airport, Victoria for an Instrument Flight Rules (IFR)^[2] training flight to Shepparton via Mangalore, and return to Tyabb. A student pilot (the student) and an instructor (the instructor) were on board. The pilots were planning to conduct a practice VOR^[3] approach to Mangalore Airport as part of the student’s training towards the issue of an instrument rating. AEM was estimated to arrive overhead Mangalore Airport at 1126.

At around the same time, a pilot (the pilot under examination) and flight examiner (the examiner) were at Mangalore Airport, Victoria, preparing for an instrument rating flight test in a Piper PA44‑180 Seminole, registered VH-JQF (JQF).

At 1111, the pilot under examination, seated in the left seat of JQF, contacted the Melbourne Centre air traffic controller responsible for the surrounding Class G non‑controlled airspace, to advise that the aircraft was taxiing for a departure from Mangalore Airport. The pilot had submitted a flight plan for a round-trip IFR flight via Essendon and Shepparton. At this time, the Mangalore automatic weather station recorded cloud as broken^[4], with a base of about 3,200 ft above mean sea level (AMSL).

After departing Tyabb, the crew of AEM climbed the aircraft to 6,000 ft and tracked north through the Melbourne Class C controlled airspace, before being instructed to contact Melbourne Centre. The student pilot first made contact with the Melbourne Centre controller at 1117:42 (Figure 1). They were informed there was no IFR traffic for the descent to Mangalore Airport. At the time the student pilot in AEM acknowledged this information, JQF had not appeared on the controller’s surveillance display. At 1120:07 the controller passed traffic information to the pilots of AEM that JQF was shortly to depart Mangalore airport heading to the south.

Surveillance data for JQF first appeared on the controller’s display at 1120:31, indicating JQF was airborne. At 1122:19, the pilot under examination in JQF made a departure call to the Melbourne Centre controller and provided information that the aircraft was passing 2,700 ft on climb to 7,000 ft and tracking to waypoint LACEY. The controller identified the aircraft on their display and replied with the area QNH^[5]. At 1122:44 the controller provided the pilots in JQF with the following traffic information:

6 [nautical] miles in your 12 o’clock is alpha echo mike, a King Air. They are inbound to Mangalore for airwork. Passing 5,000 [ft] on descent to not above 4,000 [ft].

At 1122:49, five seconds after the controller passed this traffic information to the pilots of JQF, an aural and visual short-term conflict alert (STCA)^[6] was provided to the controller. The alert indicated that the two aircraft were to come within 4.8 NM lateral and 600 ft vertical proximity in the next 60‑90 seconds. Based on the predicted velocity vectors^[7] presented on the radar display for the two aircraft, the controller assessed that the aircraft would pass each other, with JQF passing behind AEM, then acknowledged the STCA. At 1123:00 JQF acknowledged the traffic information. By this time, JQF was climbing through 3,250 ft, had a ground speed of 81 kt and had commenced a turn to intercept their planned outbound track from Mangalore Airport to LACEY (Figure 2). At the same time AEM had a ground speed of 187 kt and was descending through 4,918 ft on a track of 354⁰. At this point, there was 5.4 NM horizontally and about 1,675 ft vertically between the aircraft.

Under IFR operational requirements, the pilots in JQF were required to intercept their outbound track (in this case the direct track between Mangalore Airport and LACEY) within 5 NM of the airfield, and manoeuvre to ensure terrain clearance until above the minimum sector altitude of 3,400 ft within 10 NM of the airfield. Terrain clearance was also assured above 3,900 ft within 25 NM of the airfield.

Figure 1: Flight paths for AEM and JQF, and airspace around Mangalore, including Melbourne Class C airspace and waypoint LACEY

Source: Google Earth and Airservices, annotated by the ATSB

In addition to AEM and JQF, there were six other aircraft either taxiing on the ground at Mangalore Airport, operating in the circuit area, or in the local area monitoring the Mangalore common traffic advisory frequency (CTAF).^[8] Multiple pilots recalled each of the aircraft communicating separately on the CTAF, with one of the crew of JQF making a, rolling and circuit departure broadcast and a pilot from AEM making an inbound broadcast. However, none of the pilots in the CTAF area recalled any radio communications to arrange separation between AEM and JQF.

At 1123:51, another STCA appeared on the controller’s screen for the two aircraft. The controller acknowledged the STCA at 1124:09, whilst providing traffic information to another aircraft. At the time of the STCA activation,  the velocity vector of JQF crossed the velocity vector of AEM, with JQF predicted to pass closely behind AEM. However, the controller’s display showed there was 500 ft vertical separation between the aircraft.

At 1124:20 the aircraft collided. Following the collision, the ATC radar display reverted from a presentation of the track of each aircraft based on surveillance data to the flight planned tracks. The controller attempted to contact each aircraft numerous times, before declaring a distress phase for both aircraft.

The collision occurred about 4 NM (7.5 km) south of Mangalore Airport^[9] at around 4,100 ft. There were no witnesses to the collision. However, the pilot of a helicopter operating to the south of the collision point reported seeing one aircraft (AEM) descending rapidly, with the other aircraft (JQF) descending more slowly while spinning. Two other witnesses, one, a pilot located on the airfield, and a second closer witness, similarly reported seeing JQF spinning toward the ground.

The two aircraft impacted the ground about 1.3 km apart (Figure 2). Some lighter debris from each aircraft was located at a third location downwind from the collision point. All four pilots were fatally injured in the accident, and both aircraft were destroyed.

Figure 2: Flight path of AEM and JQF, and location of the ground impact of both aircraft

Source: Google Earth and Airservices, annotated by the ATSB

__________

1. Eastern Daylight-saving Time (EDT): Coordinated Universal Time (UTC) +11 hours
2. Instrument flight rules (IFR): a set of regulations that permit a pilot to operate an aircraft in instrument meteorological conditions (IMC), which have much lower weather minimums than visual flight rules (VFR). Procedures and training are significantly more complex as a pilot must demonstrate competency in IMC conditions while controlling the aircraft solely by reference to instruments. IFR-capable aircraft have greater equipment and maintenance requirements.
3. VHF Omni-direction Radio Range (VOR): A VHF radio navigational system which provides continuous indication of bearing from the selected VOR ground station.
4. Cloud cover: in aviation, cloud cover is reporting using words that denote the extent of the cover – ‘scattered’ indicates the cloud is covering between and quarter and a half of the sky, ‘broken’ indicates that more than half to almost all of the sky is covered, and ‘overcast’ indicates that all the sky is covered.
5. QNH: the altimeter barometric pressure subscale setting used to indicate the height above mean sea level.
6. Short Term Conflict Alert (STCA) – a tool intended to assist the controller in preventing a collision between aircraft by generating timely alerts of a potential, or actual, infringement of separation minima. See also the section titled Short term conflict alert.
7. Velocity vector: a line that extends from the surveillance track symbol to the estimated future position of the track (computed according to the track’s current ground speed) at some selected time interval into the future. Velocity vectors are based on a present track and do not account for a future variations in tracking. The velocity vector is punctuated with dots to show the tracks estimated progress along the vector at regular intervals of time. The direction of the vector indicates the track heading, while the length of the vector gives an indirect indication of the track speed. See the section titled Controller display for further information.
8. Common Traffic Advisory Frequency (CTAF): A designated frequency on which pilots make positional broadcasts when operating in the vicinity of a non-controlled aerodrome or within a Broadcast Area.
9. Distances are taken from the Mangalore Aerodrome Reference Point (S36° 53.18’ E145° 11.03’).

Context

Personnel information

All four pilots and the air traffic controller held the required licences and medical approvals. It was considered unlikely that fatigue affected the performance of any of the involved pilots, due to the time of the accident, and their previous work and rest times. Workload and fatigue assessments for the controller are detailed in a separate section below.

VH‑AEM instructor

Qualifications and experience

The instructor onboard VH-AEM (AEM) held an Air Transport Pilot Licence (Aeroplane) (ATPL(A)) issued on 29 January 2004, and a Commercial Pilot Licence (Aeroplane) (CPL(A)) issued on 13 October 1993. The instructor also held a Grade 1 flight instructor rating with endorsements for multi-engine class rating^[10] training and instrument rating training. The instructor had an English language proficiency of level 6^[11].

The instructor’s instrument rating and multi-engine aircraft rating were valid until 29 February 2020, and their flight instructor rating was valid until 30 June 2020. The instructor had previously held an examiner rating covering private pilot licence and night visual flight rules testing endorsements, and English language proficiency assessments.

