On 27 February 2016, a Jabiru Aircraft, recreational registration 55-3692, collided with terrain at Medlow Bath, New South Wales. The pilot, the sole occupant, died as a result of the accident.

NSW police is the organisation responsible for investigating this accident. As part of their investigation, they had requested that Recreational Aviation Australia (RA-Aus) provide some technical assistance related to the aircraft and engine. As part of their involvement, RA-Aus requested that the Australian Transport Safety Bureau (ATSB) assist with the examination of the engine.

To protect the information supplied by RA-Aus to the ATSB and the ATSB's investigative work to assist them, the ATSB initiated an investigation under the Transport Safety Investigation Act 2003.

The Jabiru 2200J engine was disassembled and examined at a facility at Bankstown Airport on 8 April 2016 in the presence of a number of interested parties, including the Australian Transport Safety Bureau, NSW Police, the Civil Aviation Safety Authority, and the manufacturer. The examination did not identify any anomalies that may have contributed to the development of the accident. No further assistance was provided to RA-Aus, and further enquiries should be directed to the NSW police as the investigating agency.

What happened

On 28 February 2016 at about 1642 Eastern Daylight-saving Time (EDT), a Cessna 150 aircraft, registered VH-RZP (RZP), departed from King Island Airport, Tasmania, for a flight to Barwon Heads Airport, Victoria (Figure 1). On board were a pilot and passenger.

The pilot had elected not to submit a flight plan for the visual flight rules^[1] private flight. They planned to remain outside controlled airspace but make scheduled reports^[2] to air traffic control (ATC) on the Melbourne Centre frequency during the overwater component of the flight.

At 1645, when passing through 1,600 ft above mean sea level, the pilot broadcast a departure call on the King Island common traffic advisory frequency (CTAF) using the only radio in the aircraft.

Figure 1: Approximate flight paths of Cessna 150 VH-RZP and SA227 VH-MYI

Source: Google earth annotated by the ATSB

About two minutes later, the crew of a regular public transport (RPT) aircraft (’Aircraft 2’) also broadcast on the CTAF. The crew advised that they were at 30 NM inbound to King Island and on descent through FL 115.^[3] The pilot of RZP responded to this broadcast, and reported RZP’s position and their intentions. After a brief radio discussion, the pilot of RZP agreed to advise the crew of Aircraft 2 when RZP was close to the northern coast of the island (Figure 1). The crew of Aircraft 2 had temporarily stopped their descent at 6,500 ft until they could confirm that they had safely passed RZP.

At 1650 the crew of a RPT Sharp Airlines Fairchild SA227 aircraft, VH-MYI (MYI), also made a 30 NM inbound broadcast on the CTAF. The pilot in command (PIC) was the pilot monitoring^[4] for this sector, and handling the radio calls using two radios, one on the CTAF, and one on the Melbourne Centre frequency. At the time, MYI was on descent from FL 110. The crew of Aircraft 2 responded to this broadcast, with an update of their position and current intentions.

At the same time as the pilot in MYI was broadcasting on the CTAF, the pilot in RZP contacted ATC to arrange the overwater component of their flight. RZP was now about 17 NM from the King Island Airport and had selected the Melbourne Centre frequency on their radio. Therefore, the pilot of RZP did not hear the inbound broadcast by the pilot of MYI. The call to ATC included details of RZP’s current position, the current passing altitude of 4,400 ft, and the intention to continue the climb to 5,500 ft. As they were still in the climb, the aircraft had a relatively high nose attitude, which restricted the pilot’s forward vision.

Air traffic control (on Melbourne Centre frequency) confirmed with the crew of both inbound RPT aircraft (still monitoring both frequencies) that they had heard RZP’s radio call. The crew of Aircraft 2 responded that they had, and when ATC asked again, the crew of MYI (who at the time had been broadcasting on the CTAF) advised that they had also heard the broadcast.

Air traffic control then confirmed with the pilot of RZP that they had heard both inbound RPT aircraft’s broadcasts. The pilot of RZP (still in the climb) advised ATC that they were aware of both aircraft and that Aircraft 2 had just passed above them.

Almost concurrently, the flight crew in both Aircraft 2 and MYI were calling the pilot of RZP on the CTAF, attempting to establish RZP’s current position. The pilot in RZP then momentarily switched back to the CTAF and contacted Aircraft 2 to inform them that they had just passed above RZP.

The crew of MYI unsuccessfully tried again, on the CTAF, to establish the position and altitude of RZP. MYI did not have a traffic alert and collision avoidance system^[5] (TCAS) installed so although RZP was transponder equipped, the crew in MYI had to rely on radio transmissions to ascertain the other aircraft’s position.

Not obtaining a response from RZP (as the pilot of RZP had switched the radio frequency back to Melbourne Centre) and unable to determine RZP’s exact position, the crew of MYI elected to temporarily stop their descent at 5,300 ft.

Shortly after, as RZP had reached the top of climb and the pilot was reconfiguring the aircraft, the passenger alerted the pilot to the approaching aircraft (MYI) on a reciprocal heading. About the same time, the crew of MYI reported seeing RZP ‘on a reciprocal heading and within a 100 ft of their altitude and about 200–300 m away’. The pilot of RZP quickly manoeuvred to the right, but the aircraft had passed MYI before the crew of MYI were able to react. There was a further radio exchange between the two crews after the pilot of RZP momentarily switched back to the CTAF.

Both RZP and MYI continued to their respective destinations and landed safely. Aircraft 2 had already landed some minutes earlier.

Table 1 below provides a summary of the radio calls made on both the King Island CTAF and the Melbourne Centre frequency.

Table 1: Summary of radio calls made on CTAF and Melbourne Centre

Weather

The King Island Terminal Aerodrome Forecast (TAF) valid from 1300 to 0100 the next day included a south-westerly wind of 15 kts, visibility of 10 km or greater, and showers of light rain with 6–7 okta^[6] of cloud at 3,000 ft.

One of the King Island automated weather station reports (METAR) released during this period, reported a wind from the south-west at 14 kts, greater than 10 km of visibility and overcast^[7] cloud at 1,900 ft.

Cessna 150, VH-RZP - Pilot experience and comments

The pilot held a Private Pilot Licence and had about 640 hours of total aeronautical experience.

The pilot reported the following:

• They were familiar with King Island and regularly flew from Barwon Heads to King Island and return in this aircraft.
• The pilot’s recollection of the flight was that they had made all the appropriate radio calls both on the CTAF and on the Melbourne Centre frequency.
• The pilot recalled being advised by ATC that there were two inbound RPT aircraft, but did not have a full understanding of the position of MYI in relation to RZP.
• The pilot was unaware of MYI until they had switched to Melbourne Centre frequency to commence the overwater reporting segment.
• The pilot advised that although there was cloud around the King Island Airport, they were able to remain clear of cloud during the climb to 5,500 ft, and that it was clear blue sky above the cloud from about 3,000 ft.
• RZP was fitted with one radio, therefore could only be tuned to one frequency at a time (in this case, either Melbourne Centre or the CTAF). The pilot felt that this had probably contributed to the communication breakdown.
• The transponder in RZP was on and working. The pilot was under the impression that an RPT aircraft would be able to ‘see’ RZP on TCAS, or similar equipment.
• They used an iPad with a popular navigation application, and were able to maintain the flight-planned track far more accurately than relying on navigating using a map. There was no traffic awareness facility on this software application.
• The pilot commented that in future they would not fly an almost reciprocal track to the inbound IFR aircraft. Instead, they intend to track a coastal route once departing King Island and then track to a position west of Barwon Heads in order to provide sufficient separation.

Fairchild SA227, VH-MYI – Pilot experience and comments

The pilot in command (PIC) had almost 4,000 hours total aeronautical experience with just over 1,700 hours on SA227 aircraft. The PIC advised the following:

• Due to the forecast and in flight conditions of overcast layers of cloud for the descent, the crew had elected to conduct a Global Navigation Satellite System (GNSS) arrival, with a circling approach on to runway 28.
• As per the company standard operating procedures, all communication with company ground personnel at King Island was completed prior to the top of descent.
• The crew had incorrectly assumed that because RZP was a VFR aircraft, they would therefore be staying below the extensive layers of cloud and commencing the overwater segment well below MYI’s descent profile. The crew reported that the inflight conditions they were experiencing of layers of overcast cloud had only re-enforced the belief that RZP, being VFR, would be under the layers of cloud and therefore not a conflict.
• This particular SA227 had yet to be fitted with ADS-B.^[8] The pilot advised that much of the operator’s fleet had already been fitted with this technology, but MYI was scheduled for fitment in the near future. This aircraft was also not fitted with TCAS.
• The pilot commented that King Island is a very busy airport, with an increasing number of commercial flights operating there. To date, the pilot had not had an issue operating there as the self-separation required was predominantly between other IFR commercial aircraft, and the system had worked well.

ATSB comment

This serious incident highlights the issues with different performance aircraft operating in the vicinity of non-controlled airports. Although the crew in all three aircraft were making all the required broadcasts, in this occurrence, the broadcasts were being made within seconds of each other on different frequencies. This meant that the crew of both RZP and MYI had missed the opportunity to gain a full appreciation of the other’s position, resulting in a near collision.

In the last five years, the ATSB has received almost 100 reports of near collisions, where the pilots have reported that they were in the vicinity of a non-controlled airport. The ATSB is currently working on an update of the research report into safety in the vicinity of non-controlled aerodromes (previously published in 2010). A revised iteration is expected to be released in the 2016/17 financial year.

The ATSB is also compiling a special aviation short investigation bulletin involving several recent near collisions in the vicinity of non-controlled aerodromes.

Much of the information the ATSB has gathered through the reporting process and through related investigations points to a lack of understanding between pilots of different operation types operating to and from non-controlled aerodromes. Although broadcasting and reporting on the radio often occurs, the situational appreciation of the other aircraft’s performance and positions has not occurred.

Situational awareness around high traffic routes in Class G airspace and non-controlled airports remains the responsibility of the pilot in command. The ATSB encourages pilots to consider other operations in a shared facility such as non-controlled aerodromes. The use of all available resources to confirm the intent of other aircraft by questioning transmissions which had not been fully heard or understood, as in this case, may avert a serious incident such as this.

Safety action

Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following proactive safety action in response to this occurrence, bearing in mind the VH-RZP was a private operations aircraft.

Sharp Airlines

As a result of this occurrence, Sharp Airlines has advised the ATSB that they are taking the following safety actions:

To highlight human factors issues and the risks associated with operating into and out of King Island Airport, the details of the incident will be included in the company’s quarterly newsletter.

Future flight crew human factors training courses will include the human factors associated with this occurrence.

Safety message

The ATSB’s Avoidable Accident series includes a publication, A Pilot’s Guide to safety in the vicinity of non-towered aerodromes. This publication captures many issues that occur around non-controlled aerodromes.

Section 4 of CASA’s Civil Aviation Advisory Publication (CAAP 166-1(3)) encourages pilots to consider issues surrounding the traffic mix in the vicinity of non-controlled aerodromes. Although the definition used for CTAF in this publication indicates a lateral dimension of 10 NM, Table 2 notes that higher performance aircraft will be making broadcasts earlier than this 10NM boundary. It is therefore important for all CTAF users, particularly pilots of those aircraft in the lower performance category, to understand this information.

The Airservices Australia Aeronautical Information Package (AIP) GEN 2.2-6, defines a CTAF as:

‘A designated frequency on which pilots make positional broadcasts when operating in the vicinity of a non-controlled aerodrome.’

This definition may provide a more useful way for pilots to understand operations in and around non-controlled aerodromes.

Aviation Short Investigations Bulletin - Issue 49

About this report Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2016 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. Visual flight rules are a set of regulations which allow a pilot to only operate an aircraft in weather conditions generally clear enough to allow the pilot to see where the aircraft is going.
2. Scheduled reports are an option to meet search and rescue requirements for aircraft who do not meet the normal CAR 258 requirements for overwater flight. Information available in the Aeronautical Information Publication ENR 1.1.100.
3. At altitudes above 10,000 ft in Australia, an aircraft’s height above mean sea level is referred to as a flight level (FL). FL 370 equates to 37,000 ft.
4. Pilot flying (PF) and pilot monitoring (PM) are procedurally assigned roles with specifically assigned duties at specific stages of a flight. The PF does most of the flying, except in defined circumstances; such as planning for descent, approach and landing. The PM carries out support duties and monitors the PF’s actions and aircraft flight path.
5. Traffic collision avoidance system (TCAS) is an aircraft collision avoidance system. It monitors the airspace around an aircraft for other aircraft equipped with a corresponding active transponder and gives warning of possible collision risks.
6. A meteorological unit of measurement giving the amount of cloud present at any one location.
7. Overcast means a total sky coverage of this cloud (100%).
8. ADS-B, or automatic dependent surveillance – broadcast, automatically broadcasts the precise location of the aircraft via a digital data link. The data can be used by other aircraft and ATC to show the aircraft’s position and altitude on display screens without the need for radar.
9. At the time of this publication, these aerodromes were known as non-towered. CASA have since updated this definition to include all aerodromes/airports where a control service is not currently in place. This can apply to Class C or D airports when Tower is not operating.

What happened

On the morning of 20 February 2016, the pilot of a Robinson R22 helicopter, registered VH-LYW, was conducting aerial cattle mustering operations on a property about 88 km northeast of Roma, Queensland.

The pilot had mustered in that paddock several times previously, and was aware of a set of high voltage transmission wires that had been erected across the property in the previous 12 months.

Prior to commencing mustering, the pilot overflew the paddock, sighted the powerlines and formed a plan to muster the cattle from north to south, giving due consideration to the wires running east-west. The pilot then mustered the mob from north to south, and the helicopter remained above the wires during that time.

The pilot then saw two bullocks hidden in scrub, near a dam that was situated near to and just south of the powerlines, and returned to muster them up. The helicopter then descended below the level of the wires. The cattle would not turn back, so the pilot radioed a musterer on horseback to assist. The pilot turned the helicopter to leave the area as the horse and rider arrived. The pilot then saw another vegetated area near the dam, where cattle may be hidden from view, and flew the helicopter towards it.

While the pilot’s focus was on searching for cattle in the scrub below, the helicopter neared the powerlines. The pilot’s attention suddenly returned to the wires, and sighting them close in front at the same level, immediately commenced a near-vertical climb to try to avoid them. As the helicopter climbed, the pilot assessed that it was not going to clear the earth wire, and lowered the nose of the helicopter in an attempt to pass below the earth wire and above the other wires. The tail rotor blade struck the earth wire.

The helicopter was vibrating and the pilot turned it away from the wires. The tail rotor then failed and the helicopter yawed around. The helicopter descended rapidly and continued to rotate. The pilot entered an autorotation, and closed the throttle, overriding the governor. As the helicopter neared the ground, the low rotor revolutions per minute warning horn sounded, and the pilot raised collective^[1] to try to cushion the landing. The helicopter collided with the ground nearly upright, and sustained substantial damage (Figure 1). The pilot was seriously injured.

