Safety summary

What happened

On 27 October 2020, train 2PM9, operated by SCT Logistics, departed Perth, Western Australia for Melbourne, Victoria. Near Koolyanobbing, Western Australia, a wheel fractured and disintegrated on the 58th vehicle on the consist, wagon ARFY2253s, resulting in a derailment. The derailed wagon and those trailing separated from the train, but no other wagons derailed. There were no injuries.

What the ATSB found

Detailed material examination identified that a transverse fatigue crack initiated in the vicinity of a spalling defect in the wheel tread prior to the incident journey. The crack propagated into the rim and flange of the wheel. On the day of the incident, a skidding event at the fatigue crack likely induced rapid brittle cracking in the wheel. This resulted in its fragmentation and subsequent derailment.

In the 12 months prior to the occurrence, ARFY2253s experienced various issues with brakes and overheated wheels, although it is not clear whether any of these issues contributed to the derailment.

The failed wheel was recently reprofiled, but the maintenance provider’s work instruction did not require non-destructive examination beyond a visual inspection to identify any remaining defects.

What has been done as a result

The operator and maintenance provider have developed a process for monitoring wagons that experience repeated issues, such as with braking. Inspection procedures for thermal cracks and overheated wheels have been refined, and non-destructive testing is being investigated for use in certain wheel inspections.

Safety message

Skids and hotspots may be repairable on wheels in otherwise good condition, however, they can induce wheel failure if cracks are present, as in this case. Diligent inspections and non-destructive testing can be useful for detecting and monitoring wheel cracks, which is particularly important as these cracks approach the wheel wear condemning limit.

The investigation

The occurrence

On the morning of 27 October 2020, train 2PM9, operated by SCT Logistics, departed Perth, Western Australia for Melbourne, Victoria. The train was 1,658 metres long, and consisted of 2 locomotives hauling 68 wagons, with a trailing load of 3,690 tonnes. At 0816 Western Standard Time,^[1] the train was approaching a restricted speed zone and the driver applied the automatic brakes. At 0841, while approaching Koolyanobbing, the trailing left wheel on wagon ARFY2253s fragmented, and two large pieces of the wheel were ejected. ARFY2253s was the 58th wagon in the consist. The wagon’s braking system used a WF2 triple valve, and the wagon was unloaded with a tare mass of 30.84 tonnes. The train continued without incident, and the driver applied the dynamic brake in preparation for an upcoming turn. At 0843, approximately 3.5 km beyond the initial wheel fragmentation, a third piece of the wheel was ejected, and the wagon derailed (Figure 1).

Figure 1: The derailed wheelset on ARFY2253s

Source: SCT Logistics

At this point, the crew observed dust towards the rear of the train, and applied both the dynamic and automatic brakes until the train came to rest at 0846. Upon inspection it was found that ARFY2253s and the trailing ten wagons had separated from the train. No other wagons derailed. Track damage was observed over a distance of 2.4 km between the wagon derailment and its stopping point.

Context

Wheel fracture examination

The derailed wheelset and the ejected wheel pieces were recovered from the site by Gemco Rail (Gemco), SCT Logistics’ primary maintenance provider. Gemco contracted independent consultants Bureau Veritas to conduct a metallurgical examination of the derailed wheelset in order to determine that nature of the failure, and any aspects that may have contributed.

Figure 2 shows the recovered fragments of the rim, labelled 1-3, and the three fractures that separated the different pieces, labelled A‑C. Fragments 1 and 2 were the first to be ejected from the wheel during the incident journey, with fragment 3 ejected after the brakes were applied.

Figure 2: Reassembled wheel fragments (left) and wheel hub (right)

Source: Bureau Veritas, annotated by ATSB

The Bureau Veritas analysis identified a fatigue crack at the surface of the wheel, within fracture A (Figure 3). The fatigue crack presented as a darkened region on the fracture surface, with distinct beachmarks indicating crack propagation into the wheel rim and flange from the initiation point on the surface. The fatigue appeared to have propagated through approximately 40 per cent of the wheel rim’s cross section. Bureau Veritas made no comment on the age of the fatigue crack.

Figure 3: Fracture A on fragment 1 of the wheel

Source: Bureau Veritas, modified by ATSB

The Bureau Veritas report concluded that the wheel failure originated from this fatigue crack. At some point, the fracture mode changed from fatigue to brittle cracking, indicated by the colour and surface texture change between the fatigue crack and the rest of the wheel cross section. The brittle cracking progressed towards the wheel hub. It then propagated circumferentially around the wheel, branching out to the wheel surface, resulting in the ejection of the three wheel fragments.

A heat tint mark was also present on the fracture surface. Heat tinting such as this is indicative of oxidation, a result of freshly exposed steel that is subjected to heat and oxygen. The Bureau Veritas examination also identified skid marks on the wheel surface near fracture A.

In addition to skid marks, the wheel surface near the fatigue crack had multiple spalls and gouges (see Figure 4). Fluorescent magnetic particle inspection also revealed multiple transverse and longitudinal cracks around these surface defects. Several cracks were found that extended below the wear condemning limit^[2] of the wheel rim.

Figure 4: Wheel surface adjacent to fracture A

The left image shows the various spalling and gouging observed on the wheel surface. The right image shows numerous surface cracks under fluorescent magnetic particle inspection. Source: Bureau Veritas, modified by ATSB

Hardness testing was performed on several sections of the wheel. The heat-affected regions showed some surface hardening outside of the specification for Class B^[3] forged steel wheels such as these, although this would be expected in the event of a skid. Some areas within the wheels were slightly under the minimum specified hardness, but the report did not find this to have contributed in any way to the wheel failure, and since these regions were below the wear condemning limit, this was permitted by the wheel specification.

Wheel maintenance and inspections

In the 12 months before the derailment, wagon ARFY2253s experienced a variety of issues requiring maintenance, including brake defects and uneven wheel wear. Wheelsets were replaced twice as a result. The most recent wheelset change was 4 months before the derailment, when the incident wheelset 92709 was installed on the wagon due to overheated wheels.

Prior to installation on the wagon, wheelset 92709 was re-profiled. The rim thickness was reduced to 34 mm from 44 mm to remove hollowing and spalls that were observed on the wheel tread. Gemco’s wheel reprofiling work instruction was based on the Association of American Railroads Specifications Manual. Regarding the removal of defects such as spalling and shelling, Gemco required a visual examination following wheel reprofiling, but neither document required any non‑destructive testing, such as fluorescent magnetic particle inspection.

The Australian Standard for wheel maintenance current at the time of writing (AS 7514:2018) referred to the Rail Industry Safety and Standards Board’s Code of Practice – Wheel Defects. Regarding the reprofiling of spalled wheels, it stated:

Rectify spalling or shelling by machining to a sufficient depth (3 mm minimum) to completely eliminate it, and carry out crack detection after machining.

Crack detection was not explicitly defined in the document, but it included visual inspection, magnetic particle inspection and dye penetrant inspection as examples.

Following the installation of wheelset 92709, dragging brakes were reported on the wagon on two occasions. The wheels were inspected on the second occasion and no defects were noted.

SCT Logistics investigation

As a result of the derailment, SCT Logistics contracted an independent investigator to determine any potential factors that led to the derailment. In the resulting investigation report it was noted that a wheel flat was present at fracture A, and the flat’s worn edges indicated that it may have occurred some time ago, on a previous journey. The report examined readings from wayside detectors on the day of the derailment and from previous journeys, but found no evidence of a wheel flat being detected.

The independent investigator’s report found that the fatigue crack at fracture A resulted in the wagon’s derailment. It determined that the crack originated from a spall on the wheel’s surface. The report also stated that the brittle fracture of the wheel was likely initiated by the braking event prior to entering the restricted speed zone during the incident journey.

The report stated that wagon and bogie maintenance were ‘…considered to be a major contributory factor in this derailment event.’ It highlighted previous brake-related maintenance, and suggested that it was indicative of unresolved braking issues. The report attributed the observed wheel defects, including flat-spotting, skids, spalls, and the fatigue crack to these braking issues.

The investigation also looked at train handling and crew performance during the incident journey, and found all actions to be in accordance with accepted procedures and good driving practice.

Related occurrences

ATSB Investigation (RO-2019-001)

On 6 January 2019, SCT Logistics freight train 6MP9 derailed near Cook, South Australia after a wheel fragmented on one of the wagons. Inspection of the failed wheel found that thermal damage resulted in the initiation of a fatigue crack that propagated into the wheel, ultimately leading to its fragmentation.

At the last inspection—carried out by Gemco—the flange crack was likely observable but was either not detected, or was deemed acceptable under the provided work instruction. This work instruction was less conservative than the Australian Standard, but it was not possible to establish whether compliance with the standard would have prevented the occurrence.

Following the derailment, SCT Logistics worked with Gemco to improve inspection processes for wheels with brake issues. SCT Logistics also instructed Gemco to only install Class B wheelsets in future, after the wheel manufacturer stated that Class C wheelsets—such as the one that failed—were more prone to thermal issues.

Safety analysis

Visual examination of the wheel fracture surfaces found that a fatigue crack initiated at the surface of the wheel tread, in the vicinity of a spalling defect. The fatigue crack propagated into the wheel tread and the flange, consuming approximately 40 per cent of the wheel rim cross section prior to failure. The dark colour of the fatigue region was indicative of corrosion in a low‑oxygen environment—before the crack opened at wheel failure. This suggested that the fatigue crack had existed for some time, and was certainly present before the incident journey. However, it was not possible to determine whether or not this crack existed in some form the last time the wheel was reprofiled or examined by maintenance personnel. Given that the fatigue crack might have been present when the wheel was last reprofiled (removing visible spalls), then the nearby spalling defect may have been unrelated.

The skid marks, flat spot and heat-affected regions at fracture A (Figure 2) all indicated that a skidding event occurred at this location, probably when the automatic brakes were applied before the restricted speed zone. This skidding event would have generated considerable heat, and the heat tint observed on the fracture surface is evidence that the brittle cracking occurred at the same time as this heat generation. It is therefore likely that the skidding event induced the brittle cracking at fracture A. Once the brittle cracking commenced, it quickly propagated through the wheel, resulting in the failure and subsequent derailment.

In SCT Logistics’ independent report, it was suggested that the flat spotting might have occurred on a previous journey, gone undetected by wayside monitoring, and even contributed to the fatigue crack. However, if this was the case, a second skidding event would had to have occurred at the same location during the incident run in order to generate the heat tint seen on the fracture surface.

Wagon ARFY2253s had a number of issues with brakes and overheated wheels in the 12 months leading up to the derailment. It is not clear whether these were resolved through maintenance actions, so it is possible that they contributed to the development of the fatigue crack as well as the skid during the incident journey. However, without additional evidence, it was not possible to determine the degree of contribution, if any.

Findings

From the evidence available, the following findings are made with respect to the derailment of SCT Logistics freight train 2PM9, near Koolyanobbing, Western Australia on 27 October 2020.

Contributing factor

• Prior to the incident journey, a transverse fatigue crack initiated in the vicinity of a spalling defect on the tread surface, and propagated into the wheel rim and flange.
• During the incident journey, a skidding event likely induced rapid crack growth from a pre‑existing fatigue crack. This resulted in fragmentation of the trailing left wheel and subsequent wagon derailment.

Other factor that increased risk

• In the 12 months prior to the occurrence, wagon ARFY2253s experienced various issues with brakes and overheated wheels, which can increase the risk of wheel failure.

Safety action

The operator and maintenance provider

As a result of this occurrence, SCT Logistics and Gemco have developed a process for monitoring wagons that experience repeated issues, such as with braking. Gemco staff are completing refresher courses on the field inspection of wheels, and inspection procedures for thermal cracks and overheated wheels have been refined. Non-destructive crack detection is being investigated for use on inspections following overheated or skidded wheels.

Sources and submissions

Sources of information

The sources of information during the investigation included the:

• SCT Logistics
• Gemco Rail
• Bureau Veritas
• the Rail Industry Safety and Standards Board.

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 Office of the National Rail Safety Regulator
• SCT Logistics
• Gemco Rail
• Bureau Veritas
• the wheel manufacturer.

Submissions were received from:

• the Office of the National Rail Safety Regulator
• SCT Logistics
• Gemco Rail
• Bureau Veritas
• the wheel manufacturer.

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

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.

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1. Western Standard Time (WST): Coordinated Universal Time (UTC) + 8 hours.
2. The wear condemning limit marks the maximum allowable wear in a wheel before it must be replaced
3. Class B is a specification defined by the Association of American Railroads. Wheel hardness and ductility varies with class. Class B wheels are softer than Class C wheels, with a higher fracture toughness.

Executive summary

What happened

In the afternoon of 4 November 2020, a training flight was conducted in an Aquila AT01, registered VH‑OIS (OIS) which departed Bankstown Airport with a Grade 1 flight instructor and a student onboard. The flight was conducted to assess the readiness of the student to complete the commercial pilot licence flight test for aeroplanes. The flight continued normally, proceeding to Coombing Park Aeroplane Landing Area (ALA), where the student demonstrated the conduct of a precautionary search, an expected exercise during this flight. However, following the precautionary search, a touch‑and‑go was performed. During the subsequent climb away from the runway, the aircraft collided with terrain. Both pilots received fatal injuries.

What the ATSB found

The ATSB found that pre-flight planning was likely not performed to identify if Coombing Park ALA was suitable for flight training operations. This placed more importance on the conduct of the precautionary search to identify the rising terrain hazard in the overshoot area of the runway. The precautionary search was conducted at a height and position that likely made assessing the hazard less effective, leading to the pilots deciding to conduct a touch-and-go landing and take-off toward the rising terrain beyond the runway end. Further, the take-off was conducted on an uphill slope with a probable tailwind. A standing take-off in the more favourable reciprocal direction would likely have cleared all obstacles and terrain.

Although the touch-and-go was typical of those conducted by the student, it likely used more runway than if a standing take-off was conducted, leading to the aircraft becoming airborne further along the runway, and closer to the rising terrain. Consequently, although the aircraft was likely performing normally, the aircraft had insufficient performance to outclimb the rising terrain in any direction once established on the initial climb after take-off.

The ATSB also found that the operations manual used for flight training that was based on the CASA sample operations manual allowed the use of any aerodrome (including ALAs) in the Enroute Supplement Australia to be used, although these were not assured to any operational standard. Further, the recommendations contained in CASA guidance CAAP 92-1(1) (although subsequently replaced by AC 91-02 as noted below) did not provide assurance that an aircraft would be able to outclimb rising terrain after take-off more than 900 metres from the runway end.

What has been done as a result

CASA advised that legislation and guidance relating to obstacle clearance in the approach and take-off areas of ALAs was introduced on 2 December 2021. Included in these changes were the replacement of CAAP 92-1(1) with Advisory Circular AC 91-02 titled ‘Guidelines for aeroplanes with MTOW not exceeding 5,700 kg – suitable places to take-off and land’ (the AC).

In contrast to CAAP 92-1(1), the AC included guidance for a pilot to consider and be aware of ‘lateral transition areas’ and ‘obstacles in the approach and climb-out flight paths’, in deciding if an aerodrome is suitable for operations. Further, the introduced regulations require that pilots ensure that the aeroplane has the performance to clear all obstacles by a safe margin until at the minimum height for flight.

Safety message

This investigation shows that the lift-off location following a touch-and-go is more variable and complex to predict than a standing take-off. In this case, the touch-and-goes conducted throughout the flight consistently used more runway than a standing take‑off. This contributed to the aircraft lifting off from a point where the available climb performance of the aircraft was not sufficient to outclimb the rising terrain. This characteristic is particularly important for flights to unfamiliar aerodromes, where the aerodrome characteristics should be considered to confirm if a touch‑and‑go is feasible, particularly for uncertified aerodromes. Additionally, as was the case here, the runway slope, wind and rising terrain at one runway end may mean that the optimal landing and take-off directions are in opposing directions, which cannot be achieved when conducting a touch-and-go.

The investigation also highlights the value of following operator’s procedures as an important risk control to aid planning and in-flight decision making. For this accident, the operator’s procedures did not allow landings to be conducted at the aerodrome where the accident occurred. This meant that the execution of the precautionary search was one of the last remaining defences to identify the rising terrain hazard during take-off, which was ineffective.

Operators should also be aware that aerodromes meeting the recommendations in the CASA guidance publication CAAP 92-1(1) (now obsolete) are not assured that an aircraft will be able to successfully climb away after take-off more than 900 metres past the runway end. The new performance-based recommendations of AC 91-02 now require operators to consider obstacle clearance beyond 900 metres. Flight training operators should also note that there are no standards for ALAs (listed in the ERSA as uncertified aerodromes). The published data for these uncertified aerodromes are potentially incomplete or inaccurate, including obstacle information. This means that for take-off from these aerodromes, the new guidance requires pilots and operators to know the climb gradient needed to clear all obstacles by a safe margin until the aeroplane reaches the minimum height for flight.

Summary video

Pre-flight and departure from Bankstown

In the afternoon of 4 November 2020, a training flight was conducted in an Aquila AT-01 aeroplane, registered VH‑OIS (OIS) between Bankstown Airport and Orange Airport, New South Wales (Figure 1). On board were a Grade 1 flight instructor (the instructor) employed by Soar Aviation (Soar), and a student (the student) of Soar. This flight was required by Soar to assess the readiness of the student to complete the Commercial Pilot Licence (Aeroplane) (CPL(A)) flight test administered by the Civil Aviation Safety Authority (CASA).

Figure 1: Flight path of VH-OIS and accident location

Source: Google Earth and Geoscience Australia, annotated by ATSB.

Automatic Dependent Surveillance Broadcast (ADS-B) data transmitted by OIS (the flight data)[1] indicated the aircraft started to taxi to a run-up[2] bay adjacent to Bankstown Airport runway 29R at 1419. The aircraft remained in the bay for about 5 minutes then, following engine run‑ups, the pilots[3] taxied OIS toward the runway 29R threshold, with take-off commencing at 1431 followed by an upwind[4] departure.

After departing the Bankstown Airport airspace, OIS initially tracked toward the west‑north‑west before turning left onto a west-south-westerly track about 19 km from Bankstown Airport, towards the planned track to Greenethorpe Township, about 220 km away. OIS continued tracking toward Greenethorpe until 1507, when the pilots turned right, tracking north-west toward a grassed area adjacent to the western side of the Blue Mountains.

Diversion to Orange

Flight data indicated that, once overhead the grassed area, the pilots conducted 4 left orbits[5] (blue track in lower centre of Figure 1) at an altitude between 6,000 and 7,000 ft above mean sea level (AMSL). After completion of the orbits, OIS was established on a track in the general direction of Orange township. At 1526, about 6 minutes after setting course toward Orange, the pilots of OIS contacted air traffic control and requested a flight plan amendment from the original track (to a location near Greenethorpe Township) to Orange Airport and back to Bankstown Airport, with no change to the SARTIME. The flight plan amendment and change in track was consistent with the instructor requiring the student to demonstrate an inflight diversion, as labelled in Figure 1.

At 1553, the pilots of OIS arrived overhead Orange Airport, and joined the crosswind leg of the circuit for runway 29 for the first of 4 touch-and-go landings and circuits, as shown in Figure 2. Flight data (shown by the green line in Figure 2) and eyewitnesses indicated that after the completion of the fourth touch‑and‑go on runway 29, as OIS was on the late crosswind circuit leg, a descending left turn was conducted, with the aircraft manoeuvred to align with the reciprocal runway 11. A touch-and-go landing was then conducted on runway 11 followed by a left circuit (dark blue line in Figure 2) and full stop landing on this runway at 1726. The pilots taxied to the main parking area at Orange, with flight data indicating the aircraft was stationary for about 1 minute. During this time, photographs taken by an eyewitness and CCTV footage showed the canopy partially opened and the student looking at a map, with other eyewitnesses indicating that the pilots spoke with one another.

Figure 2: Flight path of VH-OIS at Orange Airport

Source: Google Earth, annotated by the ATSB

After a total of 8 minutes on the ground, OIS entered the main runway from the eastern taxiway and backtracked toward the runway 11 threshold. At 1637, the pilots broadcast that they were rolling on runway 11 and an upwind departure was conducted. Flight data indicated that during the initial climb from the runway, OIS maintained a nominal track on the extended runway centreline for about 9 km.

Audio recordings of transmissions from the Orange common traffic advisory frequency (CTAF) indicated that during this time, both pilots of OIS were in communication with an inbound passenger carrying flight. Once at about 9 km from the runway, the pilots of OIS broadcast on the CTAF that they were on a heading of 130° magnetic and levelling out at 5,000 ft AMSL, consistent with the flight data. OIS turned right briefly toward the township of Blayney and then left to proceed on a south-easterly track for about 2 minutes before turning right onto a south-westerly heading in the general direction of the township of Carcoar and Coombing Park aeroplane landing area (ALA).

Operations at Coombing Park

At 1653 a descent was commenced when OIS was abeam Coombing Park ALA, approximately 3 km to the north of the main east-west runway (runways 07 and 25) as shown in Figure 3. The pilots conducted 3 nominally rectangular patterns around Coombing Park runway 07.

At 1704, while on the easterly leg of the third pattern, the instructor of OIS made a phone call to the property manager of Coombing Park that lasted 24 seconds. The property manager recalled the instructor identifying themselves as an instructor from Soar Aviation and requesting permission to conduct a touch-and-go at Coombing Park. The property manager reported that they thought OIS was on the downwind leg for runway 25, and on this basis approved the touch‑and-go.

The pilots positioned OIS to land on runway 07, with flight data showing the aircraft on a descending profile on the base, and final approach circuit legs. The property manager described the final approach as stable and observed OIS descending to very near the ground at the runway 07 threshold. OIS was not visible to the property manager after this time due to their vantage point being slightly below the runway, however the manager, who was also a pilot, indicated that the projected touch-down point would have been very close to the runway 07 threshold based on the observed approach.

Flight data indicated that OIS passed over the runway 07 threshold at 1708, touched down and rolled along the runway surface. About 30 seconds after passing over the runway threshold, OIS become airborne again and commenced a climb, passing through 50 ft AGL approximately 900 m from the start of runway 07.

Figure 3: Flight path of OIS while operating at Coombing Park ALA

Source: Google Earth and Aireon, modified and annotated by the ATSB

During the initial climb, OIS tracked in a straight line angled slightly left of the runway centreline. Flight data indicated that, about 20 seconds later as OIS climbed through 200 ft above the lift-off point, a climbing left turn was conducted by the pilots before flying straight again in the direction of a small dam, beyond which was a less wooded area. OIS passed over the small dam and collided with an embankment on the far side of the dam. A witness heard the sound of the impact, although they did not realise it was an aircraft accident at the time, and there were no eyewitnesses to the accident.

At 1800, air traffic services commenced trying to contact the pilots of OIS via radio. At 1832, after being unsuccessful in contacting the pilots, an INCERFA[6] was declared with the search and rescue response being transferred to the Joint Rescue Coordination Centre. Local authorities were notified, and a search was commenced in the area. At 2157, the wreckage of OIS was located, and it was confirmed that both pilots had sustained fatal injuries.

Context

Pilot information

Flight instructor

Qualifications

The instructor held a valid commercial pilot licence (aeroplane) issued in March 2009, and a flight instructor rating issued in March 2010. The instructor also held a grade 1 training endorsement to instruct in single- and multi-engine fixed wing aeroplanes.

The instructor was also endorsed to conduct training for the issue of instrument and night VFR ratings. They passed a proficiency check for the flight instructor rating on 13 January 2020 that was valid at the time of the accident. Additionally, the instructor’s flight crew licence indicated that they had completed single- and multi-engine aeroplane flight reviews on 13 January 2020 and 28 July 2019 respectively that were also valid.

Experience

A review of the instructor’s logbooks, staff files and flight data showed that at the time of the accident they had accumulated a total flying experience of approximately 3,169 hours. About 16 of those hours were in the previous 30 days and about 56 hours were in the last 3 months. Most of the instructor’s flying experience was in single-engine aeroplanes (3,002 hours), with the instructor recording approximately 2,584 hours of total experience as a CASA‑qualified flight instructor. Staff records indicated that the instructor had accumulated 2,421 hours while working for the operator. The instructor had approximately 569 hours in the AT-01, the same type flown on the day of the accident, with about 33 hours in the last 3 months on that type.

Medical information

The instructor held a Class 1 aviation medical certificate that was valid until 12 June 2021 with no restrictions. The instructor was reported to be fit and active and in a good state of mind in the days before the flight and was likely well-rested. The instructor was not reported to be taking any prescription medications and had no reported medical condition that could have affected their ability to operate an aircraft that day. A post-mortem examination identified no significant background natural disease, which could have contributed to the accident.

Student

Qualifications

The student held a recreational pilot licence for single engine aeroplanes issued in December 2018, with a navigation rating for this licence issued in September 2019. The student also held recreational licence ratings for operations in controlled airspace, operations at controlled aerodromes and for the operation of flight radio. Additionally, the student was endorsed to operate aircraft with manual propeller pitch control. The student’s licence did not have an expiry date and was valid at the time of the flight.

Experience

A review of the student’s logbooks, student files and flight data showed that at the time of the accident the student had accumulated a total flying experience of approximately 259 hours. About 10 of those hours were in the previous 30 days and about 13 hours were in the last 3 months. Operator’s records indicated that the student had accumulated 174 hours while training with the operator, with the remaining 85 hours acquired previously at another flying school. The student had approximately 72 hours in the AT-01, the same type flown on the day of the accident, with all 13 hours flown in the last 3 months being on that type.

Medical information

The student also held a class 1 aviation medical certificate that was valid until 20 October 2021 with no restrictions. The student was reported to be well rested in the days before the flight. The student was not reported to be taking any prescription medications and had no reported medical condition that could have affected their ability to operate an aircraft that day. A post-mortem examination identified no significant background natural disease, which could have contributed to the accident.

Pilot fatigue information

Based on reported sleep data alone, it is unlikely that the crew were fatigued. It is possible that the student may have experienced some mental fatigue due to the assessment nature of the flight. However, there was insufficient evidence to make that determination. Further, the instructor was unlikely to be fatigued at the time of the accident.

Aircraft information

Overview

VH-OIS (OIS) (Figure 4) was an Aquila AT01 fixed-wing aircraft manufactured in 2012. The aircraft was first registered in Australia on 14 December 2012 to Soar Aviation Aircraft Holdings Pty Ltd (Soar). The aircraft was a two-seat, low‑wing training aircraft constructed from carbon fibre and fiberglass. Control surfaces were a mixture of push rod and cable operated. The power plant was a Rotax 912S with a two-blade constant speed propeller.

Figure 4: VH-OIS

Figure 4 shows VH-OIS on display at Avalon Airshow

Source: Andrei Bezmylov, used with permission

Maintenance

OIS had a current maintenance release located in the aircraft, issued on 1 September 2020 which was valid for a period of 150 hours or 12 months, whichever was sooner. At the time of the accident the aircraft had accrued 31.6 hours since the maintenance release issue and had a total time in service recorded as 3,540.9 flight hours.

The aircraft was maintained to the airframe and engine manufacturer’s inspection schedules with an operational category of aerial work. At the time of the accident, there were no listed defects or outstanding maintenance endorsed on the maintenance release.

Aircraft weight and balance

The aircraft had a valid load data sheet, with the empty weight and centre of gravity data approved on 30 October 2013. Weight and balance calculations performed by the ATSB found that OIS was below maximum take-off weight and within centre of gravity limits for the duration of the flight.

Flight data

The aircraft was not fitted with a flight data recorder or a cockpit voice recorder, nor was either required by regulations. Some Aquila models were fitted with a KAPI electronics flight data recorder, however, the manufacturer advised that this device was not fitted to OIS at the time of manufacture.

The primary source of flight data for OIS on the day of the accident was from satellite-based ADS‑B receivers operated by Aireon. These receivers are onboard the Iridium satellite constellation.