The instructor’s logbook showed a total flying experience of 5,907.2 hours to the last recorded flight on 14 February 2020. In the previous 90 days, the instructor had flown 29.3 hours of which 7.6 hours were in the Beech D95A Travel Air (Travel Air) aircraft type. In the previous 30 days the instructor had flown 25.1 hours total, 5.4 of which were on type.

The instructor had been the operator’s Chief Pilot since March 2019, and the Head of Operations since April 2019.

Medical information

The instructor held a class 1 aviation medical certificate valid until May 2020, with a restriction that it could not be used for ATPL operations. The instructor had a mild colour vision deficiency which had been assessed by specialists as ‘extremely mild’ and had been declared to the Civil Aviation Safety Authority (CASA).

There were no restrictions preventing the instructor from undertaking commercial operations including flight instruction. Additionally, the instructor was not required to wear any vision correction in flight.

VH‑AEM student

Qualifications and experience

The instrument rating student in AEM held a CPL(A) issued on 30 April 2013. The student had also previously held a Grade 3 flight instructor rating permitting single engine aircraft, night VFR and design feature training. The student also held activity endorsements for formation flight, aerobatics and spinning. The student held a level 6 English language proficiency assessment.

The student’s logbook showed a total flying experience of 1,103.1 hours to the last recorded flight on 17 February 2020. The student’s total flying experience on the Travel Air was 6.6 hours. In the previous 90 days, the student had flown a total of 60.4 hours, including the 6.6 hours on the Travel Air; and in the last 30 days had flown 30.3 hours with 2.2 of those in the Travel Air.

Medical information

The student held a Class 1 aviation medical certificate valid until 2 September 2020. There were no restrictions on their medical certificate.

Instrument rating training

An instrument rating is an operational rating permitting a pilot to fly under the IFR.

The student passed their instrument rating theory examination on 2 October 2019. Logbook records indicate that the pilot first completed 1.1 hours in the simulator for ’NDB and instrument flying’ in June 2019. This was completed with another instructor.

Records indicate that the Travel Air instructor and the student began flying together in October 2019 for the purposes of completing the instrument rating. Table 1 identifies the flights logged in the student’s logbook, conducted as flight training toward the instrument rating with multi-engine aeroplane instrument endorsement. The first three flights were conducted as day VFR flights in the Travel Air, conducting elements of handling required for the multi-engine endorsement (see the section titled Pilot Licencing).

Table 1: Flights completed in preparation for instrument rating

[1] ILS, RNAV and VOR are types of instrument approaches.
[2] MOZZA and MONTY are IFR waypoints. See the section titled Operational information.

VH‑JQF examiner

Qualifications and experience

The examiner on board VH-JQF (JQF) held an ATPL(A) that was issued on 17 July 1978. They held a flight examiner rating permitting examination of a variety of operational ratings, including an instrument rating and multi-engine aeroplane class rating. The examiner had a level 6 English language proficiency.

The operator’s records indicate the examiner received a briefing on relevant operational policies in August 2018. However, as per the regulations, the examination flight was conducted as a private flight rather than a commercial operation.

The examiner successfully completed an instrument rating proficiency check in a Seminole on 17 February 2020, two days before the accident flight. The examiner’s instrument rating and multi‑engine class rating were valid until 28 February 2021. The examiner’s grade 1 flight instructor rating was valid until 31 December 2021.

The examiner’s flight examiner rating had exceeded the renewal date, however, operation as an examiner was still permitted under CASA EX70/18, an exemption issued by CASA to extend the requirement to conduct a proficiency check until March 2020. This exemption was issued to assist with the transition of examiners from the Authorised Testing Officer delegations to the Civil Aviation Safety Regulations Part 61^[12] Flight Examiner ratings.

A review of the examiner’s logbook showed a total flying experience of about 21,600 hours. CASA records indicate that the examiner conducted 194 flight tests in the 2 years prior to the accident, of which 34 were for the initial issue of an instrument rating.

Medical information

The examiner held a class 2 aviation medical certificate that was valid until 15 October 2020. There were two restrictions placed on the examiners medical certificate:

• Distance correction was to be worn while exercising the privileges of this licence.
• Reading correction was to be available while exercising the privileges of this licence.

The available evidence indicates that these restrictions were being complied with at the time of the accident.

VH‑JQF pilot under examination

Qualifications and experience

The pilot under examination had been enrolled in a diploma course with the operator since February 2017, and although having completed most of the flying program from Moorabbin Airport they were also familiar with operating to and from Mangalore Airport. The pilot under examination held a CPL that was issued on 24 June 2019. The final component of their training was the instrument rating and multi-engine class rating, being tested during the accident flight. The pilot had a level 6 English language proficiency.

The pilot’s logbook showed a total flying experience of 244.9 hours to the last recorded flight on 17 February 2020. The pilot’s total flying experience in the Seminole was 22.2 hours. In the previous 90 days, the pilot had completed 20.4 hours total flying (all in the Seminole), and in the last 30 days had completed 4.8 hours flying.

Medical information

The pilot’s Class 1 aviation medical certificate was renewed 3 days prior to the accident and was valid until 12 March 2021. There were no restrictions placed on their medical certificate.

Instrument rating training

The purpose of the accident flight was examination for an instrument rating, a multi-engine aeroplane instrument endorsement and a multi-engine aeroplane class rating. The pilot under examination had passed the theory component for the instrument rating on 11 November 2019.

Records indicate that the pilot began training for the multi-engine class rating and the instrument rating in August 2019. During this training, the pilot logged:

• Day multi-engine aircraft flight: 32.0 hours
• Night multi-engine aircraft flight: 7.2 hours
• In-flight instrument flight time: 17.2 hours (logged during the 39.2 day and night multi-engine aircraft flight hours)
• Simulator time: 20.4 hours

All training was completed with one instructor, and all flying was conducted in a Seminole. Documentation recommending the pilot for the flight examination was completed by this instructor after a final practice flight on 17 February 2020, which included flying to Mangalore Airport.

Air traffic controller

Qualifications and experience

The controller had worked for Airservices Australia (Airservices) since 1989. The controller was issued with ratings for area procedural control and area radar control in 1996; and was issued with an endorsement for the sector being controlled on the day (see the section titled Airspace) in January 2012. The controller held a level 6 English language proficiency.

The controller held a Class 3 medical, appropriate for air traffic controllers, which was valid until 6 October 2021, and required the controller to have reading correction available.

The most recent training completed by the controller prior to the accident was compromised separation refresher training on 2 October 2019, and effective scanning training on 26 February 2019.

Roster and workload

The controller reported that they did not feel fatigued prior to, or at the time of the accident. The controller noted that although some of the roster patterns worked could be fatiguing, controllers found ways to manage this. A review completed by Airservices did not identify any fatigue related‑ issues with the controller’s roster.

While the roster had a mix of morning, afternoon and night shifts during February, in the 3 days prior to the accident the controller had completed the following roster:

• Sunday 16 February: day off
• Monday 17 February: 1400 - 2200
• Tuesday 18 February: 1400 - 2200
• Wednesday 19 February: 1100 start

The controller recalled being asleep by midnight after the shift on Tuesday 18 February and waking to an alarm at 0800 on Wednesday morning. The controller arrived at work about 15 minutes early, to prepare for the day.

The controller described the workload on the day as having ‘a bit going on’, but not busy. It was further stated that there were no particular pressures on the day of the accident.

Medical and pathological information

Given the nature of the mid‑air and ground collisions, the accident was not survivable for any of the four pilots.

The autopsy of the examiner in JQF identified a level of ischaemic heart disease capable of causing death in isolation from other factors, but there was no evidence of an acute cardiac event having occurred at the time of the incident.

No other significant medical issues were identified in any of the remaining pilots. Further, the toxicology results did not identify any substance that could have impaired the pilots’ performance or that were not noted in their aviation medical records.

Aircraft information

Both aircraft met the equipment requirements for flight under the IFR, detailed in Civil Aviation Order 20.18 including the carriage of Automatic Dependent Surveillance – Broadcast (ADS-B)^[13] equipment (see the section titled Automatic dependent surveillance broadcast).

VH‑AEM

The Beech D95A Travel Air is a four to six seat, low‑wing, retractable-tricycle-undercarriage aircraft fitted with two 180 horsepower Textron Lycoming IO-360-B1B reciprocating engines driving constant‑speed, two-bladed propellers.