Marking of overhead cables

The Australian Standard (AS) 3891.2-2008 Air navigation – Cables and their supporting structures – Marking and safety requirements, specified requirements for permanent and temporary marking of overhead cables and their supporting structure for visual warnings to pilots of aircraft involved in intentional and legal low-flying operations. The AS included examples such as powerlines in areas where aerial agricultural activities took place. An Appendix to the AS stated that markers should be installed where regular low-level flying operations take place, and that the responsibility for requesting their installation rests with the person requesting the planned low-level flying operations.

Additionally, other than for low-level flying, Part 1 of the AS 3891.1Permanent marking of overhead cables and their supporting structures for other than planned low level flying,stipulated that any section of cable that had a height in excess of 90 m above a road, railway or navigable waterway should be marked. Cables above 90 m located in other places should be marked if they had a continuous span greater than 50 m.

Pilot comment

The pilot reported feeling substantial operational pressure to ensure no cattle were missed. They commented that this may have increased focus and attention on looking for cattle, and therefore momentarily lost awareness of the powerlines.

Figure 1: Accident site showing damage to VH-LYW

Source: Queensland Police

Safety message

Pilots and operators are reminded that they can ask the property owner and power company to have a wire marked if it presents a hazard to low-level operations, even if it is not required to be marked according to the Australian Standard due to its height and span.

ATSB research indicates that in 63 per cent of reported wirestrike incidents, pilots were aware of the position of the wire before they struck it. In this instance, the pilot was aware of the powerline, however, the pilot’s attention was diverted to looking for cattle, and they did not maintain awareness of the wires.

The Aerial Agricultural Association of Australia suggests a way to keep focus is to ask yourself:

• Where is the wire now?
• What do I do about it?
• Where am I in the paddock?

For further risk management strategies for agricultural operations, refer to the Aerial Application Pilots Manual.

The ATSB publication Avoidable Accidents No. 2 – Wirestrikes involving known wires: A manageable aerial agricultural hazard, explains strategies to help minimise the risk of striking wires while flying. Pilots are reminded to avoid unnecessary distractions and to refocus when distracted. Distraction, combined with difficulty in seeing wires makes them extremely hard to avoid at the last minute.

Aviation Short Investigations Bulletin - Issue 48

About this report Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2016 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. A primary helicopter flight control that simultaneously affects the pitch of all blades of a lifting rotor. Collective input is the main control for vertical velocity.

What happened

On 21 February 2016, the pilot of a Glaser-Dirks DG-800B glider, registered VH-IGC (IGC), was participating in a coaching flight with a second glider and pilot from Pipers Field aerodrome, New South Wales (NSW) (Figure 1). The glider pilots planned to track towards Cowra, and to remain outside a 10 NM radius of Orange Airport, both also in NSW. The gliders climbed to about 8,000 ft above mean sea level (AMSL) as they departed Pipers Field, descended to about 7,100 ft at 9 NM south-west of Pipers Field, climbed to 9,100 ft and then descended again. Not long after they departed Pipers Field, the glider pilots both selected their radio (each glider was fitted with one VHF radio) to a discrete glider frequency 122.9. The pilot of the following glider reported being at the same level and about 1,000 m behind IGC.

At about 1420 Eastern Daylight-saving Time (EDT), a Regional Express SAAB 340B aircraft, registered VH-ZLA (ZLA), taxied at Orange Airport, for a scheduled passenger service to Sydney, NSW. The flight crew consisted of a first officer, who was the pilot flying for the sector, and a captain, who was the pilot monitoring.^[1] The flight crew broadcast on the Orange common traffic advisory frequency (CTAF) when taxiing and again when rolling on runway 11.

As the aircraft climbed through 2,000 ft above ground level, the first officer initiated a slight right turn onto the departure track of 123° to track towards the waypoint ‘MEEGA’. The captain broadcast a departure call on the CTAF and then contacted air traffic control (ATC) on Melbourne Centre frequency, and in response received a clearance to enter controlled airspace. The lower limit of Class E airspace in this area was 8,500 ft AMSL.

Figure 1: Approximate aircraft tracks and relevant locations

Source: Google earth – annotated by ATSB

When climbing through about 6,000 ft AMSL, the first officer saw a build-up of cumulus cloud ahead and asked the captain to request a clearance to track 5 NM right of track to remain clear of it. As the captain started to read back the amended clearance from ATC, the aircraft was climbing through about 7,500 ft. The captain sighted the glider (IGC) ahead, just below the cloud base, and assessed there was a risk of collision. The captain immediately took control of the aircraft from the first officer, disconnected the autopilot and lowered the nose of the aircraft to ensure it passed below the glider. The flight crew estimated that the glider passed within about 100 m of the aircraft.

The glider IGC was descending through 8,560 ft AMSL, and 11 NM from Orange Airport, when the pilot of IGC sighted ZLA in their 3 o’clock position and climbing towards them. The pilot of the following glider also alerted the pilot of IGC to the aircraft on their discrete glider frequency. The pilot of IGC assessed that while ZLA was on a direct track towards IGC, due to its climb rate there was no risk of collision and elected to continue on their current track. The pilot of IGC estimated that ZLA passed about 200 m below the glider.

The pilot of the glider following IGC reported that ZLA passed between the two gliders, below IGC but at about the same altitude as the following glider. The flight crew of ZLA did not see the second glider at any stage, nor did either glider appear on the aircraft’s traffic alert and collision avoidance system (TCAS).

Notice to airmen (NOTAM)^[2] and Advisory Note

The flight crew of ZLA had reviewed the NOTAMs prior to commencing the first sector of the day from Sydney to Orange. NOTAM C0002/16 referred to increased glider activity due to gliding championships at Narromine, NSW, from 14 to 21 February 2016. The NOTAM advised that glider pilots would be on the CTAF 126.7 within 10 NM of the aerodrome (Narromine), otherwise on either frequency 122.7 or 122.9.

The Gliding Federation of Australia had also issued a Significant Gliding Activity Advisory Note, which included a significant gliding event from 6 to 12 February 2016, with 20 gliders within a 500 km radius of Narromine (which includes the Orange area), and that the associated gliding frequencies were 122.025 and the CTAF 126.7. The advisory note was sent by email to ‘regular airspace users’, which included Regional Express.

The gliders involved in the incident were not operating in association with the championships.

The Gliding Federation of Australia commented that the Advisory Note was intended to alert flight crews to gliders operating in the vicinity of the Orange CTAF (as Orange was within the 500 km radius). On the day of the incident, the gliders operating as part of the championships were north-west of the Orange CTAF.

Company procedures for Regional Express

Regional Express had special procedures to assist in maintaining separation with gliders for aircraft operating in the vicinity of Bathurst, NSW, and Narromine, but at the time of the incident, not for Orange. Orange had not been identified as a gliding location, unlike Bathurst and Narromine. These were published in the company’s route manual, which detailed normal and special requirements of every aerodrome they operate into. The waypoints and tracks used for approaches to Bathurst, the location of Pipers Field aerodrome, and tracks to be avoided were published in the En Route Supplement Australia entry for Bathurst under Flight procedures.

The special procedures for Bathurst advised of a large amount of glider activity in the Pipers Field area. It stated that the VHF frequency the gliders use was 122.7. It included a map depicting preferred tracking from Bathurst to avoid Pipers Field, and which tracks to be avoided.

These also included a recommendation that on departure from Bathurst to Parkes, flight crew broadcast on the glider frequency 122.7 prior to taxiing at Bathurst, which was the frequency most commonly used by glider pilots in the area.

There was no mention of glider frequency 122.9, which the glider pilots had selected on the incident flight.

Flight data

The aircraft operator provided the ATSB with the flight data for the incident flight. The flight data showed that as ZLA climbed through about 8,000 ft, the autopilot was disengaged, and the captain applied a nose-down elevator control deflection and the aircraft pitched down about 3 to 4°.

Pilot comments

Captain of ZLA

Due to workload, it was not always possible to broadcast on the specified glider frequency – they were required to monitor CTAF and ATC frequencies, and the aircraft was fitted with two VHF radios. In several years of broadcasting the recommended calls, the captain could not recall ever having received a response from any glider pilot to a call broadcast on the glider frequency. Due to terrain shielding, the glider pilots may not hear a broadcast from the ground at either Bathurst or Parkes.

Fundamental to the incident was a lack of communication between ZLA and the glider/s. There was no situational awareness between the aircraft. If the glider pilot had broadcast on the CTAF, they could have avoided the near collision.

Later in the day of the incident flight, the flight crew broadcast on the Narromine glider frequency when on descent into Dubbo. The responses received from glider pilots on the frequency were unhelpful and potentially distracting.

First officer of ZLA

The first officer reported that they had never encountered a glider in the vicinity of Orange before, particularly through the centreline of an active runway. The climb is a busy stage of flight – they were configuring the aircraft, and making radio calls on Melbourne Centre ATC. If they had been on descent, they would have descended through the cloud straight on top of the gliders, and the glider pilots were not on the same radio frequency as they were.

If there is a specified glider frequency active, they select that prior to broadcasting a taxi call on the CTAF and ask whether there are any gliders in the area. Once they have selected the CTAF, they remain on it (with Melbourne Centre ATC selected on the other radio).

Pilot of IGC

The pilot of IGC provided the following comments:

• The gliding club had a procedure for pilots to assist in maintaining separation with Regional Express flights out of Bathurst, but not for Orange. The procedure was documented and circulated via email to members of the gliding club. Associated maps and information were also prominently displayed in the gliding clubhouse and reiterated to pilots at pre-flight briefings.
• As they were not going to enter the Orange CTAF, the two glider pilots switched to the gliding frequency 122.9 departing Pipers Field. They normally broadcast when entering a CTAF and then monitor the frequency, but they were not going into the Orange CTAF, so did not select that frequency at any stage of the flight.
• If they heard a broadcast from a Regional Express crew, they would only respond if they anticipated a risk of collision.
• The proximity between the aircraft and glider was closer than was comfortable but they did not think there was a risk of collision.
• It was a common route for the gliders tracking from Pipers Field to Cowra via Blayney as they had identified a number of sites suitable for an outlanding^[3] if required.
• When outside the CTAF but within the identified zones of increased collision conflict, it would be good to be on a common frequency.

Class E Airspace

Class E Airspace is controlled for IFR flights, and uncontrolled for VFR flights. The Gliding Federation of Australia Airways and Radio Procedures for Glider Pilots stated that ‘Gliders are encouraged, but not required, to monitor the area frequency when operating in Class E Airspace’.

Pipers Airfield Airspace Procedures

Following the incident, an email was sent to members of the Bathurst Soaring Club to advise them of the incident, and it contained a copy of the existing procedures for members to read. The procedures included the following instructions.

• Keep a good lookout at all times.
• Study and understand the map of the Regional Express flight paths and the radio frequency you should be on.
• Monitor 119.0 MHz (which was the Orange CTAF) in the vicinity of the Regional Express flight paths to/from Orange as shown on the map.
• Monitor 119.0 MHz in the vicinity of Orange Airport and keep a good lookout especially for traffic from/to Bathurst, Sydney, Parkes and Dubbo.
• Make sensible calls on the CTAF when within 10 NM of the aerodrome to alert traffic in those areas where you are and what your intentions are.
• When operating outside the normal 10 NM but on the likely track to or from Sydney, act as if in the vicinity (i.e. within 10 NM). Recent incidents have shown that operational profiles for Regional Express flights have them much higher than we would normally expect. Do not assume that you should not respond because you believe you are too high.

ATSB comment

The separation issue in this case may have been avoided if the glider pilot had been monitoring and broadcasting on the CTAF. The crew of ZLA were monitoring and broadcasting on the Melbourne Centre ATC frequency and CTAF, and the glider pilot was monitoring a discrete glider frequency. Even if the flight crew of ZLA had broadcast on, or had been monitoring, the nominated glider frequency of 122.7, neither of the glider pilots were monitoring, or broadcasting on, that frequency, so this would have been an ineffective means of alerting the glider pilots of their intentions.

The advisory for Regional Express pilots to make an additional broadcast on a glider frequency will not necessarily reach the glider pilots targeted.

Operating under the visual flight rules, and the exemption to CAO 95.4 Instrument 2011, there was no specific requirement for the glider pilot to monitor or broadcast on the area frequency. Regional Express commented to the effect that in accordance with this exemption, separation between a glider and other aircraft is dependent on see-and-avoid only. Regional Express aircraft are fitted with VHF radios and TCAS. However, these are not capable of alerting the crew to a glider that is not fitted with a transponder and where the glider pilot is not listening or broadcasting on the same frequency as the Regional Express crew.

The crew of ZLA broadcast their position and intentions on the CTAF, but the pilot of IGC was not monitoring that frequency.

The requirement to monitor a CTAF is subject to a level of interpretation, particularly with respect to the altitude above an airfield at which the requirement applies. The Aeronautical Information Package requires a pilot to broadcast on the CTAF when they enter the vicinity of a non-controlled aerodrome. The AIP goes on to describe the vicinity of a non-controlled aerodrome as being:

…within 10 nm of the aerodrome and at a height above the aerodrome that could result in conflict with operations at the aerodrome.

The glider pilots were not monitoring the CTAF because they did not believe they were ‘in the vicinity’ of Orange Airport, or of inbound or outbound aircraft.

Existing forums and processes (managed by the Civil Aviation Safety Authority (CASA) and Airservices Australia) allow airspace users to influence the manner in which airspace is managed and propose changes to relevant documents (such as the En Route Supplement Australia). Where changes have the potential to improve safety, operators are encouraged to present proposals for consideration, using those forums and processes. One relevant forum for proposing airspace-related safety improvements is the CASA Regional Airspace and Procedures Advisory Committee.

Aircraft proximity events review

At the Regional Aviation Safety Forum in March 2012, a representative from Regional Express expressed their concerns about close proximity encounters with gliders. Along with the use of radios, avoiding known departure tracks, and the use of see-and-avoid principles, the compulsory fitment and operations of transponders to gliders was discussed. CASA’s Safety Systems Office advised that it would undertake an analysis of aircraft proximity (airprox) events.^[4]

In 2012, the Civil Aviation Safety Authority (CASA) commenced a safety review into the level of risk from gliders in aircraft proximity events in uncontrolled airspace. In response to discussions at a Regional Aviation Safety Forum in 2013, and following advice from the ATSB of an increase in the number of airprox events across all categories of operations, CASA established an Industry Airprox Working group to examine ways to reduce airprox events and enhance safety. Regional Express and industry groups including the Gliding Federation of Australia, were members of this group.

The working group concept was subsequently dropped, and CASA has since developed a process to assess the risk of complex safety issues. The ATSB was provided with a draft of CASA’s Safety Risk Profile – Aircraft Separation (Airprox) report. Note that these have not yet been finalised and may change when the final version is published.

The stated objectives of the Safety Risk Profile, were:

• to identify the current controls for managing the threat of aircraft on a collision course
• to identify and, if appropriate, recommend additional treatments, and assign accountabilities, to control risk.

The risk profile analysed Australian data from the ATSB aviation safety incident reports, and from the UK Airprox Board.