Aerodrome information

Coombing Park was classified as an ‘uncertified’ aerodrome, otherwise known as an aeroplane/aircraft landing area (ALA) and included one primary grass runway, and another shorter grass runway aligned about 70° from the primary runway (Figure 5). Coombing Park had an ICAO designator of YCPK, an elevation of 2,350 ft and had a common traffic advisory frequency (CTAF) of 119.0, shared with Orange Airport. The primary runway was nominally aligned in an east-west direction, at about 73° magnetic (85°T) (designated runway 07/25), and had a length of just over 1,200 m. The shorter runway was about 400 m long and aligned in a south-westerly and north-easterly direction and was reported as not being available for use.

The primary runway had a cleared area of more than 30 m on each side of the runway centreline that was free of obstacles. The runway at Coombing Park appeared in good condition at the time of the accident, with the surface being firm, the grass relatively short, and the conditions dry. The gradient of the runway matched the contours of the ground, rising in the direction of runway 07. Rising terrain existed to the east of the field, increasing to a local peak about 350 ft above the runway elevation about 1 km from the end of runway 07.

Two windsocks were present, one near the intersection of the 2 runways and the other near the end of runway 07 on the southern side, as shown in Figure 5. Both windsocks appeared complete, free to move, and in good condition. Powerlines were present about 200 m from the end of runway 25 crossing the extended centreline in a north-south direction less than a 5% gradient from the runway 25 threshold.

Figure 5: Coombing Park ALA facing north-east

Imaging showing a grass runway. Labels show location of the accident site, cross strip, touch down area of runway 07 and Carcoar township.

Source: ATSB

Information about Coombing Park ALA was available in the OzRunways application. This application was installed on the flight instructor’s mobile phone and was in use during the flight. At the time of the accident, the application had an additional ‘remarks’ section for Coombing Park that included:

Bird and animal hazard exist.

Rising terrain east of field.

No other procedures were included in this guide, nor were they required by any regulations. However, following the accident on 12 November 2020, additional information about Coombing Park ALA was included in the OzRunways application. The ‘remarks’ section was updated to include:

Rising terrain to East, crosswind departures from [runway] 07 only
 

Terrain at 3,953 within 3NM of field.

No go around on [runway] 07

Power lines at end of [runway] 25

Additionally, ‘procedures’ were added to the OzRunways application in the same update that included:

 

RH circuits on runway 07

Crosswind departures from [runway] 07

Up wind departures from [runway] 07 prohibited

Simulated engine failures prohibited

Engine failure on [runway] 07: make RH turn and glide to creek flat

Coombing Park ALA was not included in the Enroute Supplement Australia (ERSA).

Meteorological information

Weather information used by the pilots

Documents onboard the aircraft indicated that the student prepared a location briefing, including weather information, at 1304 using NAIPS. This briefing included a graphical area forecast (GAF)[7] for the planned area of operations, aerodrome forecasts (TAFs) and reported observations (METARs)[8]. TAFs and METARs were obtained for Bankstown and Young Airports, and METARs for Cowra Airport. Young Airport was located approximately 35 km from the originally‑planned waypoint near Greenethorpe Township. QNH[9] was also requested for the area of operations and was predicted to be 1014 for the duration of the flight.

The forecasts obtained by the student (TAFs and GAF) covered the duration of the planned flight. The TAF released at 1226 for Young Airport contained predictions for CAVOK[10] conditions. Surface winds were forecast at 12 kt from a westerly direction 290° (True), with the temperature ranging from 26‑28 °C. The GAF issued at 0924, and found onboard the aircraft, predicted visibility greater than 10 km and no significant cloud or weather phenomena for the duration and planned area of flight.

Post‑accident weather analysis

GAFs for the area of operations, TAFs and METARs for Bathurst and Orange Airports, and METARs for Cowra Airport were obtained from the Bureau of Meteorology (BoM) covering the duration of the flight. Although not requested by the student, the TAF released at 1234 for Orange Airport predicted similar operational conditions to Young. These were CAVOK, with similar surface winds at 10 kt also from a westerly direction (260° True), with a temperature of 22 °C. All forecast conditions evaluated predicted suitable weather conditions for flight under the visual flight rules.

Observed conditions at Orange Airport during circuits

The METAR for Orange Airport released at 1500, 4 minutes after OIS arrived, indicated similar conditions to those predicted by the TAF released at 1234. Visibility was greater than 10 km with no cloud detected, and surface winds were reported at 10 kt from a westerly direction (250° True), and a temperature of 24 °C and QNH 1016. Similar conditions were reported in the METAR released at 0530, 7 minutes prior to the departure of OIS from Orange. However, the wind direction changed to a south‑westerly direction (210° True) at 10 kt, with the temperature dropping to 23 °C and QNH 1015.

Estimated conditions on arrival at Coombing Park

Weather observations from Bathurst, Orange and Cowra Airports were used by the ATSB and the Bureau of Meteorology (BoM) to estimate conditions at Coombing Park ALA at the time of the accident (1709). These were the nearest aviation meteorological sites surrounding the ALA, with Cowra Airport being 50 km to the south-west, Orange Airport being 28 km north and Bathurst being 55 km to the north-east.

All METARs released at 1700 for these locations showed visibility greater than 10 km and no cloud detected, consistent with eye-witness reports from the time of the accident. QNH was recorded in METARs as 1011 at Cowra, 1015 at Orange, and 1014 at Bathurst, and was estimated as 1015 for Coombing Park, being closest to Orange. Temperature in the same METARs was 29 °C at Cowra, 23 °C at Orange and 25 °C at Bathurst, and was estimated as 24 °C at Coombing Park, based on the aerodrome elevation and proximity to Orange.

Surface wind analysis

The BoM conducted an analysis of surface winds at the accident site based on the surface winds reported in 1-minute intervals at Cowra, Orange, and Bathurst. BoM estimated a surface wind direction of westerly though north-westerly, with an estimated wind speed of 5‑10 kt, possibly up to 15 kt. Surface wind gusts were not expected to exceed 5‑15 kt, although gusts up to 20 kt were possible, consistent with observed wind gusts at Cowra, Orange and Bathurst. Based on this analysis, if the wind was north-westerly, the mean tailwind component on runway 07 was estimated between 3‑6 kt, gusting up to 13 kt.

If the wind was from a westerly direction, the mean tailwind component was estimated between 5‑10 kt and gusting up to 20 kt. The crosswind component would have likely ranged between 2‑8 kt from the left of OIS, and possible crosswind gusts up to 15 kt. Based on the runway direction, BoM reported that it was unlikely that there was a headwind component to the surface wind over the runway at the time of the accident.

Estimation of tailwind

The ATSB also estimated the tailwind component on runway 07, based on the groundspeed of OIS during approach to land. Flight data indicated that the ground speed on late final approach of OIS was about 67 kt. Based on a recommended approach indicated airspeed of 60 kt, as required by the AFM for OIS, the nil wind ground speed or true airspeed at the elevation of Coombing Park for this indicated airspeed was calculated as 62.3 kt. Based on this, the mean tailwind component was estimated to be 5 kt, within the bounds of the probable wind speed provided by the BoM.

Aircraft performance information

Touch-and-go information

Data for the accident flight showed that, following the 2 left precautionary search patterns around Coombing Park ALA, the aircraft flew parallel to the main runway (corresponding to the left downwind leg for runway 07) before a left descending turn was conducted (base leg). At the completion of this turn the aircraft was slightly right of the runway 07 centreline, approximately 1,200 m horizontally from, and 300 ft above, the runway threshold. The approach flight path indicated that a slight left tracking correction was likely performed to align the aircraft with runway 07. An eye-witness, who was a pilot familiar with the strip and situated approximately 300 m to the west of the runway 07 threshold reported that the aircraft flew about 40 ft above the trees in a very flat, low and slow approach.

The eye-witness also reported that the approach appeared to be smooth, well configured and balanced, to have lots of flap out, with the engine sounding normal. At the time the aircraft flew past, the runway was not visible to the eye-witness due to the vantage point being slightly below the runway threshold. However, the eye-witness recalled stating to a friend that they hoped the aircraft didn’t land short of the strip when observing the approach. The eye-witness expected that the aircraft would have touched down ‘right near’ the runway 07 threshold, based on the flight path and slow airspeed observed. There were no witness marks identified by the ATSB on the runway surface that were indicative of a hard or abnormal landing. The touch down area for runway 07 (Figure 5) was slightly less grassed than other parts of the runway, consistent with normal landings in that area, no marks were found that could be attributed to the touch-and-go.

ATSB evaluation of flight data along the runway strip showed that the previously‑observed descent rate during the approach was no longer discernible shortly after the aircraft crossed the runway 07 threshold. However, it was not possible to identify the exact position of touch down due to the precision of this data. This data also indicated that the aircraft crossed the runway threshold at a ground speed of approximately 60 kt, with the aircraft beginning to reduce speed about 5 seconds after this point. Within about 10 seconds, the groundspeed reduced to a minimum speed of about 44 kt approximately 400 m past the runway threshold. The flight data then indicated that OIS began to accelerate, consistent with application of engine power by the pilots. ATSB evaluation of flight data estimated that lift-off and climb to 50 ft likely occurred approximately 929 m from the runway 07 threshold, attaining a stable ground speed of about 63 kt during the initial climb.

Evaluation of touch‑and‑go length

The ATSB performed a comparative analysis between the length (distance from the runway threshold to the take‑off point) of the touch-and-go at Coombing Park compared to the length of 4 touch-and-go landings and the standing take-off conducted at Orange Airport. The purpose of the analysis was to identify any factors that may have increased the length of the touch-and-go at the ALA. Further detail on this analysis, including methodology, additional context and findings of this analysis are described in Appendix A – The influence of touch‑and‑goes to the accident involving VH-OIS, 4 November 2020. A summary of the findings from this analysis are as follows.

The length of the Coombing Park ALA touch-and-go was the third shortest of the flight. The two shortest touch‑and‑go landings conducted at Orange at 1602 and 1615 had lengths of just over 750 m. The fourth shortest touch‑and‑go was conducted at Orange at 1556 (the first approach) and had a length of about 1,000 m.

The ATSB applied corrections for aircraft mass, density altitude and surface type to estimate the length of the Coombing Park touch‑and‑go if it had been conducted at Orange (the corrected touch‑and‑go). The purpose of this correction was to allow a direct comparison between the Coombing Park touch-and-go and all take-offs conducted at Orange. The corrected touch‑and‑go was estimated to have a length between 812 m (with a 25% factor applied for dry grass) and 1,015 m (no grass strip correction) (as stated above the actual length was 929 m). Based on these estimations, it is likely that if the Coombing Park touch‑and‑go had been conducted in the same way at Orange Airport, the length would have been in the same ranked order (that is, third shortest).

The ATSB also evaluated the potential effect of OIS performing a standing take-off instead of the touch‑and‑go at Coombing Park under the same conditions, and this is also detailed in Appendix A.

From this analysis, the standing take-off length at Coombing Park was estimated to be between 630 and 836 m. The estimated zone along Coombing Park runway 07 where OIS would have climbed to 50 ft from a standing take-off is shown in pink in Figure 6. This figure also shows the location of the start of runway 07, the actual take-off for OIS, the upwind track in red-dashed lines, and an indicative track for the start of the left turn. The reference tree is shown for continuity between figures in this report.

Figure 6: Upwind track of OIS following touch‑and‑go at Coombing Park ALA, (view looking south-west)

Image showing upwind track of OIS (red dashed lines), actual take-off position of OIS and estimated take-off zone if a standing take-off was conducted

Source: ATSB

Guidance for determining touch‑and‑go length

There were no details for the calculation of touch‑and‑go length in the aircraft flight manual (AFM), nor were these required. Research by the ATSB identified a limited number of guidance publications for the calculation of a suitable runway length for a touch‑and‑go. Two articles were identified that presented anecdotal techniques for the calculation of required runway length for a touch‑and‑go. As context to the challenges associated with a touch‑and‑go in an article by Aviation Safety magazine, Burnside (2019) stated:

The principal challenge posed by the touch‑and‑go manoeuvre is managing the immediate transition from a landing to a take-off, presenting that touch‑and‑goes are more complicated than just stringing together a landing with a take-off.

Further, in an article released by the Aircraft Owners and Pilots Association (AOPA), Wright (2006) identified some of the challenges that may be encountered by a pilot during a touch‑and‑go after the aircraft has landed:

Once power is added, the pilot is now concerned with achieving a normal take-off rotation speed while ensuring that there is sufficient runway to safely clear any obstacles. Somewhere in all of this there must be a verification that the flaps really did retract, the engine instruments are giving normal readings, and all required checklist items are accomplished.

At some undefined point, the landing roll ends, and the take-off roll begins. If the runway is relatively short, it may leave you with little to no room to execute a safe rejected take-off. Likewise, floating too long during the landing or being slow in retracting flaps may bring on the same situation.

The articles by Wright (2006) and Burnside (2019) each presented a method to estimate a safe length for a touch‑and‑go to be conducted. Wright (2006) stated:

A good rule of thumb is to take the landing distance over a 50-foot obstacle and the take-off distance over a 50-foot obstacle, add them, and double (or triple) the result to get a minimum runway length.

Burnside (2019) provided a sample calculation based on 3 elements. In summary, this sample calculation involved calculating:

• The average of the landing roll and landing distance required to clear a 50-foot obstacle;
• the time on the ground to reconfigure the aircraft, and;
• the average of the take-off ground roll and take-off distance required.

In this article, Burnside (2019) identified several reasons to be more conservative than this, citing that pilot technique, a less than perfect engine, a dragging brake or a crosswind requiring drag-producing aileron input can change those numbers.

Significantly, both methods estimated that a touch-and-go length used more runway than a standing take‑off. Additionally, the analysis conducted by the ATSB also identified that all touch-and-go manoeuvres conducted by the student were likely to use more runway than a standing take-off.

Specifically, when corrected for density altitude, a standing take-off length at Coombing Park ALA was estimated by the ATSB to be between 630‑836 m for the atmospheric and weather conditions at the time of the accident, notably shorter than the actual Coombing Park ALA touch‑and‑go length of 929 m.

Initial climb performance

The ATSB evaluated the potential influence of a standing take-off on the height of OIS during the initial climb. The analysis indicated the relative height difference if a standing take-off was conducted instead of the actual touch-and-go. The climb profiles are projected in straight lines, along an extended upwind track, although these results also indicated the relative differences between a standing take-off and the touch-and-go on curved flight paths. The distance from the start of Coombing Park ALA runway 07 was used as the datum for the analysis, and this is shown on the horizontal axis of Figure 7. For reference, these distance markers are reproduced over an image of the runway area in Figure 6 and the upwind area in Figure 9.

This analysis used the estimated standing take-off distances described in the section above and is illustrated in Figure 7. The vertical axis shows the height above the estimated point of lift off and the horizontal axis shows the distance from the start of runway 07 at Coombing Park ALA, and also corresponds to the markers shown in Figure 6.

Terrain elevation is shown by the solid dark green area, with typical tree heights indicated by the translucent dark green (minimum 33 ft (10 m)) and light green (maximum 66 ft (20 m)) areas.

Figure 7: Height of initial climb profile for OIS at Coombing Park ALA, including estimations for climb profiles following standing take-off and estimated terrain profile

Figure showing plot of height vs distance travelled of OIS during the initial climb from Coombing Park ALA runway 07 compared to terrain and estimates for climb if a standing take-off was conducted.

Source: ATSB

The actual initial climb profile of OIS conducted at 1709 is shown in Figure 7 by the series with red lines and blue circles. The last data point of this series indicates the relative height of OIS immediately prior to the left turn. The red dotted series is the line of best fit for the 1709 initial climb and shows an estimated projection of the climb if the climb rate was maintained and OIS tracked in a straight line instead of turning left. The top right corner of Figure 7 shows the projected climb passing within about 45 ft (14 m) of the terrain, below the maximum nominal height.

The likely climb profiles following theoretical standing take-offs at Coombing Park ALA are shown by the blue band (labelled ‘Standing take-off climb profile’ in Figure 7). The standing take-off climb estimates show the result of translating the actual climb of OIS at 1709 to start from take-off locations of theoretical standing take-offs at Coombing Park ALA, as described in the section ‘Estimation of standing take-off distances’ in Appendix A.

The dashed lines above and below the blue band represent the limits of the analysis, with the best-case shown in orange and the worst-case shown in dark blue. The best-case scenario is derived from the shortest theoretical standing take-off (630 m), and the worst-case is derived from the longest theoretical standing take-off (836 m), as described above. The top right corner of Figure 7 shows all climbs following hypothetical standing take-offs as passing close to, but above the maximum nominal tree height at the local terrain peak, with the worst case projected to pass within about 67 ft of the terrain.

The best- and worst-case standing take-off estimates equated to OIS being between 22‑70 ft higher at each point during the initial climb if a standing take-off was conducted instead of a touch‑and-go, as shown by the height differences between these lines and the dotted red-line in Figure 7. In contrast to the initial climb after the actual touch-and-go projecting below the maximum tree height, climb projections from standing take-off estimates indicated that OIS would pass close to, but slightly above the maximum nominal tree height had an upwind departure been conducted. Further climb performance analysis for curved flight paths are discussed in the section titled Turn and final track information below.

Initial climb gradient

At the time of the accident, flight planning legislation required pilots to plan to take-off with the aircraft weight sufficiently low to allow the aircraft to achieve a minimum climb gradient. This was stipulated in paragraph 7.1 of Civil Aviation Order 20.7.4, which stated:

In the take-off configuration with landing gear extended, an aeroplane must have the ability to achieve a climb gradient of 6% at take-off safety speed, without ground effect, and with all engines operating at take-off power.

Based on flight data, the ATSB calculated the climb gradient of OIS during the initial climb from Coombing Park to be just over 7%. This was based on the flight data for OIS between 50 ft and 200 ft above the lift-off point (shown by the red line with blue circles in Figure 7). OIS was very likely outside ground effect for this segment of the flight. Further, the climb gradient of OIS was typical of climbs performed earlier in the flight at Orange.

Initial climb rate

The ATSB evaluated the climb rate of OIS after take-off from Coombing Park compared to climbs after take-offs at Orange Airport, earlier in the flight. Climbs after take-off were evaluated from 50 ft above the surface, to reduce uncertainty associated with the transition from the ground roll to a stable climb, including ground effect. Corrections for density altitude were performed on the climbs at Orange (increasing the actual values by 3.6%) to compare with the Coombing Park initial climb which had a lower elevation. Figure 8 shows the results of this comparison.

Figure 8: Climb rate of OIS after take-off at Coombing Park ALA, and climb rate for OIS at Orange Airport corrected for density altitude at Coombing Park ALA, 4 November 2020

Chart showing comparisons between initial climbs conducted at different times during the flight

Source: ATSB

The blue diamonds in Figure 8 show the mean climb rate calculated for each climb away from the runway, indicated in ft per minute by the vertical axis, with labels on the horizontal axis indicating the local time that each climb was commenced. The height of the boxes and vertical lines around the mean illustrate uncertainty in the rate of climb, with the boxes indicating where the mean climb rate likely existed, and vertical lines (whiskers) indicating where the mean climb rate very likely existed.[11]^{, [12], [13]}

The left most data point labelled ‘YCPK 1709’ shows a mean climb rate of about 460 ft per minute during the straight component of the initial climb from Coombing Park runway 07. This rate was comparable to the initial climbs conducted in OIS at Orange at 1603, 1616, 1620 and 1637. The considerably lower initial climb rate at 1610 is consistent with an aborted landing being conducted with full flaps extended, a planned exercise as part of the CPL assessment.

Based on the AFM for OIS applied to the observed conditions at Coombing Park ALA, the best rate of climb was 580 ft per minute. The best rate of climb in the AFM is calculated based on test flights conducted under normal operating conditions, typically using a new aircraft and engine, with the aircraft flown in an optimal configuration. For this reason, it is not expected that OIS would have achieved the published climb rate in the AFM. Due to the damage to OIS, it was not possible to perform further assessments to establish why the rate of climb differed between OIS and the expected rate of climb in the AFM. However, it should be noted that the examination of the wreckage by the ATSB did not reveal any mechanical faults or defects with OIS, as described in the section titled Wreckage and accident site information.

In summary, flight data analysis conducted by the ATSB identified that the climb performance of OIS during the initial climb at Coombing Park ALA was comparable to climbs conducted at Orange Airport earlier in the flight.

Turn and final track information

Flight data indicated that immediately prior to turning left, OIS was approximately 125 ft above the ground (Figure 7), tracking toward steeper terrain with a significant number of trees. Figure 9 shows an image facing in a similar direction and at a similar height to the pilots just prior to where the left turn was initiated. The projected upwind track with distance markers shows the rising terrain corresponding to the elevation profile shown in Figure 7, with the same reference tree as shown in Figure 6. The projected upwind track provides a relative guide for analysis of climb performance covered in other section and does not necessarily indicate the intended track of OIS.

Figure 9: Image looking uphill at a similar height and position to OIS immediately prior to left turn

Image showing upwind track of OIS, approximate track during left turn and projected track if OIS continued in a straight line

Source: ATSB

Figure 10 shows a top-down image of the upwind area of runway 07 for Coombing Park ALA. This shows the entire track of OIS in red lines with blue circles, including the initial upwind track for the climb profile in shown in Figure 7. For reference, common labels such as the distance markers and reference tree are included in Figure 6, Figure 7 and Figure 9.

Figure 10: Image looking down on upwind area of Coombing Park runway 07 showing track of OIS and accident site

Down-looking image of runway 07 end of Coombing Park ALA and flight track of OIS

Source: Google Earth, with image overlay and annotations by ATSB

An indicative track of the left turn and final track of OIS is also shown in Figure 10. Flight data indicated that as OIS approached a line of trees, the track changed by about 50° to the left in less than 7 seconds, corresponding to a turn rate of more than 450° per minute. The radius of the turn was estimated to be about 185 m, with an angle of bank calculated as 22°.

Compared to other climbing turns conducted during the flight, the turn rate was almost twice as high, and the bank angle was at least 60% steeper. During the turn, OIS continued to climb, although at a reduced rate, gaining about 25 ft by the completion of the turn, with the mean groundspeed decreasing slightly.

The ATSB conducted a climb performance analysis to evaluate 3 hypothetical ‘escape’ scenarios for OIS:

• continuing the left turn,
• turning right instead of turning left, or
• ceasing the left turn half-way through and flying straight up the gully (shown in Figure 9).

This involved projecting a climb profile over the terrain elevation map based on Google Earth and the estimated height of surrounding trees. Based on this evaluation, the hypothetical flight profiles for the left and right turns both passed within about 66 ft (20 m) of the ground. This was a similar height to the trees in the area.

The flight up the gully was estimated to pass within about 72 ft (22 m) of the ground. Although this was marginally higher than the trees in the area, due to uncertainty in the data, it was not possible to determine if OIS would have been able to climb away in this scenario.

Flight data and onsite measurements indicated that following the left turn, the height of OIS is likely to have been similar to the canopy height of surrounding trees for the third- and second-last data points, although the precise height could not be determined. Beyond the tree close to the flight path (shown in Figure 11), projections indicated that if the climb rate was restored after the turn and OIS had cleared this tree, the aircraft would have passed within 66 ft (20 m) of the ground in the rising terrain beyond the dam at a similar height to trees in the area.

The last 3 flight data points indicated that the ground speed of OIS likely increased, with OIS travelling approximately 110 metres in 3.2 seconds between these 3 points. OIS likely descended by at least 25 ft, possibly by 50 ft between the last 2 flight data points. This was likely to the left of and below the canopy of the tree close to the flight path. Approximately 1 second after the last flight data point, OIS collided with the embankment on the far side of the dam at a similar height.

Wreckage and accident site information

Accident site

The accident site was located on private property about 38 km south of Orange township and 27 km south of Orange Airport (Figure 1). This property was adjacent to Coombing Park ALA, with OIS located about 600 m from the end of runway 07, and about 300 m left of the extended runway centreline (Figure 3).

Wreckage examination

Site and wreckage examination did not identify any aircraft defects or anomalies that might have contributed to the accident. Examination of the area surrounding the accident site, including the tree close to the likely flight path (labelled), did not identify any trees or terrain that might have been struck by OIS prior to the wreckage location (Figure 11).

Figure 11: Image looking down on accident site and surrounding trees viewed from the direction of travel

Image showing accident site and surrounding trees

Source: ATSB

The aircraft struck the embankment of a small dam in an upright attitude. Flight data and ground scars marks indicated that OIS was tracking in a generally northerly direction at the time of the collision with terrain. The accident site was located slightly to the left of the projected track, with propeller strike marks indicating that the nose of the aircraft was pointed to the left of this track around the time of the collision. During the collision, the aircraft rotated in a counter-clockwise direction, coming to rest facing toward the south-south‑west, about 180° to the direction of travel.

The damage to OIS was consistent with significant upward and rearward forces being transferred through the aircraft structure during the collision. The left wing and left-wing flight controls, aircraft canopy, cockpit area, nose landing gear, engine cowling, propeller and tail section of the aircraft were severely disrupted by impact forces. The counterclockwise rotation during the collision was likely induced by the left side of the aircraft (mostly from the left wing that was completely destroyed) colliding with the dam embankment prior to the right side of the aircraft.

Engine and propeller

The engine assembly was examined and found to be complete with no evidence of pre-accident engine control problems or defects. The inspection found all engine controls were connected from the cockpit controls through to the engine, with all electrical wiring and hoses connected.

Both propeller blades fractured and separated from the propeller hub during the collision. Both tips of the propeller blades were located at the accident site. No evidence of pre-accident damage was identified in the propeller blades, propeller hub or propeller hub attachment to the engine crankshaft. The propellers broke into multiple fragments, and most fragments were located at the accident site. However, one large portion of blade was located about 27 m to the east of the site, consistent with this portion breaking away and being thrown through the air during the impact sequence.

Fuel

OIS was fully fuelled immediately prior to departure from Bankstown Airport and had sufficient fuel to conduct the flight. An onsite inspection identified that both the left- and right-wing fuel tanks were compromised with no fuel being identified in these tanks. Fuel was identified in both carburettor bowls and was found to be clear of contaminants, including water.

Emergency locator transmitter

OIS was fitted with an emergency locator transmitter that activated automatically during the accident sequence. This was deactivated by the ATSB onsite. The signal from the ELT was not received by emergency services, likely due to damage sustained to the antenna during the accident.

Flight controls

Flight controls were examined to the extent permitted by impact damage. Nothing was identified in the wreckage with respect to a flight control defect or malfunction that may have contributed to the accident. Complete continuity of flight controls from the cockpit to the control surface was established for the right-wing aileron, flaps, elevator, rudder, and elevator trim. The elevator trim position was unable to be established.

Continuity of the left-wing aileron and flaps was partially established from the cockpit to the control surface attachment brackets. Push rods and bell cranks associated with the wing mounts of these control surfaces were detached from the left wing during the collision, however, no pre‑existing defects were identified in these components.

The flaps were separated from the flap control actuator during the collision. The flap control actuator included a screw jack with the function of moving and holding the flaps in a fixed position. The extension of the screw jack had a corresponding flap position in the normally functioning aircraft. The ATSB was advised by the aircraft manufacturer that the measurement on the screw jack extension corresponded with the flaps being fully retracted.

Precautionary search information

A precautionary search and landing is a procedure for conducting a safe, powered landing away from an airport or ALA with known suitable landing surface conditions. It is normally conducted for two reasons:

• A landing on an unprepared landing surface made necessary due to an abnormal or emergency situation, such as deteriorating weather, insufficient remaining daylight, fuel shortage, technical problems, developing medical conditions or any other reason determined by a pilot
• A pre-planned landing when the pilot is unfamiliar with the landing area, or its condition is unknown.

Soar operations manual

Procedures at Soar were governed by an operations manual, as required by Civil Aviation Safety Regulation Part 141, regulation 141.260. This manual was available for use by flight instructors through an online portal. Version 2.5, published on 2 April 2020, was the most current version of the operations manual at the time of the accident. This operations manual was developed from the CASA sample operations manual version 2.1 dated October 2016. All relevant text cited in this report is common between the Soar Operation’s manual and the CASA sample operations manual.

Criteria for the assessment of the precautionary search

The purpose and importance of a pilot demonstrating the ability to conduct a safe precautionary search was stated in paragraph 11.1.3 of Advisory Circular 91-02[14]:

The ability to accurately assess the prevailing environmental conditions, potential obstacles, surface conditions, dimensions and ultimate suitability of a landing area, will be enhanced by using a well‑practiced procedure to maximise the likelihood of a safe landing outcome.