AEM (Figure 3) was manufactured in the United States in 1966 with serial number TD 682. It was first registered in Australia in 1967, and prior to the departure from Tyabb, the aircraft had accumulated 7,400.3 hours in service.

Figure 3: Beech Travel Air VH-AEM

Source: Aircraft operator, annotated by the ATSB.

AEM had a current Certificate of Registration, Certificate of Airworthiness and maintenance release. The last maintenance conducted on the aircraft was a calibration of the aircraft’s altimeters, air speed indicators, compass, pitot-static system and fuel quantity system, conducted on 17 January 2020.

The aircraft was certified for IFR and charter operations and was equipped with dual controls for the student and instructor. The aircraft was also equipped with a Garmin GNS530 radio communication and GNSS navigation system, together with a second communication radio. The aircraft was also fitted with a Garmin GTX335 ADS-B OUT transponder. AEM did not have any ADS-B receiving equipment.

One notable modification to the aircraft was the replacement of the original two frame windscreen with a single pane ‘speed-slope’ windscreen. The exact date of replacement was unknown, however this was a common modification to Travel Air aircraft. The speed-slope screen is a component of later-model Travel Air aircraft and Beech Baron aircraft.

The modification involved removal of the centre spine of the original screen, with no further modifications to the fuselage roof area or side frames. The lower section of the speed-slope screen protruded approximately 75-100 mm further towards the aircraft nose than the original windscreen. A larger glareshield was also fitted to the aircraft to fill the space between the instrument panel and the new windscreen.

A review of the previous two aircraft maintenance logbooks for AEM showed that the speed‑slope screen was last replaced on 5 August 2011, and that the pilot’s side window had been replaced on 25 December 2014.

VH‑JQF

The Piper PA-44 Seminole is a four-seat, low-wing, twin-engine light aircraft. It is powered by two 180 horsepower Textron Lycoming O-360-E1A6D reciprocating piston engines. JQF was fitted with three-blade, constant‑speed and full-feathering aluminium propellers. The Seminole is equipped with hydraulically‑operated, retractable, tricycle landing gear. JQF (Figure 4) was manufactured in the United States in 1979 with serial number 44-7995291. It was first registered in Australia in 1990. The aircraft was owned by the operator. Prior to the accident flight, the aircraft had accumulated a total flight time of 11,190.6 hours.

Figure 4: Piper Seminole VH-JQF

Source: Aircraft operator, annotated by the ATSB.

JQF had a current Certificate of Registration, Certificate of Airworthiness and maintenance release. The maintenance release was issued on 12 February 2020, and the aircraft had completed 18.0 hours flying since that time.

The aircraft was certified for IFR and private/airwork operations. It was equipped with dual controls for the student and instructor. The aircraft was also equipped with a Garmin GNS430 radio communication and GNSS navigation system and a second communication radio. The aircraft was fitted with an Appaero Stratus Mode-S transponder unit, which had ADS-B OUT transmit capability only.

Operational information

Airspace

Overview

Airspace in Australia is separated into different classes that may be either controlled (Class A, Class C, Class D, Class E) or non-controlled (Class G) (Figure 5). Different services are offered to aircraft that operate in these airspace classes, based on the flight rules the aircraft is operating under (see the section titled Air traffic services).

Figure 5: Australian airspace structure

Source: Airservices

Common traffic advisory frequency

Mangalore Airport is a non-controlled airport that operates on a common traffic advisory frequency (CTAF). This frequency is shared with four other airfields in the local area – Locksley Field, Nagambie-Wirrate, Wahring Field and Puckapunyal (Figure 6).

The precise boundaries of a CTAF are not defined, however, the Aeronautical Information Publication (AIP^[14]) stated that:

An aircraft is in the vicinity of a non-controlled aerodrome if it is within a horizontal distance of 10 [nautical] miles; and within a height above the aerodrome reference point that could result in conflict with the operations at the aerodrome.

Mangalore Airport is located 4 NM north of an 8,500 ft Class C control step. The accident took place almost directly underneath the 8,500 ft step boundary (Figure 6). Class G non-controlled airspace surrounds Mangalore Airport up to 8,500 ft; with Class E controlled airspace from 8,500 ft to flight level^[15] 125 (FL125) and Class C controlled airspace from FL125 to FL180. Class A controlled airspace was in place above FL180.

Figure 6: Airspace surrounding Mangalore Airport

Source: Airservices, annotated by the ATSB.

Class G airspace

Class G airspace has been operational in Australia since 1995. In Class G airspace, air traffic controllers provide a traffic information service to IFR aircraft about conflicting IFR and observed VFR flights (see the section titled Flight Information Service). Controllers have offered a similar ‘flight service’ to IFR aircraft operating in non-controlled airspace since 1963.

AEM was transferred from one Melbourne Centre controller to another Melbourne Centre controller, just prior to the 30 DME^[16] control boundary (Figure 7), where the lower level of Class C airspace increased from 4,500 ft to 8,500 ft.

The pilots of AEM first made contact with the Melbourne Centre controller at 1117:42, and they entered the airspace around 1118:22. They were not on the Melbourne Centre frequency at 1111 when the pilot of JQF made their taxi call to the Melbourne Centre controller.

Figure 7: Airspace around Mangalore Airport and the outbound IFR track to LACEY

Source: Airservices, annotated by the ATSB

Rules of the air

While both aircraft were operating in the same airspace under the IFR and were in contact with the Melbourne Centre controller, due to the airspace being class G non-controlled airspace, the controller was providing a flight information service only to these aircraft, rather than a traffic control service with positive separation (see the section titled Flight information service). This meant that, as with VFR operations in non-controlled airspace, the pilots were responsible for ensuring they maintained sufficient separation.

The Civil Aviation Regulations 1988 161 through 166 sets out a number of associated regulations detailing pilot responsibilities in relation to rules for the prevention of a collision, operating near other aircraft, right of way and operating in non-controlled airspace.

With regard to the responsibility of pilots to communicate on VHF radio, Civil Aviation Regulation 166C – Responsibility for broadcasting on VHF radio states

(1)    If:

a.    An aircraft is operating on the manoeuvring area of, or in the vicinity of, a non-controlled aerodrome; and

b.    The aircraft is carrying a serviceable aircraft VHF radio; and

c.    The pilot in command of the aircraft holds a radiotelephone qualification;

        The pilot is responsible for making a broadcast on the VHF frequency in use for the aerodrome in accordance with subregulation (2)

(2)    The pilot must make a broadcast that includes the following information whenever it is reasonably necessary to do so to avoid a collision, or the risk of a collision, with another aircraft:

a.    The name of the aerodrome;

b.    The aircraft’s type and call sign;

c.    The position of the aircraft and the pilot’s intentions.

The AIP defines a broadcast as: A transmission of information relating to air navigation for which an acknowledgement is not expected.

The AIP further clarified statements about broadcasts and collision avoidance in GEN 3.3 paragraph 7.5.1 Acknowledgement of broadcasts:

Broadcasts should not be acknowledged unless a potential collision risk exists

Flight plans

AEM

The student pilot of AEM submitted a flight plan to Airservices at 1041 on the morning of the flight. The flight plan details were to

• depart Tyabb Airport at 1055
• fly direct to Mangalore Airport and conduct the VOR hold and approach
• depart to Shepparton Airport for the Area Navigation (RNAV) Global Navigation Satellite System (GNSS)^[17] approach
• return via Mangalore and LACEY to Moorabbin for the RNAV GNSS approach before returning to Tyabb.

A witness from Tyabb reported that the instructor and instrument rating student had tried to book slots to conduct instrument approaches at airports in the Melbourne control zone but were unable to secure any on the morning of the flight^[18]. They were also unable to operate at East Sale due to military training. Therefore, it was decided to fly to Mangalore and Shepparton.

The aircraft proceeded as per the flight plan. The pilots were transferred to the Melbourne Centre controller just prior to the airspace boundary and entered the Class G airspace while maintaining 6,000 ft about 24 NM south of Mangalore Airport. About 90 seconds later, when the aircraft was about 18 NM from Mangalore Airport, the student pilot contacted Melbourne Centre to report their departure from 6,000 ft for airwork at Mangalore not above 4,000 ft (operations between ground level and 4,000 ft).

The planned instrument approach was the VOR approach to runway 23 (see the section titled Mangalore VOR). The approach required them to pass overhead the VOR not below 3,900 ft before beginning the outbound leg of the approach, and descending to no lower than 1,800 ft. There were no reported issues with the serviceability of the VOR at the time of the occurrence.