The findings of CASA’s safety risk profile included:

• That the limitations of see-and-avoid are well documented and only through continued education and training will this be an effective risk control measure.
• On-board communications i.e. the use of radios will assist in pilot awareness and upgrade see-and-avoid to alert-and-avoid, this being a more effective risk control. Treatments have been identified in the areas of carriage and use of radios, English language standards, human factors training.
• Hardware was identified as an effective recovery measure. Since its introduction, airborne collision avoidance systems (such as TCAS) have been a proven risk control in the prevention of mid-air collision. Other hardware technologies are used and emerging which offer varying degrees of protection depending on design and intended application.

The report quoted a European Aviation Safety Agency research project, Scoping Improvements to ‘See and Avoid’ for General Aviation (SISA), which reviewed initiatives taken (in Europe) to mitigate the limitations of see-and-avoid. The project assessed currently available systems to augment pilots’ visual observation including anti-collision devices. They classified and compared the systems, and assessed their relative suitability for general aviation aircraft including gliders. The use of anti-collision devices was not mandatory in Europe, but several systems were already widely used that help the pilot to identify other traffic.

Proposal for the adoption of amended standards for aircraft dependent surveillance – broadcast (ADS-B) fitment in visual flight rules (VFR) aircraft

At its 21st Surveillance Technologies Working Group Meeting in February 2016, the Australian Strategic Air Traffic Management Group drafted a proposal to CASA recommending the adoption of amended standards for ADS-B fitment in VFR aircraft. The Gliding Federation of Australia has a representative in the working group. Fitment of ADS-B technology in VFR aircraft enables awareness of other aircraft traffic, thereby improving aviation safety. The working group suggested that adopting appropriate standards and simplifying the installation process would encourage (voluntary) fitment of ADS-B technology in general aviation aircraft.

The proposal stated that if VFR aircraft were equipped with ADS-B OUT equipment, to the nominated standards, safety and efficiency would be significantly improved, because these aircraft would be visible to:

• aircraft with TCAS or other traffic advisory system;
• all aircraft with ADS-B IN; and
• air traffic control, when within line-of-sight coverage of ADS-B ground station.

Safety action

Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following safety action in response to this occurrence.

Bathurst Soaring Club

Bathurst Soaring Club amended its airspace procedure so that glider pilots are to use 122.7 or the CTAF frequencies and not any other frequency within a 40 NM radius of Pipers Field.

Regional Express – operator of VH-ZLA

As a result of this occurrence, Regional Express has advised the ATSB that they have taken the following safety actions:

Notice to flight crew

Regional Express distributed the following notice to flight crew:

Due to increased glider traffic to the East of Orange it is recommended that if operationally possible a broadcast on 122.7 be made prior to top of descent and/or prior to taxi at Orange.

Communications between Regional Express and Bathurst Soaring Club

Regional Express produced a number of charts showing approach and departure routes from Bathurst and Orange, including Figure 2, and made the following comments to the Bathurst Soaring Club:

On arrival at Orange our flight crew would typically call on the CTAF frequency at around 30 miles from the airport or at top of descent or around 6.5 minutes from the field. In most cases where they are able to use Runway 29 to land they will track to join a straight-in final at 5 miles.

On departure from Orange they would be making all the necessary calls on the CTAF frequency i.e. taxiing, entering the runway, etc.

It would be very helpful if the gliders could maintain a listening watch on the Orange CTAF frequency when in the vicinity of the possible areas of conflict, so that we could have ‘alerted see and avoid’ separation.

Figure 2: Regional Express Orange and Bathurst tracks relative to Pipers Field

Source: Regional Express

The Gliding Federation of Australia

The Gliding Federation of Australia is conducting a series of National Safety Seminars for glider pilots, which will include:

• highlighting the importance of alerted see-and-avoid in improving situational awareness
• flight planning including awareness of the airlines’ operational routes
• the importance of monitoring and broadcasting on CTAF frequencies.

In response to this incident, the Federation included an article titled ‘Conflicts with non-glider traffic’ in the Gliding Australia magazine, which depicted the Regional Express track to Orange.

Safety message

Pilots are encouraged to ‘err on the side of caution’ when considering when to make broadcasts and whether specific frequencies should be monitored, particularly noting the fundamental importance of communication in the effective application of the principles of see-and-avoid. The ATSB report Limitations of the See-and-Avoid Principle outlines the major factors that limit the effectiveness of un-alerted see-and-avoid.

Insufficient communication between pilots operating in the same area is the most common cause of safety incidents near non-controlled aerodromes.

A search for other traffic is eight times more effective when a radio is used in combination with a visual lookout than when no radio is used.

In areas outside controlled airspace, it is the pilot’s responsibility to maintain separation with other aircraft. For this, it is important that pilots use both alerted and un-alerted see-and-avoid principles. Pilots should never assume that an absence of traffic broadcasts means an absence of traffic.

The use of transponders greatly enhances safety in non-controlled airspace. The AIP states that pilots of aircraft fitted with a transponder must activate it at all times during flight. Transponders can be detected by aircraft equipped with TCAS, allowing them to detect other aircraft and initiate avoidance action. The use of ADS-B provides additional information to equipped aircraft.

Alerting technologies can be used as a ‘last line of defence’ to warn pilots of aircraft in their vicinity. The available technologies include:

• Portable TCAS, which can be plugged into a cigarette lighter or hardwired, however, these are not suitable for gliders due to their high-power draw.
• Power FLARM is low power and short range so suited to gliders but does not appear on an aircraft TCAS such as that fitted to ZLA.
• Cheaper ADS-B solutions which must have TSO approval. CASA currently does not mandate ADS-B for gliders but is examining the possibility of encouraging the voluntary use of ADS-B for all VFR aircraft if a low-cost solution is available.

The following publications provide information that may assist pilots avoid airprox events:

• Staying clear of other aircraft in uncontrolled airspace
• CAAP 166-1(3) provides advice in relation to making radio broadcasts to reduce the risk of coming in close proximity with other aircraft.

Aviation Short Investigations Bulletin - Issue 51

About this report Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2016 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) are procedurally assigned roles with specifically assigned duties at specific stages of a flight. The PF does most of the flying, except in defined circumstances; such as planning for descent, approach and landing. The PM carries out support duties and monitors the PF’s actions and aircraft flight path.
2. A Notice To Airmen advises personnel concerned with flight operations of information concerning the establishment, condition or change in any aeronautical facility, service, procedure, or hazard, the timely knowledge of which is essential to safe flight.
3. Landing somewhere other than the home airfield.
4. Note that the ATSB no longer uses the term ‘airprox’, but uses ‘near collision’ specifically for events outside controlled airspace, ‘where an aircraft comes into such close proximity with another aircraft either airborne or on the runway strip,…where immediate evasive action was required or should have been taken’.

What happened

On 1 March 2016, at 0640 Eastern Standard Time, a Tiger Airways Airbus A320 aircraft, registered VH-VNO (Figure 1), departed Brisbane, Queensland, on a scheduled passenger service to Melbourne, Victoria. On board were the captain, the first officer, four cabin crew members, and 63 passengers.

Figure 1: Tiger Airways Airbus A320, VH-VNO

Source: Victor Pody

At about 0900 Eastern Daylight-saving Time (EDT), when the aircraft was abeam Parkes, New South Wales, the cabin crew detected a strong odour in the rear of the cabin, and notified the captain. The cabin crew were unsure what the smell was, but they later described it as being like that of an extinguished cigarette. The odour dissipated soon after. About 10 minutes later, it returned and the cabin crew again advised the flight crew.

The cabin crew conducted their normal procedures in response to fumes in the cabin. This included filling bins with water to quench any possible fire, and checking lavatories, galley and the rear of the cabin in an attempt to find the source of the fumes. They also assessed whether there was any evidence of heat or fire.

As the cabin crew were unable to locate the source of the fumes or to find any heat source, the captain further asked them to check the overhead lockers and the floor above the cargo hold. They were still unable to find the source.

In accordance with standard operations with fewer than 115 passengers on board, the flight crew had the cabin air on the low flow setting. In the absence of smoke, they elected to set the airflow to high and see if that removed the odour from the aircraft. The fumes subsequently subsided.

At 0933 EDT, the aircraft was about 211 km north of Melbourne, at flight level 320.^[1] The flight crew had been cleared by air traffic control (ATC) to commence their descent for Melbourne. At that time, the cabin manager advised the captain that the fumes had returned and the odour was very strong. They also advised that three cabin crew members were feeling unwell, and that one had vomited.

The captain and first officer then reviewed the situation. They assessed that due to the cabin crew becoming ill, and the source of the fumes still unknown, they would contact ATC, declare a PAN,^[2] and request direct tracking to Melbourne. The crew also requested radar vectoring to reduce the workload required to reprogram the flight management system from the previously cleared route already entered into the system.

The cabin manager then advised the captain that the odour was still very strong. The captain recommended that all passengers be moved forwards away from the odour, which was at the rear of the cabin. The captain advised the cabin manager that they had declared an emergency and requested a direct track to Melbourne, and switched the seatbelt sign on.

The air traffic controller asked how many people were unwell and would require ambulance on arrival. The captain discussed with the cabin manager before responding that three cabin crew members and no passengers were unwell. The captain advised the passengers that fire vehicles and ambulance would be present for their arrival at Melbourne Airport.

During the approach, the captain advised ATC that they expected to conduct a normal landing and taxi clear of the runway via a high-speed taxiway. They would then stop and evaluate whether they would continue to taxi to the bay or whether an evacuation of the aircraft would be necessary.

To allow ease of access by emergency vehicles, the control of all runways had been handed from the tower controller to the surface movement controller. Aircraft movements were temporarily suspended, therefore no other aircraft were cleared to take-off or land at the airport. The aircraft landed at 0958 EDT.

The captain had directed the cabin manager to check the rear of the cabin after the aircraft taxied clear of the runway, and advise whether the odour was still there. The cabin manager reported that it was not. The captain then spoke to the commander of the aviation rescue and firefighting service, advised that they would continue to taxi to the bay, and requested that they follow the aircraft. The captain then requested a clearance from ATC to taxi to the bay. The captain also advised the passengers of the situation.

Once parked at the bay, the flight crew elected not to start the auxiliary power unit because they had been unable to determine the source of the fumes or to exclude any potential fire hazard. The captain advised the cabin crew and passengers that the cabin would go dark and the emergency lighting would come on. After shutting the engines down, the captain advised the fire commander that other than sick members of the cabin crew, everything was normal. The captain then left the cockpit to address the passengers, who disembarked normally. The fire crew did not find any source of fumes or fire, nor did a subsequent engineering inspection reveal the source.

Safety message

This incident demonstrates effective crew resource management techniques to deal with an abnormal and evolving situation.

In the event of smoke or fire, the emergency procedures are clear, time is of the essence, and a MAYDAY^[3] call is required. In this incident, however, the seriousness of the situation, the source of the fumes, and the potential risk of the situation, was difficult to assess. The crew’s decision to declare a PAN enabled air traffic control to provide assistance, without the immediacy that would have been required in the case of smoke or fire. As the situation unfolded, the flight crew continued to assess their options based on the information available. They made contingency plans in case things escalated or worsened, such as identifying the nearest airport for an emergency landing if required.

The third time the cabin crew reported the odour, and also became unwell, the flight crew had commenced descent, and the workload was very high. The flight crew demonstrated effective decision making and prioritisation based on the information available and the situation at hand. Throughout the approach to Melbourne, the flight crew communicated with each other, the cabin crew, the passengers, and air traffic control, which kept all parties informed and allowed appropriate assistance to be given.

Aviation Short Investigations Bulletin - Issue 49

About this report Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2016 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. At altitudes above 10,000 ft in Australia, an aircraft’s height above mean sea level is referred to as a flight level. Flight level 320 equates to 32,000 ft.
2. An internationally recognised radio call announcing an urgency condition which concerns the safety of an aircraft or its occupants but where the flight crew does not require immediate assistance.
3. Mayday is an internationally recognised radio call for urgent assistance.

Safety summary

What happened

On the evening of 19 February 2016, an Airbus A320 aircraft, registered PK-AXY and operated by PT Indonesia AirAsia was on a scheduled passenger service from Denpasar, Indonesia to Perth, Australia. During cruise, the captain’s flight management and guidance computer (FMGC1) failed. Due to the failure, the flight crew elected to use the first officer’s duplicate systems. For the aircraft’s arrival in Perth there was moderate to severe turbulence forecast below 3,000 ft with reports of windshear. The crew commenced an instrument landing system (ILS) approach to runway 21.

During the approach, the flight crew made a number of flight mode changes and autopilot selections, normal for an ILS approach with all aircraft operating systems available. However, some of those flight modes and autopilot selections relied on data from the failed FMGC1 and the autothrust system commanded increased engine thrust. The crew did not expect this engine response and elected to conduct a go-around. With an increasing crosswind on runway 21, the crew accepted a change of runway, to conduct a non-precision instrument approach to runway 06.

With the time available, the first officer programmed the new approach into his FMGC and conducted the approach briefing. During this period, the captain hand flew the aircraft and manually controlled the thrust. During the approach to runway 06, the crew descended the aircraft earlier than normal, but believed that they were on the correct flight path profile.

While descending, both flight crew became concerned that they could not visually identify the runway, and focused their attention outside the aircraft. At about that time, the approach controller received a “below minimum safe altitude” warning for the aircraft. The controller alerted the crew of their low altitude and instructed them to conduct a go-around. The crew then conducted another approach to runway 06 and landed.

What the ATSB found

The ATSB identified that the flight crew were unsuccessful in resolving the failure of the FMGC and had a limited understanding of how the failure affected the aircraft’s automation during the ILS approach. This resulted in the unexpected increase in engine thrust, which prompted a go-around.

The flight crew had a significant increase in workload due to the unresolved system failures, the conduct of a go-around and subsequent runway change. This, combined with the crew’s unfamiliarity and preparation for the runway 06 instrument approach, meant they did not effectively manage the descent during that approach.

The flight crew’s focus of attention outside the aircraft distracted them during a critical stage of flight. The crew did not detect that they had descended the aircraft below the specified segment minimum safe altitude.

The flight crew commenced their descent for the second runway 06 instrument approach later than normal, initially necessitating an increased rate of descent and at 300 ft the engine thrust reduced briefly to idle.

Safety message

Handling of approach to land is one of the ATSB’s SafetyWatch priorities. Unexpected events during the approach and landing can substantially increase what is often a high workload period. Adherence to standard operating procedures and correctly monitoring the aircraft and approach parameters provides assurance that the instrument approach can be safely completed. A go-around should be immediately carried out if the approach becomes unstable or the landing runway cannot be identified from the minimum descent altitude or missed approach point.

The occurrence

On the evening of 19 February 2016, an Airbus A320 aircraft, registered PK-AXY and operated by PT Indonesia AirAsia was on a scheduled passenger service from Denpasar, Indonesia to Perth, Australia. The aircraft was operated by two flight crew, four cabin crew and carried 96 passengers.