Clause 3.4(f) of Schedule 5 ‘Flight test standards’ in Part 61 Manual of Standards (MOS) page 586 dated 11 December 2018 noted that a precautionary search was required as part of the test specific activities and manoeuvres in the commercial pilot licence (CPL) flight test and was therefore also to be covered in the pre-CPL flight test. Further, Soar’s operations manual stated that the CASA standard syllabus, lesson plans and planning matrices would be used for the schools training courses.

A ‘flight test report’ form (described in the section ‘Assessment plan for the CPL flight test’ on page 24) was used by the instructor to assess CPL competency during the flight. This form included item 3.4(f) labelled ‘Conduct precautionary search’ under the section ‘Test specific activities and manoeuvres. A reference to MOS A6.4 was included for this item, and this is reproduced in Figure 12. No assessment notes were recorded against this, or other items of this section of the form.

Figure 12: Extract from Schedule 2 ‘Competency Standards’ of Part 61 Manual of Standards dated 24/09/2018 page 126

Precautionary search height

The importance of the height selection for inspection runs during a precautionary search was articulated in the following paragraph 11.1.4 from Advisory Circular AC 91-02¹³:

It will be particularly important to consider appropriate heights to be able to conduct such a procedure safely, while remaining cognisant of potential engine failure considerations, especially if the requirement for a precautionary procedure was initially necessitated by an aircraft malfunction, low fuel state, or other related issue.

Further, for the inspection of the proposed landing path, page 59 the CASA Flight Instructor Manual (FIM)[15] stated:

This preliminary inspection should be sufficiently low for the surface to be inspected but not so low that it is necessary to avoid obstacles. Another point to impress on the student is that the inspection runs should be made at a constant height whilst safely avoiding upwind obstacles. If not satisfied with the surface complete at least one other inspection run at a lower height if necessary.

Further the FIM stated:

The need for a really good lookout whilst carrying out this low flying exercise cannot be over‑emphasised.

And

This exercise should be practiced only in approved areas or at approved fields and even then, all effort should be made to avoid frightening livestock and annoying people.

Inspection heights flown by OIS

During each circuit pattern the altitude of OIS varied, with flight data indicating that the pilots descended OIS during the southerly and easterly pattern legs before returning to a nominal height between 1,000 and 1,100 ft AGL. Based on the Soar guidance to instructors for use when conducting training exercises (referred to as patter notes), the inspection pass would have been the easterly facing leg of each circuit pattern (Figure 3). Each eastern facing leg was flown just over 1 km from the centreline of runway 07. Based on flight data for OIS, each inspection pass was flown at the following heights:

• Pattern 1 (Figure 3 yellow lines): OIS descended to a minimum height of 750 ft AGL, and 400 ft above the ridge on the extended centreline for runway 07 (the ridge), during the easterly leg before returning above 1,000 ft AGL.
• Pattern 2 (Figure 3 orange lines): OIS descended to 850 ft AGL (500 ft above the ridge) during the easterly leg before climbing above 1,000 ft AGL for the northern leg and descending throughout the western leg.
• Pattern 3 (Figure 3 red lines): OIS levelled out between 450 and 475 ft AGL (100 to 125 ft above and 3.3 km from the ridge), before commencing a climb just after crossing over the extended centreline of runway 07/25 (start of pattern 3 in Figure 3). OIS continued to climb through the third easterly facing leg from about 500 to a peak height of 1,200 ft AGL mid‑way along the third northern leg. The flight instructor sought permission to conduct a touch‑and‑go from the property manager of Coombing Park ALA at some time along the southerly and/or easterly legs of this pattern.

Guidance in Aircraft flight manual for OIS

Under a section labelled ‘Emergency Procedures’, the AFM for OIS included guidance for the conduct of a precautionary search, stating that the inspection height shown be flown at an altitude above 500 ft. It is expected that this was intended to refer to height instead of altitude.

Section 2A2 of Soar’s operations manual stated ‘Where the Aircraft Flight Manual conflicts with other publications the Aircraft Flight Manual has precedence.’ However, the circumstances described in the AFM related to landing on an un-prepared field and did not include guidance for the conduct of a precautionary search and landing in normal operations or training.

Operator’s guidance

The operator produced guidance for instructors to use when conducting flight training exercises, referred to as ‘Patter Notes’. Under the patter notes for the demonstration of a precautionary search and landing, a series of 3 circuits were described, each with different heights to be flown. Each circuit was to be conducted at a nominated circuit height, with a descent during final approach to progressively lower heights for each circuit. The third circuit was listed as ‘only conducted if still uncertain about field conditions. After each circuit, the guidance suggested a climb back to the nominated circuit height.

The heights were listed in the patter notes as follows:

• Circuit height (every circuit): 1000 feet AGL ([to] simulate [d an actual height of] 500 feet AGL)
• First inspection pass: 1000 feet AGL ([to] simulate [d an actual height of] 500 feet AGL)
• Second inspection pass: 700 feet AGL ([to] simulate [d an actual height of] 200 feet AGL)
• Third inspection pass: 550 feet AGL ([to] simulate [d an actual height of] 50 feet AGL)

For each circuit, 2 sets of heights were presented, a higher, simulated set for the purpose of an exercise over an unprepared field (figures shown outside brackets above), and the other set relating to the actual heights to be flown for an effective inspection (shown within brackets). For example, the simulated height of the second inspection pass was 700 ft AGL, with the actual height listed in brackets as ‘simulated 200 feet AGL’. At the completion of the third circuit the guidance stated:

Turning final go around (if at an ALA or aerodrome, conduct short field landing).

 

In the event of a real prec search, short field landing, full stop landing. Do not taxi prior to walking the field.

At the conclusion of the precautionary search guidance, the patter notes stated:

Note: if conducting PSL at an ALA or aerodrome, actual heights may be used.

The ‘actual heights’ referred to are those listed inside the brackets above.

Other guidance

Guidance relating to the assessment of overshoot areas and the recommended heights that this assessment should be flown are included in various sources. However, the minimum height recommended for the conduct of an inspection run varied. Page 61 of the CASA FIM provided detail for the conduct of an air exercise by a flight instructor to demonstrate a practiced precautionary search and landing:

When in a suitable area descend to about 500FT above the ground and tell the student to assume poor weather conditions with a cloud base of about 600FT and poor visibility. Choose a suitable airstrip and demonstrate how to inspect the surface. Fly at low safe cruising speed with the optimum flap setting. Fly over the field slightly to the right of the intended landing path at about 100FT to make the first check. On this run check the surface and drift and note any high ground and obstacles in the overshoot area.

In ‘A pilot’s guide to safe flying’[16], for a precautionary landing procedure, this guide includes:

Confirm the acceptability of the landing area by carrying out an inspection run at 200 feet AGL (or well above possible obstructions), into wind, and slightly to the right of the intended landing area. Check out the following:

• …
• Obstacles, both on approach, and possible overshoot.
• …

Guidance was also produced by the New Zealand Civil Aviation Authority[17]. For the first circuit, the guidance for the focus during the inspection includes:

On this and subsequent legs, …, with particular emphasis on surrounds in the approach and climb-out areas.

Guidance for a second inspection run stated:

Assuming the chosen landing site appears suitable up to this point, a second inspection is carried out at a minimum of 200 feet AGL.

…

Established on and parallel to final, a gradual descent to a minimum of 200 feet AGL is carried out.

Descent below 200 feet AGL is not recommended, because it takes considerable concentration to fly the aeroplane level and look at the landing site surface. Also, there is a possibility of unseen obstructions, and since a climb to 500 feet AGL will be initiated on completion of this inspection, the climb is minimised. Unless committed to the landing, never descend below the highest obstacle in the go-around path.

Selection of take-off and landing direction

Influence of wind

Pilots are required to choose the most suitable direction for landing and take-off when operating at any aerodrome. Generally, the main factor for this decision relates to the wind strength and direction. On a flat runway, a take-off or landing into wind (a headwind) will reduce the distance required in each case, whereas a tailwind will increase the distance required. For OIS, performance charts indicated that a tailwind component of 1 kt would lead to increases to the landing and take-off distances between 2.5‑2.8%. This equates to about 12 metres for the ground roll and a further 12 metres to clear a 50 ft obstacle per 1 kt of tailwind.

Influence of runway slope

In a section titled ‘Inclined runways’, Geeting and Woerner (1988)[18] stated:

Where possible, plan upslope landings and downslope take-offs.

This is because conducting a landing on a runway with an uphill slope reduces the landing distance required, whereas a take-off on an uphill slope increases the required take-off distance. An extract from guidance about Coombing Park ALA in the OzRunways applications described that the ‘airfield follows ground contour, rising to the east’. OIS conducted the touch-and-go in an easterly direction at Coombing Park ALA (runway 07).

For the landing component of the touch-and-go conducted by OIS, the tailwind condition (as described in the section titled Post accident weather analysis) and slight uphill runway slope had opposing effects on the landing distance. Estimations performed by the ATSB indicated that the deceleration advantage provided by an uphill landing at Coombing Park ALA was in a comparable range to the disadvantage provided by the tailwind.

The tailwind component was probably relatively low, based on the climb gradient of OIS being comparable to earlier climbs, and the pilots likely assessing the wind strength and direction from the two serviceable windsocks at the ALA. However, due to uncertainty in the actual wind conditions, it was not possible to determine the relative impact that the tailwind and the runway slope had on the touch-and-go length. Therefore, it was not possible to determine which runway direction would have provided the shortest distance for landing at the time of the accident.

During the take‑off phase of the touch-and-go, the tailwind and uphill slope would have both combined to increase the distance for OIS to become airborne. However, the touch-and-go length was comparable to others conducted at Orange earlier in the flight as discussed earlier, and it was again not possible to determine the relative contribution that the tailwind and slope had on the touch-and-go length. Once airborne however, the tailwind component would likely have had an adverse effect on the aeroplane’s climb gradient, although this could not be quantified.

Considerations for use of runway 25

Conducting a touch-and-go on runway 25 would have required the pilots to approach over the rising terrain and trees to the eastern end of the field. This would have required a steeper angle than the approach flown for runway 07, or for the pilots to touchdown part way into the runway. Due to the same uncertainty in the wind strength noted above, it was not possible to determine the length of a touch-and-go on runway 25, and the relative influence of a downhill landing or the headwind components.

The ATSB also considered the effect of conducting a standing take-off from each runway. For take-off on an inclined runway, Geeting and Woerner (1988)¹⁷ stated:

Always take-off downhill in light wind conditions. Acceleration is greater, less runway is required, and obstacles are cleared more easily. During take-off, a 1° downslope is roughly equivalent to having 10% more runway; a 2.5° upslope is equivalent to having a 7 kt tailwind during take-off.

For the take-off of OIS on runway 07, the tailwind conditions and uphill runway slope would have increased the distance required compared to a take‑off conducted on runway 25. Additionally, the final approach gradient of OIS to runway 07 was estimated to be about 6.5%, shallower than the climb-out gradient of about 7%.

Significantly, this indicated that OIS would likely have cleared all obstacles and terrain after a standing take-off from runway 25.

Operational information

Commercial pilot licence flight test assessment plan

Section 3D1 of the operations manual titled ‘Training Plans and Syllabuses’ stated:

Soar Advanced Flight Training has elected to use standard syllabuses, lesson plans and planning matrices prepared by CASA. These syllabuses are reproduced IAW those listed in Volume 5. In designing various courses, the school may vary the lesson times or add lessons in the syllabuses as required to be consistent with the training course in use.

This is consistent with interviews with instructors who stated that the CPL syllabus followed the requirements of Part 61 of the Manual of Standards.

Section 5A2.3 of the operations manual titled ‘Assessment plan’ stated.

A student may be deemed competent to conduct a solo flight, be recommended for a flight test or issued a qualification when competency is demonstrated on at least two occasions (each occasion being on a separate flight). Pre-solo and end of course assessments have been planned on this basis. End of course assessments take into account all of the units of competency mentioned in the Part 61 MOS for the licence, rating or endorsement.

Based on previous flights, this flight would have constituted the first of two pre-CPL flight assessments for the student. All units of competency mentioned in the Part 61 MOS for the commercial pilot licence would apply. This was consistent with a partially completed ‘Flight Test Report’ form 61-1490 found onboard the aircraft. Based on this, the assessment was to include diversions, aborted landings, practiced forced landings, short-field and flapless landings, and precautionary searches. Based on flight data for OIS, these exercises appear to have been performed during the accident flight.

Pilot roles and responsibilities

For this flight (and other training flights) with the student and instructor onboard, the flight instructor was the pilot-in-command. This is confirmed in section 3B1.17 of the operations manual titled ‘Instructor-student co-ordination’:

The Pilot In Command for dual training flights is the flight instructor. The flight instructor is responsible for ensuring that there is no doubt as to who has physical control of the aircraft at any given time; hence, the hand-over and take-over procedures shall be adopted for all dual training flights.

Further, section 3B1.1 of the operations manual titled ‘Authorisation of training flights’ stipulated:  ‘prior to despatching any training flight in a School aircraft, the Pilot in Command is to ensure that they have checked the following:

• …
• changes or restrictions concerning the use of the aerodrome and training area;
• …

Therefore, for this flight, the operations manual confirmed that the flight instructor was expected to check if any restrictions existed with respect to using the Coombing Park ALA for flight training.

Pre-flight information

Purpose of flight

The purpose of the flight was for Soar to assess the competency of the student, prior to the student undertaking the CPL flight test (the pre-CPL assessment). The pre-CPL assessment was required by Soar for every student and acted as a final check to ensure that the student was ready for the actual flight test. Accordingly, the pre-CPL assessment flight was structured to include exercises for the student to demonstrate competency against the CASA CPL syllabus as directed by the flight instructor.

Flight arrangement by student

The pre-CPL assessment flight was intended to be conducted later in the week, however, on the morning of the flight, the student noted that the weather was suitable for flying and called Soar between 0830 and 0900 to ask if there were any senior instructors available. The student was informed that the instructor and an aircraft were available during the afternoon, and this was subsequently scheduled.

Just after this time at about 0900, the instructor likely started their shift as was typical for most days. The student left home at about the same time to drive to Soar at Bankstown Airport, with this trip typically taking between 40 to 50 minutes and the student likely arriving close to 1000. At 1145, the instructor conducted a dual training flight with another student involving a session of circuits at Bankstown Airport for just over 1 hour in duration.

Pre-flight preparations by student

At 1332, a flight plan was lodged for OIS using the National Aeronautical Information Processing System (NAIPS). This plan detailed a flight departing Bankstown at 1400 and tracking directly toward a set of coordinates just over 240 km to the west before returning to Bankstown Airport. These coordinates were 8 km south of the township of Greenethorpe (although lines that were drawn on flight charts were directly to the township) . The flight plan also stipulated a search and rescue time (SARTIME) for arrival at Bankstown by 1800.

Student likely unaware of actual waypoints

Prior to lodgement of the flight plan, other flight instructors at Soar reported that the student spoke with the instructor directly. Although it is not known what was discussed, it is expected that the discussion would have involved setting forward requirements for the flight to allow the student to lodge the flight plan and commence the flight. Therefore, it is not expected that the student was aware of the actual destinations or location of inflight diversions that occurred during the flight due to the exercises required by the CPL flight test. Further, it is unlikely that the student was aware that the flight would proceed to Coombing Park ALA.

Flight chart information

Pencil lines were found on the relevant world aeronautical chart (WAC) and visual navigation chart (VNC) located onboard the aircraft. Firm, straight lines between Bankstown Airport and Greenethorpe township indicated that the student had likely used Greenethorpe township for flight planning calculations and navigation. Lighter curvy pencil lines between the approximate location of the orbits and Orange Airport were also drawn on the WAC (the location of this inflight diversion is labelled in Figure 1) . These lines were likely drawn by the student inflight, consistent with being directed by the instructor to conduct an inflight diversion to Orange Airport.

A pencil line between Orange Airport through the south-west of Blayney on the WAC chart was drawn, intercepting the original planned route near the township of Burraga. This line was firmer and relatively straighter than the original diversion line, possibly indicating that this was drawn while the aircraft was on the ground at Orange, consistent with eyewitness and photographic evidence.

Coombing Park ALA was not marked on the charts used by the student, and there were no pencil markings identified on the WAC toward this region. This may indicate that the course deviation toward Coombing Park ALA after departing Orange Airport (shown in Figure 1) was a second inflight diversion exercise prior to the precautionary search and landing.

In summary, the pencil lines on the student’s flight charts were consistent with the student being unaware of the flight proceeding to Coombing Park ALA until after departure from Orange Airport. Further, there was no evidence that the student had been to Coombing Park ALA prior to this flight.

Operations to aeroplane landing areas

Company requirements

The Soar operations manual included guidance for flights to aerodromes, with section 3B1.5 titled ‘Aerodrome Suitability’ including the statement:

Except in an emergency, aeroplanes operated by Soar Advanced Flight Training will only be operated to or from aerodromes that are listed in En-Route Supplement Australia (ERSA) or Aeroplane Landings Areas (ALAs) that conform to the guidance provided in CASA publication CAAP 92-1(1).

The wording of this text was directly taken from that detailed in the CASA sample operations manual version 2.1 dated October 2016, which stated:

Except in an emergency, aeroplanes operated by [Sample Aviation Flight Training Pty Ltd] will only be operated to or from aerodromes that are listed in En-Route Supplement Australia (ERSA) or Aeroplane Landings Areas (ALAs) that conform to the guidance provided in CASA publication CAAP 92 1(1).

Further, under the section titled ‘Company register of suitable ALAs’, the operations manual included:

Form 4B13 (Aeroplane Landings Areas (ALA) Report Form) is to be used for compiling a company register of suitable ALAs of fixed wing aeroplane landing areas that are not listed in the ERSA, but have been approved by the HOO.
 

Information listed in the register is advisory in nature. The HOO should be advised if an amendment is considered necessary.

These requirements were in place in the Soar operations manual for at least one year prior to the accident and were included in the previous version of the operations manual, and possibly earlier iterations.

Form 4B13 contained fields to provide detail of the ALA, including a diagram of the landing area, and ALA characteristics including the slope, surface, elevation and obstructions. A signature box stating ‘Approved for company OPS’ was at the bottom of the form. This form could have been used to assess an ALA such as Coombing Park against the guidance of CASA publication CAAP 92-1(1), as required by section 3B1.5 of the operations manual.

At the time of the accident, Soar did not have a company register of suitable ALAs compiled.

Recommendations for aerial work and charter operations in CAAP 92-1(1)

Paragraph 8.2 of CAAP 92-1(1) stated:

A pilot should not use a landing area without taking all reasonable steps to ensure the physical characteristics and dimensions are satisfactory. For aerial work and charter operations the operator should provide evidence to the pilot on the suitability of a landing area prior to its use.

Soar Aviation’s Air Operator’s Certificate included approvals to conduct CASR Part 141 flight training. This was classified as an aerial work operation.

Scenario based training

Soar had 10 published scenarios that were available for use by their instructors for CPL training. These generalised scenarios allowed for any ‘suitable aerodrome’ to be used during the flight, with the aim to provide a more realistic training environment for students. Based on Soar’s operations manual, this included any ALA in the ERSA.

Certification standards for aerodromes

The CASA website included descriptions of 3 different categories of aerodromes under CASR Part 139. This included descriptions of where the standards were defined, and those responsible for certification of the aerodrome. For aeroplane landing areas, under the subject ‘Who is responsible for certification?’, the table noted these as an unregulated facility, with use to be:

in accordance with Aircraft Operators Certificate and/or pilot’s responsibility to determine suitability of the facility.

It was also noted that there were no defined standards, although guidance for use was included under CAAP 92-1.

Aeroplane landing area entry requirements into ERSA

All requirements for entry of an aerodrome into the ERSA related to the periodic review and provision of up to date data, covered under CASR Part 175.D as part of the Aeronautical Information Package (AIP).There were no requirements to demonstrate the suitability of ALAs listed in the ERSA, including assurance of obstacle clearance heights in the take-off and approach areas of each runway.

The CASA website included the question: ‘Are aerodrome details published in ERSA/NOTAM?’. For ALAs, this stated: ‘Airservices Australia may publish basic information for aerodromes that were previously regulated’. This was confirmed with Airservices personnel to potentially relate to some legacy aerodromes.

In response to an inquiry from the ATSB, CASA confirmed that the ERSA contained ALAs that may have been previously regulated and those ALAs that were not previously regulated. For previously regulated ALAs that did not transition to a certified standard, these were allowed to remain in the ERSA, but with operational information removed. In correspondence to the ATSB, CASA also clarified:

The exact content in the ERSA is between the aerodrome operator and Airservices Australia. However, runway distance data (LDA, TORA, TODA etc) is removed. Any flight operation/airspace information is CASA’s responsibility.

CASA also confirmed that there is no assurance of obstacle clearance for ALAs in the ERSA. CASA also noted that:

Pilot’s still have responsibilities for safe conduct of flight and minimum height rules.

The ERSA current at the time of the accident under the section ‘Aerodrome Information’ stated:

4.3 Aerodromes with limited information
 

a. Other aerodromes, also known as [Aeroplane] Landing Area (ALA) may be included in ERSA with limited information.

b. ALA are depicted in ERSA with a grey background as shown in INTRO.

c. Operators conducting regular public transport or charter operations into ALAs need to be aware of their obligations under the CASA regulations.

Prior to commencing a flight to an uncertified aerodrome, a pilot or operator must contact the Aerodrome Operator to ensure currency of aerodrome information.

Coombing Park ALA was eligible for entry into the ERSA at the time of the accident and could have been added by Airservices Australia if requested by the manager following compliance with CASR Part 175.

Discussion between instructor and manager of Coombing Park

Under the section titled ‘Company register of suitable ALAs’, the Soar operations manual also included:

The PIC must obtain permission to use the ALA when required and is responsible for determining that the area is suitable for the intended operation.

The property manager of Coombing Park recalled that, just after the pilots commenced the third precautionary search pattern overhead the ALA (indicated by ‘Pattern 3’ in Figure 3), they received a phone call from a person identifying themselves as a flight instructor from Soar. Telephone records identified that the duration of the call was 24 seconds, commencing at 1704. The property manager, who was in the vicinity of the runway, could see and hear OIS in the circuit area and confirmed with the instructor that it was them in the circuit area.

The property manager recalled that the instructor asked, ‘Do you mind if I do a touch‑and‑go?’ The property manager reported that based on:

•  the instructor identifying themselves as a flight instructor
• OIS already being in the circuit area
• the manager assuming that OIS was going to land on runway 25
• a desire not to distract the pilots further

 the property manager granted the instructor permission to land without further discussion.

The property manager reported that normally, people called up an hour or so ahead of time, and that advice on local procedures and potential hazards was provided. The manager also reported that this was the first time they had spoken with the flight instructor and couldn't recall talking to anyone from Soar Aviation in the past.

Instructor familiarity with Coombing Park

Staff members representing Soar reported that the flight instructor may have been familiar with Coombing Park ALA. However, the precise nature of the instructor’s interactions with the ALA were not known. Further, it was reported that Soar previously held a register of ALAs that included Coombing Park. It was reported that this register had been misplaced, possibly during an office move, and was unable to be provided to the ATSB for review.

The ATSB examined data from flights previously conducted by the flight instructor to evaluate any previous instances of operating in the circuit area of Coombing Park ALA, and any other ALAs. This analysis used data stored in the flight instructor’s OzRunways account, and publicly available location data for ERSA and non-ERSA ALAs, including Coombing Park. The flight instructor’s data was limited to times when the instructor was using the OzRunway mobile phone application and the phone was in range of a telecommunications tower.

Limitations in the accuracy and fidelity of the available data prevented identification of whether a landing occurred at any of the locations. Flights to ALAs within range of Bankstown Airport and flown past within 5.5 km (indicating the 3 nm circuit area) by the instructor were of particular interest (Figure 13).

Figure 13: Aeroplane landing areas within range of Bankstown Airport and within 5.5 km of flights conducted by the instructor between 2016 and 4 November 2020

Image showing relative location of ALAs flown past by the instructor compared to Bankstown Airport and Coombing Park ALA

Source: ATSB

The analysis revealed that the instructor passed at least 59 ALAs at least once from a total of 138 flight data files between 2016 and the time of the accident. Forty-three of these ALAs were located in New South Wales, 10 in Queensland and 6 in Victoria. Approximately half of these ALAs (30) were not included in the ERSA, with the remaining 29 ALAs being listed. The flight data revealed that for most flights there was no evidence of the aircraft joining the circuit pattern at these ALAs, however, these locations were sometimes used as waypoints, characterised by a change in direction of the aircraft track. The most common locations passed were on the eastern side of the Great Dividing Range and between Newcastle to the north and Goulburn to the south.

Coombing Park was passed once by the instructor on 21 September 2018, with 2 heading changes occurring as the aircraft passed overhead (Figure 14). However, there was no evidence to suggest that any circuit or landing (including a precautionary search) was conducted at that time. No other evidence was identified for flights by the instructor to Coombing Park.

Figure 14: Flight by the instructor within 5.5 km of Coombing Park on 21 September 2018

Image showing top down map of Coombing Park ALA and Carcoar township. Red line depicts the flight track.

Source: Google Earth, annotated by the ATSB

There were 2 occasions identified where precautionary searches likely occurred at ALAs (Mangrove Mountain ALA and The Oaks ALA), with a landing possibly occurring at The Oaks. The flight data also indicated that a precautionary search was likely conducted at Mangrove Mountain ALA, a non-ERSA ALA on 3 November 2018.

In this case, the flight track did not pass along, or directly approach the runway, indicating that a landing did not occur. One flight, on 14 January 2017 indicated that the Oaks ALA (which was included in the ERSA) was likely used for a precautionary search and landing. In summary, the instructor’s previous flights stored by OzRunways did not provide evidence of any previously conducted landings at non-ERSA ALAs.

Civil Aviation Advisory Publication 92-1(1) Guidelines for aeroplane landing areas

As detailed previously, the Soar operations manual only allowed operations to non-ERSA ALAs when they had been assessed to conform to the recommendations in Civil Aviation Advisory Publication (CAAP) 92-1(1) - Guidelines for aeroplane landing areas (the CAAP), and this had been approved by Soar’s head of operations. Such an evaluation of Coombing Park ALA had not been performed by Soar.

CAAP 92 overview

At the time of the accident, the introduction of the CAAP, released in July 1992, noted:

This publication sets out methods that may be used and which experience has shown should, in the majority of cases, ensure compliance with the Regulations. However, before using the information in this publication the user should always read the Civil Aviation Regulations listed…’

The CAAP then stated:

These guidelines set out factors that may be used to determine the suitability of a place for the landing and taking-off of aeroplanes. Experience has shown that, in most cases, application of these guidelines will enable a take-off or landing to be completed safely, provided that the pilot in command: (a) has sound piloting skills; and (b) displays sound airmanship.

CAAP 92 assessment of Coombing Park

The ATSB assessed Coombing Park ALA against the obstacle clearance recommendations of the CAAP. This recommended the ‘approach and take-off areas to be clear of objects above a 5% slope for day...operations’. This was an area extending 900 m beyond the end of the runway and is illustrated in Figure 15. The accident flight path was within this area prior to the final left turn (Figure 10).

Figure 15: Summary of eligibility requirements for ‘other’ physical characteristics of a CAAP 92-1(1) aeroplane landing areas

Source: Civil Aviation Safety Authority, CAAP 92-1(1) ‘Figure 2A – Single engined [sic] and Centre-Line Thrust Aeroplanes not exceeding 2000 kg MTOW (day operations)’

Table 1 shows Coombing Park ALA compared to the minimum recommended requirements of the CAAP for the approach and take-off area slope. The 2 left-most columns show the required CAAP value and relevant characteristic, with the 4 right-most columns relating to measurements conducted for Coombing Park ALA. Three sets of measurements were conducted for Coombing Park ALA based on the actual runway length, and characteristics if the runway length was shorter. The purpose of the theoretical measurements was to examine if the minimum recommended obstacle clearance requirements of the CAAP could be met at Coombing Park if runway 07 was shortened, increasing the distance between the runway 25 threshold and the rising terrain and obstacles to the East of the field.