JQF

The pilot under examination submitted a flight plan at 0949. The flight plan detailed:

• an 1100 departure from Mangalore Airport and climb to 7,000 ft while tracking to LACEY
• conduct of an ILS^[19]approach at Essendon Airport
• a return to Mangalore for the VOR approach
• conduct of an NDB^[20] approach at Shepparton Airport before returning to Mangalore for an RNAV approach.

The flight plan submitted to Airservices did not specify the route planned to LACEY, other than Mangalore Airport direct to LACEY. However, a copy of a handwritten flight plan indicated the intention to track from Mangalore to LACEY along the published IFR route W481 (Figure 7).

JQF commenced the take-off roll from runway 23 at Mangalore just prior to 1120. The aircraft initially departed in an extended upwind direction, before commencing a series of left turns that resulted in the aircraft tracking towards the planned route to LACEY (Figure 8).

The pilot under examination made a departure call to the Melbourne Centre controller with the first communication commencing at 1122:19. At the time of this call, during which the pilots were provided traffic information about AEM, the track maintained by JQF was direct to LACEY. This may have been intentional, or co-incidental due to the increased workload of the student during the take-off phase and climb phase and managing the radio during the Melbourne Centre call. It was at this time the controller reviewed the velocity vectors that were based on the track of the aircraft not the flight planned track, and assessed that JQF would pass behind AEM (see the section titled Short term conflict alert). However, at the end of the radio communication, JQF resumed the turn towards the planned route to LACEY via route W481.

Figure 8: Track of JQF after take-off from Mangalore Airport

Source: Google Earth and Airservices, annotated by the ATSB

Mangalore VOR

The Mangalore VOR is one of four such navigation aids in Victoria. As part of the 2016 Navigation Rationalisation project, in a move towards using a Global Navigation Satellite System (GNSS), 179 ground-based navigation aids were decommissioned across Australia. Twenty eight of the decommissioned instrument approaches were in Victoria, including five VORs. The Mangalore VOR was maintained as part of the back-up network, along with VORs at Melbourne, Avalon and Mildura airports. Despite fewer available local VORs since the decommission of navaids, IFR traffic numbers using Mangalore Airport have decreased (see the section titled Aerodrome information).

Figure 9 details the published VOR instrument approach to Mangalore Airport.

Figure 9: Mangalore Runway 23 VOR approach

Source: Airservices, annotated by the ATSB

Pilot Licencing

Licencing of pilots with operational ratings and endorsements, such as the multi-engine aeroplane class rating and the instrument rating, requires the pilot to demonstrate relevant competencies to a flight examiner. These competencies are set by CASA and mandated under Part 61 of the Civil Aviation Safety Regulations (CASR).

The CASR Part 61 Manual of Standards (MOS) details these competencies both for initial testing and recurrent examination. At all stages of pilot licencing, competence in non-technical skills must be demonstrated by pilots under examination, including

-   Maintain effective lookout

-   Maintain traffic separation using a systemic visual scan technique at a rate determined by traffic density, visibility and terrain;

-   Maintain radio listening watch and interpret transmissions to determine traffic location and intentions;

-   Recognise and manage threats

Of the Part 61 MOS competencies outlined for the instrument rating, there were two competencies that were relevant to the departure path flown by the pilot of JQF:

-   2.2 (e) conduct instrument departure to comply with obstacle clearance requirements.

-   4 (w) pilot's responsibility in an IFR visual departure.

If either of these competencies were not demonstrated, then it would be marked as a failure item for the test. 

In complying with 2.2(e), the AIP ENR 1.5 stated:

4.4 Take-off minima for other IFR aeroplanes

   4.4.3 – It is a condition of the use of the minima in Section 4.4 that the pilot in command of the aeroplane must ensure that:

a. terrain clearance is assured until reaching either an en-route LSALT^[21] or departure aerodrome MSA^[22]

As identified on the VOR chart (Figure 9), the minimum sector altitude within 10 NM of Mangalore Airport was 3,400 ft, and the minimum sector altitude within 25 NM to the south and south‑east of the airport was 3,900 ft. Therefore, the pilot of JQF had to ensure terrain clearance was maintained until the aircraft climbed to 3,400 ft.

In complying with 4(w), AIP ENR 1.1 paragraph 10.6.2 stated:

The pilot of a departing aircraft is required to establish the aircraft on the outbound track as soon as possible after take-off, and in any case, within 5 nm of the departure aerodrome.

JQF departed from runway 23, and was flight planned on a published IFR route southbound via waypoint LACEY. Figure 10 identifies the latest position at which JQF could have intercepted this outbound track and complied with the requirement to be ‘established’.

Figure 10: JQF track flown and planned track to LACEY

Source: Google Earth and Airservices Australia, annotated by the ATSB

Another competency for a multi-engine aircraft class rating is the requirement to demonstrate how to safely manage a simulated engine failure. The ATSB considered the possibility that the examiner of JQF had simulated an engine failure for the pilot under examination take-off from Mangalore. However evidence provided by the operator suggested that this would not have been the standard practice of the examiner and the recorded climb performance was indicative of the aircraft climbing at a normal two‑engine climb rate.

Neither the student in AEM or the pilot under examination in JQF were likely to have been wearing an IFR ‘hood’, used to simulate instrument conditions, at the time of the accident. AEM had been in cloud for most of the descent from 6,000 ft and the hood for JQF was found in a basket behind the pilot seats, having not been used for the flight.

Self-separation by radio

As previously detailed, while operating in non-controlled airspace, even under the IFR, pilots remain responsible for ensuring their own separation from other aircraft. While the occupants of the two aircraft were provided with traffic information, where the possibility for traffic conflict occurs, communication between pilots over the radio remains the primary means for ensuring separation.

Interpreting location information heard over the radio into a useful mental model is a practical skill taught to pilots during initial training, and developed with experience. Once a pilot hears where another aircraft is through a radio call, they must:

• process the audio information
• identify where that aircraft is in relation to their own aircraft
• determine where both aircraft are heading
• assess whether there is a potential conflict and, if so, communicate this risk with the other aircraft.

Despite the importance of this skill, there is limited written guidance to pilots on how to communicate and arrange this separation. CASA CAAP 166-2 (2013) is one document that provided the following written guidance to pilots on suggested methods for traffic separation by radio:

Accurate provision and interpretation of traffic information for the purposes of separation to or from another aircraft is an essential pilot skill. Four commonly used ways of providing and interpreting traffic information by radio communication for the purpose of airborne separation are practised at non‑controlled aerodromes. All methods have their advantages depending upon circumstances.

-   Separation by ‘clock code’ – Pilots maintain traffic separation by reference to the central axis and numbers of an analogue clock face. Particular care must be given to identifying which aircraft is the central axis of the clock. You are at my 2 o’clock and low has the opposite meaning to I am at your 2 o’clock and low. The weakness of this method of separation is that is requires at least one pilot to have seen, identified and made contact with the other aircraft.

-   Separation by ground reference – Pilots maintain separation by radio by either identifying that each is in different places relative to a ground feature(s), or by agreeing to remain on different sides of a readily identifiable ground feature such as a runway extended centreline, road, town or railway line. The advantage of this method of separation is that it does not required either aircraft to have actually seen each other (although this is desirable). The weakness of this method of separation is that ground features could be misidentified. The uncertainty or confusion can distract from the effort of retaining separation through see-and-avoid.

-   Separation by altitude reference – Pilots maintain separation by radio by identifying that each is at a different altitude or by one aircraft descending/climbing to another level. Provided that both aircraft altimeters are set to the correct subscale reference (QNH) this method should provide separation for both aircraft regardless of visual contact.

-   Separation by navigational or avionic reference – Pilots maintain separation by identifying that each is in a different place relative to a known navigational point or line (radial), or separated by distance from a fixed point (e.g. Global positioning system (GPS) or a radio navigation aid). This method of separation does not require either aircraft to have actually seen each other (although this is desirable). The weakness of this method of separation is that differing avionic equipment or pilot navigational skill can lead to incorrect assumptions being made about the usability of the separation information offered.

Air traffic services

Overview

Airservices is the national air traffic services (ATS) provider for other than military‑related airspace within Australia. A number of different services are provided by Airservices based on the airspace classification (Table 2), broadly described as either an air traffic control service, or a flight information service.