For the flight to Perth, the captain was the pilot flying (PF), with the first officer the pilot monitoring (PM).^[1] A late requirement to change aircraft delayed the departure of the flight by 2 hours and the updated arrival time into Perth was estimated to be about 2130 Australian Western Standard Time.^[2]

Departure and cruise

On departure from Denpasar Airport, the aircraft climbed to the cruise altitude of FL 370.^[3] The flight proceeded normally until the aircraft was just over an hour from Perth when, at approximately 2024, the crew noticed that the captain’s multipurpose control and display unit (MCDU1)^[4] had frozen and the captain’s navigation display (ND)^[5] had the advisory message MAP NOT AVAIL. In addition, the first officer’s MCDU (MCDU2) displayed the message INDEPENDENT OPERATION, which indicated to the crew that the captain’s flight management and guidance computer (FMGC1)^[6] had failed. Figure 1 depicts the location and interaction between the various equipment.

Figure 1: Schematic of A320 cockpit, depicting the location and interaction between various equipment

Source: Airbus Flight Crew Operating Manual

At the time of the FMGC1 failure, flight data indicated the aircraft was flying at a calibrated airspeed of 253 kt. A short time later, the captain recalled disengaging autopilot 1 (AP1)^[7] and engaging autopilot 2 (AP2).

The flight crew reported that in an attempt to resolve the issues associated with the frozen MCDU1 screen and apparent FMGC1 failure, they referred to the Quick Reference Handbook (QRH) and the Flight Crew Operating Manual (FCOM) but they determined that there was no specific action for the failures. Instead, as the first officer’s FMGC (FMGC2) appeared to be operating normally, they decided to continue to Perth using his ND and MCDU, because these utilised the functioning FMGC. At 2040, about 15 minutes after the failure occurred, the crew climbed the aircraft to FL 380. The remaining 30 minutes of the cruise was uneventful.

Pre-descent planning and approach

Prior to the descent, the flight crew reviewed and briefed the approach altitude minima, planned arrival route, weather, go-around procedures, as well as conducting other normal pre-descent activities. For the aircraft’s arrival in Perth, moderate to severe turbulence was forecast below 3,000 ft, with visibility greater than 10 km and no significant cloud below 5,000 ft. As the crew had not identified any specific procedure for managing the FMGC failure, and the first officer’s duplicate systems appeared to be operating normally, his MCDU was used to program the arrival procedure and instrument landing system (ILS)^[8] approach. The crew briefed that the first officer would take over as PF during the approach, as they believed it was better for the PF to have the functioning ND and MCDU.^[9] The crew later reported that they did not identify or conduct further investigation to determine how the FMGC failure may affect continued flight operation or the conduct of the approach.

At about 2115, the flight crew commenced descent into Perth to conduct the JULIM 2A standard instrument arrival^[10] and ILS approach to runway 21.^[11] As the aircraft descended through 9,000 ft, the captain took over the role of PM while the first officer became PF.

The flight crew selected managed lateral and vertical descent modes^[12] with AP2 selected. At about 2140 while descending through 5,000 ft, the crew received the first of three speed restrictions from air traffic control (ATC), which required a change from a managed speed mode to a selected speed mode,^[13] to control the aircraft’s speed.

At about 2143, with the approach mode armed, the flight crew engaged AP1 and received a CAB PR LDG ELEV warning.^[14] The warning was a result of engaging AP1 with an inoperative FMGC1.^[15] This was because with both autopilots engaged, FMGC1 took precedence over FMGC2. The data programmed into FMGC1 at that time did not include the landing and approach data required for the aircraft’s flight management system to determine the cabin’s pressurisation schedule for the descent and landing. To resolve the cabin pressure warning, the crew set the cabin pressure to manual and continued the approach.

ILS approach to runway 21 and go-around

See Figure 2 for a profile view of the runway 21 ILS approach. At about 2144, the aircraft intercepted the localiser and the glideslope for the runway 21 ILS (Appendix A contains the aircraft track overlaid on the approach chart along with the flight data for the approach). At 2144:38, after reducing the aircraft’s selected speed to 160 kt and establishing the aircraft on the ILS, the selected altitude on the flight control unit (FCU)^[16] was set to the go-around altitude, consistent with the operator’s standard operating procedure. A short time later, the flight crew elected to select a managed speed mode. This change resulted in the auto flight system attempting to capture the speed target contained in FMGC1 when it failed (which was 253 kt) and the autothrust system commanded an increase in engine thrust.

The flight crew recognised the increasing engine thrust and airspeed but they did not understand why it occurred. The captain told the first officer, ‘make a go-around’^[17] and then advised ATC that they were conducting a go-around. From 2144:57, there was a period of 25 seconds where dual sidestick control inputs occurred. During this time, the autopilot automatically disengaged and the captain disconnected the autothrust system.^[18] The recorded data indicated that neither the captain nor first officer pressed the priority takeover button^[19] during this period. The captain recalled that at about 2,500 ft, at the flap 0 speed, he stated ‘okay, my control’ and took over as PF with the first officer taking the PM responsibilities. Recorded data indicates the captain had sole control of the aircraft at 2145:24, at an altitude of about 2,500 ft.

Figure 2: Profile view of the runway 21 ILS approach with aircraft flight profile (blue). The aircraft was on the ILS profile until the increase in engine thrust and go-around

Source: Naviga (modified by the ATSB)

After the go-around and vectoring for the runway 06 VOR approach

After taking control of the aircraft, the captain reconnected the autopilot and autothrust. The recorded flight data indicates that the AP1 was engaged for 12 seconds, with the autothrust engaged and active for 10 seconds. The captain then decided to disconnect the autothrust to manually fly the aircraft, due to his uncertainty over the thrust increase during the previous approach and failure of FMGC1. The recorded data indicates that when the autothrust was disconnected the thrust lever was below the climb detent. This positioning of the thrust lever meant that it was unlikely the flight crew received a thrust lock (further information is provided in the Autothrust system sub-section in the Context).

At 2146, the first officer requested ATC provide radar vectors for another ILS approach to runway 21. ATC provided radar vectoring and issued clearance for the approach. However, about 4 minutes later, ATC advised the flight crew that the crosswind for runway 21 had increased to 22 kt, with gusts to 25 kt. Due to the increased crosswind, ATC offered the crew the option of conducting a VHF Omni Directional Radio Range (VOR)^[20] approach and landing on runway 06.^[21] At 2152, after confirming the crew’s preference to land on runway 06, ATC vectored them to the final approach track to conduct the VOR approach.^[22] The captain considered there was sufficient time to prepare for the approach, so did not perceive a need to enter a holding pattern to complete the briefing. At 2156, ATC informed the crew that a new ATIS was current and that there was moderate to severe turbulence below 3,000 ft.

The first officer later recalled programming FMGC2 for the VOR approach, and briefing the captain for the approach. The first officer also cross-referenced the information in the FMGC with his paper copy of the instrument approach chart. The captain stated that they conducted a short briefing instead of a full briefing because the situation was moving so quickly.

VOR approach to runway 06 and subsequent go-around

At 2200, ATC asked the flight crew twice if they were established on the 248 radial (which was the inbound track for the VOR procedure) and the first officer responded that they were 10 NM from the runway. ATC again asked the crew to confirm they were established, and the first officer replied stating, that they were ‘established on the inbound radial 068’.^[23] In response, ATC cleared the crew to conduct a VOR runway 06 approach, with 10 NM to touchdown. Shortly after, the captain recalled the first officer asking, ‘do we descend now captain?’ In response, captain initiated a descent from 2,500 ft when the aircraft was at 9 DME^[24] (Figure 3). Soon after, the landing gear was extended and the first officer selected 1,600 ft on the FCU for the next descent altitude limit. However, the operator’s Flight Crew Training Manual (FCTM) required that the go-around altitude be set on the FCU when established on final approach.^[25] Coincidentally, 1,600 ft was the corresponding segment minimum safe altitude for the runway 03 VOR approach, whereas the published altitude for that stage of the runway 06 approach was 1,900 ft.

The captain elected to continue manually flying the aircraft using his primary flight display (PFD) and the first officer’s ND, and manually controlling the engine thrust due to the apparent automation failures. The first officer continued to monitor the descent gradient and vertical speed, and later recalled believing that they were on the correct descent profile. However, for most of the descent, the aircraft’s rate of descent exceeded the recommended rate (700 ft/min) that was published on the approach chart for the aircraft’s groundspeed. The maximum recorded rate of descent briefly reached 1,550 ft/min.

As the approach continued, the flight crew became concerned that they could not see the runway, and both crew became focused on locating the runway. The first officer later reported that because of this, he was no longer monitoring the approach segment minimum safe altitude constraint or was aware of the aircraft’s below flight path deviation during the descent. Although the FCU altitude was set to 1,600 ft, the autopilots were not engaged and the aircraft descended through the selected altitude without capturing the target altitude.

To assist in locating the runway, the first officer asked ATC if they were on the ‘left side of the runway or right side of the runway’. At about the same time, the ATC radar displayed a minimum safe altitude warning (MSAW). In response, the approach controller instructed the flight crew to ‘go round, you are low, low altitude alert, go round’. The flight crew acknowledged the alert and immediately conducted a missed approach. The aircraft had descended to an altitude of 1,473 ft, before the climb was initiated, which was about 400 ft below the segment minimum safe altitude (Figure 3). Aircraft track and flight data for the approach is available in Appendix B.

Figure 3: Profile view of first runway 06 VOR approach with aircraft flight profile (blue). The flight profile shows the crew descending the aircraft below the 2,500 ft segment minimum safe altitude and continuing below the 1,900 ft segment minimum safe altitude before conducting a go-around.

Source: Naviga (modified by the ATSB)

Preparation and conduct of the second runway 06 VOR approach

After completing the go around, ATC radar vectored the flight crew for another VOR approach for runway 06. At around 2204, while the aircraft was being radar vectored, the captain requested that the first officer take over as PF so he could review the approach chart.

At about 2208, the flight crew engaged the autothrust. It remained engaged and active for about 4 minutes, before the FCU autothrust pushbutton was pressed at 2212 and the thrust lock became active until the thrust levers were moved from the climb detent.^[26] The crew re-engaged the autothrust about a minute later, and it remained active for 25 seconds before being disengaged, again via the FCU autothrust push button and resulting in a second thrust lock. The crew again moved the thrust levers clearing the thrust lock warning. The crew did not re-engage the autothrust for the remainder of the flight.

During the second VOR approach while the first officer was the PF, there were four occasions where the captain made sidestick control inputs. These inputs were between 2 and 3 seconds in duration and the recorded data indicates that they were not sufficiently large to activate the dual input alert. Neither of the flight crew could recall why the dual inputs occurred.

At about 2212, the captain requested ATC turn on the high intensity lighting on runway 06 as they were still having difficulty seeing the runway. ATC responded that there were no high intensity runway lights for that runway. At 2214, when the aircraft was at an altitude of 2,500 ft, inbound on the final approach track of the VOR and at about 8 DME, the captain took over as PF and the first officer resumed the PM role. At about the same time, ATC asked the crew if they had the runway in sight and informed them that the tower had increased the runway lighting intensity. Approaching 6 DME, the flight crew selected the FCU altitude to the minimum descent altitude for the VOR approach, again contrary to the operator’s procedure for conducting a non-precision instrument approach. The captain confirmed to ATC that the runway was in sight, and at about 5 DME, initiated descent from 2,500 ft to land on runway 06 (see Figure 4 for the profile view of their second approach to runway 06).

Due to the late commencement of the descent from 2,500 ft, the aircraft exceeded the recommended rate of descent (700 ft/min) for the aircraft’s groundspeed until 1,100 ft above the height of the runway threshold. In addition, the aircraft’s rate of descent was greater than 1,200 ft/min^[27] for a period of 40 seconds, from an altitude of about 2,100 ft to 1,200 ft. In this period, the rate of descent averaged 1,380 ft/min. When the aircraft was 1,000 ft above the height of the runway threshold, the rate of descent was below 700 ft/min. For a period of 22 seconds, from 430 ft to 120 ft above ground level (AGL), the aircraft’s vertical speed exceeded 700 ft/min and increased to a maximum of 1,100 ft/min. As this decent rate was below 1,200 ft/min, it did not require a callout by the first officer. At 300 ft AGL, the engine thrust reduced briefly to idle and at this point, the aircraft did not meet the stabilised approach criteria. Aircraft track and flight data for the approach is available in Appendix C.

Recorded flight data indicated dual sidestick control inputs occurred, one at 300 ft AGL for one second, then three times from 120 ft AGL until landing with durations of 3 to 5 seconds, these inputs would have resulted in a dual control input alert. However, the aircraft landed without further incident.

Figure 4: Profile view of second runway 06 VOR approach with aircraft flight profile (blue)

Source: Naviga (modified by the ATSB)

__________

1. Pilot flying (PF) and Pilot monitoring (PM) are procedurally assigned roles with specifically assigned duties at specific stages of a flight. The PF does most of the flying, except in defined circumstances; such as when planning for the descent, approach and landing. The PM carries out support duties and monitors the PF’s actions and aircraft flight path.
2. Australian Western Standard Time (AWST) was Coordinated Universal Time (UTC) +8 hours.
3. At altitudes above 10,000 ft in Australia, an aircraft’s height is measured in hundreds of feet above the standard atmospheric pressure datum of 1013.25 hPa. A height 37,000 ft above that standard pressure datum would be expressed FL 370.
4. The MCDU is used by the flight crew to enter flight planning into the flight management guidance system and can also display various flight navigation information.
5. The ND is a flight deck information display that is part of the electronic flight instrument system which displays a selected navigation information to the flight crew.
6. The FMGC provides aircraft navigation, lateral and vertical guidance and aircraft performance functions along a pre-planned flight route.
7. AP1 utilises data from FMGC1.
8. A standard ground aid to landing, comprising two directional radio transmitters: the localizer, which provides direction in the horizontal plane; and the glideslope, for vertical plane direction, usually at an inclination of 3°. This is a type of precision approach procedure, designed for 3D instrument approach operations.
9. It would have been possible for the captain’s ND to mirror the first officer’s, if their ND range and mode settings were the same.
10. A designated arrival route that links a significant point along the planned route to a point from which a published instrument approach procedure can be commenced.
11. Runway 21 was a precision approach runway, equipped with a category I ILS and visual approach aids.
12. Managed modes: When the aircraft is using managed targets, the Flight Management and Guidance System (FMGS) guides it along lateral and vertical flight paths and speed profiles computed by the Flight Management function (FM) from data in the MCDU. FM manages the guidance targets.
13. Selected modes: When the flight crew is using selected targets, the FMGS guides the aircraft along lateral and vertical flight paths and speed profiles to meet targets that the flight crew has selected manually on the FCU. The flight crew selects the guidance targets.
14. This warning indicates that the elevation of the landing airport is not available from the FMGC and consequently, the landing elevation must be manually selected.
15. With a single autopilot engaged the on-side FMGC is master. With both autopilots engaged, FMGC1 is master.
16. Flight control unit: Located on the cockpit glareshield and is the short-term interface between the flight crew and the FMGC. It is used to modify flight parameters and engage or disengage the autopilot and autothrust functions. Different guidance modes can be selected to change various targets (speed, heading, track, altitude, flight path angle and vertical speed).
17. A manoeuvre in which the flight crew discontinues the approach, increases engine thrust and reconfigures the aircraft to climb.
18. The autothrust was disconnected via the instinctive disconnect pushbutton on the thrust lever.
19. See further details in REF _Ref458419455 \h \* MERGEFORMAT Handover/takeover procedures section.
20. A ground-based navigation aid that emits a signal that can be received by appropriately-equipped aircraft and represented as the aircraft’s bearing (called a 'radial') to or from that aid.
21. Runway 06 was a non-precision approach runway, equipped with visual approach aids and a navigation aid at the airport provided directional guidance to complete a straight-in approach.
22. This was a non-precision approach procedure, designed for 2D instrument approach operations.
23. To fly inbound towards the VOR on the 248° radial, the crew needed to select 068° on the omni bearing selector.
24. Distance Measuring Equipment (DME) is a ground-based transponder station. A signal from an aircraft to the ground station is used to calculate its distance (in nautical miles) from the ground station.
25. This procedure was stipulated to avoid any unwanted autopilot capture of the selected target altitude.
26. See REF _Ref499907660 \h \* MERGEFORMAT Types of dual control inputs section for further information on the thrust lock condition and how crew are to respond to it.
27. During the final approach, the PM was required to call out ‘sink rate’, when the descent rate exceeded 1,200 ft/min.