Runway length requirements (CAAP 92(1)-1 Clause 5.1) and theoretical shortened runway calculations were based on 2 scenarios. The first scenario labelled ‘Theoretical shortened runway– AT01 Nil wind TODR [take‑of distance required]’ simulated a scenario where the runway was shortened to match the take-off distance required for VH-OIS on the day of the accident in nil wind. This represents a baseline scenario.

This calculation was based on VH-OIS performance charts for the estimated density altitude on the day of the accident, with an increase of 25% length for a short dry grass surface at Coombing Park. This data was considered ‘factored’ for the purpose of CAAP 92(1)-1 clause 5.1 that recommended an additional 15% be added to the length when using ‘unfactored’ data. The other scenario labelled ‘Theoretical shortened runway– worst case standing take-off’ is the result of a 5% slope applied from the location of the longest estimated standing take-off (836 m), as described in the section titled Evaluation of touch‑and‑go length and shown in Figure 7.

Table 1: Partial comparison of Coombing Park ALA to recommended minimum physical characteristics of landing areas according to CAAP 92-1(1) section 5 for Aquilla AT01 day operations

The assessment against CAAP 92-1(1) recommendations revealed that Coombing Park ALA likely did not meet obstacle clearance recommendations for VH-OIS at the time of the accident. Approach and take-off area slopes are illustrated in Figure 16 relative to the terrain profile (and upwind climb profile of OIS for reference), as also shown in Figure 7. These slopes are shown by the yellow, blue and orange lines, and have labels prefixed with ‘CAAP 92 surface...’ in Figure 16. Each of the 3 obstacle clearance slopes terminated 900 horizontal metres from the (simulated and actual) runway ends, as per the recommendations in CAAP 92-1(1). For reference, the horizontal axis shows the distance from the start of runway 07, corresponding to figures shown earlier. This shows that the CAAP 92-1(1) obstacle clearance surface originating from the end of runway 07 penetrated the rising terrain about 150 m from the runway end (orange line), as also noted in Table 1.

Figure 16: CAAP 92(1)-1 Runway approach and take-off obstacle clearance slope from various theoretical runway end positions projected onto the terrain profile of Coombing Park ALA compared to actual climb performance of VH-OIS

Figure showing plot of height vs distance travelled of OIS during the initial climb from Coombing Park ALA runway 07 compared to terrain and projections for the CAAP 92 obstacle clearance slope

Source: ATSB

The approach and take-off slope originating from the theoretical ‘nil wind’ shortened runway distance (shown in yellow) did not intersect with the terrain within the 900 m horizontal limit. However, this may have intersected with some of the trees in this area, and the projection of the shortened runway slope intersected the rising terrain approximately 250 m beyond this point.

The approach and take-off slope from the estimated worst-case standing take-off for VH-OIS is also shown in Figure 16 by the blue line. This also shows that the approach and take-off slope may have passed the CAAP 92 recommendation for a 5% obstacle clearance within 900 m, although this intersected with the terrain almost immediately after this point. However, it is likely that trees in this area would have penetrated this slope. Note that the CAAP 92 slopes from both theoretical shortened runways shown in Figure 16 correspond to theoretical take-offs shown in Figure 7 of the same colour.

Related occurrences

The ATSB’s national aviation occurrence database was reviewed to identify accidents and serious incidents involving collisions with terrain at ALAs that were reported to the ATSB in the 30 years between 1991 and 2020. These records were refined to occurrences where the characteristics of the runway and surrounding terrain may have influenced the outcome. In total 9 occurrences were identified meeting these criteria over this period.

Three of the occurrences identified related to ALAs listed in the ERSA and were therefore approved for use by Soar’s operations manual. One of the 3 ALAs were located at a similar or shorter distance than Coombing Park ALA was to Soar’s base of operation at Bankstown Airport (within range of Soar). A summary of these occurrences is below.

• ATSB investigation AO-2018-025 Runway excursion and collision with terrain – Van’s RV-6A, VH-OAJ, Somersby ALA, New South Wales on 18 March 2018. This investigation found that features surrounding the runway, including undulating terrain and a small watercourse immediately at the end and trees at the edge, increased the likelihood and severity of occupant injury in the case of a runway excursion. And further, that CAAP 92-1(1) did not have guidance for the inclusion of a safe runway overrun area.
• ATSB occurrence 200903966 Collision with terrain involving a Piper Aircraft Corp PA-31, Bungle ALA (Bellburn), Western Australia on 06 June 2009. During final approach to runway 10, the aircraft's right wing tip struck a tree branch, causing minor damage to the leading edge. This was a commercial charter flight with one pilot and 9 passengers onboard. A review of the approach area to runway 10 at Bungle ALA did not reveal any significant undulation in terrain, however there appeared to be slight height variation near the runway threshold. This ALA was in the ERSA and the occurrence is also notable because it relates to a charter operations to an ALA in the ERSA that was not assured as meeting CAAP 92-1(1) obstacle clearance recommendations.
• ATSB Occurrence 199700351 Collision with terrain involving an unknown ultralight aeroplane, Coominya ALA, Queensland on 9 February 1997. The pilot was attempting an uphill take-off. Soon after becoming airborne, the pilot reported becoming concerned about the closeness of the trees off the end of the runway. The pilot commenced a 180-degree turn, although the aircraft struck trees before the turn was completed. Subsequently, the aircraft struck the ground nose first and the pilot received serious injuries during the impact.

A further 2 occurrences were identified by the ATSB that were within range of Soar but were not listed in the ERSA. Therefore, these aerodromes were not approved for use for Soar operations without further risk assessments being conducted. These occurrences appear to be related to either obstacles and or terrain in the take-off and landing areas. These are of note because all aerodromes were eligible for entry in the ERSA (subject to a risk assessment), making them approved for use by the Soar operations manual.

• ATSB investigation AO-2018-013 Collision with terrain involving Cessna 206, VH-WZX, Apollo Bay ALA, Victoria on 31 January 2018. There was a pilot and 5 passengers on board. The ATSB found that a go-around commenced late during the landing and the pilot did not immediately follow the go-around procedure. These factors, combined with the heavy aircraft weight and rising terrain, reduced obstacle clearance and the aircraft struck the airfield boundary fence.
• ATSB Occurrence 201901041 Collision with trees involving Piper Aircraft Corp PA-38, VH‑CNT, Currandooly ALA, New South Wales on 23 February 2019. During the initial climb, the aircraft was unable to outclimb rising terrain and stuck trees. The aircraft subsequently collided with terrain resulting in substantial damage to the aircraft and minor injuries to the pilot. The occurrence is notable because the sequence of events and terrain appear similar to the accident scenario for VH-OIS. The aerodrome was within range of OIS from Soar’s base of operations at Bankstown Airport.

Safety analysis

Introduction

While conducting an assessment in preparation for a commercial pilot’s licence flight test, an Aquila AT01 registered VH-OIS (OIS), conducted a precautionary search at Coombing Park Aeroplane Landing Area (ALA), about 27km south of Orange Airport, New South Wales. Flight data indicated that after three precautionary search patterns were flown, a touch‑and‑go was conducted, with the aircraft climbing toward rising terrain after take-off. As the aircraft approached an area of steeper terrain, a climbing left turn was conducted toward a slightly lower and less wooded area. The aircraft continued to fly in a controlled manner, likely accelerating and descending slightly toward an open area of rising terrain beyond a small dam. After flying over the dam, the aircraft collided with an embankment, bordering the dam and the open area.

Site and wreckage examination, and aircraft performance assessments did not identify any defects, anomalies or sudden performance loss that might have contributed to the accident. Additionally, no evidence was found to suggest any medical or fatigue related issues that would have affected the pilots’ performance on the day of the flight. Therefore, this analysis will focus on the operational factors that led to an experienced flight instructor and a commercial student pilot to conduct a touch‑and‑go toward rising terrain that the aircraft was unable to outclimb.

Development of the accident

Pre-flight planning

Due to the nature of the flight, in preparation for the commercial pilot licence flight test, only the instructor is likely to have been aware of Coombing Park ALA being a waypoint for the flight prior to departure, although it is not known if a landing was originally planned by the instructor. Coombing Park ALA was not listed in the ERSA and therefore, use of the ALA for landing was not approved by the company operations manual without further assessment, which had not been performed. This requirement was likely known to the instructor as it had been in the operations manual for at least one year. For this accident, if this procedure was followed, the aircraft would not have landed.

It was reported by staff at Soar that a previous register existed which contained Coombing Park ALA as an approved aerodrome. However, this register could not be provided to the ATSB. Further, if a risk assessment was performed by Soar for Coombing Park ALA previously, it is unlikely that it would have been identified as suitable for conducting a landing. This is due to the rising terrain to the east not meeting the recommendations of CAAP 92-1(1). It is also considered likely that the flight instructor would have reached the same conclusion if this hazard was assessed prior to flight.

It was also reported that the flight instructor was likely familiar with the ALA. This is consistent with one previous flight identified by the ATSB, where Coombing Park ALA was likely used as a waypoint by the instructor. However, there were no flights identified where the instructor conducted a precautionary search or landing at Coombing Park ALA. Therefore, there was no evidence that suggests the instructor had an opportunity to effectively assess the rising terrain hazard for conducting a take-off, touch-and-go or landing at Coombing Park ALA in previous flights.

The flight instructor contacted the manager of Coombing Park ALA to seek permission to conduct a touch-and-go while OIS was in the circuit area after 2 complete precautionary search patterns. This phone call only lasted 24 seconds. This was the only telephone call that the manager of Coombing Park ALA received from the instructor that day and could not recall receiving a phone call from any instructor from Soar in the past. The manager of the ALA reported that they usually provided a more in depth briefing for people calling ahead of time. This likely represents a missed opportunity to gain a knowledge of present conditions, operating procedures and hazards to be aware of.

It should be noted that until the point where the decision was made to conduct a touch-and-go, the flight had proceeded as expected. This included conducting the precautionary search patterns. Although it could not be confirmed, it is likely that the instructor considered the risk of a touch-and‑go to be low. This was likely based on Coombing Park ALA having a sufficient runway length for a landing (not a touch-and-go). It was not established if the instructor had intended on flying to Coombing Park ALA before the flight. However, the timing of the phone call to seek permission to conduct a touch-and-go after completion of two precautionary search patterns, may indicate that the decision to conduct a touch-and-go by the instructor was a last-minute decision. This was possibly under a motivation to provide a realistic experience for the student.

Overall, it is likely that if the suitability of conducting a touch-and-go at Coombing Park ALA was assessed prior to flight, the instructor would have identified Coombing Park ALA as unsuitable for landing. Therefore, it is expected to be likely that there was limited planning conducted prior to the flight with respect to assessing the suitability of Coombing Park ALA for a landing, take-off or touch‑and‑go. It is also possible that the decision to conduct a touch-and-go was an impromptu deviation from the original plan. Further, the lack of planning, or deviation from the original plan, removed a defence, placing more pressure on assessments in flight (which were also ineffective). These factors reduced assurance that the aircraft could outclimb the rising terrain, which subsequently led to the accident occurring.

Conduct of precautionary search

The southerly and easterly legs of each precautionary search pattern flown at Coombing Park ALA likely provided the best opportunity for the pilots to identify the rising terrain hazard to the east.  

The easterly inspection legs running parallel to the runway in the direction of landing were the inspection runs, For the duration of the third easterly leg, OIS was in a climb from 500 to 800 ft AGL, about 150 to 450 ft above the ridge and over 1 km to the right of the runway centreline. During this leg, the elevated nose position of OIS would have likely made assessing the rising terrain more difficult. Additionally, the changing perspective of the terrain may have been more apparent if the aircraft was in a straight and level configuration. In the two earlier patterns, the easterly legs were flown at more than 750 ft AGL, more than 400 ft above the ridgeline. Further, in all legs, OIS was more than 1 km to the right of the runway centreline, reducing the opportunity for the pilots to assess the overshoot area (and the runway surface).

At the start of the third pattern while tracking on the southerly leg (the third southern leg), OIS descended to a minimum height of about 450 ft AGL. Although this leg was only about 100 ft above the ridgeline on the extended centreline for runway 07 (the ridge), it was 3.3 km away from OIS.

Southerly legs were not considered inspection runs in the Soar ‘patter notes’ (these were the eastern legs), with these inspection runs noted to be flown at the lowest heights during the precautionary search patterns. Despite this, the third southern leg was flown at the lowest height of any legs at Coombing Park ALA during the precautionary search, prior to the final approach for the touch-and-go. This was at least 250 ft higher than recommended by the Soar ‘patter notes’ when conducting an actual precautionary search inspection run. This guidance was generally aligned with procedures for other organisations.

It is expected that the perspective offered by the ridge being slightly below the aircraft and more than 3 km away on the third eastern leg, reduced the likelihood that the pilots would identify this as unsuitable for take-off from runway 07. Further, the (easterly) inspection runs were flown at heights above the ground and offset positions from the runway centreline that likely reduced the pilots’ ability to detect the significance of the ridge at the end of runway 07 for take-off.

Therefore, it is likely that the heights and positions of OIS during the precautionary search patterns flown at Coombing Park ALA likely limited the opportunities for the pilots to detect the rising terrain hazard at the end of the runway, contributing to the decision to conduct a touch-and-go.

Take-off direction

It is likely that the ideal direction for landing and take-off were in opposite runway directions at Coombing Park ALA at the time of the accident. For landing, the light tailwind on runway 07 was countered by an uphill slope. Therefore, it is possible that either runway 07 or runway 25 would have allowed the shortest landing distance. However, there were fewer obstacles on approach to runway 07, likely making the approach less demanding on the pilots compared to runway 25.

The headwind component and downhill slope on runway 25 indicated that using that runway for a standing take-off would likely have allowed OIS to take-off in a shorter distance along the runway compared to runway 07. Further, due to no significant obstacles beyond the end of runway 25, it is very likely that OIS would have been able to safely climb away after lift-off. Finally, a standing take-off on runway 25 would have allowed OIS to start the take-off roll from the beginning of the runway, allowing the entire length to be used.

Therefore, a landing on runway 07, followed by a standing take-off on runway 25 would have likely prevented the accident.

The ATSB conducted further analysis (described in the next section) for a standing take-off compared to a touch-and-go on runway 07. This indicated that OIS may have been able to clear the terrain if a standing take-off was conducted on runway 07.

Touch-and-go

All touch-and-goes conducted by the student at Orange Airport likely used more runway than the standing take-off at Orange Airport (based on the distance from the runway threshold to the end of the take-off (where the aircraft climbed to 50 ft)). The touch-and-go conducted at Coombing Park ALA was likely typical of those conducted at Orange, with the approach reported by an eye‑witness as appearing normal. Based on flight data and calculations from the aircraft flight manual for OIS, the estimated standing take-off length at Coombing Park was estimated to be between 630 and 836 m, shorter than the actual touch‑and‑go length of 929 m. Therefore, it is very likely that a standing take-off would have led to OIS becoming airborne earlier along runway 07, reducing the likelihood of a collision with terrain.

There are more factors involved with the conduct of a touch-and-go compared to a standing take-off. This is supported by available literature and flight data for OIS that indicated a higher variability and longer length rolls from every touch-and-go compared to a standing take-off. This supports that there is likely less consistency with the length of a touch‑and‑go compared to a standing take-off.

ATSB analysis identified that the reduced runway length required by conducting a standing take-off at Coombing Park ALA was estimated to increase the height of OIS between a worst-case of 22 and a best-case of 70 ft at each point in the initial climb. This would have increased the margin between OIS and the terrain, in particular the trees. Adding the worst-case standing take-off height gain (22 ft) to the projections for the touch-and-go for different initial climb routes shows that all climb routes would have likely cleared the terrain by a greater height than the trees.

For a worst-case standing take-off, these estimations predicted these initial climb options pass the terrain by about 67 ft if tracking on the runway centreline up to 92 ft if a flight up the gully was conducted. The options to turn right, continuing the left turn, or climbing away from overhead the dam were all predicted to the terrain by a minimum of 88 ft. However, based on these estimations, and the maximum nominal height of trees being about 66 ft, it should be noted that any escape flight path would have still been at a very low height.

Therefore, the additional height offered by the worst-case standing take-off would have likely provided more options to the pilots, likely allowing the pilots to climb away from the terrain.

Forced landing

During the initial climb, the aircraft was likely performing normally. A projection of the flight path for OIS on the original track during the initial climb showed the aircraft likely would have collided with trees if flight was continued in that direction. It is likely that the pilots realised that the aircraft would be unable to outclimb the terrain and elected to turn left toward terrain that was less steep. Flight data analysis indicated that it was unlikely the pilots could have continued the left turn or conducted a right turn without colliding with trees. The aircraft rolled level flying toward the small dam, with flight data indicating that the aircraft was likely accelerating and descending just prior to crossing the surface of the dam. This indicates that the aircraft was likely in a controlled state at this point, about 1 second prior to impact. Based on this data, possibly after realising they would be unable to out climb the terrain, it is likely that the pilots were attempting to gain airspeed to affect a transition for an uphill forced landing. There was also likely minimal time for the pilots reconfigure the aircraft for a forced landing. During this attempted forced landing, the aircraft collided with the embankment of the dam.

Operator’s procedures

Soar's operations manual allowed training flights to be conducted to any aerodrome deemed suitable as part of a scenario-based training program. All aerodromes listed in the ERSA were considered as suitable for flight training operations. Therefore, Soar procedures did not require further assessment of ALAs listed in the ERSA. Further, for entry and ongoing listing in the ERSA, ALAs did not require any assessment of aerodrome suitability for aircraft operations.

In contrast, to be considered as suitable for flight training operations, ALAs not included in the ERSA were required to be assessed and found to meet all recommendations in CAAP 92-1(1). Therefore, Soar’s operations manual was inconsistent in the treatment of operational hazards between operations to ALAs listed in the ERSA and non-ERSA ALAs. This means that there were fewer controls in place to assure that obstacle clearance surfaces were suitable for use by Soar at ALAs listed in the ERSA.

Based on Soar operating in the aerial work category, the guidance in CAAP 92(1)-1 was suggesting that Soar would be expected to provide evidence to pilots on the suitability of landing areas. Although Coombing Park ALA was not in the ERSA, it was eligible to be without any further assurance that it was suitable for use by Soar. This is important because this ALA could have been approved for Company operations and would have resulted in the accident occurring at an ALA considered as suitable for company operations.

In summary, the CASA sample operations manual wording adopted directly by Soar Aviation provided approval for operation to ALAs in the ERSA without providing evidence and assurance that these were suitable for use by company aircraft.

CAAP 92 Recommendations

The Soar operations manual required that all ALAs not in the ERSA be assessed against the recommendations of CAAP 92-1(1) prior to use. Although this assessment was not performed for Coombing Park ALA, it could have been.

Section 5.5 of CAAP 92-1(1) included the recommendation that the terrain be clear of objects above a slope of 5% up to a distance of 900 m, however, there was no requirement for obstacle clearance beyond this distance. Coombing Park ALA had terrain that became steeper away from the runway. These circumstances may lead to situations where an aircraft is unable to safely climb away from the runway, despite the ALA meeting CAAP 92-1(1) obstacle clearance recommendations. There is also no assurance that other ALAs do not exist with these characteristics.

Coombing Park ALA did not meet the CAAP 92-1(1) recommendations for obstacle clearance beyond runway 07. However, if runway 07 was shortened, increasing the distance by displacing the runway 25 threshold, but still remaining at a suitable length for use by the accident aircraft, it is possible that the ALA would have met these recommendations. With the displaced runway 25 threshold, the ALA would likely have met these recommendations if several trees were removed from the take-off and approach area at the end of runway 07.

ATSB analysis showed that if the accident aircraft had conducted a standing take-off, it probably would have cleared the trees and terrain during the upwind climb by a very narrow margin. This situation would have been worse in an aircraft meeting minimum climb gradient requirements.

In summary, the CAAP 92-1(1) guidance did not assure that an aircraft would be able to safely outclimb rising terrain located more than 900 m from the end of a runway. This would have applied at Coombing Park ALA if the runway ended near the point of lift off.

Findings

From the evidence available, the following findings are made with respect to the collision with terrain involving Aquila AT01, VH-OIS, Coombing Park ALA, 27 km south of Orange Airport, New South Wales, on 4 November 2020.

Contributing factors

• It is likely that pre-flight planning was not performed to ascertain the take-off area was clear of obstacles at Coombing Park ALA as required by the operations manual. Consequently, this reduced assurance that the pilots would identify and mitigate the risk of rising terrain that the aircraft was unable to outclimb at the end of runway 07.
• The pilots were conducting the precautionary search at heights and positions that would have likely made assessing the hazard of rising terrain from the air less effective. This likely contributed to the pilots’ decision to conduct a touch-and-go landing and take-off toward rising terrain that exceeded the climb performance of the aircraft and required a low-level turn to avoid rising terrain.
• The take-off was conducted on an uphill slope with a probable tailwind and toward rising terrain beyond the runway end. A standing take‑off conducted in the more favourable reciprocal direction would likely have cleared all obstacles and terrain.
• The conduct of the touch-and-go, rather than a standing take-off, reduced assurance that the aircraft would commence the climb from a position along the runway that could clear the terrain during the initial climb after take-off.
• The combination of loss in climb performance during the turn, trees and rising terrain in the new direction likely led to the pilots conducting an uphill forced landing. It is likely that the aircraft had insufficient performance for the uphill forced landing, leading to the aircraft colliding with the embankment of a small dam.

Other factors that increased risk

• The CASA sample operations manual used by the operator that allowed any aerodrome in the Enroute Supplement Australia to be used for flight training did not assure that these aerodromes were suitable for use. (Safety Issue)
• Recommendations in CASA guidance CAAP 92-1(1) requiring obstacle clearance out to 900 m may lead to circumstances where ALAs meet these requirements however, aircraft are required to manoeuvre below a safe height or be unable to outclimb rising terrain after take-off more than 900 m past the runway end. (Safety issue)

Safety issues and actions

Sample operations manual

Safety issue number: AO-2020-059-SI-01

Safety issue description: The CASA sample operations manual used by the operator that allowed any aerodrome in the Enroute Supplement Australia to be used for flight training did not assure that these aerodromes were suitable for use.

CAAP 92 Guidance

Safety issue number: AO-2020-059-SI-02

Safety issue description: Recommendations in CASA guidance CAAP 92-1(1) requiring obstacle clearance out to 900 m may lead to circumstances where ALAs meet these requirements however, aircraft are required to manoeuvre below a safe height or be unable to outclimb rising terrain after take-off more than 900 m past the runway end.

Safety action not associated with an identified safety issue

Additional safety action addressing safety hazards at Coombing Park ALA

The property manager of Coombing Park ALA advised that the airstrip has been lengthened, extending the threshold of runway 07 by 300 metres to the west. Additionally, the threshold of runway 25 was displaced by 150 metres to the west, increasing the distance between this threshold and the rising terrain to the east of the field. Five large trees were also removed on the rising terrain to allow an escape route away from the rising terrain.

Glossary

ADS-B              Automatic Dependent Surveillance Broadcast

AIP                   Aviation information publication

ALERFA           Alert phase

ATC                 Air traffic control

CASA               Civil Aviation Safety Authority

CASR               Civil Aviation Safety Regulations

CCTV               Closed-circuit television

ERSA               En route supplement Australia

IAS                   Indicated airspeed

ICAO                International Civil Aviation Organization

INCERFA         Uncertainty phase

Runway end      End of runway in use.

Threshold         Beginning of usable portion of runway, i.e. downwind end.

Touch-and-go   Practice landing in which the aeroplane is permitted to touch runway briefly; in many cases flaps are moved to take-off setting while weight is on wheels.

Sources and submissions

Sources of information

The sources of information during the investigation included:

• accident witnesses
• Airservices Australia
• the Bureau of Meteorology
• the Civil Aviation Safety Authority
• the manager of Coombing Park ALA
• Soar Aviation Aircraft Holding Pty Ltd
• recorded data transmitted from the aircraft
• recorded data from the instructor’s OzRunway’s account
• photographs and videos taken of the aircraft on the day of the accident

References

Australian Transport Safety Bureau (2008). AR-2007-053 Analysis, Causality and Proof in Safety Investigations, Canberra, Australia.

Burnside, J. (2004). Airmanship: Touch and Goes? Aviation Safety Magazine, 20 September 2004.

Geeting, D. & Woerner, S. (1988). Mountain flying (First edition), TAB Books Inc., Blue Ridge Summit, PA.

Vendeth, S (2003). A Pilot’s Guide to Safe Flying, A Manual for General Aviation Pilots (First Edition), Mt Eliza, Victoria, Australia

Wright, C. (2006). CFI to CFI rite of passage: The touchy subject of touch and goes. Flight Training Magazine, May 2006. https://www.aopa.org/

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 Bureau of Meteorology
• the Civil Aviation Safety Authority
• the manager of Coombing Park ALA
• Soar Aviation Aircraft Holding Pty Ltd.

Submissions were received from:

• the Bureau of Meteorology
• the Civil Aviation Safety Authority
• the manager of Coombing Park ALA
• Soar Aviation Aircraft Holding Pty Ltd.

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

Appendices

Appendix – The influence of the touch‑and‑go landing on the accident involving VH-OIS, 4 November 2020

This appendix documents a short study conducted by the ATSB to investigate the potential contribution that conducting a touch-and-go may have had on the accident involving OIS on 4 November 2020 at Coombing Park ALA. The key objective was to show the differences that conducting a touch-and-go in comparison to a standing take-off may have had on the ability of OIS to outclimb the rising terrain in the upwind area of runway 07.

Methodology

Aireon flight data was used to estimate the distance between the runway threshold and the aircraft reaching a height of 50 ft. The runway threshold (at the beginning of the runway) was used as a relative reference marking the start of the take-off run or touch‑and‑go. This was to allow comparison between standing take-off runs and touch‑and‑goes. As such, this indicates the overall average performance of the aircraft and pilot flying combination. As this was a pre-CPL flight test assessment, the pilot flying is expected to be the student pilot in every case.

The flight data point indicating the climb to 50 ft (and hence take-off) was identified by firstly reading backward in time from an established initial climb to the local minima in the data. The 50 ft point was then found by reading the first data point 50 ft above the local minima after the time of the local minima. Although there were undulations along the runways at Orange Airport and Coombing Park ALA, this was not expected to have affected the results in the locations where the initial climbs started. Further, this is expected to be within the tolerances of the flight data rounded to the nearest 25 ft. Distances were estimated as great circles using the haversine formula[19] between the latitude and longitude of the runway threshold and the flight data point as OIS passed through 50 ft. The results of this analysis are shown in Figure 17.

Results

Estimation of take-off distance

The horizontal axis of Figure 17 shows the distance between the runway threshold, at the beginning of the take-off run, and climb to 50 ft above ground level. Values associated with Orange Airport are prefixed with ‘YORG’ and are colour coded as orange for runway 29, and yellow for runway 11. The touch‑and‑go at Coombing Park is indicated in purple and prefixed ‘YCPK’. Bars indicating touch‑and‑goes include ‘T/G’ in the label, with the standing take off at Orange Airport labelled ‘YORG T/O RWY 11 0537UTC’.

Figure 17 also shows calculated take-off distance required for each runway used at Orange Airport from the aircraft flight manual for OIS, with the label of these calculated values prefixed by ‘YORG AFM TODR’. These are based on the reported winds, density altitude and aircraft weight at Orange Airport at 1600 and 1630. Labels are all suffixed with the local time at the start of each run or the time of weather observation. Further, the open blue bars prefixed with ‘YCPK T/G est. at YORG’ show an estimated range of the Coombing Park touch‑and‑go distance if conducted at Orange Airport. The bar labelled ‘grass’ includes a correction for the dry grass runway, as required by the AFM for OIS, with the bar labelled ‘no grass’ indicating results without a surface correction. This analysis is described further below.