Table 2: Services provided to IFR  aircraft in Australian Airspace

Source: CASA

The AIP defines an air traffic control service as:

A service provided for the purpose of:

a.     preventing collisions:

(1)   between aircraft; and

(2)   on the manoeuvring area between aircraft and obstructions; and

b.     expediting and maintaining an orderly flow of air traffic.

An air traffic control service is provided in controlled airspace, such as in Class A, C, D and E airspace in Australia. These classes of airspace have a separation standard for aircraft operating in these control areas. In controlled en route^[23] airspace with surveillance services, the minimum separation requirements between IFR aircraft are 5 NM lateral separation and 1,000 ft vertical separation.

A flight information service (FIS), such as that provided in Class G airspace, is defined in the AIP as:

A service provided for the purpose of giving advice and information for the safe and efficient conduct of flights.

A flight information service differs from an air traffic control service in that pilots are not provided with positive separation between aircraft, and there are no separation standards for aircraft. Instead, pilots of IFR flights are provided with traffic information, and are required to comply with the rules of the air to maintain their own separation (see the sections titled Rules of the air and Flight information service).

Air traffic control surveillance

Both AEM and JQF were broadcasting ADS-B and SSR and were identified by the controller, therefore the pilots were receiving traffic information through a surveillance service rather than a procedural information service. All aircraft information on the controller’s display is filtered to update once every 5 seconds (see the section titled Recorded data)

The Manual of Standards (MOS) Part 172 (paragraph 10.2.3) required controllers to verify level information being broadcast by aircraft as being within ±200 ft, and that:

ATC must verify displayed pressure altitude-derived level information:

a.     On initial contact with the aircraft or, if this is not feasible, as soon as possible after initial contact; and

b.     By simultaneous comparison with:

i.    Altimeter-derived level information received from the same aircraft by radiotelephony.

On first airborne contact with each aircraft, the controller validated the altitude information provided by the pilots in the radio transmissions against the altitude displayed on the controller’s console. At this check AEM was indicating 100 ft higher than the pilot reported (6,100 ft rather than the reported 6,000 ft), as it was again when the pilot reported the start of descent for airwork at Mangalore. The altitude displayed on the controller display matched the altitude reported by the pilot of JQF. This was within tolerance for both aircraft.

Flight information service

At the time of the accident, AIP GEN 3.3 paragraph 2.16 outlined the traffic information provided in Class G airspace. This information was available to both pilots and controllers. Key information in this section of the AIP included:

2.16.1       In Class G airspace, a traffic information service is provided to IFR flights about other conflicting IFR and observed VFR flights.

2.16.1.1    An IFR flight reporting taxiing or airborne at a non-controlled aerodrome will be advised of conflicting IFR traffic which is not on that CTAF.

2.16.1.2    An IFR flight inbound to a non-controlled aerodrome will be advised of conflicting IFR traffic. The ATS obligation to provide the pilot with traffic information ceases when the pilot reports changing to the CTAF.

2.16.1.3    Traffic information will continue to be provided about an IFR flight following cancellation of its SARWATCH^[24], until expiry of the flights ETA. Traffic information may be provided to an IFR pilot who has cancelled SARWATCH where workload and communications permit.

2.16.2       In accordance with the preceding paragraphs, traffic information will be provided to IFR flights when:

   a.           requested;

   b.           notifying intention to change level;

   c.           reporting either taxiing or airborne or departure, whichever is first; or

   d.           the ATS officer becomes aware of conflicting traffic.

2.16.3       Pilots of IFR aircraft should advise ATS of the callsign(s) of relevant IFR traffic, previously intercepted, to avoid receiving the same traffic information from ATS.

2.16.4       Traffic information will be provided in accordance with the preceding paragraphs whenever there is a possibility of confliction between aircraft in the following situations:

   a.          aircraft that climb, descent or operate with less than 1,000 ft vertical spacing and less than 15 NM lateral or longitudinal spacing;

   b.          overtaking or opposite direction aircraft on the same or reciprocal tracks with less than 1,000 ft vertical spacing and less than 10 minutes longitudinal spacing based on pilot estimates;

   c.          more than one aircraft arriving at, or departing from, the same aerodrome with less than 10 minutes between arrival and/or departure and falling within these guidelines.

2.16.5       When the traffic assessment is based entirely on the use of an ATS surveillance system, traffic information will be provided when, in the opinion of the controller, it is warranted by the proximity of the aircraft to each other.

2.16.7       Traffic information will include relevant factors from the following:

   a.           the identification of the conflicting aircraft;

   b.           the aircraft type;

   c.           the route of the aircraft;

   d.           the last position report received from the aircraft;

   e.           intentions of the pilot (if known), and, as required;

   f.            the aircraft’s initial departure track and intended cruising level;

   g.           inbound track or direction, level and next estimate; and

   h.           any other data which may enhance the value of the information.                     

An ATS surveillance service is defined in the AIP as a:

Term used to indicate an air traffic service provided directly by means of an ATS surveillance system.

An ATS surveillance system is defined in the AIP as:

A generic term meaning variously, ADS-B, primary surveillance radar, secondary surveillance radar or any comparable ground-based system that enables the identification of aircraft.

AEM and JQF were under a surveillance service, once they were identified by the controller following their first airborne radio calls. Therefore, AIP paragraph 2.16.5 was applicable, with the controller providing traffic information when warranted by controller opinion rather than through the requirements of 2.16.4. There was no requirement for the controller to pass updated traffic information to aircraft that had already received traffic information, even when the information passed no longer accurately reflected the current position the aircraft were in.

An air traffic controller overseeing Class G airspace has the responsibility to provide traffic information to IFR aircraft until they report changing to CTAF. This is a historical procedure that was in place when aircraft commonly only had one radio and remains despite many aircraft being fitted with dual radio systems. However, this procedure remains in the latest edition of the AIP, current 2 December 2021 (AIP GEN 3.3, paragraph 3.3.7.2).

Guidance in the Airservices and Department of Defence Manual of Air Traffic Services (MATS) supports the AIP information, and provides controllers with further advice about how to provide traffic position information to pilots:

9.1.6.5      Position information

Provide position information by:

a.     Clock reference;

b.     Bearing and distance;

c.     Related to a geographical point;

d.     Reported position and estimate; or

e.     Position in the circuit

Airspace

The Melbourne Centre controller was responsible for monitoring a section of airspace known as ‘Alpine’ that spanned an area from the Melbourne control zone to Canberra (Figure 11). This airspace included Class C and E controlled airspace, as well as Class G non-controlled airspace.

Where workload required, the ‘Alpine’ airspace can be sub‑divided into three sectors – Hume (HUM), Ovens (OVN) and Dookie (DOK). At the time of the accident, the controller was operating the three sectors combined.

Figure 11: Alpine airspace, including Dookie, Ovens and Hume sectors and key aerodromes

Source: Airservices, annotated by the ATSB.

Controller display

Air traffic controllers have multiple screens on their console, displaying information such as a map view of the aircraft in their sector; flight plans of active and future aircraft; weather and NOTAM^[25] information. Co-ordination of aircraft passing into their sector may occur either through verbal communication with another controller or through data messages sent between controllers.

The position of AEM and JQF as they operated under a surveillance service were identified through a combination of secondary surveillance radar (SSR) and ADS-B. Airservices advised that, when SSR information was available, this was the primary source of traffic information displayed to the controller. Additionally, data presented to the controller was only updated every 5 seconds (see the section titled Recorded data).

The controller had the ability to zoom into sections of the airspace on the display. This gave the controller the ability to further inspect information available about each aircraft, including callsign, altitude and flight plan information. The controller used this function to inspect alerts that were generated (see the section titled Short term conflict alert).

Following the accident, Airservices recreated the controller’s display for the period that AEM and JQF were operating in Class G airspace. While this did not replicate where the controller had the information labels^[26] placed for each aircraft, it did display the same information as the controller would have seen.

The controller operated with the default display setting, with 2 minute velocity vectors projected ahead of each aircraft in their sector. The vectors were based on the current track of the aircraft, and not on any information included in the flight plan. Therefore, following the departure call from the pilot under examination in JQF, when traffic information about AEM was passed to the occupants of JQF (see the section titled Communication, Melbourne Centre), the vectors indicated that JQF would pass behind AEM (Figure 13). However, this projected information did not consider the flight planned track and the intent of the pilot in JQF to turn and intercept the Mangalore to LACEY track within 5 NM of Mangalore Airport (see the sections titled Flight plans and Pilot Licencing). Unlike the velocity vectors that projected where in space an aircraft would be if they continued on the same track and with the same groundspeed, there was no numerical predictive information provided to the controller relating to the projected altitude of a climbing or descending aircraft in that 2 minute timeframe. If needed, this information had to be determined by the controller through processing a combination of climb or descent arrows, known aircraft performance, flight plan information or speed information.