Context

Personnel information

The captain

The captain was an Indonesian national and held an Indonesian Airline Transport Pilot Licence (ATPL) and had accumulated about 13,500 hours of aeronautical experience. Of these, about 9,250 hours were in command and about 5,200 hours were on the A320. The captain reported flying into Perth 3 to 4 times a month (including a night approach on 13 February 2016), and conducting a VHF Omni Directional Radio Range (VOR) approach on runway 06 previously, although not often. The captain had conducted a VOR approach on 18 February, the day prior to the occurrence and reported that he regularly conducted non-precision VOR approaches into his home port of Denpasar.

The captain’s proficiency check records indicated that during the 6-month period prior to the occurrence he had successfully completed a non‑precision approach during his cyclic simulator training. His training record for September 2015 recorded competency with managing a flight management and guidance computer (FMGC) or instrument failure. The captain had been assessed as meeting the requirements of the International Civil Aviation Organization (ICAO) English language proficiency^[28] at a level 4 standard.

The captain held the relevant Indonesian Certificate of Medical, First Class. That certificate required the pilot to wear corrective lenses for vision.

The first officer

The first officer, a Japanese national, held an Indonesian Commercial Pilot (Aeroplane) Licence (CPL) and had accumulated about 4,200 hours of aeronautical experience, with approximately 3,100 hours on the A320. The first officer had flown into Perth previously, but the occurrence flight was the first time he had conducted an approach into Perth at night, and it was his first runway 06 VOR approach. The first officer had conducted a VOR approach on the day prior to the incident and reported that he regularly conducted VOR approaches into Denpasar.

The first officer’s proficiency check records indicated that during the 6-month period prior to the occurrence he had successfully completed a non‑precision approach during his cyclic simulator training, including a non-precision approach and landing. The first officer had been assessed as meeting the requirements of the ICAO English language proficiency at a level 5 standard.

The first officer held the relevant Indonesian Certificate of Medical, First Class. That certificate required the pilot to wear lenses that correct for distance vision and possess glasses that correct for near vision.

Fatigue considerations

The flight crew reported feeling alert during the approaches. The ATSB reviewed their flight and duty times and 72-hour history prior to the occurrence, and found no evidence that they were likely to be affected by fatigue at the time of the incident.

Approach speed

The approach speed (VAPP) was computed for the crew by the flight management guidance computer (FMGC) and was based on the aircraft’s stall speed in the selected landing configuration, plus one third of the headwind component calculated from the airport wind entered by the flight crew into the FMGC.^[29]

When operating in managed speed mode and to assist with maintaining the energy state of the aircraft in changing wind conditions, the FMGC also continuously calculated a target speed that took into account the instantaneous wind being experienced by the aircraft. That resulted in the target airspeed displayed to the crew on their primary flight displays increasing with strengthening headwind gusts and decreasing with weakening headwind or tailwind gusts (but not below VAPP). If the wind entered by the crew into the FMGC was the same as the instantaneous wind, then the target speed would be VAPP.

For the non-precision approaches to runway 06, the crew were operating the aircraft without the autopilot, autothrust engaged and consequently, were in selected speed mode, and the target speed displayed to the flight crew was VAPP.

Weather

At the time of the approaches, moderate to severe turbulence was forecast below 3,000 ft and ATC had received reports of windshear below 1,600 ft (see Table 1).

Table 1: Actual weather conditions as reported by successive ATIS reports at around the time of the flight by PK-AXY

Analysis of the recorded information confirmed that turbulent conditions existed in the vicinity of Perth Airport at the time of the aircraft’s arrival. However, there were no activations of the aircraft’s windshear warning system^[31] nor activation of the aircraft’s low-speed flight envelope protection systems.

Airport beacon and runway 06 lighting

The control tower at Perth Airport was equipped with a rotating aerodrome beacon, used to indicate the location of the airport from the air. The beacon alternated between a white and green flashing light, once every 6 seconds.

Runway 06/24 was equipped with high intensity runway lighting, selectable by the tower controller to six stages of intensity. It was also equipped with medium intensity runway lighting, selectable to three stages of intensity. There was no high intensity approach lighting for runway 06 or other lighting^[32] to assist pilots identify the runway threshold, and nor was such lighting required. The high intensity runway lighting was selected to stage six (maximum intensity) for the crew’s second approach to runway 06.

Flight management guidance system failure

During the cruise, the flight crew received a red text message on the captain’s blank navigation display (ND) stating MAP NOT AVAIL and the first officer’s multipurpose control and display unit (MCDU2) displayed INDEPENDENT OPERATION. The captain’s ND remained inoperative, with the MAP NOT AVAIL message for the remainder of the flight.

The operator’s Flight Crew Operating Manual (FCOM) indicated that a ND may display a MAP NOT AVAIL message for several reasons:

• The MODE CHANGE or RANGE CHANGE message has been displayed more than 6 seconds, or
• The FMGC has failed, or
• The FMGC has delivered an invalid aircraft position.

The MCDU may display an INDEPENDENT OPERATION message when the FMGCs operate independently of each other. In this case, the flight directors (FD) will also operate independently from one another, with the captain’s FD receiving data from FMGC1. The flight crew had access to the aircraft’s Quick Reference Handbook (QRH) and FCOM during flight. These documents were available for the crew to reference in the event of an aircraft system issue, such as a flight management guidance system (FMGS) failure.

Quick reference handbook

Within the ‘Abnormal and emergency procedures’ section of the QRH, under auto flight there is only one listed procedure, ‘Loss of FMS Data in Descent / Approach (Severe Reset)’. This procedure would not have been relevant at the time of the failure, as it occurred during cruise. However, the computer reset table located in the ‘Miscellaneous procedures’ section was relevant. The crew could not explain why they were unable to locate the relevant information.

The Airbus A320 QRH included a procedure to address one locked or blank MCDU, and another for both MCDUs locked (or blank) or FMGC malfunction. The inflight procedure for one locked/blank MCDU was to ‘Pull the CB [circuit breaker] for the locked or blank MCDU and push it back after 10 s[econds]’. The QRH procedure for both MCDU’s locked / FMGC malfunction was:

Short FMGC Reset: …

In flight:

‐ FD 1(or 2) (OFF)

‐ Pull the CB [circuit breaker] of the affected FMGC

‐ Reset it after 10 s[econds].

Long FMGC Reset: …

In flight:

‐ FD 1(or 2) (OFF)

‐ Pull the CB of the affected FMGC

‐ Reset it after 15 min[utes].

Note: Consider a long FMGC reset only if a short FMGC reset has no effect.

In this instance, the crew recognised that the frozen MCDU1 screen and other system indications suggested a FMGC failure, but conducted neither procedure.

Flight crew operating manual

The FCOM contained a number of different types of FMGS failures and related procedures. These were located in the Procedures section, under ‘Supplementary Procedures’. The table of contents for the supplementary procedures contained a section on auto flight with a subsection related to ‘FMGS Reset and Other Abnormal procedures’. The crew could not explain why they were unable to locate the relevant information.

The failure mode that most closely represented the messages the crew received, related to one flight management system (FMS) failing and latching, but with the FMS continuing to send valid but frozen guidance targets, corresponding to the last valid targets sent before the FMS failed. With this type of failure, the autopilot and FD on the affected side may remain available, and the failed FMGC continues to guide the aircraft using the frozen targets. The FCOM stated that the procedure for this failure is to:

DISREGARD the information coming from the failed side

DO NOT USE the AP [autopilot] on the affected side

- If the AP is engaged on the affected side:

FLY the aircraft back on the intended path

ENGAGE the AP on the operative side, according to the Recommended Practice for

Autopilot Engagement (Refer to FCTM/OP-030 Autopilot/Flight Director)

- If time permits:

PERFORM a long reset of the failed FMGC

Refer to PRO-SUP-22-10 Manual FMGS Reset - Manual Reset of One FMGC

- If the failure affects FMGC1, and if the FMGC1 is still failed and latched before the approach:

DO NOT USE AP1 for the approach

- Before disconnecting AP2:

REVERT to selected speed

DISCONNECT A/THR [autothrust]

Note: It prevents the A/THR from switching to the frozen speed target of the failed FMGC1 when the flight crew disconnects the AP2 for landing.

Dual control inputs on the sidestick

On the A320, each pilot has a sidestick that they can use to manually control the pitch and roll attitude of the aircraft. When the autopilot is engaged, the sidesticks are locked in the neutral position. If a pilot applies a force above a specific threshold, the sidestick becomes free and the autopilot disengages.

The handgrip on the sidestick contains a takeover push button. This button can be used to disconnect the autopilot or takeover from the opposite sidestick.

When the pilots move both sidesticks simultaneously, neither takes priority, and instead the system adds the signals of both sidesticks, with the total limited to the maximum deflection of a single sidestick. If there is a simultaneous deflection of both sidesticks, with a 2º off-neutral deflection, the two green ‘sidestick priority’ lights in the instrument panel’s glareshield illuminate and there will be a ‘dual input’ voice message.

Either pilot can deactivate the other sidestick and take full control by pressing and holding down the priority takeover pushbutton. If the takeover pushbutton is depressed for 40 seconds, the other sidestick is deactivated. It can be reactivated by momentarily pressing the pushbutton of either sidestick.

There was no record of either the captain or the first officer pushing the priority takeover pushbutton during the ILS approach, go-arounds, or during the remainder of the flight.

Handover/takeover procedures

To transfer controls the FCOM stated that the crewmembers must use the following callouts:

‐ To give control: The pilot calls out “YOU HAVE CONTROL”. The other pilot accepts this transfer by calling out “I HAVE CONTROL”, before assuming PF duties.

‐ To take control: The pilot calls out “I HAVE CONTROL”. The other pilot accepts this transfer by calling out “YOU HAVE CONTROL”, before assuming PM duties.

In addition, the Flight Crew Training Manual (FCTM) stated that ‘If the PM (or Instructor) needs to take over, the PM must press the sidestick takeover pushbutton, and announce: “I have control”.’

Types of dual control inputs

Airbus has analysed dual sidestick input events that have been reported to them. In Safety First, The Airbus Safety Magazine (December 2006), Airbus reports that they have found that there are three types of occurrences:

The “Spurious” Dual Stick inputs

Typically due to an inadvertent movement of the stick by the PNF [PM].

For example when grabbing the FCOM or when pressing the R/T [radio].

A spurious dual stick input only marginally affects the aircraft behavior due to only time limited & small inputs.

The “Comfort” Dual Stick inputs

Typically due to short interventions from the PNF [PM] who wants to improve the aircraft’s attitude or trajectory:

These are generally experienced in approach, during a capture (altitude localizer), or in flare, and have minor effects on the aircraft’s altitude/trajectory.

However, as the PF is not aware of the PNF’s [PM] interventions, he may be disturbed and may counteract the PNF’s [PM] inputs.

The “Instinctive” Dual Stick Inputs

Typically due to a “reflex” action on the part of the PNF [PM] on the stick. This instinctive reaction may come about when an unexpected event occurs, like for example an AP disengagement, an overspeed situation or a dangerous maneuver.

Such interventions are more significant in terms of stick deflection and duration. Usually in such situations, both pilots push the stick in the same direction, which may lead to over control, a situation illustrated by the above occurrence.

Autothrust system

Autothrust can be activated when the thrust levers are in the climb detent and the flight crew press the autothrust pushbutton on the flight control unit (FCU). When active the autothrust controls either airspeed or engine thrust as appropriate.

The autothrust will disconnect if the:

• autothrust fails
• autothrust pushbutton on the FCU is pressed^[33]
• instinctive disconnect button on the thrust lever is pressed
• both thrust levers are set to idle.

The thrust lock function is activated when the thrust levers are in the climb detent and either of the flight crew pushes the autothrust pushbutton on the FCU, or the autothrust disconnects due to a failure. When this occurs, the thrust is locked at its level prior to disconnection. Moving the thrust levers out of the climb detent suppresses the thrust lock and associated warnings and gives the crew manual control with the thrust levers.

When the thrust lock function is active:

• THR LK flashes amber on the flight mode annunciator (FMA)
• electronic centralised aircraft monitor (ECAM) displays ENG THRUST LOCKED and this message flashes every 5 seconds
• ECAM displays THR LEVERS …... MOVE
• A single chime sounds and the master caution light flashes every 5 seconds.

Stabilised approach criteria

The FCOM specified that in visual conditions the approach should be stabilised at 500 ft above ground level (AGL). In order to be stabilised all of the following conditions had to be verified and meet at the stabilisation height:

• the aircraft is on the correct lateral and vertical flight path
• the aircraft is in the desired landing configuration
• the thrust is stabilised, usually above idle, in order to maintain the target approach speed along the desired final approach path
• there is no excessive flight parameter deviation.

If the aircraft was not stabilised by 500 ft AGL in visual conditions the crew were required to conduct a go-around, unless the flight crew estimated that only small corrections were necessary to rectify minor deviations from stabilised conditions due, amongst others, to external perturbations.

Non-precision instrument approach

The Flight Crew Training Manual (FCTM) indicated that the overall strategy for conducting a non-precision instrument approach was to fly it ‘ILS alike’ with the same mental image or representation and similar procedure. The use of autopilot was recommended for all non-precision approaches as it reduced flight crew workload and facilitated monitoring of the procedure and the aircraft’s flight path. If the flight crew correctly programmed the FMGC, the autopilot and FD would ensure lateral and vertical managed guidance was available to conduct the approach.

Depending on whether the autopilot was being used, the PF either monitored the progress of the approach or provided the manual inputs to manage the aircraft’s lateral and vertical navigation, normally using the guidance targets displayed on the FD. In addition, the FCTM indicated that when conducting a non-precision instrument approach, the PF ‘should expand the instrument scan to include outside visual cues’ as the aircraft approached the minimum descent altitude.