Figure 17: Distance from runway threshold to take-off for VH-OIS at Orange Airport and Coombing Park ALA, 4 Nov 2020

Source: ATSB

Comparison of Coombing Park ALA take-off position with previous touch‑and‑go runs

The measured distance between the runway threshold and take-off (the touch‑and‑go distance) at Coombing Park ALA was compared to the same distances for touch-and-goes conducted at Orange Airport. The length of the Coombing Park ALA touch-and-go was the third shortest of the flight. The two shortest touch-and-goes conducted at Orange Airport (1602 and 1615) had a length of just over 750 m. With the fourth shortest touch‑and‑go being the first approach conducted at Orange Airport (1556) at about 1,000 m.

Corrections for aircraft mass, density altitude and surface type were applied to the measured touch-and-go distance at Coombing Park to compare the length of the touch‑and‑go conducted at Coombing Park with those conducted at Orange Airport, as shown by the open blue bars in Figure 17. No correction was performed for wind to show potential variation from this as a factor. These corrections were performed as follows. The take-off distance required by the AFM (the AFM TODR) were calculated for Orange Airport and Coombing Park ALA based on the estimated aircraft take-off mass, pressure altitude and temperature at each location. The ratio between the AFM TODR between Orange Airport and Coombing Park ALA was calculated, and this was multiplied with the actual touch‑and‑go distance at Coombing Park, measured from OIS flight data, and is summarised by the following equation.

Where, L_{YCPK at YORG} represents the estimated length of the Coombing Park ALA touch‑and‑go if it was conducted at Orange Airport. TODR_YORG and TODR_YCPK represent the take-off distances required for Orange Airport for reported conditions at 1600, and Coombing Park at 1700 respectively. Finally, L_CPK represents the actual touch‑and‑go distance at Coombing Park measured from OIS flight data. The results of this calculation are shown by the ‘YCPK T/G est. at YORG (no grass)’ bar in Figure 17. In addition to this calculation, a correction for the grass runway was applied by multiplying TODR_YCPK by 1.25, as recommended for a dry grass runway in the AFM for OIS and shown by the ‘YCPK T/G est. at YORG (grass)’ bar in Figure 17.

The estimated equivalent length of the touch‑and‑go conducted at Coombing Park ALA to Orange Airport accounting for grass was 812 m, about 8% longer than the shortest touch‑and‑go at Orange Airport. Without accounting for grass, the Coombing Park ALA touch‑and‑go projection was about 260 m longer than the shortest touch‑and‑go at Orange Airport, and marginally longer (about 15 metres) than the first touch‑and‑go conducted at 1556. The surface at Coombing Park appeared in good condition at the time of the accident, with the surface being firm, the grass relatively short, and the conditions dry. It is expected that the grass correction factor is an upper limit for the calculation of the potential length, with the lower limit being the calculation without accounting for grass.

The touch-and-go approaches at 1609 and 1619 had lift-off points considerably further along the runway than the other runs and were consistent with flight assessment exercises being conducted. The altitude profile of the 1609 touch‑and‑go was consistent with a go-around followed by a second, later touch-down, possibly simulating an early upwind engine failure. The touch‑and‑go at 1619 was likely following a practiced glide approach onto the reciprocal runway 11. These exercises were expected elements to assess the suitability to conduct a CPL flight test.

As no wind correction was applied to the estimated projection of the Coombing Park ALA touch‑and‑go length to Orange Airport, this calculation reflects the wind speed and direction as applicable at Coombing Park ALA during the touch‑and‑go at 1708. The Bureau of Meteorology identified that there was unlikely to be a headwind component during the touch‑and‑go at Coombing Park ALA. Further, based on the reported wind conditions at 1600, it is likely that a headwind component of approximately 6 kt was present at about the time of the shortest touch‑and‑go at 1602 at Orange Airport. In addition, the touch‑and‑go at 1556 likely used more runway than the Coombing Park ALA touch‑and‑go if this was conducted at Orange Airport, despite the likelihood of a 6 kt headwind component at Orange Airport during this touch‑and‑go. Therefore, a weaker headwind component is expected to have contributed to a longer landing at Coombing Park ALA than the shortest touch‑and‑goes conducted. However, based on the uncertainty in the meteorological data, and the ground speed of OIS from flight data being close to the published short field approach speed, it was not possible to determine the precise impact of wind on the touch‑and‑go distance at Coombing Park ALA.

In summary, compared to the length of the touch‑and‑goes conducted at Orange Airport, the Coombing Park ALA touch‑and‑go was the third shortest of the flight. The touch‑and‑go at Coombing Park ALA was the third shortest touch-and-go of the flight with and without density altitude corrections. Although the precise impact of the grass surface could not be determined, it is expected that this would have had the effect of reducing the projected length toward the two shortest touch‑and‑goes. Additionally, the touch‑and‑go conducted at Orange Airport at 1556 likely used more runway than an equivalent length touch‑and‑go conducted at Coombing Park at 1708, despite the 1556 touch‑and‑go likely having a larger headwind component. Based on analysis of the flight data for OIS, it appears likely that the touch down length was within the normal variability of touch-and-goes conducted by the student. Therefore, the above suggests that the length of the touch-and-go conducted by the student at Coombing Park ALA was typical of touch-and-goes conducted at Orange Airport earlier in the flight.

Estimation of standing take-off distances

The ATSB conducted an analysis examining the potential effect from performing a standing take‑off instead of the touch‑and‑go at Coombing Park ALA under the same conditions. The purpose was to estimate the maximum distance where OIS would have lifted-off along the runway at Coombing Park ALA if a standing take-off was conducted using two independent methods. One method (the ratio method) to estimate this distance was similar to the projection of the Coombing Park ALA touch-and-go to Orange Airport described above. For this method, the ratio between the standing take-off at 1637 and the measured touch‑and‑go distance was calculated, and this result was multiplied by the length of the Coombing Park ALA touch-and-go distance (929 metres). The other method was estimated standing take-off distance based on the AFM. Results from both methods are shown in Table 2.

Table 2: Standing take-off distance estimations for OIS at Coombing Park ALA runway 07

The ratio of the shortest touch‑and‑go at 1602 at Orange Airport was calculated as 0.90, equating to the longest estimated standing take-off length of 836 m. The same was performed for the 1556 touch‑and‑go, with a ratio of 0.68, and representing an upper limit of the normal touch‑and‑goes conducted. This equated to the shortest estimated standing take-off at 630 m. Standing take-off estimates based on the take-off distance required from the AFM for OIS were between the ratio‑based estimates. These were both factored by 25% to account for the short-dry grass runway for no wind, and a 5 kt tailwind.

The headwind component of the 1556 and 1602 touch‑and‑goes on runway 29 (about 6 kt) was likely greater than the headwind component of the standing take-off on runway 11 (about 1 kt), based on the reported wind conditions in METARs at 1600 and 1630. A greater headwind component would have allowed OIS to become airborne in a shorter distance with all other conditions the same. Given these conditions, the actual ratio between the standing take-off length and minimum touch-and-go length is expected to be slightly lower, making the estimated standing take-off distances slightly shorter. This indicates that the difference between the standing take-off and touch-and-goes using the ratio method is expected to be larger, and is therefore conservative.

In summary, the standing take-off length at Coombing Park ALA was estimated to be between 630 and 836 m, notably shorter than the actual Coombing Park ALA touch‑and‑go length of 929 m.

Initial climb projections

The ATSB evaluated the potential influence of a standing take-off on the height of OIS during the initial climb. This analysis used the estimated standing take-off distances described in the section above and is illustrated in Figure 18. The vertical axis shows the height above the estimated point of lift off and the horizontal axis shows the distance from the start of runway 07 at Coombing Park ALA, and also corresponds to the markers shown in Figure 6. Terrain elevation is shown by the solid dark green area, with typical tree heights indicated by the translucent dark green (minimum 10m) and light green (maximum 20m) areas.

Figure 18: Height of initial climb profile for OIS at Coombing Park ALA, including estimations for climb profiles following standing take-off and estimated terrain profile

Figure showing plot of height vs distance travelled of OIS during the initial climb from Coombing Park ALA runway 07 compared to terrain and estimates for climb if a standing take-off was conducted.

Source: ATSB

The actual initial climb profile of OIS conducted at Coombing Park ALA at 1709 is shown in Figure 18 by the series with red lines and blue circles. The last data point of this series indicates the relative height of OIS immediately prior to the left turn. The red dotted series is the line of best fit for the 1709 initial climb and shows an estimated projection of the climb if the climb rate was maintained and OIS tracked in a straight line instead of turning left. The top right corner of Figure 18 shows the projected climb above the minimum nominal tree height but intercepting below the maximum nominal height.

Theoretical climb profiles representing each of the estimated standing take-off lengths shown in Table 2 are shown by the dashed light blue, dark blue, yellow, and orange lines. These were formed by translating the actual climb profile horizontally (indicated by the red-dotted line) to commence from each calculated standing take-off distance along runway 07.

The orange dashed line in Figure 18, labelled ‘YCPK standing take-off estimate (from YORG T/G 1556)’, shows the best-case estimate for a climb profile following a standing take-off at Coombing Park ALA, based on the estimated standing take-off length of 630 m. This estimate translated to be an estimated 70 ft higher than the climb following the actual touch-and-go at Coombing 1709 initial climb at each point in the climb. This was based on the mean difference between the intercepts from the equations of these lines shown in Figure 18. Similarly, the height of the worst‑case estimated standing take-off (836 m) was estimated to be 22 ft higher than the climb following the actual touch-and-go at Coombing Park ALA (shown by the dark blue dashed line in Figure 18). This represents the lower limit of the height difference. The climb profiles for the AFM-based standing take-off estimates listed in Table 2 are shown by the yellow and light blue dashed lines in Figure 18, between the other projections.

In summary, the vertical height difference between a standing take-off climb profile and the touch‑and-go climb profile was estimated by the ATSB. This was based on calculating the vertical difference between the actual climb profile following the touch-and-go at Coombing Park ALA, and theoretical climbs originating from the estimated location of standing take-offs. The analysis found that if a standing take-off was conducted at Coombing Park ALA, the height at each point during the initial climb would have likely been between 22 and 70 ft higher than the actual touch-and-go conducted by the student. The top right corner of Figure 18 shows all climbs following hypothetical standing take-offs as passing close to, but above the maximum nominal tree height at the local terrain peak.

Conclusion

Based on analysis of the flight data for OIS, the ATSB found that the length of the touch-and-go conducted by the student at Coombing Park ALA was typical of touch-and-goes conducted at Orange Airport earlier in the flight. The length of all touch-and-goes during the flight were notably longer than the standing take-off conducted at Orange Airport when corrected for density altitude (when the length was measured from the runway threshold to the point of take-off). These touch‑and-goes were also all longer than calculations using the aircraft flight manual for the accident aircraft (VH-OIS). When corrected for density altitude, a standing take-off length at Coombing Park ALA was estimated by the ATSB to be between 630 and 836 m for the atmospheric and weather conditions at the time of the accident, notably shorter than the actual Coombing Park ALA touch‑and‑go length of 929 m. This equated to OIS being between 22‑70 ft higher at each point during the initial climb if a standing take-off was conducted instead of a touch-and-go. In contrast to the initial climb after the actual touch-and-go projecting below the maximum tree height, climb projections from standing take-off estimates indicated that OIS as passing close to, but slightly above the maximum nominal tree height.

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 2023 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 the morning of 23 October 2020, an Airbus A320-232 was being operated by Jetstar Airways on a flight from Brisbane to Cairns, Queensland. As power was being applied for take-off, the crew reported feeling a vibration and hearing a ‘popping’ noise that rapidly increased in frequency and volume. At the same time, the aircraft diverged to the right of the runway centreline despite the pilot flying applying full left rudder pedal deflection. The captain immediately selected reverse thrust and brought the aircraft to a stop.

Some passengers onboard, a Brisbane air traffic tower controller, and flight crew of a following aircraft all reported momentarily seeing flames coming out the right engine. The aircraft was taxied back to the airport gate. Engineers then reported finding metallic debris in the tailpipe of the right engine.

On disassembly of the engine, it was discovered the high-pressure compressor (HPC) had sustained significant damage and a screwdriver tip was found in the combustion section.

What the ATSB found

The screwdriver tip was determined to have been in the engine for over 100 flights. The ATSB concluded the tool bit had been left in the engine after maintenance and when the engine was running, it entered the HPC leaving dents and nicks in numerous rotor blades and stator vanes. At least two of these defects initiated fatigue cracks that resulted in a blade failing during the occurrence take-off. The liberated blade caused greater damage to the HPC and the engine surged.

What has been done as a result

As a result of the occurrence Jetstar Airways issued a Safety Alert to their maintenance engineers, which highlighted the need for all tooling to be accounted for. They also conducted a risk assessment to better understand the on-going risk.

Safety messages

Tool control is an important part of maintenance processes that ensures they do not lead to foreign object damage. Small and seemingly insignificant tool components can, and have, caused significant incidents or accidents. Tool control should extend to pseudo consumable items such as screwdriver tips and drill bits.

Modern training methods include the use of high-fidelity training devices such as full motion flight simulators. Their design aims to maximise the realism of an artificial environment. However, there is a limit to their ability to replicate extreme events. Flight crew should be aware that the noise and vibration from an actual engine failure may be greater than, or different to, that experienced during simulator training and this could contribute to the effects of startle.

The investigation

The occurrence

On the morning of 23 October 2020, an Airbus A320-232 was being operated by Jetstar Airways on a flight from Brisbane to Cairns, Queensland. The first officer was the pilot flying and the captain was the pilot monitoring.^[1]

After push back, the first officer taxied the aircraft for a planned take-off on runway 01L. The crew completed the pre-take-off checks during the taxi in anticipation of a rolling start to the take-off. After being cleared for take-off on approach to the runway, the aircraft was lined up and, without stopping, the thrust levers were set for Flex.^[2] The crew reported that as both engines spooled up to the requested power setting, a vibration and ‘popping’ noise could be heard that rapidly increased in frequency and volume. At the same time, the aircraft diverged to the right of the runway centreline despite the first officer applying full left rudder pedal deflection. In response, the captain immediately selected reverse thrust and brought the aircraft to a stop. The aircraft reached a maximum ground speed of 30 knots.

Upon returning the thrust levers to idle, the vibration subsided and the popping stopped. The aircraft instrumentation then sounded two master caution alarms and the Electronic Centralised Aircraft Monitoring (ECAM) system^[3] reported two messages for Engine No. 2 (right) ‘STALL’ and ‘EGT LIMIT EXCEEDANCE’.^[4] The captain called for the cabin crew to move to stations.^[5]

The cabin crew relayed to the flight crew that passengers had seen flames coming from the right engine. Both the airport tower controller and the flight crew of a following aircraft similarly reported seeing flames coming from the rear of the right engine for a short period of time. The tower dispatched Airport Rescue and Firefighting services, who observed no apparent abnormalities with the aircraft.

The captain cancelled the flight and the aircraft was taxied back to the airport gate where both engines were shut down. Immediately after the passengers had disembarked, engineers reported finding small balls of metallic debris in the tailpipe of the right engine (Figure 1). A review of recorded data indicated the right engine had surged.

Figure 1: Debris in right engine tailpipe

Source: ATSB

Context

Engine Description

The IAE V2527-A5 engine is a variant of the V2500 family of engines. The two‑spool, axial‑flow, high‑bypass turbofan comprises low- and high-pressure stages. The low-pressure section consists of a fan stage and four low-pressure compressor (LPC) stages (labelled booster stages) connected to five low-pressure turbine (LPT) stages. The high-pressure section consists of ten high-pressure compressor (HPC) stages (numbered 3 to 12) connected to two high‑pressure turbines (HPT) (Figure 2).

Figure 2: IAE V2527-A5 engine station and stage numbering diagram

Source: IAE Training Manual.
Note: The low-pressure spool is shown in grey and the high-pressure spool in black.

An engine surge is caused by a loss of air compression on the inlet side of the engine. This can be caused by disrupted airflow ahead of the engine, ingestion of foreign matter, excessive thrust changes or an airflow disruption internal to the engine.

Regardless of the cause, the sudden breakdown in compression results in reversal of the flow and violent expulsion of the previously compressed air out the inlet of the engine. The process is often cyclic resulting in a vibratory noise. Additionally, disruption to the airflow can allow unburnt fuel to escape the combustion chamber and ignite in the turbine section or tailpipe.

Post-flight Inspections

On wing inspection

A borescope inspection of the right engine found there was damage to HPC stages 3, 5, 6, 7, 8 and 9 (Figure 3) consistent with foreign object damage (FOD).^[6] As the damage was outside maintenance manual limits, the engine was removed from the aircraft and sent for a teardown inspection.

Figure 3: Borescope image of stage 7 HPC and stage 8 stator vanes

Source: Jetstar

Teardown inspection

Upon disassembly of the engine, the following observations and anomalies were found:

• The fan blades and LPC contained no visible damage.
• The rear fairing to the LPC bleed valve mechanism was in place but had one Torq-set screw with a damaged head. Although of an incompatible shape, testing showed that due to the damage, the head would also accept a Phillips screwdriver tip (Figure 4).
• In the HPC section, rotor blades (blades) and stators (vanes) in stages 3 and 4 contained dents and minor tears.
• Approximately half of one stage 5 blade (Figure 5) and a whole stage 6 vane (Figure 6) were missing and had failed due to cyclic fatigue. Some of the remaining stage 5 blades exhibited tip curl,^[7] dents and/or missing material.
• Four stage 7 blades and one stage 8 blade were missing and had failed due to overstress. In this section all remaining blades and vanes exhibited hard body damage resulting in severe bending and tearing to both leading and trailing edges. One stage 8 vane contained a distinctive hexagon shaped dent (Figure 7).
• Damage after stage 8 was limited to minor dents and nicks with minimal damage occurring to the final stage components.
• Bleed valve screens at stages 7 and 10 contained large amounts of metallic fragments.
• Small metallic debris and a ¼” hexagon drive screwdriver tool bit (screwdriver tip) was found between the combustion liner and engine case. The screwdriver tip was burnt/discoloured and the tip eroded due to heat and mechanical damage (Figure 7).
• Nozzle Guide Vane (NGV) cooling passages contained small metallic debris.
• Two stage 1 HPT blades contained leading edge nicks attributed to material impacts.
• Small debris was found throughout the LPT.

Figure 4: Interstage screw heads

Source: Jetstar

Figure 5: Stage 5 blade fatigue failure

Source: Jetstar, annotated by the ATSB

Figure 6: Stage 6 vane fatigue failure

Source: Jetstar, annotated by the ATSB

Witness marks on many components throughout the HPC matched the shape of the screwdriver tip found in the combustion section (Figure 7).

Figure 7: Screwdriver tip and witness marks

Source: Jetstar

A failure analysis was conducted by an engine maintenance facility. The fractured stage 5 blade showed minor leading edge mechanical damage at approximately half span, which initiated a fatigue crack that propagated through approximately two-thirds of the chord. The remaining third of the chord failed in material overstress.

The fractured stage 6 vane sustained a tear near the aerofoil root to a depth of approximately 10 per cent chord. This initiated a fatigue crack that ended 2 mm from the trailing edge with the remaining material exhibiting a material overstress signature.

Both fatigue fracture surfaces displayed fine striations consistent with a high frequency load spectrum, likely from aerodynamic vibrations. While no fatigue growth rate analysis was conducted, based on similar occurrences, it was estimated the components took tens of flight cycles to fail.

Aircraft maintenance program

The aircraft maintenance program required a fairing to be removed in the engine to lubricate the LPC Bleed Valve Mechanism every 4,000 flight hours. The task was last accomplished 112 flight cycles prior to the engine surge. This task occurred with many others as part of preparations to return the aircraft to service after being parked for approximately 4 months.

The LPC Bleed Valve Mechanism task procedures contained specific highlighted caution notes regarding the loss of any screws or other loose objects down the bleed duct. The note highlighted that lost articles would progress to the HPC and break blades and vanes. This occurs because during engine start and idle the bleed valve opens.

Engine failure during take‑off

Both flight crew commented that the event startled them due to its unexpected onset, the volume of the popping noise and particularly the levels of vibration. Additionally, the pilot flying reported that, despite the application of full left rudder, the aircraft still diverged to the right of the runway centreline. Both pilots commented that the noise and vibration was far more severe than what they had experienced during flight simulator training sessions when practicing for similar types of events.

Flight crew training includes many different failure scenarios. Being a particularly critical phase of flight, take-off is trained for extensively including engine failures that involve high-speed rejected take-offs (RTO) and post V₁ flight continuations.^[8] One crewmember commented they had never performed a low-speed RTO with engine failure.

For a high-speed engine failure, crews are trained to recognise the failure and maintain runway direction through use of the rudder, which is effective at speeds above V_MCG.^[9] The take-off is then either continued or rejected. If rejected, the thrust asymmetry is reduced by idling the remaining engine/s.

Low-speed RTOs are those which occur below V_MCG where the aircraft’s rudder is not effective enough to counter the large thrust asymmetry and thus the aircraft will diverge from the runway centreline uncontrollably if continued. This situation is countered by differential braking and promptly returning the engines to idle, thereby reducing or nullifying the thrust asymmetry.

Low-speed RTOs, while considered less dangerous because they occur at lower speeds, involve a loss of directional control. Lateral divergence from the runway centreline can be larger than for a high-speed engine failure (>V_MCG) and can cause considerable damage if the aircraft departs the side of the runway.

Related Occurrences

ATSB investigation (199800615)

On 28 February 1998, at a height of about 100 ft after take-off, the crew of a Boeing 767 reported hearing a series of loud bangs and the right engine exhaust gas temperature indicator rose rapidly into the red range. The right thrust lever was retarded to idle, resulting in the temperature indications returning to normal. ATC also observed a series of flashes from the right engine as the aircraft departed and declared a local emergency. The crew returned the aircraft to the airport and landed without further incident.

An internal borescope inspection revealed extensive damage to blades of the thirteenth compressor stage. The engine was subsequently removed for further inspection, resulting in a replaceable Philips screwdriver tip being found in the core of the engine.

The operator reported that the incident occurred on the first flight after the aircraft had undergone an 'A' maintenance check. The screwdriver tip probably entered the engine through the variable bleed valves, which are open when the engine is not operating.

Safety analysis

The damage to the HPC section and the screwdriver tip found in the cooling cavity were consistent with the screwdriver tip falling into the LPC bleed duct, passing through the interstage duct and into the HPC. The lack of damage to the LPC indicated the tip was not FOD from the runway. The damage to the rear fairing screw meant it was likely the screwdriver tip had been left in the screw or had fallen into the bleed duct during maintenance. At the next engine start-up, it then travelled through the HPC section striking various components, in some cases leaving witness marks, before being held captive adjacent to the combustion chamber.

There was evidence that fatigue cracks initiated from the impact damage in a stage 5 blade and stage 6 vane. These cracks propagated until one reached a critical size due to aerodynamic forces and vibrations, and additionally for the blade, centripetal forces. As the engine surge event occurred during the application of take-off power and acceleration of the engine internal componentry, it is more likely the blade failed first due to the increase in centripetal acceleration.

Regardless of whether the blade or vane failed first, one likely impacted the other and both then caused downstream damage, including the failure of a further five compressor blades. The resulting disruption to aerodynamic flow through the HPC allowed the engine to surge and led to the loss of engine performance.

Findings

From the evidence available, the following findings are made with respect to the engine power loss.

Contributing factors

• A screwdriver tip, left in a fairing screw or bleed duct, travelled through the high‑pressure compressor (HPC) section of the right engine before becoming lodged in the combustion section. This resulted in impact damage to HPC blades and vanes.
• Fatigue cracks initiated at damaged locations in at least one HPC blade and vane, with one crack propagating to failure. This resulted in secondary damage to the engine and surging on take-off.

Safety actions

Safety action by Jetstar Airways

As a result of this incident, the operator advised the ATSB:

• the Jetstar Aircraft Maintenance Organisation had issued a Safety Alert to maintenance engineers, which highlighted the need for all tooling to be accounted for.
• they had conducted a risk assessment to better understand the on-going risk.

Sources and submissions

Sources of information

The sources of information during the investigation included:

• the flight crew
• VH-VFF direct access recorder
• Jetstar Airways
• Christchurch Engine Centre

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 flight crew
• Jetstar Airways

Submissions were received from:

• Jetstar Airways

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

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.

__________

1.  Pilot Flying (PF) and Pilot Monitoring (PM): procedurally assigned roles with specifically assigned duties at specific stages of a flight. The PF does most of the flying, except in defined circumstances. The PM carries out support duties and monitors the PF’s actions and the aircraft’s flight path.
2.  Flex is an engine thrust setting used for take-off which is below the maximum rated thrust for an engine. The engine thrust requested for a given take-off is calculated based on aircraft weight, flap setting, runway length available and ambient temperature, and is used to reduce engine wear.
3.  Electronic Centralised Aircraft Monitoring (ECAM) is a system that monitors aircraft functions and relays their status to flight crew. It also produces messages detailing failures.
4.  EGT – Exhaust Gas Temperature
5.  A ‘Call to stations’ is a notification via the public address system from the flight crew to the cabin crew that they are assessing an emergency situation and that an evacuation may be necessary. On receipt of this notification, cabin crew prepare by undertaking actions such as checking conditions outside their assigned door, maintaining control of passengers in the cabin and reporting any abnormal conditions to the flight crew.
6.  Foreign Object Damage (FOD) is any article or substance, alien to an aircraft or system, which could potentially cause damage. The term FOD is used to describe both the foreign objects themselves and any damage attributed to them.
7.  Tip curl is a signature of compressor or turbine blades making contact with the engine casing.
8.  V1 is a decision speed where, thereafter, the pilot can continue the take-off safely using the remaining runway on the remaining engine/s. If a decision to abort the take-off occurs before V1 is achieved, the aircraft has enough distance to safely come to a stop on the remaining runway available. It can be said that V1 is the ‘commit to fly’ speed. V1 is calculated for every take-off as it is based on aircraft available thrust, aircraft weight, flap setting, runway length and slope, wind conditions, and airport density altitude.
9.  VMC means the minimum control speed with the critical engine inoperative and the remaining engine/s at maximum power permitted for the situation. VMC can be further separated into VMCG (ground) and VMCA (airborne) which, while both involve engine failure, are limited by different factors.

Overview of the investigation

The occurrence

On 2 October 2020, at about 1117 Eastern Standard Time,^[1] a SCT Logistics freight train 3PG1 travelling from Port Germain, South Australia to Parkes, New South Wales, began to lose brake pipe air, resulting in the application of the brakes. The train subsequently came to a stand with the leading locomotive at about 904 track km, 90 km west of Ivanhoe, New South Wales.

In response to the loss of air, the driver and driver assistant (both employed by Momentum Rail) commenced an inspection of the wagons. However, they stopped before arriving at the back of the train as the driver considered the issue to be a computer error. They returned to the lead locomotive and the driver tried to restore the brake pipe air by resetting the electronic air brake system, which was unsuccessful. The driver assistant re‑inspected the wagons, finding and closing an open brake pipe tap on the back of the last wagon (ABSY2792Y). They reported this to the driver, but for differing reasons, the end of train marker was not checked or the number of the last wagon was not confirmed.

The train’s brake pipe air was restored, allowing the brakes to release. The driver reported to train control that the loss was due to an animal strike and the trip resumed. On arrival at the Darnick yard limit board (YLB), the previously issued train order (Kaleentha loop to Trida YLB) was cancelled and a new train order from Darnick YLB to Ivanhoe YLB was issued. The crew of 3PG1 did not check whether their train was complete at this location and the train controller did not request confirmation, as required by the Australian Rail Track Corporation train order working procedure.

However, due to concerns with not having checked the end of train marker, the driver assistant conducted a roll-by inspection as the train proceeded into the Ivanhoe loop. At that time, they identified that the train consist was incomplete and the last 4 wagons were missing. The crew concluded that the missing wagons were likely left behind at the point where the train had lost brake pipe air pressure, about 2 hours prior. The section of track with the 4 parted wagons was left without protection with another train waiting at Darnick to enter the occupied section.

Investigation activities

During the investigation, the ATSB:

• interviewed the train crew and network controller
• conducted analysis of data from the locomotive’s event recorder
• reviewed recorded communications between train control and the crew
• reviewed the track access and labour agreements in place between the involved parties
• reviewed the experience, training and competencies held by the train crew
• conducted analysis of possible contributors to the parting, including a review of the wagon inspection results and maintenance history
• analysed the practical actions required, including actioning applicable rules and procedures when train crews respond to a loss of brake pipe air event
• reviewed the tasks conducted post-occurrence to recover the lost wagon.