Short term conflict alert

A short term conflict alert (STCA) is an aural and visual alert received on a controller’s console when two aircraft come within a defined proximity of each other. In describing the intent of the STCA, the International Civil Aviation Organization (ICAO, 2016) noted:

The objective of the STCA function is to assist the controller in preventing collision between aircraft by generating, in a timely manner, an alert of a potential or actual infringement of separation minima.

In the Australian ATC system STCAs occur in both controlled and non-controlled airspace, with alerts inhibited in some areas. Specifically, Airservices advised that STCAs in Class G airspace are inhibited below 4,500 ft in the Brisbane flight information region^[27], but occur to the ground in areas of the Melbourne flight information region.

When two aircraft are assessed by the system as likely to pass within prescribed vertical and lateral parameters in a particular time window, the controller will receive a pop-up window on their display with aircraft details. The parameters for an alert on aircraft in Class G airspace are the same as the parameters for aircraft in an en-route controlled environment. Aircraft operating below FL285, under a surveillance service will generate a STCA if they are projected to pass within 4.8 NM and 600 ft in the next 60-90 seconds.

The STCA only alerts for aircraft operating under a surveillance service. Both AEM and JQF were included in this, as they were both operating under a flight plan, broadcasting ADS-B and SSR data, and had both been positively identified by the controller. Some aircraft, such as 2 VFR aircraft in non‑controlled airspace operating without a submitted flight plan, will not generate a STCA even if a conflict situation develops.

The procedures documented for the response to a STCA did not differentiate between controlled airspace, where a STCA indicates an infringement of separation minima, and non-controlled airspace where there is no published separation minima.

In terms of prioritisation of alerts, the National ATS procedures manual (NAPM) identified the STCA as one of the highest priority alerts, indicating a system detected safety net critical event, requiring immediate attention.

The response procedure for a controller receiving a STCA was:

14.1.3.1    Alert integrity

On receipt of a STCA:

1.     Assess its integrity; and

2.     Issue a ‘Safety Alert’ or ‘Avoiding Action’ advice when appropriate.

The process for ‘assessing integrity’ of a STCA was undefined. Airservices advised the ATSB that it was an assessment based on controller judgement and experience, and there was no documented checklist or criteria that controllers used to complete this assessment. A STCA may be assessed as not having integrity if the procedure of passing mutual traffic information to two aircraft had been completed, and the aircraft were expected to be self-separating on the CTAF.

It was reported by the controller that it was not unusual to receive a STCA in the airspace being controlled after traffic information was passed. This statement was supported by the Airservices accident investigation report, which noted that other controllers operating the same Alpine sector received a high number of nuisance^[28] STCAs. These STCAs activated between aircraft in the circuit or between aircraft on diverging tracks or who had already passed each other. It was reported that IFR aircraft in the vicinity of non-controlled aerodromes often pass within the STCA parameters when self‑separating and did not normally need further intervention after traffic information was passed.

After a controller assessed the integrity of a STCA, and determined that escalation was required, the information for controllers in the MATS regarding safety alerts stated:

9.1.4.1     Vigilance

                Remain vigilant for the development of safety alert or traffic avoidance advice situations

9.1.4.2     Responsibility

Do not assume that because another controller has responsibility for an aircraft that an unsafe situation has been observed and a safety alert or traffic avoidance advice has been issued.

9.1.4.3     Issuing a safety alert

Unless the pilot has advised that action is being taken to resolve the situation or that the other aircraft is in sight, issue a safety alert prefixed by the phrase ‘SAFETY ALERT’ when you become aware that an aircraft is in a situation that places it in unsafe proximity to:

a.     Terrain;

b.     Obstruction;

c.     Active restricted or prohibited areas; or

d.     Other aircraft

9.1.4.3.1   Airspace classes – safety alerts

You may issue safety alerts, including those based on visual observation, in all classes of airspace both within and outside ATS surveillance system coverage.

Advice to pilots in AIP GEN 3.3 current at the time of the accident stated:

5.1           ATC will issue a Safety Alert to aircraft, in all classes of airspace, when they become aware that an aircraft is in a situation that is considered to place it in unsafe proximity to:

a.          terrain;

b.          obstruction;

c.          active restricted or prohibited areas; or

d.          other aircraft.

5.1.1         When providing an ATS surveillance service, ATC will issue advice to pilots regarding avoiding action as a priority, when they become aware than an aircraft is in a situation that is considered to place it at risk of collision with another aircraft.

5.1.2         ATC will prefix advice to turn or change level with “suggest” unless the alerts are for controlled flights with reference to other controlled flights.

5.1.3         ATC may discontinue issuing Safety Alerts or advice regarding avoiding action when the pilot has advised action is being taken to resolve the situation or has reported the other aircraft in sight.

The AIP guidance for safety alerts stated that pilots would receive a safety alert whenever two aircraft were deemed by a controller to come within an unsafe proximity of each other, whether in controller or non-controlled airspace. When the combination of the MATS and NAPM guidance was followed after receipt of a STCA, a safety alert may not be issued if the controller deemed other risk controls were in place such that the proximity was safe. However, the guidance did not preclude a safety alert being issued when a controller deemed it necessary after a STCA, or at any other time.

There was no definition for what ‘unsafe proximity’ between aircraft was when operating in non‑controlled airspace under pilot separation as there was no separation standard in non‑controlled airspace. Further, when pilots were in the vicinity of a CTAF and had been provided traffic information, there was an expectation from controllers that the pilots were in radio contact with each other and self-separating.

The information in MATS regarding traffic avoidance advice was:

9.1.4.4      Traffic avoidance advice

Issue traffic avoidance advice, prefixed by the phrase ‘AVOIDING ACTION’, to an aircraft that:

a.     Is receiving an ATS surveillance service; and

b.     In your judgement, is in a situation that places it at risk of a collision with another aircraft under surveillance.

In the time between JQF taking off and the collision, there were three STCA alerts generated (Figure 12).

Figure 12: STCA activation and vertical profiles of AEM and JQF

Source: Airservices

Notes:

• Callsigns of other aircraft redacted. Controller was actively communicating with either pilots or other controllers at these times.
• ASD is an abbreviation for ‘Air Situation Display’, meaning the controller display.
• Times on the graph are displayed in UTC (local time – 11 hours at the time of the accident).
• Data is displayed in graph in 3 second intervals and is not representative of the 5 second intervals that the controller display was updated with.​

On the basis of analysis conducted by an ATC subject matter expert and technical detail provided by Airservices, it was assessed that:

• The first STCA, at 1122:42, was a nuisance alert generated by JQF conflicting with VFR traffic in the Mangalore circuit area.
• A second STCA, at 1122:49, occurred as the controller passed traffic information to JQF (Figure 13). At that stage, indications were that the aircraft would pass abeam each other. The STCA was assessed by the controller but not cleared from the screen at this point.
• The controller re-inspected the two aircraft at 1123:30 after JQF had turned towards the planned outbound track. The velocity vectors indicated that lateral displacement would be maintained, with JQF passing behind AEM in about one minute. At that time, the controller’s display showed AEM at 4,800 ft while JQF was at 3,400ft.

A final STCA alert occurred at 1123:51. The controller zoomed in to inspect the aircraft flight paths and altitudes again and acknowledged the STCA at 1124:09. The controller identified that JQF was going to pass across the track of AEM, but at that time, 11 seconds prior to the collision, indications on the controller’s display showed AEM at 4,500 ft and JQF at 4,000 ft, with 0.9 NM lateral separation between the aircraft.

Figure 13: Recreation of STCA display at 1122:49

Source: Airservices data, annotated by the ATSB

Note: Not to scale or necessarily representative of how the controller had the labels configured.

When each of the STCAs displayed, the controller assessed the integrity of the alert in accordance with the NAPM procedure. The controller reported checking the path of each aircraft using the set velocity vectors, the vertical separation of the aircraft, and confirming that traffic information about each aircraft had been passed to the other aircraft. Having assessed that the aircraft would pass each other and:

• the STCA was designed as an alert for a breakdown in separation standards
• there was no set separation standard in non-controlled airspace
• the pilots were responsible for their own separation

they decided that a safety alert or traffic avoidance advice was not required, and cleared the aural alert.