The operator’s FCTM stipulated setting the go-around altitude on the FCU when the aircraft was established on final approach and if in a selected mode, the current aircraft altitude was below the missed approach altitude. The FCTM also prohibited setting the minimum descent altitude as the target altitude on the FCU, which could cause a spurious altitude capture and destabilisation of the approach at a critical stage.

Communication and standard callouts

The FCTM stated that if, for any reason, one parameter deviates from stabilised approach conditions, the PM will make the appropriate callout as follows:

Altitude callouts were also to be made by the PM through to landing. Neither the captain nor first officer recollected any callouts being made.

Related occurrences

A search of the ATSB database for similar occurrences in the last 5 years was conducted. The search did not identify any occurrences where a flight crew had difficulty locating Perth Airport or the runways in CAVOK conditions.

The database contained six occurrences where an enhanced ground proximity warning system (EGPWS) glideslope warning had occurred during the runway 06 VOR approach. Of these, four related to the inadvertent selection of the ILS for another runway. There were a further 25 cases of glideslope warnings where the runway was not identified in the occurrence details. There was one record of an EGPWS terrain warning occurring at Perth although the approach involved was not identified. The occurrence details in that case suggested the terrain warning was spurious. There were no occurrences recorded in the ATSB occurrence database where an minimum safe altitude warning was issued by ATC during a runway 06 approach.

ATSB investigation AO-2010-027

On 4 and 29 May 2010, an Airbus A330 aircraft, operated by AirAsia X was involved in two separate occurrences on approach to the Gold Coast, Queensland, where the aircraft were descended below the segment minimum safe altitudes.^[34] On both occasions, there was low cloud and reduced visibility on arrival at the Gold Coast. The ATSB found that these events were indicators of a minor safety issue regarding the operator's training of its flight crews, in relation to non-precision approaches.

ATSB investigation AO-2011-086

On 24 July 2011, a Boeing Company 777-3D7 aircraft, operated by Thai Airways, was conducting a runway 34 VOR approach to Melbourne Airport, Victoria.^[35] During the approach, the tower controller observed that the aircraft was lower than required and asked the flight crew to check its altitude. The tower controller subsequently instructed the crew to conduct a go-around. However, while the crew did arrest the aircraft’s descent, there was a delay of about 50 seconds before they initiated the go-around and commenced a climb to the required altitude.

The ATSB established that the pilot in command may not have fully understood some aspects of the aircraft’s automated flight control systems and probably experienced ‘automation surprise’ when the aircraft pitched up to capture the VOR approach path. As a result, the remainder of the approach was conducted using the autopilot’s flight level change mode, where the aircraft’s rate of descent may be significantly higher than required. In addition, the flight crew inadvertently selected a lower than stipulated descent altitude, resulting in descent below the specified segment minimum safe altitude for that stage of the approach.

ATSB investigation AO-2011-076

On 30 June 2011, an Airbus A320 aircraft, operated by Tiger Airways Australia conducted a go-around procedure at Avalon Airport, Victoria, after an unsuccessful approach to runway 18.^[36] While re-positioning the aircraft for another approach, this time on the reciprocal runway 36, the aircraft descended without further ATC clearance to below the assigned altitude. The flight crew was subsequently cleared for a visual approach; however, the aircraft descended to below the minimum permitted altitude of 2,000 ft, to 1,600 ft. The ATSB investigation found that the flight crew’s understanding of the aircraft’s position during the second approach was probably influenced by the workload associated with the runway change.

ATSB investigation AO-2016-124

On 11 September 2016 an Airbus A330 aircraft, operated by AirAsia X descended below the segment minimum safe altitude, near the Gold Coast Airport, Queensland.^[37] The flight crew were cleared to conduct a RNAV-Z (GNSS) instrument approach to runway 14 at Gold Coast Airport in visual meteorological conditions. During the approach, the aircraft was observed to descend below a segment minimum safe altitude. At the time of publication, the ATSB investigation was ongoing.

__________

28. ICAO has defined six levels of language proficiency, the top three levels (4, 5 and 6) are acceptable for operational flight crew. Level 4 (operational) requires retesting every 3 years, level 5 (extended) requires retesting every 6 years and level 6 (expert) does not require further testing.
29. The calculation of VAPP by the FMGC was limited to the stall speed plus 5 kt as a minimum and stall speed plus 15 kt as a maximum. The FMGC-calculated value of VAPP can also be modified by the flight crew.
30. Ceiling and visibility OK, meaning that the visibility, cloud and present weather are better than prescribed conditions. For an aerodrome weather report, those conditions are visibility 10 km or more, no significant cloud below 5,000 ft or cumulonimbus cloud and no other significant weather within 9 km of the aerodrome.
31. Windshear detection is provided during takeoff and landing. During landing, the system is active from 1,300 ft to 50 ft radio altitude, with wing slat/flap selected.
32. Such lighting could include runway lead-in lighting, runway threshold identification lights and sequenced flashing lights.
33. This is not a recommended method of disconnecting the autothrust, as it will result in the engines entering the thrust lock mode.
34. ATSB AO-2010-027, Operational non-compliances - Airbus A330, 9M-XXB, Gold Coast Airport, Queensland, 4 and 29 May 2010. Available from www.atsb.gov.au.
35. ATSB AO-2011-086, Operational non-compliance involving Boeing 777, HS-TKD, 15 km south Melbourne Airport, Vic, 24 July 2011. Available from www.atsb.gov.au.
36. ATSB AO-2011-076, Descent below the minimum permitted altitude, Airbus A320, VH-VNC, 15 km SSE of Avalon Airport, Vic, 30 June 2011. Available from www.atsb.gov.au.
37. ATSB AO-2016-124, Decent below segment minimum safe altitude involving Airbus A330-343X, 9M-XXI, near Gold Coast Airport, Qld, on 11 September 2016. On completion, a copy of the investigation report will be available from www.atsb.gov.au.

Safety analysis

During the flight, the captain’s flight management guidance computer (FMGC1) failed. The flight crew’s response to this and their utilisation of FMGC1 during the runway 21 instrument landing system (ILS) approach, resulted in an unexpected increase in engine thrust and subsequent go-around. After conducting the go-around, they were required to change runways due to increased crosswind and conduct a VHF Omni Directional Radio Range (VOR) approach onto runway 06. During this VOR approach, air traffic control (ATC) received a minimum safe altitude warning, prompting the controller to alert the crew of their low altitude and instructed them to conduct a go-around. Subsequently, the flight crew made another approach for runway 06 and the aircraft landed safely.

The following analysis discusses the crew’s understanding and management of the FMGC failure, their systems knowledge, and the human performance factors that affected the management of the approaches, which resulted in two go-arounds.

Crew response to the flight management guidance system failure

During the cruise, when the captain identified that his multipurpose control and display unit (MCDU1) had frozen and the navigation display (ND) map became unavailable, the flight crew correctly identified an FMGC1 failure. However, they could not locate any information about how to resolve it in the aircraft’s manuals. Had they found the MCDU and FMGC reset procedures in the Quick Reference Handbook (QRH), the crew may have been able to rectify the failure. This would have provided normal operation of the captain’s navigation display ND and MCDU. With an operational MCDU, the captain would have been able to input the approach and aerodrome data into the FMGC1 and the unexpected increase in engine thrust would not have occurred.

Additional information on the failure mode was available in the Flight Crew Operating Manual (FCOM), but the flight crew did not find this information in that manual. The investigation was unable to determine why the crew did not locate the relevant information. This failure to find and action the QRH and FCOM, meant the aircraft systems remained degraded for the rest of the flight.

Understanding of system interactions and subsequent crew decision making during the runway 21 ILS approach

The flight crew discussed the FMGC1 failure during their first approach briefing and decided to use the first officer’s functioning MCDU (MCDU2) and ND on the descent. Because the crew had not previously found the information in the FCOM relating to the failure, they did not understand how it could affect the interactions between the aircraft systems and hence the conduct of the descent. They were therefore unaware that both autopilots, and in particular autopilot 1 (AP1), should not have been engaged during the instrument approach. The reason for not engaging AP1 was that FMGC1 took primacy over the first officer’s FMGC (FMGC2) when both autopilots were used and the data in FMGC1 had frozen at the time of failure.

When the flight crew engaged AP1 during the first approach, they did not recognise that the subsequent cabin pressure fault was related to the engagement of AP1 and its utilisation of FMGC1 data. Additionally, the crew did not realise that the FMGC1 target speed at the time of failure (253 kt) would be utilised when the speed mode was changed from a selected mode (which had a target speed of 160 kt at the time), to a managed mode after AP1 was engaged.

The issue of flight crew understanding systems interactions is not limited to this occurrence. In response to the increase in incident and accident reports of flight crew experiencing difficulties using flight path management systems, a United States Federal Aviation Administration-led Flight Deck Automation Working Group analysed several data sources to produce findings and recommendations for the use of automation on modern flight decks. The working group found that operators had concerns with the level of flight crew skills required for managing automated system malfunctions and/or failures. The working group was cognisant that it was impossible to train pilots in all possible malfunction situations or failure scenarios. They stated that pilots needed to be prepared to recognise the results of partial and complete system failures and intervene appropriately (PARC/CAST Flight Deck Automation Working Group, 2013).

Crew’s understanding of systems interactions and dual control inputs

In this case, the flight crew’s lack of understanding of how the systems interacted led to inappropriate system selections and resulted in the increase in engine thrust. Although the failure of FMGC1 had not been resolved by the flight crew prior to the aircraft commencing descent, FMGC2, MCDU2, autopilot 2 (AP2) and engine autothrust were all capable of normal operation and could have been used to complete the approach normally.

Although the flight crew elected to conduct a go-around when the engine thrust unexpectedly increased, there was a period of 25 seconds where dual sidestick control inputs occurred, prior to the captain taking over control of the aircraft. These dual control inputs indicate a level of confusion and lack of communication regarding conduct of the go-around and about which pilot was in control of the aircraft. There were other instances of dual control inputs of short duration (less than 5 seconds). While these inputs did not affect the flight, there have been other instances where sustained dual control inputs have had a detrimental effect on the control of the aircraft.

Reaction to automation functionality and decision making

Following the go-around and without understanding the reason for the increase in engine thrust or the effect the FMGC1 failure had on the system, the flight crew briefly re-engaged AP1. Due to doubts about the functionality of the automation, the captain then elected to reduce the level of automation, and manually fly the aircraft. This decision presented as being intuitively derived from patterns of behaviour the captain had used successfully in the past. The decision had the effect of removing the potentially problematic automation, but it also increased the crew’s workload.

Researchers (Klein 2008, Kahneman, 2011) have stated that, in time-constrained environments, individuals can make decisions using intuitive reasoning where the steps are often unconscious and based on pattern recognition. For intuitive or naturalistic decision-making, an experienced individual will identify a problem situation as similar or familiar to a situation they have dealt with before and will extract a plan of action from memory. If time permits, they will confirm their expectations prior to initiating action. If time does not permit, actions will need to be initiated with uncertainty that may result in a poor decision.

Crew workload after the initial go-around

Workload has been defined by Orlady and Orlady (1999) as:

…reflecting the interaction between a specific individual and the demands imposed by a particular task. Workload represents the cost incurred by the human operator in achieving a particular level of performance (p.203).

The available cognitive resources are finite and will vary depending on the experience and training of the individual as well as the level of stress and fatigue experienced. Workload is managed by balancing task demands such that, when workload is low, tasks are added and when workload becomes excessive, tasks are shed (Orlady and Orlady, 1999). Tasks, such as internal and external communication, can be shed in an efficient manner by eliminating low priority tasks or they can be shed inefficiently by abandoning important tasks. The task demands can be influenced by the mental and physical requirements of the task, as well as the time available (Wickens and Hollands, 2000).

Factors increasing crew workload

After the first approach, the flight crew’s workload increased substantially with the following conditions:

• although the engine autothrust, AP2 and FMGC2 were still operating normally, the crew became uncertain about the automation’s functionality and elected to manually control the engine thrust and fly the aircraft using raw data.
• the crew had limited experience, outside of simulator sessions, flying approaches manually.
• the turbulent conditions increased the attention required by the captain to maintain desired heading, pitch attitude and airspeed.
• the unexpected runway change meant the crew needed to program the approach into the first officer’s MCDU, review the approach and conduct a briefing prior to the approach.
• the unexpected runway change and reduced timeframes limited the time available for the crew to review the approach charts.
• the captain’s ND was still in operating in a degraded mode and was not displaying lateral tracking guidance for the VOR approach nor the information from the distance measuring equipment (DME). For that information, the captain needed to refer to the first officer’s ND on the other side of the cockpit instrument panel.
• the captain’s flight director (FD) was still referencing the frozen FMGC1 and was not providing valid FD attitude guidance targets.
• while the crew were experienced in flying non-precision VOR approaches, they had limited experience flying the Perth runway 06 VOR approach at night. The first officer reported never having flown the approach before.

Recorded data indicates that there was 8 minutes from making the decision to conduct the VOR approach to when the flight crew confirmed they were established on the approach, at 10 NM. The limited time available to prepare for the approach, combined with the degraded systems, would have further increased their workload.

Effect of increased workload

Workload and time pressure can lead to a reduction in the number of information sources an individual may access, and the frequency or duration of time these sources are checked (Staal, 2004). Amongst other effects, a high workload can result in individuals not understanding the implications of the information they are presented with.

In this occurrence, the captain’s workload was increased due to the decision to hand-fly the aircraft using the first officer’s ND for lateral tracking guidance and distance information during the VOR approaches. This increased workload made it more likely that, in the visual conditions, he would try and continue the approach using external visual reference.

The flight crew’s workload impacted their ability to manage the approaches and was evidenced by the shedding of tasks, such as:

• reviewing the approach charts,
• monitoring of the flight profile,
• descending the aircraft without confirming the aircraft position,
• neither crew member observing the DME distance,
• breakdown in the crews’ use of standard operating procedures, such as selecting altitudes other than the missed approach altitude on the flight control unit, while conducting the non-precision instrument final approach.

Had the flight crew elected to hold and prepare prior to conducting the approach, they may have reduced their workload, improved their preparations and conducted a thorough briefing prior to conducting the unfamiliar approach.

Preparation and conduct of the first runway 06 VOR approach

During the first runway 06 VOR approach, the flight crew’s focus of attention was outside the aircraft, attempting to locate the runway. Although the crew were conducting the instrument approach in visual conditions, more attention should have been given to maintaining the aircraft on the prescribed instrument approach flight path profile, until reference was made to the runway landing environment and/or the instrument approach was discontinued. The following content explains how the crew's ability to monitor and maintain the correct flight profile and altitude during the approach was likely hindered. This resulted in the aircraft descending below the specified minimum safe altitude without being detected by the crew.