ATSB observations

From the investigation, the ATSB determined:

• The coupler locking block and knuckle on the leading end of wagon ABSY2792Y were worn, which very likely resulted in 4 rear wagons parting, and train 3PG1 subsequently loosing brake pipe pressure.
• The crew did not identify that the end of train marker was not present on the last coupled wagon or otherwise identify that the 4 rear wagons had parted. Instead, during an inspection of the train, the driver assistant closed an open brake pipe air tap on the back of the last coupled wagon, which allowed all the wagon brakes to release. Consequently, the train resumed the journey incomplete.
• The 4 parted wagons were left occupying the track section when the protection on the section of track (Kaleentha to Darnick) was removed. The crew of 3PG1 cancelled the existing train order without conducting a further inspection.
• The driver assistant was not experienced in the role they were undertaking. This, combined with having only partially completed the relevant driver qualification, contributed to them not recognising the potential reasons for an open air tap on the back of the last wagon, which included the risk that the train had parted. This likely compromised the crew's understanding of the occurrence and led them to incorrectly attribute the problem to a known cause.
• The lock blocks on three couplers, including the coupler that initiated the parting, were not replaced at previous 'B' inspections. However, the replacement was a requirement in SCT Logistics’ maintenance provider’s (Gemco Rail) procedures. Subsequently, the component was in use past its intended service life when the parting occurred.

Reasons for the discontinuation

The ATSB gives priority to transport safety investigations that have the potential to deliver the greatest public benefit through systemic improvements to transport safety.

Given the ATSB’s constrained resources, the ATSB considered it was unlikely that further investigation would identify systemic safety issues or identify opportunities for the enhancement of transport safety. Consequently, the ATSB has discontinued this investigation.

The ATSB has briefed SCT Logistics and Momentum Rail about its observations and potential learnings. However, it considered that broader communication of this information would not be of significant benefit to other parties.

The evidence collected during this investigation remains available to be used in future investigations or safety studies. The ATSB will also monitor for any similar occurrences that may indicate a need to undertake a further safety investigation.

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1.  Eastern Standard Time (EST): Coordinated Universal Time (UTC) + 10 hours.

This investigation was conducted under the Transport Safety Investigation Act 2003 (Commonwealth) by the Office of Transport Safety Investigations (NSW) on behalf of the ATSB in accordance with the Collaboration Agreement. Released in accordance with section 25 of the Transport Safety Investigation Act 2003.

Safety summary

What happened

On 13 October 2020, TrainLink passenger service SN68, was operating from Moss Vale to Campbelltown, New South Wales with approximately 20 passengers on board.

The train driver stopped the train at Yerrinbool Station after being alerted to a small fire at the rear of the train. The fire was identified as coming from the vicinity of an axle bearing on the rear wheelset of the train. The passengers were evacuated onto the platform and the driver attempted to extinguish the fire using an on-board fire extinguisher.

The fire was subsequently extinguished by Fire and Rescue NSW. As a result of the fire, parts of the axle box were heat affected and sustained significant damage to the speed sensor and rubber suspension components. There were no reported injuries.

What the ATSB found

The investigation determined that the fire was the result of a collapsed axle bearing on wheel 8 on the trailing bogie on car 2811, the end of the train. The axle bearing failed when the axle end cap bolts loosened and one fractured which caused the collapse of the bearing and frictional heat to be generated. The resulting fire was fuelled by grease, oil and rubber suspension components in the immediate vicinity of the axle box.

It is likely that during the last overhaul of bogie NJA31, the locking plate tabs retaining the axle end cap bolts were not fitted correctly against the sides of the bolts. The axle bearing installation process was not sufficient to ensure the tabs on the locking plate were installed correctly during a refurbishment three months before the incident.

A wayside monitoring system at Burradoo on the Down Main line detected an elevated temperature on one bearing, but the temperature recorded was below the threshold for an alarm to be sent to network control.

What has been done as a result

Following the occurrence Sydney Trains, which is the maintenance provider for NSW Trains, initiated an inspection of similar axle boxes in the fleet and undertook an audit of the contracted maintainer’s practices.

Sydney Trains have advised the following actions have taken place to prevent a recurrence:

• Improvements have been made to the contracted maintainer’s quality assurance processes to ensure that bolts and locking tabs are correctly installed.
• An improved process was implemented to review and retain the contracted maintainer’s certificate of completion checklists.

Safety message

Bearing failures continue to occur within the Australian rail network. This occurrence emphasises the significance of having adequate bearing installation processes and ensuring that axle bearings are correctly maintained and monitored throughout their operational life.

The occurrence

On Tuesday 13 October 2020, TrainLink passenger service SN68, operated by NSW Trains,^[1] departed Moss Vale at 1757.^[2] The two-car Endeavour train was crewed by a driver in the front cab and a guard in the rear cab. There were approximately 20 passengers on board the train as it departed Moss Vale (Figure 1). The train was to make 11 stops before being scheduled to arrive at Campbelltown at approximately 1900.

The train stopped at Burradoo and Bowral before departing Mittagong at approximately 1809. The train crew said they had experienced no problems with the train before Yerrinbool.

At 1820, as the train was slowing to stop at Yerrinbool Station, the guard, from inside the cab at the rear of the train, heard a loud noise and noticed smoke outside the window. The guard used the train’s bell system to ask the driver to stop. The driver brought the train to a stand at Yerrinbool Station.

Figure 1: Incident location and path of SN68

Source: Geoscience Australia, annotated by OTSI

Once the train stopped at Yerrinbool Station, the guard used the trains’ public address system to ask the passengers to move to the front of the train. The guard made a second announcement shortly afterwards, requesting passengers disembark onto the platform. The driver walked along the platform to the rear of the train and observed a flame and dark smoke coming from the last wheelset of the train, wheel 8 on axle 4 under the bogie of car 2811.

The driver spoke to an Australian Rail Track Corporation (ARTC) network controller at Junee requesting permission to go down onto the track to attempt to extinguish the fire. The network controller applied signal blocking to prevent rail traffic in both directions and then gave permission for the driver to access the track. Another passenger service, SN61, was stopped by the signaller at a signal before the platform at Yerrinbool. This provided protection on the adjacent line so the driver could go onto the track. The driver went onto the track and used the on-board fire extinguisher to attempt to put out the fire. The fire continued to smoulder/burn as the heat source remained.

Fire and Rescue NSW arrived on site at approximately 1828 and ensured the fire was extinguished before departing at 1850. Train passengers were transferred to buses which replaced train services between Campbelltown and Moss Vale in both directions. There were no reported injuries as a result of this incident.

The maintenance shift manager at Eveleigh Maintenance Centre organised for the Rail Emergency Recovery Unit to arrange pony bogies (Figure 2) to be fitted under all wheels of bogie NJA31 and the train was worked back to Eveleigh over the next two nights. Under the supervision of Office of Transport Safety Investigations (OTSI) investigators, Office of the National Rail Safety Regulator representatives and Sydney Trains engineering staff a partial disassembly of the axle end cap and removal of bolts from the affected bearing was undertaken. A further strip down inspection of the axle bearing assembly was conducted at bogie maintainer United Group Limited Unipart (UGLU) at Auburn, also under the supervision of OTSI investigators and Sydney Trains engineering staff.

Figure 2: Heat affected area and pony bogie fitted under NJA31

The inset image shows the axle cover removed. Two bolts were found to be missing from the end cap and one bolt was broken. All three bolts remained within the axle housing.

Source: OTSI

The damage was contained to this localised area around the trailing axle of the rear bogie. Parts of the axle box were heat affected and the speed sensor and rubber suspension components were significantly damaged.

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1. NSW Trains is an operating agency of Transport for New South Wales, it is responsible for the operations of TrainLink services.
2. Times shown in 24-hour time as Australian Eastern Daylight Time (AEDT).

Context

Environment

The Bureau of Meteorology (BOM) automatic weather station at Moss Vale, recorded the temperature as 24.4 °C at 1500 on 13 October 2020. Yerrinbool is approximately 30 km north-east of Moss Vale. Weather conditions were fine and clear.

Location

Yerrinbool Station is on the Main South line in the Southern Highlands of New South Wales (Figure 3). Yerrinbool is located at 116.310 km.^[3]

Figure 3: South-bound Endeavour two-carriage set at Yerrinbool Station

The figure shows south-bound (Down) Endeavour set at Yerrinbool Station. Image of car 2811 inset

Source: railgallery.wongm.com, annotated by OTSI

Train crew

The train was crewed by a driver, operating the train in the front driver’s compartment, and a guard located in the rear drivers’ compartment. The train crew were appropriately qualified and held the required route qualifications.

Train information

Train SN68

The passenger train involved in the incident, SN68, was an Endeavour railcar two-carriage set. This diesel-powered multiple unit train was operated by TrainLInk and built by ABB Transportation in Dandenong, Victoria. There were 14 Endeavour sets in service at the time of the incident and they first entered service in March 1994. Twenty-three Xplorer cars which have the same bogie types and axle bearings were also in service at the time of the incident.

The leading car of SN68 was LE2861, with TE2811 being the trailing car. The LE carriages feature a dedicated luggage space and can seat 95 passengers. The TE carriages feature a wheelchair accessible toilet and can seat 82 passengers.

The drivers’ cab, positioned at each end of the train, is a full width driving compartment with the driver's seat offset to the left-hand side. Passengers enter and exit through power activated doors operated and controlled by the driver or the guard. Dry chemical fire extinguishers are fitted in the drivers’ compartment.

Bogies

The bogies fitted to the Endeavour and Xplorer sets are NJA and PJA bogies. The bearing collapse occurred on an NJA bogie, the rear trailing bogie on car 2811. The NJA bogie is the trailer bogie (Figure 4), as opposed to the PJA powered bogie. Built for the State Rail Authority in 1994, the bogie involved in this incident was designated as NJA31. This bogie was installed on    car 2811 on 7 July 2020 and had travelled approximately 66,087 km since installation.

Figure 4: NJA31 bogie
 

Source: OTSI

Axle bearing installation

The maintenance and installation processes for critical components holding the axle bearing were examined as part of the investigation.

Each bogie has two wheelsets which have an axle bearing at each end of the axle (four bearings per bogie). The axle bearings were Timken SP130 type bearings. Securing the axle end cap were three different brands of bolts with the head markings showing: NLGS, JDF and HEC (Figures 5 and Figure 6). The axle end cap bolts were hexagonal head, metric 16 mm diameter (M16), 40 mm length (fully threaded), 2 mm pitch, and class 8.8. There are two types of end caps used, a standard or combined end cap suitable for mounting a phonic wheel. The phonic wheel is used as part of the train’s on-board system for recording speed and detecting wheel slide during braking, this end cap was the phonic wheel type.

Figure 5: Three types of axle end cap bolts removed from hub following incident

Source: OTSI

Figure 6: Side view of three axle end cap bolts, including broken NGLS bolt

Source: OTSI

The locking plate was a Timken brand K-422091 R.S 120-130. Stamped on the plate was the axle number (073275) and installation date (07 20 – July 2020) (Figure 7).

Figure 7: Locking plate

Source: OTSI

The requirements for installing the SP130 bearings onto the axles is documented in a Sydney Trains Standard Instruction.^[4] This instruction provided maintenance workers with the details for installing the end cap, torque requirements for bolts and installing the locking tabs. There was a wheelset certificate of completion used by the maintenance workers to show that bogie NJA31 was refurbished. This work was completed on 1 July 2020. There are check boxes on a form that the maintenance workers complete when each task is done. These were all checked as completed and the installation tolerances for the bearing were correct at the time of installation.

The axle bearing installation process commences with the bearing being pressed onto the axle journal before being retained on the journal by an end cap. The end cap is secured by three M16 bolts with a new locking plate positioned underneath the bolt heads. The bolts are screwed in threaded holes and using a calibrated torque wrench are finally torqued to 80 – 100 Nm.

The bolts are torqued in sequence until there is no further movement of the bolt resulting from the application of the specified torque. It may be necessary to further tighten the bolt to align the head with the locking plate tabs. The tabs on the locking plate are then bent up to engage with the sides of the bolt head to form a tight fit. After the process is complete a witness mark is applied to the bolt head and adjacent area to show the original position of the bolts (Figure 8). Movement can be visibly determined during any subsequent inspections.

Figure 8: Correct bolt and locking tab installation bolt

Inset image shows a close of the locking tabs correctly bent up and in contact with the head of the bolt as well as the witness mark (white paint pen).

Source: OTSI

Involved parties

The Australian Rail Track Corporation (ARTC) is the rail infrastructure manager that manages the Main South Line from Macarthur on the outskirts of Sydney to Melbourne, including the wayside monitoring device. 

NSW TrainLink provides rail services in NSW and also operates some interstate services to Victoria and Brisbane.

Sydney Trains is responsible for maintenance activities on the trains operated by Sydney Trains and NSW TrainLink.

United Group Limited Unipart (UGLU) are contracted maintenance providers to Sydney Trains and serviced the bogies of the Endeavour and Xplorer fleet. UGLU is a joint venture between United Group Limited and Unipart.

Track and infrastructure information

The section of track at Yerrinbool was standard gauge (1435 mm). It consisted of an Up Main line and a Down Main line. At the time of the incident SN68 was travelling towards Sydney on the Up Main line.

ARTC maintains operational control for this area from Network Control Centre South at Junee.

Wayside detectors

The ARTC, operates and maintains the wayside monitoring systems in the vicinity where this incident occurred. There are different types of wayside devices including but not limited to detectors for hot bearings, wheel impact loads, acoustic wheel monitoring, and dragging equipment (Figure 10).

At Burradoo, 138.000 km, on the Down Main line, an operational wayside device detected an elevated bearing temperature as SN68 as it passed, in the Down direction, on the way to Moss Vale. This occurred at 1703 when the elevated temperature was recorded on car 2811 (wheel 8 on axle 4), the location of the subsequent collapsed bearing. The temperature was recorded as 84°C, below the threshold to trigger an alarm. The temperature of the other bearings on the bogie were recorded as 73°C, 65°C and 69°C.

The ARTC has two threshold categories for hot bearing detector alarms.^[5]  When a threshold temperature is exceeded an alarm is sent to the network controller who must ensure the category of alarm condition is understood by the driver and is responded to according to the required action outlined below (Figure 9).

 Figure 9: Wayside Device Alarm Categories

Source: ARTC

The other wayside monitoring system between Campbelltown and Moss Vale was  located at Menangle on the Up Main at 67.25 km. It is likely that the hot bearing would have been detected here, 50 km past Yerrinbool.

Sydney Trains also checked previous passes by car 2811 over wayside monitoring systems and did not identify any other warm bearing temperature for this wheelset for the period 5 July 2020 to the incident date on 13 October 2020.

Figure 10: ARTC Network wayside detectors

Source: ARTC, annotated by OTSI

Related occurrence

On 1 December 2020, less than two months after the incident at Yerrinbool, a related incident occurred when a hot bearing on an Xplorer train was detected by a Sydney Trains wayside detector on the Up Main at Wyee, NSW. TrainLink passenger service, NP24, travelling from Armidale to Sydney was stopped at Wyee after the driver was notified of a hot bearing. After inspection, the train proceeded at a low speed (under 25 km/h) to Wyong where the passengers were disembarked. There was no injury or damage.

The Xplorer was subsequently examined at Eveleigh Maintenance Centre where it was found that two axle end cap bolts on car 2508 (wheel 8) had moved from their original position. It was also found that the locking plate tabs were incorrectly bent up. The last refurbishment of the wheelset was 22 months before the incident on 1 March 2019.

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3. The kilometre distance is measured from Platform 1, Central Station, Sydney, New South Wales.
4. Sydney Trains Standard Instruction, Installation of Metric SP type Package Unit Bearings, TRS1516.00, Vol 3, Section G, 8. Applying the end cap.
5. ARTC, Response & Management of Wayside Monitoring Device Alarms – Wayside Device Alarm Categories.

Safety analysis

Mechanism of bearing collapse

The investigation determined that the fire in the wheel area of SN68 at Yerrinbool was caused by a collapsed bearing on wheel 8 on the trailing bogie on car 2811. This led to frictional heat to be generated and a fire started. The fire was fuelled by grease, oil, and rubber suspension components in the immediate vicinity of the axle box. The fire did not spread to other parts of the train.

The likely precipitating events to the bearing collapse was the loosening of two of the three axle end cap bolts which placed higher loading on the remaining bolt which then started to fracture. During every cycle of the bearing there are micro movements within the system. The locking plate tabs, if positioned correctly against the face of the bolts, assist in retaining the bolts in position. The two bolts, inadequately restrained by the locking plate, continued to loosen and fell out and the remaining bolt then fractured completely (Figure 11). With the end cap unsecured the outer cone of the bearing was able to move on the axle. Wayside data indicated that once the bolt fractured it took approximately 15-20 minutes for the failure to be identified.

Figure 11: Axle end with protruding failed bolt

Insert image showing the inside collapsed axle box and failed bolt protruding.

Source: OTSI

An initial inspection of the axle bearing and components was conducted following the incident at Eveleigh Maintenance Centre. All three bolts and the locking plate were recovered and, although damaged, were able to be examined. There were three different brands of bolts used and the failed bolt was identified as a NLGS bolt. A further inspection at UGLU Auburn Maintenance Centre was conducted when the bogie was disassembled. Present at these inspections were representatives from OTSI, Sydney Trains and UGLU. Measurements were taken and recorded for critical items, such as bearing end float, end cap installation torque and axle diameters on the other three undamaged bearings. These measurements were all were consistent and within specification.

Torque values were also measured on the other three undamaged bearing axle end cap bolts. Four out of the nine torqued bolts remaining on the bogie exceeded the 80‐100 Nm torque range and two bolts were recorded at 180 Nm and 200 Nm. The differing torque amounts was attributed to bolts being tightened further to achieve the alignment with the locking tabs. This torque was the breaking torque, not the original application torque.

An independent metallurgical examination was also conducted on the bolts and the locking plate, as well as a sample of other similar bolts. The scope of this analysis included: examination and fractography, hardness testing on all bolts, microscopy analysis of the grain structure, tensile testing and compliance to applicable standards. A report was produced following this examination.^[6]

The metallurgical examination showed that the bolts had no material or surface defects and complied with the requirements of the Australian Standard.^[7] The use of differing bolt brands was initially identified as a concern but was later ruled out as an issue as all brands complied with the requirements of the standard. The metallurgical examination also showed the locking plate to be without issue. Other results from the metallurgical examination were:

- Damage was most severe on the first two bolts which loosened and fell out. These bolts were damaged after being tumbled around inside the case.

- The third bolt had the least damage as it had fractured after the first two bolt had fallen out.

- The third bolt had partially unscrewed about 4-5 mm before failure.

- The third bolt failure occurred progressively over a period of approximately one to two hours.

- The locking plates were made of low hardness steel which provided less resistance to loosening if the stresses in the system were sufficient to unscrew the bolts.

- The locking plate showed heavy damage and bent arms at the hole where the third bolt fractured.

The metallurgical report stated: ‘A potential factor in the failures was insufficient tensioning of the bolts on installation, however, annular impressions around the locking plate holes were mostly similar, which is a rough indication that torqueing of the bolts had been similar. This observation is very subjective, and the conclusion of similar torqueing may be erroneous.’ The investigation could not verify what torque level was applied to the axle end cap bolts that came loose.

Bearing installation process

An inspection of the processes undertaken at UGLU Auburn Maintenance Centre demonstrated that standard processes were in place, marked components were used, and calibrated torque wrenches available to be used by appropriately qualified personnel. Despite this, the physical evidence shows that it is likely that during the last refurbishment of the wheelset, on 1 July 2020, just over three months before the incident, the locking tabs were not sufficiently bent up against the face of the bolts.

There was completed documentation showing the processes had been checked off by a qualified maintenance person. The relevant checkboxes for all items were completed, this included:

- checking the bolt torque (new bolts used)

- tabs locked flat on the screw head face

- torque marking of screws.

However, at the time of the refurbishment there was no additional quality assurance check once this process was completed.

The subsequent Sydney Trains investigation report into this incident at Wyee on 1 December 2020 showed strong similarities with the incident at Yerrinbool. The detection of the locking plate tabs not being bent up supports the same findings for Yerrinbool.

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6. MetallTech, Metallurgical investigation Endeavour bolt failure – axle box bolt, Report M2020/09-1, 23 November 2020.
7. Australian Standard AS 4291.1 / ISO 898.1 Mechanical properties of fasteners made of carbon steel and alloy steel.

Findings

From the evidence available, the following findings are made with respect to the collapsed bearing on passenger train SN68 at Yerrinbool, New South Wales on 13 October 2020.

Contributing factors

• The fire that occurred on SN68 was the result of excessive heat generated from a collapsed bearing on the trailing bogie of locomotive TE2811.
• The bearing collapse was the result of two axle end cap bolts becoming loose and the remaining bolt fracturing due to the increased load. Once the three bolts were no longer holding the end cap in position the bearing rapidly collapsed.
• It is likely that during the last NJA31 bogie overhaul the tabs on the locking plate were not installed correctly. This enabled the two axle end cap bolts to loosen.
• The axle bearing installation process was not sufficient to ensure the tabs on the locking plate were installed correctly. (Safety Issue)

Other (key) finding

• The brake and bearing temperature alarm detected an elevated temperature on an axle bearing at Burradoo as SN68 passed over it approximately 60 minutes before the fire was noticed at Yerrinbool. The temperature recorded was below the threshold for an alarm to be sent to network control.

Safety issues and actions

Axle bearing installation

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

Safety issue description: The axle bearing installation process was not sufficient to ensure the tabs on the locking plate were installed correctly (Safety Issue).

Sources and submissions

Sources of information

The sources of information during the investigation included the:

• Australian Rail Track Corporation
• NSW Trains
• Sydney Trains
• United Group Limited Unipart.

References

Australian Standard AS 4291.1 / ISO 898.1 Mechanical properties of fasteners made of carbon steel and alloy steel.

MetallTech (2020), Endeavour Bolt Failure – Axlebox Bolt – Metallurgical Investigation, 23 November 2020

Rail Industry Safety and Standards Board (2021), Glossary of Terms.

Sydney Trains (2020), Systemic Safety Investigation Report Collapsed bearing on car 2811 at Yerrinbool on 13 October 2020.

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:

• Australian Rail Track Corporation
• NSW Trains
• Office of the National Rail Safety Regulator
• Sydney Trains
• Transport for NSW

Submissions were received from:

Office of the National Rail Safety Regulator

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

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.

Safety summary

What happened

A privately operated Fairchild Industries SA226-T aircraft, registered VH-LDQ, landed at Gunnedah Airport, New South Wales, on 19 August 2020, where it was then parked overnight. The following day, at about 1230 Eastern Standard Time, the pilot commenced a take-off run on runway 29. As the aircraft accelerated, the pilot saw that there were two holes excavated from the runway pavement. The pilot attempted to avoid the holes, but the aircraft’s left main landing gear struck them. The aircraft sustained damage to the left main landing gear assembly, which resulted in it collapsing, and the left propeller striking the ground. The aircraft veered off the runway and came to rest outside the flight strip.

What the ATSB found

The ATSB found that during pre-flight planning, the pilot had not checked for relevant NOTAMs, including one stating that Gunnedah Airport was closed due to works in progress. Prior to entering the runway and commencing the take-off run, the pilot did not see evidence of the runway works.

A white cross had been placed at the main windsock, visible to aircraft arriving overhead, however, when the pilot had landed the previous afternoon the aerodrome was still open. Further, there was no works safety officer on site or any ground-visible unserviceability markings on the runway, as required by the Civil Aviation Safety Regulations Part 139 Manual of Standards (MOS) for Aerodromes. Aerodrome works staff were not aware of the updated MOS requirements that had come into effect 7 days earlier and had interpreted the superseded MOS to not require unserviceability markings if the whole aerodrome was closed.

What has been done as a result

The Gunnedah Airport operator has added folding signs to all entry gates to the airfield, which will display any total unserviceability or restricted operations signals that are currently being displayed  in the signals area adjacent to the primary windsock.

Additionally, the airport operator updated their contact details with CASA to ensure timely receipt of updates to requirements.

Safety message

An essential component of pre-flight planning is to check all NOTAMs relevant to the planned flight. This includes NOTAMs regarding all aviation facilities that a pilot plans to use.

To ensure receipt of correspondence that may affect safety of aircraft operations, aerodrome operators should ensure CASA is provided up to date contact details, particularly following changes to staff.

The investigation

The occurrence

A privately operated Fairchild Industries SA226-T aircraft, registered VH-LDQ departed Bankstown aerodrome, New South Wales (NSW) on 19 August 2020 at 0720 Eastern Standard Time (EST)^[1] for a private flight to Mudgee Airport, NSW.

The aircraft arrived in Mudgee at about 0900, before departing for Dubbo City Regional Airport, NSW, at about 1130. During this time, at 1047, a NOTAM^[2] was published, closing Gunnedah airport, NSW, on the following day, 20 August, between 0700 and 1500 for emergency runway works.

The pilot departed Dubbo at about 1515 and arrived at Gunnedah Airport, at about 1550. As the aircraft was taxied to the parking bay, the pilot noticed a rough spot on the asphalt near the end of the runway. The aircraft was then parked for the night.

On 20 August, at about 1225, the pilot advised Brisbane Centre air traffic control that the aircraft was taxiing at Gunnedah for departure. On receiving the taxi call, the controller checked for any current notices to airmen (NOTAM) and found one current for the airport, stating that it was closed due to works in progress. The controller attempted to inform the pilot but was unable to establish contact.

About 5 minutes later, the pilot commenced the take-off run on runway 29 after taxiing by the works in progress (Figure 3) to the threshold and turning around. The pilot reported seeing patches on the pavement in the distance. As the aircraft accelerated and progressed along the runway, it became apparent to the pilot that there were two holes excavated from the runway pavement (3 m wide by 5 m long), which were about 30 cm deep (Figure 1). The pilot attempted to avoid the holes but was unable to clear them with the aircraft’s left main landing gear.

Figure 1: Pavement work in progress on runway 29

Source: Airport operator

The aircraft sustained damage to the left main landing gear assembly that resulted in it collapsing and the left propeller striking the ground. The aircraft veered off the runway and came to rest outside the flight strip (Figure 2).

Figure 2: Aircraft’s position after the attempted take-off

Source: Airport operator

Context

Gunnedah airport

Gunnedah airport is a certified and non-controlled aerodrome located in northern NSW. It has one asphalt runway and one grass runway that intersect. It is primarily used by the Gunnedah aero club and Gunnedah Flight School. There were no regular public transport services.

Runway works

On 14 August 2020, following jet operations that had been conducted with a pavement concession,^[3] the aerodrome reporting officer (ARO) at Gunnedah Airport identified some lifted pavement in the centre of runway 29. The damage was located about 215 m along the runway from the runway 29 threshold, 15 m past the taxiway intersection (Figure 3).

Figure 3: Location of holes on runway in relation to taxiway

Source: Google Earth and airport operator, annotated by the ATSB

On 19 August, the asphalt crew advised the ARO that they would be able to conduct runway repairs on the following day. The ARO reported contacting Airservices Australia by phone, who advised that the airport could be closed at short notice (within 24 hours) with a NOTAM in place if emergency works were required. Additionally, the ARO reported that they confirmed their interpretation of the Civil Aviation Safety Regulations’ Manual of Standards (MOS) for Aerodromes, that unserviceability markings would not be required if the aerodrome was closed. A NOTAM was published at 1047 stating that the aerodrome was not available due to works in progress between 0700 and 1500 EST on 20 August.

At about 1200, the works crew conducting pavement work left the aerodrome for lunch, returning to find the damaged aircraft. After the incident, the NOTAM closing the aerodrome was extended for an additional 24 hours and was cancelled at 1457 on 21 August, following completion of the works.