Radio communication

Common traffic advisory frequency

Table 3 shows the guidance provided by CASA (2019) to pilots on the recommended CTAF broadcasts in the vicinity of a non‑controlled aerodrome.

Table 3: Recommended positional broadcasts in the vicinity of a non-controlled aerodrome

Source: CASA (2019)^[29]

In addition to this guidance, the En-Route Supplement Australia (ERSA)^[30] identified a local procedure for pilots to make a report about intentions when conducting practice instrument approaches at Mangalore (see the section titled Practice instrument approaches). The ERSA also noted the following minimum number of radio calls for aircraft operating at Mangalore:

Taxiing, entering (a runway), departing: Inbound, Joining, Base and Final with position, altitude and intentions.

Note: Pilots must respond to radio requests from other traffic for their intentions, position or altitude.

Based on evidence provided by other students trained by the instructor, due to the higher performance of the Travel Air, the instructor encouraged students to make their inbound CTAF call around 15 NM from the airport. The operator of JQF advised that they had a similar procedure to make CTAF broadcasts around 15 NM from Mangalore Airport.

Radio transmissions on the Mangalore Airport common traffic advisory frequency (CTAF) were not recorded, nor were they required to be. Several witnesses stated the CTAF was often congested, but due to the weather at the time of the accident, there was limited flight training and so the CTAF was not as busy.

The ATSB interviewed the pilots operating in the Mangalore area at the time of the accident regarding calls made from the pilots of AEM and JQF. None recalled the pilots of AEM and JQF talking to each other to arrange separation. Various pilots recalled a pilot in JQF making a rolling call, and a departure from the circuit call, and one pilot remembered details of an inbound call made by a pilot of AEM, including mention of an altitude of 3,900 ft.

The CTAF frequency at Mangalore was not equipped with an aerodrome frequency response unit (AFRU)^[31]. There was no evidence to suggest either aircraft had selected the incorrect radio frequency or that an AFRU would have changed the sequence of events. The radios installed in AEM were too damaged to be analysed, but notes found in the aircraft, and details provided by another pilot about an inbound call from AEM, indicated it was likely that AEM broadcast on the correct CTAF frequency.

The two radios from JQF were recovered and analysed by the ATSB. One was set to the Melbourne Centre frequency and the other to the Mangalore CTAF. The audio panel configuration was found in a position consistent with the pilots of JQF either broadcasting or intending to broadcast on the CTAF.

Melbourne Centre

The required radio reports for IFR pilots operating in Class G airspace are listed in the AIP (Table 4). Transmissions between each aircraft and the controller were made on the ATS Melbourne Centre 122.4 MHz frequency and were recorded.

Table 4: Required reports for IFR pilots operating in Class G airspace

Source: AIP

Table 5 outlines the communications that occurred between each of the aircraft and the controller providing traffic information (see the section titled The occurrence). A review of the radio recordings confirmed that the pilot of JQF made taxi and departure calls to Melbourne Centre. The student in AEM also made the appropriate calls when changing to the Melbourne Centre frequency and before changing level, when they started the descent from 6,000 ft into Mangalore.

Table 5: Key traffic information on Melbourne Centre frequency

Source: Airservices, annotated by the ATSB

A review conducted by Airservices following the accident concluded that both aircraft were provided with, and acknowledged receipt of, mutual traffic that contained all relevant information. They also assessed that pilot communications with the controller were generally consistent with the AIP phraseology and the required content was included in the transmissions. A subject matter expert was independently asked by the ATSB to review the recordings and confirmed that the controller provided traffic in accordance with the procedures in the AIP and MATS.

Figure 14 details analysis conducted by the ATSB of ADS-B data and Melbourne Centre recordings provided by Airservices.

Figure 14: Approximate timeline of transmissions and key actions from 1117 to the collision

Source: ATSB, based on data provided by Airservices

Note: Radio transmissions on the Melbourne Centre frequency were recorded so correspond to exact times (see Table 5). The ATSB calculated data is based on ADS-B data. Due to a lack of available information, the following assumptions were made:

• The start of the JQF take off, at 1120:00 corresponds to the first recorded ADS-B point, which occurred when the aircraft was approximately one third down the runway and around 50ft above the runway. It is likely that the pilot’s rolling call, and the start of the take-off roll occurred some seconds before this time. The time from application of power to attaining a height of 50ft has been estimated to be 20-25 seconds.
• The pilots of AEM had a number of opportunities to listen to the Automated Weather Information Service (AWIS)[1] – before and after the descent call to the Melbourne Centre controller at 1119:35. As the aircraft was fitted with two radios, the pilots would likely have selected the AWIS frequency instead of the CTAF for the period of time required. This means they were unable to monitor the CTAF for this time period. A previous student of the instructor described setting up the AWIS frequency in the cruise so that it could be listened to as soon as it came into range, and before top of descent.

When the pilot under examination in JQF made a taxi report at 1111, AEM was not yet in the controller’s airspace. Therefore, at that point AEM was not assessed as conflicting traffic and so no information was provided to the pilots of JQF. Additionally, the expected arrival time of AEM at Mangalore was outside the 10-minute window to be considered arriving ‘traffic’ for JQF in accordance with the guidance provided in AIP GEN 3.3 paragraph 2.16.4c for non-surveillance traffic. The controller indicated awareness of this in interview with the ATSB.

AEM was not given traffic information about JQF when they first called the Melbourne Centre controller at 1117, or initially at 1119 when calling to notify their descent. While JQF had made the taxi call to Melbourne Centre by that time, JQF had not appeared on the controller’s screen as a prompt at that point.

However, the controller did identify JQF as potential traffic for AEM by 1120:07 and called the pilot of AEM. The pilot did not initially respond to this call, however, they did respond to a second call from the controller a short time later at 1120:15. It could not be determined why the pilot did not respond to the initial call, but consideration was given to whether the pilots were listening to the automated weather information services (AWIS) (see the section titled Meteorological information) or making an inbound call on the CTAF as at this point they were about 18 NM from Mangalore. The information given to the pilots of AEM was that JQF was shortly to depart Mangalore southbound via LACEY on climb to 7,000 ft.

Analysis of high-resolution ADS-B information identified that JQF’s take‑off coincided with the pilots of AEM’s call to Melbourne Centre to inform of their descent into Mangalore for airwork. This timing suggests that the pilots of JQF were unlikely to have been actively monitoring transmissions on the Melbourne Centre frequency at this time, including advice of AEM’s descent, due to their focus on the take-off.

AEM reached 15 NM from Mangalore at around 1120:30, just as they finished receiving traffic information from the Melbourne Centre controller. This is the position that previous students of the instructor identified that the instructor encouraged students to make their inbound call. The aircraft reached 10 NM around 1122:30 (Figure 14), which is the latest point the student should have made an inbound call-in accordance with expected CTAF procedures. It is therefore likely that an inbound CTAF broadcast was made during this 2-minute time period. Significantly, that time interval coincided with the time that JQF was in the initial climb, and making a departure call to Melbourne Centre. Therefore, it is possible that the pilots of JQF did not hear this inbound call, nor the pilots of AEM hear the CTAF circuit departure call or the Melbourne Centre departure call from JQF.

AIP GEN 3.4 paragraph 6.16.8 contained information about the standard phraseology expected from pilots making reports after take‑off in particular operating environments. The standard phraseology for a departure report made from a non-controlled aerodrome in a non‑surveillance environment was:

DEPARTED (location)(time in minutes) TRACKING [TO INTERCEPT] (track) CLIMBING TO (intended level) ESTIMATING (first reporting point) AT (time)

The standard departure report phraseology from non-controlled aerodromes under surveillance when notifying departure and identification was expected with the departure report was:

(location reference departure aerodrome) PASSING (current level) CLIMBING TO (intended level) ESTIMATING (first reporting point) AT (time)

AIP ENR 1.1 paragraph 10.6.4 also includes the information

If the pilot transmits the departure report before intercepting the departure track the report must include advice that the aircraft is manoeuvring to intercept departure track.