Crew focus of attention

The captain could not identify the runway and requested assistance from the first officer. Both flight crew then focused on locating the runway, with neither appearing to monitor the aircraft’s flight profile. The crew first became aware of the altitude constraint and that the aircraft had descended below it when advised by ATC. This indicates that both crew were distracted and neither was monitoring the approach at this time. Further indications that the crew was distracted from monitoring the approach included:

• the captain took the first officer’s question about when to initiate descent as a prompt to descend without confirming the aircraft’s position.
• the lack of detection that the aircraft was descended early.
• the first officer thought aircraft was on correct profile because he observed an appropriate initial descent rate.
• the descent rate increased substantially above that necessary for a 3-degree approach.
• neither crew member observed the DME distance, after initiation of descent.
• the first officer could not recall communicating altitude or distance information during the approach.

Crew ability to monitor the approach

Monitoring is an extensive set of behavioural skills that all flight crew are expected to have. This skill set is specified in the aircraft operator’s standard operating procedures and involves the primary roles of monitoring the aircraft’s flight path, communications and the activities of the pilot flying. The UK Civil Aviation Authority (UK CAA) (2013) has defined monitoring as:

The observation and interpretation of the flight path data, configuration status, automation modes, and on-board systems appropriate to the phase of flight. It involves a cognitive comparison against the expected values, modes, and procedures. It also includes observation of the other crew member and timely intervention in the event of deviation. (p.9)

The difficulties that flight crew have with maintaining effective monitoring are thought to be due to not directly controlling the system being monitored. Humans are inherently poor at maintaining vigilance for infrequent events and equipment failures in modern airline operations are rare. Flight crew rarely receive direct feedback on the effectiveness or consistency of their monitoring unlike the feedback they would receive when they may fly an aircraft manually (UK CAA, 2013).

Researchers (Dismukes & Berman, 2010) found that in most instances where flight crew were failing to monitor the aircraft state or position, there were competing concurrent task demands on the crew’s attention. Humans have a limited ability to divide attention amongst tasks and generally, have to switch attention back and forth between tasks. This leaves an individual vulnerable to losing track of the status of one task while being engaged in another.

Other factors affecting awareness of the flight profile

Believing they were on the correct profile, based on the vertical speed the first officer observed early in the descent, combined with the night conditions, and unfamiliarity with the approach reduced the visual cues outside of the cockpit available to the crew regarding the aircraft’s position. The reduced external visual cues along with the crew not utilising the available internal visual cues, such as the course deviation indicator, distance information and multifunction display, led to the crew not understanding where they were on the flight profile or where they were with respect to the runway.

Communication during the approach

The flight crew missed opportunities to identify the early descent, higher than normal rate of descent and descent below the segment minimum safe altitude because they were focused outside the cockpit rather than monitoring their primary flight instruments. The first officer did not provide the captain with the standard altitude and distance callouts, nor with an alert about the rate of descent, which resulted in the aircraft flying below the flight profile. This potentially reduced the captain’s awareness of the deviations from the standard approach and limited his ability to correct it. That communication was particularly important given that the crew had not optimised the aircraft’s remaining systems, with the captain attempting the approach without his ND and FD attitude guidance targets on his primary flight display.

Preparation and conduct of the second runway 06 VOR approach

During the vectoring for the second runway 06 VOR approach, the captain took on the pilot monitoring role. This gave the captain the opportunity to review the approach data and familiarise himself with the required flight profile. The captain returned to the role of pilot flying soon after the initial approach fix and elected to obtain visual contact with the runway prior to initiating the descent. Due to the late descent, the aircraft’s rate of descent was greater than 1,200 ft/min for a period of the approach (although it was stabilised by 1,000 ft).

Due to the captain manually controlling the engine thrust and the turbulence, the engine thrust was briefly at idle at about 300 ft above ground level, which did not meet the stabilised approach criteria and was coincident with an increasing rate of descent. Unstable approaches are known to increase risks in landing, although in this instance the landing was completed without further incident.

Findings

From the evidence available, the following findings are made with respect to the operational event involving an Airbus A320, registered PK-AXY and operated by PT Indonesia AirAsia that occurred 17 km west-south-west of Perth Airport, Western Australia on 19 February 2016. These findings should not be read as apportioning blame or liability to any particular organisation or individual.

Safety issues, or system problems, are highlighted in bold to emphasise their importance. A safety issue is an event or condition that increases safety risk and (a) can reasonably be regarded as having the potential to adversely affect the safety of future operations, and (b) is a characteristic of an organisation or a system, rather than a characteristic of a specific individual, or characteristic of an operating environment at a specific point in time.

Contributing factors

• The flight crew’s diagnosis of the captain’s failed flight management guidance computer was accurate, but after they did not find the procedure to follow, the failure was not appropriately managed. This resulted in degraded systems capability for the approach.
• The flight crew had a limited understanding of how the captain’s failed flight management guidance computer would affect the use of the aircraft’s automated systems during the instrument landing system approach. This meant that their decision to engage autopilot 1 resulted in the frozen data stored in the failed guidance computer being utilised by the auto flight system, leading to an unexpected increase in engine thrust and prompted the crew to conduct a missed approach.
• The unresolved system failures, combined with the conduct of a missed approach procedure and the subsequent runway change increased the flight crew's workload. This likely reduced their ability to analyse the actual extent to which their automation was degraded, and effectively manage the subsequent approaches.
• During the first runway 06 non-precision approach, the flight crew’s focus of attention was outside the aircraft, attempting to locate the runway. This distraction, along with their unfamiliarity with the approach procedure, inhibited their ability to monitor and maintain the correct flight profile and altitude during the approach. The flight crew did not detect that the aircraft had descended below the segment minimum safe altitude for that stage of the approach.

Other safety factors

• During the flight, multiple dual control inputs occurred, which in other circumstances have resulted in aircraft responding in an unexpected manner.
• The aircraft's flight path profile was not adequately monitored or communicated between the flight crew during the non-precision instrument approaches to runway 06. This reduced the captain’s awareness of any deviation from the prescribed approach and limited his ability to correct it.
• The second runway 06 non-precision instrument approach did not meet the stabilised approach criteria for a short period during the final approach, increasing the safety risk of the landing.

Safety issues and actions

All of the directly involved parties were provided with a draft report and invited to provide submissions. As part of that process, each organisation was asked to communicate what safety actions, if any, they had carried out or were planning to carry out.

Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following proactive safety action in response to this occurrence

As a result of this occurrence, PT Indonesia AirAsia have taken the following proactive safety action:

• Implemented additional classroom sessions on aircraft line-check into the re-training program.
• Incorporated the incident as a subject of the SPOT (Special Orientation Training) in the simulator syllabus.

Sources and submissions

Sources of information

The sources of information during the investigation included the:

• aircraft operator, PT Indonesia AirAsia
• aircraft flight crew
• provider of air traffic services, Airservices Australia
• manufacturer of the aircraft, Airbus.

References

Dismukes, R.K., and Berman, B. (2010). Checklists and monitoring in the cockpit: Why crucial defences sometimes fail. NASA/TM-2010-216396, NASA Ames Research Centre, Moffett Field, CA.

Kahneman, D. (2011). Thinking, fast and slow. Allen Lane: London, UK.

Klein, G. (2008). Naturalistic decision making. Human Factors, Vol 50, No.3, pp.456-460.

Orlady, H.W., and Orlady, L.M. (1999). Human factors in multi-crew flight operations. Ashgate: Aldershot, UK.

PARC/CAST Flight Deck Automation Working Group. (2013). Operational use of flight path management systems. US Federal Aviation Administration.

Staal, M.A. (2004). Stress, cognition, and human performance: A literature review and conceptual framework. NASA/TM-2004-212824, NASA Ames Research Centre, Moffett Field, CA.

UK Civil Aviation Authority. (2013). Monitoring matters: Guidance on the development of pilot monitoring skills. Loss of Control Action Group, CAA Paper 2013/02, West Sussex, UK.

Wickens, C.D., and Hollands, J.G. (2000). Engineering psychology and human performance (Third edition). Prentice Hall: New Jersey, US.

Submissions

Under Part 4, Division 2 (Investigation Reports), Section 26 of the Transport Safety Investigation Act 2003 (the Act), the Australian Transport Safety Bureau (ATSB) may provide a draft report, on a confidential basis, to any person whom the ATSB considers appropriate. Section 26 (1) (a) of the Act 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 PT Indonesia AirAsia, the aircraft flight crew, Airservices Australia, the Civil Aviation Safety Authority, Airbus and the French Bureau d'Enquêtes et d'Analyses pour la sécurité de l'aviation civile.

Submissions were received from PT Indonesia AirAsia, Airservices Australia, the Civil Aviation Safety Authority, Airbus and the French Bureau d'Enquêtes et d'Analyses pour la sécurité de l'aviation civile. The submissions were reviewed and where considered appropriate, the text of the report was amended accordingly.

Appendices

Appendix A – Runway 21 ILS approach, aircraft track and flight data

Figure A1: Runway 21 ILS approach with aircraft track (blue)

Source: Naviga (modified by the ATSB)

Figure A2: Flight data showing autopilot and mode selections with a resulting thrust and speed increase during the runway 21 ILS approach. The descent depicted is from 3,000 ft to 2,000 ft.

Note:

1. At 2143:04 AP1 was engaged

2. At 2144:37 the auto speed was changed to a managed mode resulting in an increase in the target airspeed (to 253 kt)

3. At 2144:51 the go-around was initiated

Source: ATSB

Appendix B – First runway 06 VOR approach, aircraft track and flight data

Figure B1: First runway 06 VOR approach with aircraft track (blue) and approximate location of go-around (red cross)

Source: Naviga (modified by the ATSB)

Figure B2: Flight data from first runway 06 VOR approach from 2,500 ft to 1,473 ft

Note:

1. At 2200:45 descent initiated

2. At 2201:57 the go-around was initiated, at an altitude of 1,473 ft

The target CAS is the speed target that would appear on the speed tape of the primary flight display.

Source: ATSB

Appendix C – Second runway 06 VOR approach, aircraft track and flight data

Figure C1: Second runway 06 VOR approach with aircraft track (blue)

Source: Naviga (modified by the ATSB)

Figure C2: Flight data from second runway 06 VOR approach from 2,500 ft to landing

Note:

1. At 2215:20 descent was initiated, at about 5 DME

Source: ATSB

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 2018 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

On 14 February 2016, at about 0945 Eastern Standard Time (EST), the pilot of a Cessna R182 aeroplane, registered VH-PFZ, was returning to a private airstrip near Ingham aircraft landing area (ALA), Queensland. The pilot, who was the only person on board, had just completed a routine one-hour property inspection and decided to complete the flight with some practice touch and go circuits.

The pilot reported that the weather was fine, with minimal wind and a temperature of about 30 °C.

The pilot approached the circuit with the aircraft in the same configuration used for the inspection flight. This was with 20 inches of manifold pressure, the propeller set at 2,000 revolutions per minute (RPM), and the landing gear retracted.

The pilot joined downwind for runway 22 as per their normal procedure, and conducted their downwind checks. However, they inadvertently omitted one of the checks. Although they extended the landing gear, they did not return the pitch control to the HIGH RPM (full fine) position. The pilot continued with the approach, and selected full flap, but again omitted the pre-landing checks on final approach. This oversight left the pitch control lever at about 2,000 RPM.^[1]

The pilot described the approach and initial touchdown as a little faster and higher than normal, with the touchdown point about 300 m into the 1,100 m airstrip (Figure 1).The aircraft ballooned slightly. At about 10-15 ft above ground level, the pilot commenced a go-around and applied full throttle, with the propeller remaining at 2,000 RPM. With an airspeed of 64 kt, the pilot assessed there was sufficient airspeed to climb out, so retracted all of the flap and then the landing gear.

Figure 1: Initial touchdown point on runway 22, and VH-PFZ (far end)

Source: Pilot

However, the aircraft began to sink, and the nose dropped. Moments later, the main landing gear struck the ground. This second ‘touchdown’ was about 265 m beyond the first, (about 565 m along the airstrip). The pilot attempted to keep the nose of the aircraft raised. However, the propeller struck the ground and the pilot realised that the nose wheel had retracted, so closed the throttle. The aircraft continued to skid along the runway. The propeller stopped rotating when the aircraft had travelled about another 77 m. The aircraft then continued to slide sideways, and the right main landing gear retracted (Figure 2). The pilot was not injured, but the aircraft sustained substantial damage.

Figure 2: VH-PFZ showing retracted nose wheel and right landing gear, and damaged propeller

Source: Pilot

Pilot experience and comments

The pilot had attained almost 4,000 hours of flight experience, 2,800 of which were in VH-PFZ.

The pilot reported that there had been no particular issues affecting the flight on the day, the weather was good, and the inspection flight had been enjoyable. However, the temperature was 30 °C, which increased the density altitude.^[2] The pilot could not attribute any particular reason for the checklist oversight.

The pilot reported that during their early flying training, when they had been training for a go-round, they had been instructed to retract all the flap with their right hand, then immediately move their right hand onto the landing gear selector, and retract the landing gear. The pilot commented that ‘the flap travelling up reduced the lift being produced, and the landing gear retracting reduced the drag. These two actions balance out each other.’ The pilot qualified this statement by stating that this technique should only be attempted once a positive rate of climb has been achieved. On this occasion this had not occurred.

The pilot consulted the aircraft’s performance charts post-accident. With the correct propeller (2,400 RPM) and manifold pressure settings, the aircraft delivers the maximum brake horsepower (BHP).^[3] For any of the take-off configurations (see POH data below), it is a requirement to have the propeller in the full fine position of 2,400 RPM. The charts do not cater for propeller settings of 2,000 RPM. The pilot reasoned that landing further along the runway than normal may have contributed to a slight rushing of the go-round sequence. It is possible, that this mindset also contributed to retracting the flap and landing gear prior to achieving a positive rate of climb.

The pilot also reported that possibly being too comfortable in the aircraft, and the reliance on its performance, had created an expectation that all would be well.

The pilot summarised that engine RPM was insufficient to produce enough thrust to maintain altitude and climb at the critical point of change in aircraft configuration, while retracting the flap and landing gear.

Cessna R182 Pilot operating handbook (POH)

Information from a generic 1981 Cessna R182 pilot operating handbook stated that the propeller control should be moved to HIGH RPM (full fine) prior to landing.

The Normal Take-off checklist included:

• Propeller HIGH RPM (2,400 RPM)
• Climb speed 70 kt indicated airspeed (KIAS) (Flaps 20°)
• Climb speed 80 KIAS (Flaps UP).
• Brakes – APPLY momentarily when airborne
• Landing gear – RETRACT in climb out
• Wing Flaps – RETRACT

The Short Field Take-off technique included:

• Propeller HIGH RPM (2,400 RPM)
• Climb speed – 59 KIAS until all obstacles are cleared.
• Landing gear – RETRACT after obstacles are cleared
• Wing Flaps – RETRACT slowly after reaching 70 KIAS.

ATSB comment

The pilot could not recall any particular reason as to why the pre-landing check (propeller control to HIGH RPM (full fine)) was overlooked on two occasions in the circuit.