Aerodrome closures

The MOS required aerodrome operators to ensure that aerodrome works do not create a hazard to aircraft or cause confusion to pilots. If an aerodrome is used for scheduled air transport operations or has emergency services aircraft based at the aerodrome, a method of working plan is required for aerodrome works, unless the aerodrome is closed with 14 days’ notice, or the works are of an emergency nature.

Works are defined to be of an emergency nature if they are to repair unforeseen damage to part of the manoeuvring area, or to remove an obstacle.

Aerodrome unserviceability markings

As defined by the MOS, unserviceability markings are temporary markings used for temporary and permanent closures of runways or taxiways. They consist of white or yellow crosses of various sizes displayed on the surface of a closed or unserviceable area for airborne and taxiing aircraft. When used to mark a runway as unserviceable, the MOS requires a white cross at each end of the runway and at intervals of less than 300 m.

These unserviceability markings are not required on an unserviceable runway at an aerodrome not controlled by an air traffic control provider if all the following exist:

• the runway unserviceability is of less than 24 hours duration
• the total works period is less than 5 days
• a NOTAM has been issued
• a works safety officer is present with a vehicle equipped with a radio that allows for emergency 2-way communication with aircraft
• if the aerodrome has been closed: a total unserviceability signal is displayed in the signal area (if it exists).

Unserviceability markers

As defined by the MOS, unserviceability markers are a 50 cm tall white cone with a 25 cm wide horizontal red stripe. These markers must be placed at the entrance to, and across, any part of the movement area of an aerodrome (including runways) that are not to be used by aircraft. Additionally, at least three must be displayed across the centreline of any portion of a taxiway, apron or holding bay that is unserviceable.

Aerodrome ground signals

The MOS current at the time of the occurrence, had provision for an optional ground signal area, where temporary ground signals for airborne aircraft can be displayed. The MOS noted that the area was ‘neither compulsory nor necessary because of the requirements for radio carriage and use at certified aerodromes, and the requirement for NOTAMs to be issued for the aerodrome in the event of changes in conditions.’

The aerodrome signal area must be black, 9 m in diameter and located near the primary wind direction indicator. It must have a 1 m-wide border or at least 5 spaced white markers. The markings that could be placed in the signals area included:

• total unserviceability signal – consisting of a white cross; must be displayed when an aerodrome is closed to landing aircraft.
• restricted operations signal – consisting of a white barbell; to indicate that aircraft are only to use sealed runways, taxiways, and aprons.

At the time of the occurrence, a total unserviceability signal was displayed in the signals area at Gunnedah airport.

Update to Manual of Standards (Aerodromes)

On 13 August 2020 (seven days before the incident), the Civil Aviation Safety Regulations Part 139 (Aerodromes) Manual of Standards (2019) came into force, replacing the previous 2014 MOS. This manual sets out the standards required of certified aerodromes.

A new section was added in Chapter 8 to articulate specific circumstances where unserviceability markings are not required, given that other visual aids or conditions are met. This included the addition of the requirement for a works safety officer with a vehicle and radio. The requirements for the use of unserviceability markers was expanded from situations where it was ‘possible for aircraft to bypass the area safely’, to require marking of all unserviceable movement areas.

Additionally, requirements for the notification and planning of aerodrome works and method of working plans were clarified and updated.

Communication of changes

The Civil Aviation Safety Authority (CASA) began engaging with certified aerodrome operators regarding upcoming changes to MOS 139 in April of 2020 by email and letter, with information provided on the CASA website. CASA sent this information to a mailing list that included an email address associated with Gunnedah Airport, for a person that was no longer working for the airport operator.

The Gunnedah Airport operator’s email system did not generate an ‘undeliverable’ bounce message for email addresses that have previously existed. CASA advised the ATSB that they rely on these bounced emails, or updates from aerodrome operators to ensure that information is received by a nominated person.

Flight Planning

Civil Aviation Regulation 239, required pilots to study all available information appropriate to the intended operation, including current weather reports and forecasts for the route and aerodromes, and the condition of aerodromes to be used.

Aerodrome condition information is typically communicated via a NOTAM. NOTAM and weather information can be obtained through the National Aeronautical Information Processing System Internet Service, a phone briefing, AVFAX or by radio.

The pilot had not checked NOTAM information for Gunnedah Airport before commencing take-off from runway 29.

Safety analysis

Communication of closure

The Gunnedah Airport operator had issued a NOTAM for the emergency runway works in accordance with requirements. The NOTAM issued stated that the aerodrome would be closed due to works in progress, was in place 20 hours prior to the closure and active at the time of the occurrence. Had the pilot checked the NOTAMs prior to flight, as required, they would have been alerted to the fact that the aerodrome was not available for use.

Evidence of works

As well as the active NOTAM at the time of the incident, Gunnedah airport had a total unserviceability signal displayed adjacent to the primary wind direction indicator, to warn pilots that the aerodrome was closed. However, this signal was not visible to a pilot on the manoeuvring surface and nor is it designed to be.

There were no other unserviceability markings or markers in use on this occasion. The Part 139 Manual of Standards (MOS) in force at the time required both, however the use of unserviceability markers on the runway would not have been required had a works safety officer been present. The aerodrome reporting officer was unaware of the introduction of the updated MOS and believed they had adhered to the correct standards. In addition, they interpreted the guidance received from Airservices as confirmation of their understanding of the requirements.

The use of unserviceability markers on the runway or a presence of the works safety officer together with the use of unserviceability markers would also have provided additional risk controls against the attempted take off from the closed runway.

Communication of changes to MOS

CASA relies on aerodrome operators ensuring that they have a valid, monitored email address registered for the distribution of timely updates on associated legislation and requirements. The registered contact for Gunnedah Airport had left the role and new contact details had not been provided to CASA, which mean that this mechanism for receiving updates was unavailable.

Findings

From the evidence available, the following findings are made with respect to the take-off from a closed runway at Gunnedah Airport, New South Wales, involving a Fairchild Industries SA226-T aircraft, registered VH-LDQ on 20 August 2020.

Contributing factors

• The pilot had not checked NOTAMs, which advised of the aerodrome closure, and did not see evidence of works.
• There was no works safety officer at the aerodrome, or ground visible unserviceability markers or markings on the runway, as required under the Manual of Standards for Aerodromes.
• Aerodrome works staff were not aware of the new Manual of Standards requirements and interpreted the previous version to not require unserviceability markers or markings during an aerodrome closure.

Safety actions

Safety action by Gunnedah Airport operator

Gunnedah Airport operator has added folding signs to all entry gates to the airfield that will reflect any ground signals active in the signals area (Figure 4). They have also updated their contact details with CASA.

Figure 4: New signals signage at Gunnedah airport

Source: Airport operator

Sources and submissions

Sources of information

The sources of information during the investigation included:

• Civil Aviation Safety Regulations Part 139 (Aerodromes) Manual of Standards 2019 (as amended 13 August 2020)
• Civil Aviation Regulations 1988 (as amended 13 August 2020)

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:

• Gunnedah Airport operator
• the Civil Aviation Safety Authority
• Airservices Australia
• the pilot

Submissions were received from:

• the Civil Aviation Safety Authority

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

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.

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1. Eastern Standard Time (EST) was Coordinated Universal Time (UTC) + 10 hours.
2. NOTAM: A notice distributed by means of telecommunication containing information concerning the establishment, condition or change in any aeronautical facility, service, procedure or hazard, the timely knowledge of which is essential to personnel concerned with flight operations.
3. A pavement concession is a privilege granted to an aeroplane operator, allowing the landing, take-off, taxiing or parking of an aeroplane on a runway, taxiway or apron which would not otherwise be available. It allows an aircraft heavier than the rated load capacity of the pavement to use the pavement under specific conditions.

Safety summary

What happened

On 23 September 2020, the pilot of a Piper PA-28 aircraft, registered VH-TBB, was conducting a ferry flight from Moree to Scone, New South Wales. Shortly after take-off, the pilot began to feel unwell with a warm feeling in their chest, dizziness, breathlessness, some confusion and disorientation. The pilot then observed a localised discolouration on the disposable carbon monoxide (CO) chemical spot detector. As the pilot looked closer at the detector, they noticed the spot rapidly getting darker. The pilot immediately returned to the airport, reduced engine power and opened all the fresh air vents and the side window. The aircraft landed safely at Moree and the pilot was subsequently taken to hospital for medical examination.

What the ATSB found

The ATSB found that the positive indications on two separate disposable CO chemical spot detectors, both during the flight and prior to the post-incident inspection, indicated that the pilot was likely exposed to elevated levels of CO in the aircraft cabin. Despite the pilot’s carboxyhaemoglobin level being mildly elevated, it was likely that their physical symptoms and cognitive effects were associated with CO poisoning.

Safety message

Carbon monoxide is a colourless and odourless gas, and its presence may not be detected until the development of physical symptoms and cognitive effects. Therefore, operators and owners of piston-engine aircraft are strongly encouraged to install a CO detector with an active warning to alert pilots to the presence of elevated levels of CO in the cabin. Should any smell or sensation of illness develop, pilots should check their CO detector, ensure cabin heat has been turned off, open all fresh air vents and windows, make prompt decisions to land as soon as possible, and use all available resources for assistance. Further information on CO poisoning and detectors can be found at the following:

Are you protected from carbon monoxide poisoning?

Carbon Monoxide: A Deadly Menace

Detection and Prevention of Carbon Monoxide Exposure in General Aviation Aircraft

The investigation

The occurrence

On 23 September 2020, the pilot of a Piper PA-28 aircraft, registered VH-TBB, was conducting a ferry flight from Moree to Scone, New South Wales. At about 1418 Eastern Standard Time,^[1] the pilot started the engine, carried out engine run-ups^[2] and then taxied the aircraft to the runway for departure. The pilot reported the engine was running for about 10 minutes while on the ground in Moree, with the side window, fresh air vents open and the heater off. Prior to take-off, the pilot closed the window and vents.

Shortly after take-off, the pilot began to feel unwell, with a warm feeling in their chest, dizziness, breathlessness, some confusion and disorientation. The pilot then conducted a visual scan of the flight instruments and observed a localised discolouration on the disposable carbon monoxide (CO) chemical spot detector. As the pilot looked closer at the detector, they noticed the spot rapidly getting darker. The pilot immediately turned the aircraft back toward the airport, reduced engine power, and opened all the fresh air vents and the side window.

The aircraft was landed safely at Moree and the engine shut down at 1435. The pilot was subsequently taken to hospital for a medical examination. While receiving supplemental oxygen, the pilot was starting to feel better after about 2 hours.

Context

Medical information

General health and fitness

The pilot was well rested and felt fit to fly on the day of the incident. They had completed two flights in a different aircraft prior to the incident, one of which was from Tamworth to Moree. The pilot felt normal throughout those flights and only became unwell during the incident flight.

The pilot was a non-smoker, was not taking any medication, and had no pre-existing medical condition that could have contributed to the incident.

Carboxyhaemoglobin

A blood sample taken from the pilot about 1.5 hours after engine shut down, indicated a carboxyhaemoglobin (COHb) level of 1 per cent. The pilot was administered oxygen at the hospital, starting about 15 minutes before the blood sample was taken. In total they were on supplemental oxygen for about 5 hours, until their oxygen saturation levels were at 100 per cent.

Carbon monoxide is an odourless, colourless and tasteless gas formed by the incomplete combustion of carbon-containing materials. When inhaled, it preferentially binds to haemoglobin, the oxygen carrying molecule in red blood cells. This creates COHb compounds and prevents oxygen from binding to the molecule and being transported, resulting in oxygen starvation.

As previously discussed in ATSB investigations AO-2020-026 and AO-2017-118, normal endogenous levels of COHb are generally within the range of 0.4-0.7 per cent. However, smokers, and those living in an urban area, may have higher than average levels of 1-6 per cent (Baselt, 2014).

After the source of CO has been removed, COHb will reduce to half its initial value within 4‑5 hours at sea level. This can decrease to 80 minutes with the administration of pure oxygen. Taking into account the CO half-life, the elapsed time since the symptoms and effects were first detected, and the pilot’s brief time on oxygen prior to the blood test, the ATSB estimated that the pilot’s COHb levels were likely between 1.5 to 2 per cent.

Although individuals’ reactions can vary, the physical symptoms and cognitive effects of CO poisoning tend to worsen with an increasing level of COHb (Lacefield et al., 1982). Typically, COHb levels of 10-20 per cent can result in symptoms of breathlessness, while levels of 30-40 per cent can result in mental changes, dizziness and confusion (Knobeloch & Jackson, 1999; Lacefield et al., 1982). While physical symptoms do not generally show at levels below 10 per cent, researchers have found that a person’s ability to perform complex tasks can be adversely affected at levels of 10 per cent or less (Baselt, 2014). Hawkins (1993) also noted that the effects of CO can begin to show with the deterioration of psychomotor function at COHb levels of about 3 per cent.

Aircraft maintenance

Post-incident aircraft inspection

After the incident, and prior to any maintenance activity, engineers conducted ground runs and confirmed that CO was leaking into the cabin with a positive indication on a new, disposable CO chemical spot detector. The engineers then inspected the aircraft, focusing on the engine exhaust system and airframe. The inspection revealed 4-5 pinholes in the exhaust stack that were not covered properly and unserviceable scat (air duct) hoses. No breaches were found in the firewall or the aircraft belly, and the cabin heat valve was functioning correctly. The pinholes were repaired and the scat hoses were replaced. Ground runs were conducted after the repairs and the chemical spot detector showed no indication of CO in the cabin.

Most recent periodic inspection

The last periodic maintenance inspection was completed on 22 May 2020, about 4 months prior to the incident, where the exhaust system was visually inspected using a torch and mirror. The inspection of the exhaust system included the removal of the muffler shroud, security of the baffle cones and the cabin heat flexible hoses. The engineer reported that, exhaust stains on the engine and/or cowling can indicate the existence of an exhaust leak, which was something they looked for during inspections. However, in this case, there were no exhaust system defects recorded in the maintenance documentation.

The owner, who operated the aircraft a few days prior to the incident, reported never having observed a positive indication on the CO detector, nor had they felt unwell during or after a flight. However, they would sometimes smell exhaust fumes when they turned the heater on. The owner advised that they typically never left it on for very long, as CO was always in the back of their mind.

A study conducted by the United States Federal Aviation Administration (2009) noted that a small crack or imperfection can be difficult to see during a visual inspection, which is further impeded by densely packed engine compartments. Further, defects can form after the inspection from erosion and internal fatigue.

Carbon monoxide detector

The aircraft was fitted with an Aviation Supplies and Academics disposable CO chemical spot detector, attached to the instrument panel (Figure 1). The detector was only 4 months old, which was within the manufacturer’s 12-month replacement period. It consisted of an orange‑coloured circle (spot) in the middle of the card, which was designed to change colour to grey/black following a chemical reaction with CO in the immediate vicinity. The spot then returns to normal (orange) after it has been exposed to fresh air. The chemical reaction depends on the concentration of CO in the air and the time of exposure. This detector was designed to react to a minimum of 50 parts per million (ppm) of CO within 30 minutes, 100 ppm within 10 minutes and 200 ppm within 4 minutes.

The ATSB’s investigation and corresponding safety advisory notice for AO-2017-118, highlighted the limitations of these types of detectors. Although commonly used in general aviation, they are a passive device that rely on the pilot regularly monitoring the changing colour of the detector throughout the flight. Further, identifying a positive indication is also dependent on the detector being easily visible and accessible, in a well-lit position particularly when operating in a low  ambient light environment.  

Figure 1: Slightly discoloured carbon monoxide detector, after engine shutdown and the detector being exposed to fresh air

Source: Pilot

Similar occurrences

ATSB investigation (AO-2017-118)

On 31 December 2017, the pilot and five passengers of a de Havilland Canada DHC-2 floatplane, registered VH-NOO, were fatally injured when the aircraft collided with water in Jerusalem Bay, New South Wales. The occupant’s toxicology results identified that they had higher than normal levels of COHb in their blood. This was almost certainly due to elevated levels of CO in the aircraft cabin. The ATSB’s wreckage examination established that several pre-existing cracks in the exhaust collector ring very likely released exhaust gas into the engine/accessory bay. This then very likely entered the cabin through holes in the main firewall where three bolts were missing from the magneto access panels.

ATSB investigation (AO-2020-026)

On 22 December 2019, the crew of a Cessna 172R aircraft, registered VH-YXZ, were conducting aerial shark patrols. About 2 hours into the second flight of the day, the crew started to experience symptoms typically associated with CO poisoning, and subsequently observed a localised discolouration on the disposable CO chemical spot detector. Soon after, the aircraft was landed safely and the three crew were taken to hospital for assessment. While blood tests confirmed all crew had mildly elevated COHb levels, their physical symptoms and cognitive effects likely resulted from exposure to elevated CO levels in the aircraft cabin. The CO source within the aircraft could not be established. Further, the discrepancy between the low COHb levels and severity of experienced effects could not be resolved.

National Transportation Safety Board investigation (CEN17LA101)

On 2 February 2017, shortly after take-off, the pilot of a Mooney M20C aircraft became incapacitated. The aircraft continued flying until running out of fuel and then collided with terrain, but the pilot survived. The pilot’s COHb level, taken 4.5 hours after the accident, was 13.8 per cent. However, given the half‑life of CO, the pilot’s level would have been at least 28 per cent at the time of the accident. A post-accident inspection of the aircraft identified several cracks in the exhaust muffler. In response to the experience, the pilot stated that:

Current technology has made portable CO detection very accurate and inexpensive. A high resolution detector would have not only prevented this accident flight, but may have alerted me to a compromise in my exhaust system many flight hours before the incident.

Safety analysis

Elevated levels of carbon monoxide

The post-incident aircraft ground runs produced elevated levels of carbon monoxide (CO) in the aircraft cabin, which was resolved once repairs to the exhaust stack and the scat hoses were complete. This indicated that the source of the CO was associated with the items repaired. No obvious breaches were identified that would have allowed CO to enter the cabin and therefore, it was not immediately clear how the exhaust gasses entered the cockpit on this occasion.

However, the observed physical symptoms and cognitive effects reported by the pilot were more likely associated with CO poisoning. This was further supported by the positive indications on the CO chemical spot detector and the blood test indicating a mildly elevated level of carboxyhaemoglobin (COHb). While the extent of the pilot’s symptoms for the recorded COHb level were inconsistent with the literature, research has shown that adverse effects on cognitive functions can occur at levels as low as 3 per cent and that individuals can react differently to COHb.

Findings

From the evidence available, the following findings are made with respect to the partial pilot incapacitation involving a Piper PA-28, registered VH-TBB that occurred 19 km south-east of Moree Airport, New South Wales, on 23 September 2020.

Contributing factors

• An exhaust leak likely exposed the pilot to elevated levels of carbon monoxide in the aircraft cabin, resulting in mild incapacitation.

Sources and submissions

Sources of information

The sources of information during the investigation included the:

• pilot
• aircraft owner
• repairer for VH-TBB
• maintenance organisation for VH-TBB.

References

Baselt, R.C. (2014). Disposition of Toxic Drugs and Chemicals in Man (10th ed.). Seal Beach: Biomedical Publications.

Hawkins, F. H. (1993). Human Factors in Flight (2nd ed.). Aldershot, England: Ashgate Publishing.

Hossein Cheraghi, S., Jorgensen, J., & Myose, R.Y. (2009). Detection and prevention of carbon monoxide exposure in general aviation aircraft (DOT/FAA/AR-09/49). Retrieved from Federal Aviation Administration website: http://www.tc.faa.gov/its/worldpac/techrpt/ar0949.pdf

Knobeloch, L & Jackson, R. (1999). Recognition of Chronic Carbon Monoxide Poisoning. Wisconsin Medical Journal, 98(6):26-9. Retrieved from https://www.researchgate.net/publication/12696822_Recognition_of_chronic_carbon_monoxide_poisoning

Lacefield, D. J., Roberts, P. A., & Grape, P. M. (1982). Carbon monoxide in-flight incapacitation: An occasional toxic problem in aviation (FAA-AM-82-15). Oklahoma City, Oklahoma: Federal Aviation Administration.

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:

• pilot
• aircraft owner
• repairer for VH-TBB
• maintenance organisation for VH-TBB.

A submission was received from the pilot. The submission was reviewed and, where considered appropriate, the text of the report was amended accordingly.

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.

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1. Eastern Standard Time (EST): Coordinated Universal Time (UTC) + 10 hours.
2. Run-up: a high-power run-up check is carried out in a piston-engine aircraft to check the aircraft’s ignition and other systems before commencing an initial take-off.

Summary of principal conclusions

1. At approximately 1303 hours Eastern Standard Time on 22^nd September 1966 Viscount 832 Type aircraft VH-RMI operated by Ansett Transport Industries (Operations) Pty. Ltd. (trading as Ansett-A.N.A.) experienced a structural failure in flight and struck the ground about 13½ miles on a bearing of 260° magnetic from Winton Aerodrome in the State of Queensland.

2. The aircraft was totally destroyed.

3. At the time of the accident the aircraft was engaged on a regular public transport service from Mt. Isa to Brisbane via Longreach. The service was authorised by an Airline Licence issued to the operator and the flight was designated as Flight 149.

4. The aircraft carried a crew of four and twenty passengers, all of whom were lost as a result of the accident.

5. At the time of the accident the aircraft was proceeding to make an emergency landing at Winton Aerodrome following an emergency descent en route.

6. The forecast weather conditions and the weather conditions actually existing at the time of the flight were not such as to suggest any unusual or hazardous circumstances and had no bearing on the accident.

7. The aircraft departed from Mt. Isa at 1208 hours Eastern Standard Time.

8. The aircraft was loaded within permissible limits and there is no evidence to suggest that anything relating to the load contributed to the accident.

9. After leaving Mt. Isa the aircraft climbed to its cruising height of approximately 17,500 feet and proceeded at that level with the automatic pilot engaged until about 1247 hours.

10. At about 1247 hours the automatic pilot was disengaged prematurely and this was followed shortly after by a descent described in a message from the aircraft as an emergency descent.

11. Messages from the aircraft show that the emergency was indicated by a fire warning being received in the flight compartment.

12. At 1257 hours the crew reported they had a visible fire in No. 2 engine and that they were tracking to Winton.

13. Appropriate action was taken to prepare the aircraft and passengers for an emergency landing.

14. The crew, both pilots and hostesses, were adequately and properly trained and competent to operate VH-RMI on the 22nd September, 1966.

15. Both pilots held appropriate licences and ratings pertinent to the flight and had met the required medical standards.

16. There is no evidence to suggest that on the day of the flight the pilots were not medically fit to undertake their respective duties.

17. The flight plan was correctly and properly prepared and the quantity of fuel carried was more than adequate for the flight.

18. There is no evidence that the flight crew was aware of any unserviceability of the aircraft or any of its components prior to take-off.

19. The evidence supports a conclusion that [the Captain's] decision to divert to Winton rather than continue the flight to Longreach was an appropriate one and that he acted properly in following this course rather than electing to make a forced landing.

20. The crash of the aircraft followed the failure in an upward direction of the port wing between No. 1 and No. 2 engines at approximately 1302½ hours Eastern Standard Time when the aircraft was at a height of 3,500 feet to 4,000 feet above ground level.

21. The port wing failed as a result of a weakening of the main spar due to a fire in No. 2 cell of No. 2 fuel tank.

22. The fire originated in the No. 2 cabin blower and travelled through the rear of No. 2 engine nacelle and port wheel bay to the fuel tank.

23. The fire in No. 2 cabin blower was initiated as a result of a rotor break-up, the blower subsequently being driven in an out-of-balance condition by the quill shaft long enough for the metering unit to become separated from the rear end cover by the resulting vibration.

24. The metering unit continued to be driven after separation and lubricating oil continued to be supplied. The driven rotor lost its rear stub shaft location and caused metal-to-metal contact which generated a temperature sufficiently high to ignite the oil in that area.

25. It is not possible on the evidence to determine what was the cause of the rotor break-up.

26. The rotor break-up was not due to incorrect assembly of the extractor seal shell and the ball bearing and its housing at the last overhaul by Ansett-A.N.A ..

Safety summary

What happened

On 29 September 2020, the crew of a Eurocopter AS365 ‘Dauphin’ helicopter, registered VH‑WPX and operated by the Western Australia Police Air Wing, were conducting water winching training exercises near Swanbourne, Western Australia. While conducting winching to a small vessel, a rescue crewman attached to the aircraft winch cable was pulled overboard and dragged through the water. The rescue crewman was recovered a short time later without injury and the helicopter was undamaged.

What the ATSB found

The ATSB found that the winching recovery sequence was interrupted when the rescue crewman lost footing on the deck of the vessel. The interruption, although communicated by the winch operator, was not recognised by the pilot, who expected the usual sequence to continue as had previously occurred on numerous occasions. As a result, the pilot instinctively increased the distance between the helicopter and vessel, and the rescue crewman was dragged overboard by the winch cable.

Further investigation found that crewman overboard drills were not regularly briefed or practiced, contributing to a breakdown in communication. This reduced the crew’s preparedness to respond effectively to such an event.

Finally, and though not a factor contributing directly to this event, the ATSB found that changes to sea state limitations contained within the Western Australia Police Air Wing Rotary Wing Operations Manual, were approved without the required review by the operator’s Safety Action Group. The absence of that review reduced the opportunity to identify any increased risk associated with the change. 

What has been done as a result

Following an internal safety review, the Western Australia Police Air Wing amended training and pre-flight briefings to include a crewman overboard scenario, and implemented crewman overboard drills during winch simulation training.

Furthermore, the Police Air Wing has introduced an alternative approach to open water vessel winching, that eliminates the risk while still maintaining the same level of rescue capability to the community.

With respect to easing of sea state limitations, the Police Air Wing has reinforced the importance of following change management principles and formal reviews to mitigate future foreseeable risks.

Safety message

Effective communication between pilots and crewmen is critical when undertaking helicopter winching as the pilot is required to safely manoeuvre the aircraft while unable to visually monitor the progress of the activity.

This incident demonstrates that even during highly trained and well-rehearsed operations, human performance limitations such as expectancy and reduced attention associated with a familiar task, together with deviations from standard phraseology, can have undesired outcomes.

The occurrence

Overview

On 29 September 2020, the crew of a Eurocopter AS365 ‘Dauphin’ helicopter, registered VH‑WPX and operated by the Western Australian Police Air Wing, were conducting water winching training exercises to a vessel in waters off the Perth coastal suburb of Swanbourne, Western Australia. During the training, a rescue crewman was pulled overboard while attached to the aircraft winch and dragged through the water. The rescue crewman was recovered a short time later without injury and the helicopter was undamaged.

Pre-incident flights

The crew for the training exercises comprised the pilot, four tactical flight officers (TFOs) and one TFO instructor. The day’s training involved the TFOs rotating through the positions of winch operator, rescue crewman and diver. The plan was to conduct an initial vessel winching operator proficiency check for one of the TFOs, as well as recency flights for two of the other crewmembers. The training was conducted with a volunteer marine rescue vessel, Stacy Hall.

The crew commenced duty at 0700 Western Standard Time^[1] at the operator’s base at Jandakot, before completing the daily briefing and pre-flight preparation. Data from the onboard GPS unit showed VH-WPX departed Jandakot at 0933 and travelled to the designated training staging area at Rous Head, Fremantle, landing at about 0950.

At 0953, VH-WPX departed for the first training sortie, which was a familiarisation exercise for a novice winch operator in preparation for the planned initial winch training. This exercise was conducted close to shore at a nearby beach.

At 1032, VH-WPX took off on the second training sortie and travelled about 17 km from Rous Head to rendezvous with Stacy Hall, about 1 km offshore from Scarborough. The wind was north-westerly with a westerly swell, and the vessel tracked north through the water to provide a headwind component for VH-WPX.

During the second sortie, the crew onboard the helicopter remarked that the conditions were windy and observed the Stacy Hall was moving around significantly in the water. In response, the TFO instructor requested that the crew of Stacy Hall establish a speed of 10 kt, in order to make a flatter path through the waves. On the advice of the pilot, the vessel’s course was also altered to 330°, to make a more oblique approach to the swell.