Radio communication between the Melbourne Centre controller and the pilot under examination in JQF after take‑off was as follows:

      (Note this call was interrupted internally by another Melbourne controller)

While the controller positively identified JQF, the statement made was by the pilots of JQF that they were tracking to LACEY, without the specific information that they were  tracking to intercept the IFR airway from Mangalore to LACEY (Figure 10). Additionally, it did not include detail of the position of JQF with reference to Mangalore, which at the time of the departure report was about 2.2 NM south-south‑west of the airport. While it could not be determined whether the pilots of AEM heard this departure report, the information had the potential to provide them with an incorrect mental model of the aircraft’s relative position. The Airservices investigation report identified that at this time the two aircraft had 8.6 NM lateral separation, and 2,600 ft vertical separation.

There was also a discrepancy with the traffic information, in referencing AEM as a King Air rather than a Travel Air. However, that was unlikely to have had a significant impact on the understanding of the presence of traffic, or its performance, as the groundspeed of AEM was similar to the approach speed of the type of King Air that frequented Mangalore Airport.

Based on the information presented by the velocity vectors, when giving this traffic information the controller judged that JQF would pass behind AEM.

While it would not be expected, as traffic self-separation broadcasts would generally be made on the CTAF, a review of the recording confirmed that neither aircraft attempted to contact the other using the Melbourne Centre frequency.

A review of the air traffic control recordings and transcripts indicated that between 1123:12 and 1124:08, the controller was actively engaged with other aircraft, or co-ordinating aircraft with another controller. It was during this time that the final STCA for the two aircraft occurred.

Automatic Dependent Surveillance Broadcast

Overview

ICAO (2018) defined Automatic Dependent Surveillance Broadcast (ADS-B) as:

A means by which aircraft, aerodrome vehicles and other objects can automatically transmit and/or receive data such as identification, position and additional data, as appropriate, in a broadcast mode via a data link.

ADS-B uses the GNSS for positioning. ADS-B data can be both broadcast (ADS-B OUT) and received (ADS-B IN).

Under Civil Aviation Orders 20.18, both AEM and JQF were required to be fitted with ADS-B OUT equipment to operate under the IFR. Both aircraft were fitted with transponders that complied with this requirement.

To provide an ADS-B based surveillance service, Airservices has a range of ground-based ADS-B receivers. The resulting ADS-B coverage at an altitude of 5,000 ft across Australia is shown in Figure 15. Mangalore Airport was within the coverage area at this altitude. ADS-B coverage improves as altitude increases, and at 30,000 ft almost all flights within Australia can be conducted under an ADS-B surveillance service.

Figure 15: ADS-B coverage at 5,000 ft across Australia

Source: Google Earth and Airservices, annotated by the ATSB.

Cockpit traffic display

Neither aircraft was fitted with a system to receive ADS-B information directly from other aircraft, nor were they required to be. As such, all the positional guidance the pilots had about other traffic was received from the controller and via any received radio broadcasts.

It is possible to receive ADS-B information from other aircraft directly into an aircraft. Aircraft that are fitted with such a receiver (ADS-B IN) can be configured with a cockpit display of traffic information (CDTI) to identify where other aircraft are relative to their position.

CDTI may give an image of the traffic over a moving map or directional guidance about the location of other aircraft. Some of these systems are also able to provide audible and visual alerts to pilots about identified traffic risks.

The CASA CNS/ATM guide (2017) identified some limitations with cockpit displays:

CDTIs will help you spot other ADS-B traffic more easily by showing you where to look. However:

-     Depending on the unit’s filtering capability, your CDTI might not show all ADS-B traffic

-     CDTIs will not display non-ADS-B traffic

-     Don’t try to second-guess ATC instructions with CDTI information

-     Do not attempt to take evasive action, or to separate your aircraft from other traffic, using a CDTI. It is there to enhance situational awareness, not to replace separation procedures.

Cockpit display of traffic information does not replace see-and-avoid. You still have to look out the window for other traffic.

Electronic flight bag

The student pilot in AEM was using ‘AvPlan’ electronic flight bag (EFB)^[33] software installed on an iPad. In addition to the EFB, this pilot was also carrying a paper flight plan and set of relevant approach charts.

AvPlan has an option to display traffic information overlayed on the map display.

Traffic information can be obtained either by:

• having an external ADS-B receiver attached
• using the ‘AvPlan live’ feature.

Use of the AvPlan live traffic information system required the live tracking feature to be turned on, a data connection and a connection to a GPS position. The iPad in AEM was fitted with a SIM card capable of providing the required data connection to AvPlan live, but was not fitted with an external ADS-B receiver. The AvPlan user manual identified that traffic displayed using the AvPlan live function was from:

…other connected airborne AvPlan EFB users, a network of ADS-B ground receivers, and FLARM^[34] ground receivers.

Data displayed using AvPlan live was updated every 5 seconds, rather than every second when an ADS-B receiver was attached. The software had no capability to identify aircraft using other EFB software, or non-ADS-B equipped aircraft. The AvPlan user manual noted:

Note that this traffic is a great start for situational awareness, however it does not include all traffic. Always be on the lookout/maintaining a listening watch for traffic.

Due to the damage to the tablet sustained in the impact, it was not possible to recover data from the iPad to determine whether the traffic information overlay display was selected at the time of the collision.

The ADS-B ground receiver network used by AvPlan for traffic information was not the same as the network used by Airservices for receiving ADS-B data, and there was limited coverage for the AvPlan network in the Mangalore area. Information provided by AvPlan after the accident identified that aircraft in the approximate location of the collision, 5 NM south of Mangalore airport, were not visible as traffic on AvPlan below approximately 4,900 ft. Therefore, as the pilots in JQF were not carrying an AvPlan‑connected iPad and it was unlikely that the AvPlan ADS-B ground network received broadcasts from JQF it is probable that JQF would not have appeared as traffic on the iPad used in AEM, even if the traffic information overlay had been selected.

The use of an external ADS-B receiver significantly increases the frequency of updated traffic information and receives ADS-B broadcasts directly from ADS-B OUT equipped aircraft within range of the receiver. Information from the AvPlan user manual stated:

When AvPlan EFB is connected to an ADS-B receiver, traffic as far as the receiver can observe will be displayed. Traffic sources from the receiver will be coloured green to allow quick identification of a traffic target’s source. No height or distance limitations are placed on traffic delivered by an attached device. Traffic received via this method is updated once every second”.

At the time of the accident, neither AvPlan nor OzRunways, another Australian EFB provider, provided audible alerts about proximal traffic, although at the time of writing AvPlan offered this feature.

Collision avoidance systems

ADS-B also has the ability to feed into an aircraft collision avoidance system (ACAS). Neither aircraft were required to have ACAS fitted.

In describing ACAS, the ICAO (2021) stated:

The objective of airborne collision avoidance systems (ACAS) is to provide advice to pilots for the purpose of avoiding potential collisions….

ACAS has been designed to provide a back-up collision avoidance service for the existing conventional air traffic control (ATC) system while minimizing unwanted alarms in encounters for which the collision risk does not warrant escape manoeuvres. The operation of ACAS is not dependent upon any ground-based system.

By providing pilots with visual information about where other aircraft are operating in their proximity, pilots are able to make more timely decisions based on displayed information and take avoiding action, thereby reducing the risk of collision.

At present in Australia, there are no regulatory requirements for aircraft of the size and operational category involved in this accident to have any form of ACAS fitted to the aircraft.

In 1991 the Bureau of Air Safety Investigation (the predecessor to ATSB) issued the Civil Aviation Authority (the predecessor to CASA) with a recommendation that:

In light of the serious limitations of the see-and-avoid concept, the CAA should closely monitor the implementation of TCAS^[35] in the US and should consider the system for Australia.

In 1998, CASA accepted this recommendation and stated the system would be introduced when cost effective.

Under the current regulations in Australia, an approved ACAS must be fitted any turbine-engine aeroplanes operating under Part 121 (Australian Air Transport Operations – Larger Aeroplanes) that:

Paragraph 11.21

a. Either:

   i.          has a maximum take-off weight of more than 15,000kg; or

   ii.         has a maximum certificated passenger seating capacity of more than 30; or

b. Is first registered, in Australia or elsewhere, on or after 1 January 2014, and:

   i.          has a maximum take-off weight of more than 5,700 kg but not more than 15,000kg; or

   ii.         has a maximum certificated passenger seating capacity of more than 19 but not more than 30.

Aircraft operating under Part 135 (Australian Air Transport Operations – Smaller Aeroplanes) must be fitted with an approved ACAS if they are turbine-engined, have a maximum take-off weight of more than 5,700kg and was first issued with a certificate of airworthiness on, or after, 1 January 2014. There are no regulations requiring fitment of an ACAS to aircraft equivalent to AEM and JQF.

Meteorological information