Although the aircraft could have landed safely in this configuration, attempting to climb with the propeller still at 2,000 RPM created a chain of events from which the pilot did not recover.

The pilot’s decision to retract the flaps all at once, followed immediately by the landing gear, prior to obtaining a positive rate of climb at a low altitude also decreased the aircraft’s performance. The elevation of the airport was 1,100 ft above mean sea level. This, coupled with a warm day of around 30 °C, translated to a higher density altitude,2 resulting in reduced performance.

Safety message

Although the pilot did not recall any distraction which could have led to the omission of the checklist item on both the downwind and final approach checklists, this omission fits a familiar pattern.

Any change of routine or even cognitive thoughts can distract a pilot from an essential checklist item. Research conducted by the ATSB found that distractions, or a change in routine, were an everyday part of flying, and that pilots generally responded quickly and efficiently. The report, Dangerous Distraction: An examination of accidents and incidents involving pilot distraction in Australia between 1997 and 2004 speaks to these issues.

This research commented that pilot distractions in the study did not always occur in response to non-normal tasks. In fact, the research indicated that distraction can occur when pilots are conducting normal routine tasks.

Aviation Short Investigations Bulletin - Issue 47

About this report Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2016 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. High RPM (full fine) was 2,400 RPM for that aircraft.
2. An increased density altitude would have increased the power required and decreased the power available.
3. BHP is the power developed by the engine

What happened

On 14 February 2016, the pilot of a Robinson R44 helicopter, registered VH-HXY, conducted a local private flight from a property about 90 km north of Hughenden, Queensland.

After operating for about 1 hour, the pilot landed near a water trough to check a float. During the approach and landing, the pilot sighted powerlines strung across the trough, and manoeuvred to remain clear of them.

While the helicopter was on the ground, the wind veered from a south-west to a southerly direction, so that to take off into wind, the helicopter would track perpendicular to the powerlines. After completing the pre-take-off checks, the pilot turned his attention to a mob of cattle, to ensure the noise of the helicopter would not send them through a fence.

The helicopter lifted off initially parallel to the powerlines, and the pilot then turned the helicopter to manoeuvre around a tree and climbed to about 20 ft above ground level. The tree momentarily obscured the powerlines and the pilot’s attention was on the cattle.

As the helicopter rounded the tree, at an airspeed of about 50 kt, the skids struck the powerlines. The pilot heard the wires contact the helicopter and it decelerated rapidly. The pilot lowered the collective^[1] and pulled back on the cyclic^[2] control, but the helicopter rolled forwards over the wires, descended rapidly, and collided with the ground left side down in a nose-down attitude.

The wire was hooked on the helicopter’s right skid, with electrical power still running through it. After the blades stopped turning, the pilot exited the helicopter. The pilot was not injured and the helicopter was destroyed (Figure 1).

Figure 1: Accident site of Robinson R44 helicopter, registered VH-HXY

Source: Helicopter owner

Safety message

ATSB research indicates that in 63 per cent of reported wirestrike incidents, pilots were aware of the position of the wire before they struck it. In this instance, the pilot was aware of the powerline however, they were unable to see the wires from the helicopter’s position on the ground due to a tree. The pilot’s attention was then diverted to the cattle and did not maintain awareness of the wires.

The Aerial Agricultural Association of Australia suggests a way to keep focus is to ask yourself:

• Where is the wire now?
• What do I do about it?
• Where am I in the paddock?

For further risk management strategies for agricultural operations, refer to the Aerial Application Pilots Manual.

The ATSB publication Avoidable Accidents No. 2 – Wirestrikes involving known wires: A manageable aerial agricultural hazard, explains strategies to help minimise the risk of striking wires while flying. Pilots are reminded to avoid unnecessary distractions and to refocus when distracted. Distraction, combined with difficulty in seeing wires makes them extremely hard to avoid at the last minute.

Aviation Short Investigations Bulletin - Issue 47

About this report Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2016 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. A primary helicopter flight control that simultaneously affects the pitch of all blades of a lifting rotor. Collective input is the main control for vertical velocity.
2. A primary helicopter flight control that is similar to an aircraft control column. Cyclic input tilts the main rotor disc varying the attitude of the helicopter and hence the lateral direction.

What happened

On 6 February 2016, at about 1250 Eastern Daylight Time (EDT), the pilot of a Nanchang CJ-6 aircraft, registered VH-ALO (ALO), was completing the first in a series of formation ‘combat’ joy flights booked for that day. The ‘combat’ flight, which consisted of a pilot and passenger on board each of two Nanchang aircraft (ALO and Number 2), had departed Barwon Heads airport, Victoria, about twenty-five minutes earlier. The pilot of ALO acted as the leader aircraft (or ‘Number 1’)^[1] for the formation flight.

At the chosen ‘break-point’^[2] on upwind, Number 2 positioned ahead of ALO in the circuit. The two Nanchang aircraft remained in this single-file sequence behind a Pipistrel aircraft, which had joined the circuit on the downwind leg for runway 36. The Pipistrel aircraft landed, then rolled through to the end of the runway in order to exit; Number 2 followed suit. As ALO touched down, third in a close landing sequence, the pilot realised that they had not completed the pre-landing checks, and the landing gear had not been extended. The aircraft slid along the sealed runway, coming to a stop just off the centreline (Figure 1). The pilot and passenger were not injured, and were able to safely egress. The aircraft sustained damage to the propeller, engine and the underside of the fuselage.

Figure 1: Nanchang VH-ALO, on runway 36 after a wheels up landing

Source: Pilot

Events leading to the wheels up landing

As the formation joined upwind, the pilot from a parachute aircraft operating at the airport, broadcast that tandem parachutists (student and instructor) had been dropped, and that this parachute aircraft was now conducting a second pass to drop the final student(s).

Figure 2: Barwon Heads airport showing relative positions of the formation, Pipistrel and the drop zone

Source: En Route Supplement Australia entry for Barwon Heads; annotated by the ATSB

To avoid any issues for the novice parachute jumpers, and to prevent Number 2 from flying too close to the drop zone in the preferred echelon right,^[3] ‘dead side’^[4] of the circuit join, the pilot in ALO made the decision that the formation would remain in the echelon left configuration and join over the top of runway 36. At the break point, Number 2 would move ahead, and both aircraft would conduct an early turn onto crosswind. This would keep both Nanchang aircraft well clear of the remaining parachute jumpers approaching the drop zone (Figure 2).

However, while the formation was still on upwind, the pilot of a smaller Pipistrel aircraft broadcast their intention to join the downwind leg for runway 36 (Figure 2), further delaying the Nanchang’s turn onto crosswind. To maintain a reasonable separation from the Pipistrel, the two Nanchang pilots conducted a much wider crosswind leg, and resultant circuit, than normal.

The pilot in ALO continued to check for the remaining parachute jumpers, while broadcasting and responding to pertinent radio reports on behalf of the formation; and also managing the ‘slowing down’ of the formation. Once the Pipistrel has passed abeam the formation’s position, and because the runway at Barwon Heads is too narrow to allow a formation landing, the pilot in ALO instructed the pilot in Number 2 to ‘break’. The landing order became the Pipistrel, followed by Number 2 and then ALO.

The Pipistrel touched down, and took some time to roll through to the only available exit taxiway at the end of runway 36. The pilot in Number 2 requested the pilot in the Pipistrel to expedite the exit, as they wanted to land, but could not land until the Pipistrel was clear of the runway. The pilot in ALO reported keeping a close eye on proceedings in front of their aircraft. This included sideslipping the aircraft to maintain a clear view of the runway movements as the Nanchang has limited vision over the nose at slow airspeeds.

Once Number 2 had landed and cleared the runway, the pilot in ALO reported flaring the aircraft in preparation for landing. It was not until the pilot heard the noise of the aircraft scraping the runway that they realised that the landing gear had not been extended.

Pilot experience and comment

The pilot had around 2,950 flying hours, with about 1,800 of these on Nanchang aircraft.

• The pilot reported that although feeling relatively fresh on the day, due to other demands, the previous week had been personally ‘full on’ and somewhat draining. This may have had played a small part in the oversight of the downwind and pre-landing checklists.
• With the combination of the parachute activities, the slower aircraft in the circuit, and the less than optimal echelon left formation configuration, the pilot in ALO reported their attention moved from their own aircraft into the Number 2 aircraft. Still maintaining the duties of Number 1 of the formation, but in the unusual ‘behind’ position, they had checked that Number 2’s landing gear had been extended, and kept a close watch on the spacing of the three aircraft.
• The pilot reported the Nanchang is always a challenge to slow down until the landing gear is extended. The landing gear can be extended once the airspeed had reduced to 108 knots (usually during the downwind checks). The extension provides sufficient aerodynamic drag to reduce the airspeed closer to the desired approach speed.
• The pilot reported that it was more common for these combat flights to operate from Moorabbin Airport, where the wider runways allowed a formation landing.
• These events and conditions, combined with no landing gear warning system being fitted to these early military training aircraft, allowed the pilot’s attention to remain distracted and the landing gear was not selected down.

Safety message

The combination of factors distracting the pilot’s attention during the approach and landing led to the downwind and pre-landing checklists being overlooked. The lack of any landing gear warning system fitted to the aircraft, which would have alerted the pilot to the incorrect configuration, left no protection between the distraction and the final action.

According to an Interruptions / distractions briefing note by the Flight Safety Foundation, interruptions and distractions usually result from the following factors:

• flight crew-ATC, flight deck or flight crew-cabin crew communication
• head down work, and
• response to an abnormal condition or unexpected situation.

Further information is available at:

Flight Safety Foundation Approach-and-landing accident reduction Briefing note 2-4, Interruptions / distractions.

Research conducted by the ATSB identified 325 occurrences between 1997 and 2004, which involved distractions. Of these, 54 occurred during the landing phase of flight.

ATSB (2006). Dangerous Distraction: An examination of accidents and incidents involving pilot distraction in Australia between 1997 and 2004. (Research and Analysis report B2004/0324).

Aviation Short Investigations Bulletin - Issue 48

About this report Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2016 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. In an echelon formation, number 1 (ALO in this instance) is the lead aircraft, and makes the decisions for the formation and also makes and responds to all radio communication for the formation; each individual pilot is still responsible for their own aircraft’s safety.
2. The position in the circuit, where the pilot in the lead aircraft (ALO) in the formation determines that the formation will manoeuvre into single file, usually with Number 1 in the lead.
3. An echelon formation is where the aircraft (usually military) are arranged diagonally. In a left echelon, each station (in this case Number 2) was stationed behind and to the left of the lead aircraft) ALO (adapted from Wikipedia definition).
4. The non-active side of the circuit.

What happened

On 7 February 2016, the pilot of a Kavanagh G-450 balloon, registered VH-RUW, conducted a 30-minute scenic flight from Mareeba, Queensland with 18 passengers on board.

Shortly before 0627 Eastern Standard Time (EST), the balloon approached the target landing area. The pilot referred to his iPad, which showed the location of the balloon and a set of powerlines strung across the paddock. The balloon was then about 30 ft above ground level, travelling at a ground speed of 7 kt, with a descent rate of 50 ft per minute. The pilot confirmed that all the passengers were in the correct landing position.

The pilot sighted two power poles either side of the landing area, but was unable to see the wires. The pilot estimated where the wires would be based on the crossbars on the poles, and assessed that the balloon had sufficient height to pass over the powerlines. The pilot then sighted the powerlines, about half a metre ahead of and below the basket. The pilot applied all four burners to try to climb and avoid the powerlines, but the left side of the basket contacted one wire, breaking it. The pilot heard a loud fizzing noise and immediately realised they had struck a powerline.

The pilot checked that the passengers were all ok and still in the landing position, and checked that there was no evidence of fire. Due to the amount of heat in the balloon, the balloon was climbing. The pilot then conducted a normal controlled descent and landing into a paddock about 500 m beyond the original planned landing site. The balloon landed without further incident and no one was injured. The wicker basket sustained scorching (Figure 1) and a stainless steel cable fixed to the underside of the basket sustained arc damage.

Figure 1: Scorch marks on wicker basket

Source: Balloon operator

Landing site

The balloon operator and the pilot had used the paddock on many occasions for both launching and landing.

The balloon’s track crossed the powerlines at an angle (Figure 2). As the balloon approached the wires, the pilot lost sight of the pole to the left and used the pole on the right to gauge their height. However, the left pole was situated on a hill and higher than the right pole, and the wires sloped upwards from the right pole to the left. The pilot’s assessment of sufficient height was based on the lower pole; consequently, the left side of the basket struck the wires to the high side.

The powerlines were difficult to see as the area was heavily vegetated. The sun was to the right of the balloon and did not affect the pilot’s vision of the wires.

Figure 2: Balloon track and location of powerlines

Source: Balloon operator

Powerlines and markings

The balloon operator used the following strategies to improve powerline awareness:

• The operator had developed an iPad application which pilots used in-flight as an early powerline warning system, which showed all of the powerlines on a google earth map, and the balloon’s current location. The energy company provided updates to the location of the powerlines at six monthly intervals.
• The operator maintained a map of powerlines identified by the company pilots to be of low visibility. These were highlighted on the application to draw pilots’ attention.
• Company pilots were required to visit the site of identified low-visibility powerlines to familiarise themselves with the location of the lines.
• In addition, ground personnel were expected to identify from the ground any powerlines in the balloon’s flight path, which may pose a risk to the balloon on approach to land, and to confirm that the pilot was aware of the lines and their location.
• The balloon operator had designated the powerlines at the site to be low-visibility, and had paid the energy provider to fit white marker flags with a reflective green centre to the wires to increase the pilot’s ability to see the lines (or flags). Despite being clearly visible from the ground, the pilot was unable to see the flags. This may have been due to the effect of the wind deflecting the flags at an angle, and possibly their colour.

Pilot comments

Two other balloons had already landed in the paddock. The pilot elected to fly on rather than conduct an emergency descent after the wirestrike, because a high rate of descent from that height carried a risk of injury to the pilot and passengers, and to avoid a collision with the balloons that had landed ahead.

Safety action

Balloon operator

As a result of this occurrence, the balloon operator has advised the ATSB that they are taking the following safety actions:

Review of powerline markings

The operator is investigating the installation of more visible three-dimensional powerline markings such as balls.

Communication to company pilots

The operator will circulate a copy of their investigation report and findings to all company pilots. Pilots are reminded to consider the possibility of sloping powerlines and apply an appropriate clearance margin when overflying them.

Safety message

The ATSB research report, Wirestrikes involving known wires: A manageable aerial agriculture hazard, explains a number of strategies to assist pilots manage the risk of wirestrikes. These include:

• ensure you are fit to fly
• prioritise safety
• conduct thorough pre-flight planning
• avoid unnecessary distractions
• don’t rely on your ability to react in time to avoid a wire
• have a systematic approach to safely managing wires.

The Australian Ballooning Federation produced safety advisory notice pilot circular number 18 in 2012, detailing strategies to avoid wirestrikes.

Aviation Short Investigations Bulletin - Issue 48

About this report Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2016 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.

Aviation Short Investigation Bulletin - AB-2016-044