The TFO Instructor conducted a demonstration winch cycle then requested the crew of Stacy Hall increase speed to 12 kt to further assess conditions for initial winch training. At the conclusion of the alterations to the vessel’s speed and course, the TFO instructor proposed cancelling the planned initial winch training, because the conditions were perceived as rougher than it looked. The pilot asked whether the remaining qualified crew could undertake the training and the TFO instructor agreed that was possible, but a group discussion/assessment should be conducted first. Consequently, the helicopter returned to Rous Head.

After landing about 1054, the crew discussed the conditions and whether they should continue training with the qualified crew who required operator proficiency checks and recency training. A joint decision was made to assess the sea state from the air and with the vessel underway. While the helicopter was on the ground at Rous Head, the wind had backed to a more westerly direction, and it was agreed that may have created more suitable conditions for continuation of the training with the experienced crew.

At 1131, VH-WPX departed for the third training sortie. The crew contacted the crew of the Stacy Hall en route and requested they alter course to 300° and maintain a speed of 10 kt. During a dummy run to the vessel the winch operator observed that the Stacy Hall was bouncing in the waves, so the crew requested further course and speed changes.

With the Stacy Hall maintaining 12 kt at 320°, the crew conducted the next phase of the training, which was a winch to the vessel with the rescue crewman remaining attached to the winch hook. The exercise progressed to completion, though as the rescue crewman was winched clear of the deck, they swung towards the canopy on the forward end of the deck and required the use of their arms to fend off. The rescue crewman was then safely winched into the helicopter, with the winch operator commenting to the crew that the sequence ‘…was pretty hairy’.

The crew then conducted the third and fourth phases of the training, which were a vessel winching involving the rescue crewman disconnecting from the winch hook and then a helocast and water winch recovery exercise.^[2] There were no issues encountered in either exercise, after which the helicopter returned to Rous Head.

The incident flight

At 1203, the helicopter landed at Rous Head and the TFOs rotated roles. For the incident flight, the operational crew consisted of the pilot, the TFO instructor observing the exercise, and three TFOs, one observing and two undertaking the respective roles of winch operator and rescue crewman.

At 1210, VH-WPX took off to rendezvous with the Stacy Hall, which was located about 8 km north of the Rous Head landing area and between 1 and 2 km offshore, west of Swanbourne. After take-off, the crew completed fly‑away checks, pre-landing checks, pilot brief and winch checks. The pilot brief confirmed the crew would undertake two winches onto the vessel, and the vessel would be travelling on a course of 300° at a speed of 12 kt.

The helicopter approached the Stacy Hall and the pilot established the helicopter at the datum position.^[3]The crew then conducted a dummy approach run, during which the pilot reported having a good visual hover reference of the vessel. At the completion of the dummy run, the pilot terminated the helicopter at the on-station position.^[4]

Onboard winch video recordings showed that at about 1215, the helicopter had moved from the on‑station position to the transfer position^[5] and the winch operator commenced lowering the rescue crewman to the deck of the vessel. At 1216, the rescue crewman landed on the aft deck of the rescue vessel and completed simulated checks. Within 2 seconds of landing on the deck, the rescue crewman gave the thumbs-up signal to indicate they were positioned, had completed checks and were ready to be winched up.

The winch operator acknowledged that the rescue crewman had signalled they were clear to be recovered and reported to the pilot ‘one thumb up’ and ‘taking up the slack’. The winch operator then winched in slack in the cable and reported that he and the rescue crewman were ‘ready to winch’. The pilot gave clearance to winch and the winch operator commenced winching.

At the same, the vessel’s interaction with the swell resulted in its deck pitching higher as it travelled over a wave. As a result, the rescue crewman lost their footing and moved down and backwards onto their back as the vessel’s aft deck rose on the swell. The winch operator reported ‘crewman has fallen’ and immediately payed out cable to prevent it from becoming taut.

As the winch operator reported the rescue crewman was ‘adjusting his feet’, the pilot moved the aircraft back and left, increasing separation between the aircraft and the vessel. In response to that movement, the winch operator advised the pilot to move the helicopter ‘forward two’ (see the section titled Winching procedures), then with increased urgency in his tone ‘forward two, forward two’.

Despite those instructions from the winch operator, the separation between the helicopter and vessel increased. As a result, the winch cable became taut and the rescue crewman was dragged aft along the deck, into the transom and overboard into the water (Figure 1). The following then occurred in quick succession:

• The winch operator instructed the pilot ‘back, hold, hold, hold, hold’ with increasing urgency.
• The pilot responded, ‘I am holding’.
• The aircraft ceased moving away from the vessel and started moving forward as the pilot attempted to maintain position in vicinity of the vessel’s aft deck. The forward movement of the helicopter caused the rescue crewman to be dragged forward through the water towards the vessel.
• The winch operator commenced winching in, and the onboard video showed the rescue crewman emerge from the water.
• The pilot asked, ‘where is he?’, with the winch operator responding, ‘he’s just here underneath me’.

About 6 seconds elapsed between the crewman falling from the vessel, and emerging clear of the water. Due to the forward momentum of the helicopter, there was a slight swing to the cable as the rescue crewman left the water, which the winch operator controlled by hand. The rescue crewman was then winched into the helicopter, and once inside, confirmed they were uninjured.

The pilot, winch operator and TFO instructor then discussed whether the training should continue. They decided to conduct another dummy run and briefly discussed their observations regarding the incident. The review of the incident did not include discussion of the helicopter movement. However, the TFO instructor provided feedback that in the event of a crewmember falling from the vessel, the correct response was for the winch operator to call ‘crewman overboard’ and ‘hold’.

About 1218 the crew conducted another dummy run, then decided to continue with the original planned training exercises. The crew conducted two further planned vessel winching evolutions followed by a helocast and water winch recovery. Having completed the training sorties, the aircraft returned to Jandakot, landing at 1243.

Figure 1: Rescue crewman overboard

A series of still images captured from on-board video highlighting the commencement of separation and rescue crewman going overboard.

Source: Western Australia Police Force annotated by the ATSB

__________

1.  Western Standard Time (WST): Coordinated Universal Time (UTC) + 8 hours.
2.  Helocast and water winch recovery describes the rescue crewman exiting the aircraft unattached and entering the water once safe altitude and airspeed above the water’s surface has been achieved, then recovered using water winching techniques..
3.  Aircraft maintaining reference and pace with the vessel at a distance of approximately 100 m.
4.  Aircraft maintaining station and no closer than three rotor diameters to the vessel, providing the pilot and winch operator with the best view of the vessel.
5.  Aircraft maintaining hover reference with the vessel at adequate height clearance to allow for changes in swell, where the rescue crewman can be lowered to the deck with minimal risk of injury or likelihood of cable being fouled.

Context

Environmental conditions

Weather

The Bureau of Meteorology (BoM) forecast for 29 September 2020 was for winds west to north‑westerly at 10 kt, increasing to 10 to 15 kt during the morning and reaching westerly 15 to 20 kt in the afternoon.

The weather at the time of the incident was overcast with clear visibility (Figure 2). The temperature was about 19°C with wind from the north‑west at 21 km/h (11 kt) gusting to 30 km/h (16 kt).

Sea state

Seas were forecast to be below 1 m, increasing 1 to 1.5 m during the morning with a west to south-westerly swell 1 m to 1.5 m increasing to 1.5 m to 2 m.

Recorded wave data indicated a combined wave height of 0.89 m consisting of a swell height of 0.37 m from 228° (south‑west) and sea 6eight 0.81 m from 264° (west).^[1]

Figure 2: Western Australia Department of Transport Swanbourne Beach camera

Source: Western Australia Department of Transport

Flight crew information

The flight crew for the day’s training comprised the pilot, four tactical flight officers (TFOs) and a TFO instructor. Two TFOs drove a vehicle towing a refuelling trailer to the Rous Head staging area while the remainder flew in VH-WPX. The TFOs rotated through roles on the aircraft according to the training, proficiency and recency requirements of each individual.

While the TFO instructor was onboard observing at the time, only the following crew were directly involved and relevant to the incident.

The pilot

The pilot joined the Australian Army as a Blackhawk pilot in 2008 and commenced with the Western Australia (WA) Police Air Wing as a helicopter line pilot in September 2019. At the time of the incident the pilot had accumulated 3,566 flight hours, including 497 hours of helicopter winching - 53 hours of which were water winching. About 320 of their flight hours had been accumulated on VH-WPX.

The winch operator

The winch operator had been with the WA Police Force for almost 20 years and at the Air Wing for just over 10 years, commencing as a TFO in June 2010. At the time of the incident the winch operator had accumulated 1,596 crewman flight hours including 560 winch operator hours. Within this time, the crewman had filled the role of winch operator for 110 cycles of water winching. The winch operator qualified as a TFO instructor in September 2017 but was not performing that role at the time of the incident.

The rescue crewman

The rescue crewman had been with the WA Police Force since 2011, before commencing as an aeroplane TFO in June 2017. After about 12 months in that role, the rescue crewman moved into helicopter operations and had accumulated 864 crewman flight hours. This included 74 cycles filling the role of rescue crewman.

Aircraft information

VH‑WPX is a Eurocopter (subsequently Airbus Helicopters) AS365N3+ Dauphin 2 helicopter, configured for single‑pilot operation and equipped with a rescue winch fitted behind the pilot on the right side (Figure 3). It was manufactured in 2011 and operated by the Western Australia Police Air Wing. At the time of the incident, the aircraft had accumulated a total of 4,237 flight hours and 5,671 landings.

After the incident, aircrew viewed onboard winch boom video imagery and identified potential cable shock loading during the recovery of the rescue crewman. WA Police Technical Log records showed that on 1 October 2021, a full cable inspection was conducted in accordance with the Goodrich Rescue Hoist Component Maintenance Manual, with no defects identified.

Figure 3: VH-WPX rescue winch

Source: Western Australia Police Force annotated by the ATSB

Vessel information

The Stacy Hall, callsign ‘Green 1’, is a 12 m aluminium vessel manufactured by Legend Boats (Figure 4). It was powered by twin 450 hp Caterpillar diesel motors capable of sustained operations for up to 24 hours. The vessel was fitted with integrated chart-plotter, sounder and radar, 27MHz, VHF and HF marine radios, radio direction finders and a FLIR infrared camera.

The Stacy Hall had about a 4 m beam with open aft deck, towing post on the fore-aft centreline and folding transom. The vessel was considered to have a large enough aft deck for water winching operations and was regularly utilised when WA Police Force vessels were unavailable.

Figure 4: Volunteer sea rescue vessel Stacey Hall.

Source: Western Australia Police Force

Operator procedures

Operations manual

The WA Police Air Wing Rotary Wing Operations Manual contained six volumes encompassing administration, aircraft operations, training and checking, airworthiness and special operations. Volume 4 provided guidance and requirements for all training and checking whilst volume 6 provided the guidance and instructions for special operations. Volume 6B1 Winching Operations, was accepted by the Civil Aviation Safety Authority in April 2020. The volume detailed aircraft winching training, equipment requirements, guidance, and standard operating procedures.

Planning

Pre-flight planning was conducted in accordance with the Rotary Wing Operations Manual and utilised the Bureau of Meteorology (BoM) combined sea state lookup table (Table 1). BoM sea state tables provide a projected combined sea state based on the forecast sea and swell height.

Table 1: Bureau of Meteorology total wave height lookup table

Source: Bureau of Meteorology

Volume 6, Winching Operations, section 6B1.55.6 Winching to Vessels – Training stated that:

All training that requires live vessel transfers will only be done:

- In calm to slight sea conditions not exceeding a sea of 1.0m or swell of 1.0m and a combined sea state of 1.4 m (see BOM sea state lookup table on the Bureau of Meteorology website). If conditions are greater than above, then consideration should be given to conducting operations in protected waterways where calm to slight conditions prevail.

- To appropriately sized vessels when underway: an appropriately sized vessel is one where the pilot can be confident of easily maintaining an uninterrupted hover reference from the most overhead winching position, noting that as a minimum there must be at least 10 feet of clearance above the highest obstruction within the immediate aircraft operating area on the vessel.

- To vessels where the winch transfer area is free of obstructions likely to foul the cable or endanger any person during the winching exercises.

- For vessels underway it is acceptable to conduct the transfer to a soft dinghy or raft being towed behind the vessel. The pilots hover reference then can be the vessel towing the soft dinghy or raft.

On 22 September 2020, Operations Manual Bulletin No’ 7-2020, noted that live vessel training sea state conditions were very restrictive for training with fully qualified crews. As a result, the operator’s head of flight operations (HOFO) approved a change to sea state limitations for training of fully qualified crew. The approval increased the nominal conditions for water winch training and live vessel transfer to:

- Seas 2.5 m or less

- Swell 2.5 m or less

- Combined sea and swell 2.5 m or less.

According to Volume 1, Administration, Policy and Procedures, section 1A2.1.1 of the Western Australia Police Air Wing Rotary Wing Operations Manual, the head of flight operations or their delegates, were the only persons who could authorise revisions to the Rotary Wing Operations Manual after such changes have been formally reviewed by the Safety Action Group. On this occasion, no such review by the Safety Action Group was undertaken.

For the training undertaken on 29 September 2020, planning considered information issued by BoM for that day, forecasting a sea height of 1.5 m and a swell height of 1.5 m, resulting in a combined forecasted wave height of 2.1 m (obtained from Table 1). Consequently, training for a fully qualified crew was approved under the operator’s updated procedures.

Winching procedures

The primary source of helicopter winching procedures was volume 6, part 6B1 of the WA Police Air Wing Operations Manual. The procedures for vessel winching included that the helicopter crew were to approach the vessel and conduct an assessment from a reference datum, prior to the transfer of the con^[7] to the winch operator. The procedures were then for the winch operator to con the helicopter pilot to the final winch position, before winching the rescue crewman onto the deck of the vessel.

During the conning phase of winch operations, the winch operator issues commands to the helicopter pilot to manoeuvre the helicopter into position, while maintaining clearance from hazards. Conning commands include a numerical indication of the distance to run to the target location, line corrections, rate of closure and rate of descent. While the winch operator has the con, the pilot is generally expected to only manoeuvre the helicopter in response to the winch operator’s commands.

The ATSB reviewed footage from the helicopter winch camera during the incident flight. There were no indications of any issues with how the pilot, or the other crew conducted the approach to the vessel, during the conning of the helicopter to the vessel, or during the winch of the rescue crewman onto the vessel.

Procedures for winching in rescue crewmen

Once the rescue crewman has conducted the required tasks onboard the vessel, the winch operator and the pilot must then conduct the winching in procedure. According to the operations manual, the sequence of commands and steps for this procedure were as follows:

• The winch operator calls:
  • ‘crewman has the hook in hand’ to indicate the rescue crewman had hold of the rescue hook
  • ‘hook connected, conducting checks’ to indicate the rescue crewman had connected the hook and was confirming the connection and equipment before winching
  • ‘one thumb up’ to indicate they had seen the rescue crewman give the hand signal indicating the rescue crewman was ready to be winched
  • ‘taking up the slack’ to indicate they were winching in the slack cable to prepare for the winch
  • ‘ready to winch’ to indicate the winch operator was ready to lift the rescue crewman from the deck.
• The pilot calls ‘clear to winch’ to indicate they had a good hover reference and were ready for the winch operator to commence winching in
• The winch operator calls:
  • ‘winching in’ to indicate they were winching in
  • ‘clear of the deck’. The Winching Operations Manual stated that this call indicated that the rescue crewman had been winched from the deck of vessel and ‘…is in a position where if they were to drift rearward relative to the vessel they would clear all rails and obstacles’.
  • ‘move back and right/left’ to indicate the aircraft was clear to move away from the vessel.

During the incident flight, the crew conducted all calls and steps up to and including the winch operator calling ‘winching in’. Immediately after the winch operator made that call, the winch operator saw that the rescue crewman had fallen on the deck and called ‘crewman has fallen’. The winch operator did not call ‘clear of the deck’.

The pilot advised the ATSB that they commenced moving the helicopter away from the vessel in response to hearing the ‘winching in’ call from the winch operator. The pilot acknowledged that this was not consistent with the procedure, which was to wait until the winch operator called ‘clear to move back and left’.

The pilot believed that they instinctively separated from the vessel because that was the expected sequence of events, based on the procedure and their previous experiences in many similar exercises. The pilot identified that training vessel winch exercises were normally conducted quickly, and they were therefore expecting to commence separating from the vessel immediately after hearing ‘winching in’.

Crewman overboard procedures

Crewman overboard emergency procedures were detailed in the winching operations section of the helicopter operations manual 6B1.48 Winching Emergencies. With regards to ‘rescue crewman overboard – vessel transfers’, the operations manual stated that:

- The winch operator shall announce ‘CREWMAN OVERBOARD’

- The winch operator should take appropriate action to ensure the rescue crewman’s safety. The pilot will manoeuvre the aircraft under direction from the winch operator.

- Once the rescue crewman is clear of the water, the winch operator should give appropriate clearances from the vessel to the pilot.

On this occasion, the winch operator did not announce ‘crewman overboard’, instead they said ‘back’ and ‘hold, hold’ repeatedly with increasing urgency.

__________

6.  Recorded at 1149 by the Western Australia Department of Transport Cottesloe wave buoy, 6 km offshore west south west of the incident location.
7.  To direct the steering of a vessel or aircraft

Safety analysis

Introduction

The days training on VH‑WPX was to include initial winch operator training for a novice winch operator and several operator proficiency checks and operator recency checks for other qualified tactical flight officers (TFOs). A combination of the swell direction coming from the west, and the wind direction coming from the north-west, resulted in conditions that were moderately challenging but within the operator’s requirements.

The incident flight was the fourth sortie of the day and several operator recency and proficiency checks had been completed during the earlier flights.

The following analysis will discuss the rescue crewman’s fall and the responses and actions of the helicopter crew after the rescue crewman was dragged overboard by the winch cable. The analysis also considers the operators change to sea state limitations for water winch training approvals.

Rescue crewman fall

After completing a dummy approach, the rescue crewman was winched to the aft deck of the vessel and completed safety checks. They then signalled they were ready to be winched up with one raised thumb. Following the winch operator’s communication that they were ready to winch the pilot gave clearance to winch and the winch operator commenced winching.

At about the same time, the vessel experienced increased swell and the deck pitched higher as it travelled over a wave. As a result of that increased movement, the rescue crewman lost their footing and moved down and backwards onto their back as the vessel’s aft deck rose on the swell.

In response to the rescue crewman’s fall, the winch operator stopped the winching recovery and payed out winch cable to enable the rescue crewman to safely regain their footing without the cable becoming taut.

Pilot response

After the winch operator called ‘winching in’, the normal sequence of events involved the pilot promptly being given clearance to separate from the vessel. On this occasion, the winching sequence was interrupted by the crewmember’s fall, during which the winch operator stopped winching in. However, the pilot instinctively continued with the usual winching sequence and separated from the vessel without the rescue crewmember being clear of the deck.

Studies show there will be an inevitable reduction in intentional effort and vigilance as procedural tasks become routine and habitual. As described by Dismukes (2008): for experienced pilots, execution presumably becomes largely automatic and does not require deliberate search of memory to know what to do next. Pilots do not need to form an episodic intention to perform each task and each action step—rather the intention is implicit in the action schema for the task, stored as procedural memory.

Because of this, when routines are interrupted or changed there is an increased likelihood of errors. Reason (1990) described such phenomena as strong habit intrusions, noting that slips of action are most likely to be committed during the performance of highly automatised tasks, in familiar surroundings while experiencing some form of preoccupation or distraction. Dismukes (2008) summarises that:

cues that normally trigger the habitual action are so strongly associated that the habitual action is often retrieved and executed automatically instead of the intended action if the individual does not consciously supervise the process.

Most motor vehicle drivers will appreciate this concept, with the familiar experience of intending to make a stop on our daily commute and instead driving all the way home. The power of such well‑rehearsed routines is that we learn to conduct them without a high level of attention or cognitive effort, making it more difficult to identify when they are changed.

For the pilot of VH-WPX, the vessel winch procedure was frequently practiced. On the day of the incident the pilot had conducted over a dozen manoeuvres overhead and then away from the vessel as planned, and therefore the routines associated with these manoeuvres were particularly well rehearsed at the time. As a result, the pilot probably allocated a lower level of conscious attention to each and every aspect of the vessel winching procedure, including when to commence separating from the vessel.

Expectancy also has a powerful influence on attention and perception, and people are much less likely to notice information they are not expecting – particularly in the context of challenging work. When the pilot heard the winch operator call ‘ready to winch’, they likely expected to continue with the normal procedure and move the helicopter away from the vessel. Consequently, the pilot was less likely to identify that the winch sequence had been interrupted and they needed to maintain position with the vessel.

In summary, reduced attention due to the conduct of a frequently practiced task and low expectation of any interruption probably led to the pilot moving the helicopter away from the vessel without the rescue crewman being clear of the deck.

Communication breakdown

The pilot’s reaction, moving the helicopter back and left, resulted in the rescue crewman being unexpectedly dragged overboard by the winch cable. In response to the initial helicopter movement the winch operator said ‘forward two, forward two’ attempting to con the aircraft back towards the moving vessel. After the rescue crewman fell into the water, the winch operator did not use accepted phraseology in accordance with the operations manual. Instead, they focussed on bringing the helicopter to the hover to prevent the crewman being dragged through the water by telling the pilot to ‘hold’ repeatedly with increasing urgency.

The pilot, unable to directly observe the crewman, did not understand the developing situation or the position of the rescue crewman, who at that time was in the water. As a result, the pilot took the meaning of ‘hold’ to mean maintain a constant position with respect to the moving vessel. The rescue crewman was subsequently dragged through the water, following the moving vessel.

The winch operator’s attention remained focussed on the rescue crewman in the water and consequently their level of communication reduced. This in turn required the pilot to ask ‘where is he’ in an attempt to increase their own situation awareness and mental picture of the developing situation.

The winch operator told the ATSB that ‘crewman overboard’ was a drill and phraseology that, while taught, was not expected to be used. By contrast, all other emergencies were regularly drilled in recency and proficiency checks, including cable fouling, runaway cable, and communications failure and included in briefings.

Responding effectively to a ‘crewman overboard’ emergency is a critical risk control when conducting water winching operations. Regular training, drills and briefings form an integral part of emergency preparedness increasing competence and confidence of crew. The absence of such briefings and drills was a missed opportunity to ensure the crew would respond appropriately.

Additionally, while the crew reviewed the incident immediately after it occurred, the discussion focussed on the actions and phraseology of the winch operator rather than the pilot’s movement of the helicopter as the rescue crewman attempted to regain their footing. Discussion of that element would have provided an opportunity to confirm that the required level of communication/coordination between the pilot and winch operator was in place before the winching activity re-commenced.

Sea state limitation change

On 22 September 2020, Operations Manual Bulletin No’ 7-2020, detailed a change to the operator’s procedure 6B1.55, Winching to Vessels – Training. The change, approved by the Head of Flight Operations, permitted training in a combined sea state up to 2.5 m, an increase from 1.4 m.

The operator’s internal review of this occurrence identified that the easing of sea state tolerances was not tabled for review by the operator’s Safety Action Group in accordance with their change management requirements. However, there was no evidence that a review would have resulted in other thresholds or influenced this event. According to Western Australia Department of Transport data the sea state about the time of the event was observed to be within the revised tolerances. Although conditions were challenging because wind and sea were travelling from different directions, the conditions were not the most difficult previously experienced by the crew.

While the absence of a formal review did not contribute to this incident, it reduced the opportunity to identify any change‑related increase in risk.

Findings

From the evidence available, the following findings are made with respect to the helicopter winching incident involving Eurocopter AS365, registered VH-WPX, that occurred on 29 September 2020 near Swanbourne, Western Australia.

Contributing factors

• After signalling they were ready to be winched from the aft deck of the vessel, the rescue crewman slipped and lost footing. This interrupted the usual sequential flow of water winching recovery from a vessel.
• With the rescue crewman still on the deck, the pilot reacted to a verbal communication from the winch operator and moved the aircraft away from the vessel, dragging the rescue crewman overboard.
• Having provided the ‘clear to winch’ call and received the ‘winching in’ response, the pilot had a high level of expectancy that they would shortly be given clearance to separate from the vessel. This expectancy probably led to the pilot instinctively applying the well‑rehearsed actions to separate and not identifying that the winch sequence had been interrupted.

Other factors that increased risk

• After the rescue crewman fell into the water, the winch operator did not use the standard phraseology of 'crewman overboard'. Because of this, the pilot did not have an understanding of the position of the rescue crewman.
• Crewman overboard drills were not regularly conducted or briefed prior to the conduct of vessel winching training. This reduced the crew’s preparedness to respond appropriately to such an incident.
• The operator increased the tolerances of sea state tables for training without conducting a formal safety review in accordance with their change management procedures. This reduced the opportunity to identify any increased risk associated with the change.

Safety actions

Safety action not associated with an identified safety issue

In response to an internal investigation into the incident, the Western Australia Police Air Wing advised the ATSB that:

• crewman overboard phraseology and response actions have been introduced into Western Australia Police Air Wing Flight Operations and Tactical Flight Officer:
  • operator proficiency check annual and biannual recency exams.
  • winch operator training emergency response.
  • winch simulator training.
  • open water vessel winching briefs.
• Operations Bulletin No. 7-2020, detailing the easing of sea state restrictions, not being reviewed by the Air Wing Safety Action Group prior to distribution was tabled for discussion by the senior management group during the formal investigation review. That discussion emphasised the importance of change management principles to mitigate any foreseeable risks.
• Western Australia Police Psychology department is working with Police Air Wing Safety and Quality to develop and introduce mindfulness guidance and training to the Air Wing non‑technical training syllabus.
• Police Air Wing have subsequently reviewed open water vessel winching and concluded the inherent risk of open water vessel winching outweighed the operational reward. The Air Wing has consequently removed open water vessel winching to small vessels underway from the Air Wing operational capability and is introducing the process of deploying a rescue raft while winching or helocasting a rescue crewman to the water when required for emergency response purposes. This response method eliminates the risk of transferring persons to small vessels underway while still maintaining the same level of rescue capability to the community when required.

Glossary

BoM                 Bureau of Meteorology

TFO                 Tactical flight officer

Sources and submissions

Sources of information

The sources of information during the investigation included the:

• crew
• onboard video and audio recordings
• Western Australia Police Air Wing
• Civil Aviation Safety Authority.

References

Dismukes RK (2008) ‘Prospective memory in aviation and everyday settings’, in Kliegel M, McDaniel MA and Einstein GO (eds) Prospective memory: Cognitive, neuroscience, developmental, and applied perspectives, Taylor & Francis Group LLC, New York.

Reason J (1990) Human error, Cambridge University Press, Cambridge UK.

Western Australia (WA) Police, Western Australia Police Air Wing Rotary Wing Operations Manual, Issue 2, revision 5, April 2020.

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 crew
• the Western Australian Police Air Wing
• the helicopter manufacturer (Airbus Helicopters) and the French Bureau d’Enquêtes et d’Analyses pour la sécurité de l’aviation civile (BEA)
• the Civil Aviation Safety Authority.

No submissions were received on the draft report.

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.

What happened

At about 0830 EST on 17 September 2020, an Airborne XT-912 Tourer, recreational registration 32-6225, while on approach, collided with runway 01 at the Gatton Airpark authorised landing area, Gatton, Queensland. The pilot was fatally injured and the aircraft was destroyed.

In response, Recreational Aviation Australia (RAAus) commenced an investigation into the occurrence. Due to COVID-19 travel restrictions, RAAus requested technical assistance from the Australian Transport Safety Bureau (ATSB) to document and photograph the wreckage and accident site.

To facilitate this work the ATSB has initiated an external investigation under the Transport Safety Investigation Act 2003. These tasks were completed, and the factual information was provided to RAAus on 21 September 2020.

With the completion of this work, the ATSB has concluded its involvement in the investigation of this accident. Any enquiries relating to the accident investigation should be directed to RAAus at: www.raa.asn.au.

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The information contained in this update is released in accordance with section 25 of the Transport Safety Investigation Act 2003 and is derived from the initial investigation of the occurrence. Readers are cautioned that new evidence will become available as the investigation progresses that will enhance the ATSB's understanding of the accident as outlined in this update. As such, no analysis or findings are included.