Warning devices

Investigation summary

What happened

On 25 June 2025, the flight crew of a Jetstar Airways Airbus A321-251, VH-OYF, were conducting a scheduled passenger transport flight, JQ38, from Denpasar International Airport, Bali, Indonesia, to Sydney, New South Wales. The first officer was the pilot flying and the captain was the pilot monitoring.

During the landing at Sydney Airport, the aircraft floated for a prolonged period along the runway, was subject to a right crosswind and drifted left of the runway centreline. The captain responded by commanding a go-round which the first officer executed. 

The crew proceeded to continue with the published missed approach procedure and subsequently landed without further incident. 

What the ATSB found

The ATSB found that after the first officer initiated the flare manoeuvre, their control inputs resulted in a lateral deviation from the runway centreline when the aircraft floated for a prolonged period in crosswind conditions. 

After the captain commanded a go-around, they inadvertently manipulated their sidestick control, which resulted in a brief period where simultaneous control inputs occurred. The crew were alerted by a ‘dual input’ generated voice message and the captain took control. There was a moment of preoccupation which resulted in the first stage of flap being retracted out of sequence, however, there were no associated flight envelope exceedances or negative effects on aircraft performance. 

Safety message

Sound go-around decision-making is an effective defence against the hazards associated with low-level manoeuvring during the landing phase of flight, such as lateral runway excursions. If adequate safety margins cannot be maintained during an approach and landing, the correct and expected response is to go around.

Being go-around minded improves crew readiness and supports timely, coordinated actions during a period of high workload. This should involve crew members reviewing potential go‑around scenarios, procedures and responses prior to conducting an approach. 

When flight crews are faced with the unexpected need to execute a go-around even at the final stages of landing, effective crew resource management, with clear communication between flight crew, is essential. This promotes effective teamwork when responding to disruptions and increased workload under stress, ensuring that the aircraft remains on a safe flight path and is correctly configured for the relevant phase of flight.

The investigation

The occurrence

On the evening of 25 June 2025, a Jetstar Airways Pty Limited Airbus A321-251 registered VH‑OYF was operating on a schedule passenger transport Jetstar flight, JQ38, from Denpasar International Airport, Bali, Indonesia, to Sydney, New South Wales. The flight was scheduled to arrive at Sydney Airport the following morning at 0630 AEST.[1] The operating crew included the captain, first officer, 6 cabin crew and 234 passengers. For the flight to Sydney, the first officer was the pilot flying (PF) and the captain was the pilot monitoring (PM).[2]   

After departing Denpasar, the aircraft climbed to flight level (FL) 330[3] and later descended to FL310 after reaching Australian airspace due to turbulence en route. Due to the turbulence en route, the captain elected not to take any controlled rest on the nearly 6‑hour flight, while the first officer stated they would not usually take controlled rest in flight. 

Prior to descent, the flight crew briefed for the arrival at Sydney, recalling that the turbulent conditions and the crosswind for the approach and landing were the main considerations. 

At 0554, the flight crew commenced their descent to the west-south-west of Sydney Airport and was cleared for the approach for runway 16R[4] which was conducted in day visual meteorological conditions[5] using the autopilot. The flight crew recalled there was a 30 kt crosswind down to about 500 ft above mean sea level (AMSL) and the approach up to that point was ‘pretty normal.’ Air traffic control (ATC) advised the crew to expect an 8 kt right crosswind for landing and the first officer chose to land in the flap 3 configuration,[6] which was consistent with guidance for landing in ‘rough’ conditions. (The first officer was procedurally restricted to a maximum crosswind landing component of 20 kt).

The aircraft reached 500 ft at 0621:14 and the captain called ‘stable’ (see Stabilised approach criteria). The first officer disengaged the autopilot 5 seconds later as the aircraft approached 400 ft and recalled encountering turbulence which placed the aircraft ‘a little higher’ on the approach. At 0621:45 at 90 ft, the first officer pitched forward, which they observed resulted in a 900 ft per minute rate of descent. 

At 0621:51, the first officer initiated the flare at 50 ft and reduced the thrust levers to idle at around the final approach speed (VAPP)[7] of 150 kt, which included a wind correction of 5 kt. At this point the first officer recalled they ‘over flared’. The captain also observed that the first officer applied the flare technique that was consistent with the technique for landing in the flap full configuration. The aircraft subsequently floated for a prolonged period along the runway after the first officer’s flare manoeuvre.

During the prolonged float, the aircraft was subjected to the crosswind conditions for a greater length of time. After observing the centreline deviation, the captain commanded a go-around approximately 600 m past the runway threshold, just prior to touchdown. The captain recalled they were ‘startled by the need to go around’ as the approach seemed ‘benign’ aside from the crosswind. They also reported a sudden stress response at this time as they had to rapidly transition from landing to commencing the go-around.

In response to the captain’s command, the first officer set take-off/go-around thrust at 0621:59 (Figure 1), which initiated the published missed approach procedure for the 16R GBAS landing system (GLS)[8] approach in the aircraft flight management system. The first officer also referenced their primary flight display (PFD) to command a target pitch attitude of 15° nose up.   

At this point, the captain recalled they instinctively applied control inputs via their sidestick while the aircraft was just above the runway, and the crew were alerted to this by the aircraft’s ‘dual input’ voice message (see Sidestick priority logic). 

The captain then engaged their sidestick pushbutton, and the first officer recalled hearing the ‘priority left’ voice message and the captain announce, ‘I have control.’ The captain subsequently took control of the thrust levers and the first officer relinquished control and became PM after the aircraft achieved a positive rate of climb. It was the role of the PM to retract the flap ‘one step’ at this point (see Go-around procedure). 

Figure 1: Overview of go-around 

Source: Google Earth, annotated by the ATSB

The captain announced the active flight modes on their PFD, which prompted the first officer to call ‘positive climb.’ The captain subsequently instructed the first officer to retract the landing gear, which was accomplished 42 ft above the runway at 0622:20. 

At this time, the captain looked up to the flight control unit located on the cockpit glareshield to engage the autopilot. After this was actioned, they looked back to their PFD and was ‘startled’ when they noticed that the aircraft suddenly banked right and responded by disengaging the autopilot at 0622:22. They subsequently realised that the aircraft flight director was providing commands for the published missed approach procedure and subsequently re-engaged the autopilot at 0622:29. 

The captain then requested flap 1, but the first officer noticed they were still configured with Flap 3 and retracted the flap by one step and announced, ‘flap 2.’ This occurred at 0622:32 when the airspeed reached 174 kt, which was below the maximum flap 3 speed of 195 kt.

They continued to follow the missed approach procedure, and the first officer advised ATC they were going around. The crew were given instructions to track for a right downwind for runway 16R at 4,000 ft. The captain recalled conducting a welfare check on the first officer, briefed the cabin manager via the interphone and made an announcement to the passengers through the public address system. 

The captain elected to remain as PF for the remainder of the flight, with the first officer acting as PM. The crew then conducted a second GLS approach for runway 16R, landing at 0638 without further incident.

Context

Flight crew information

The captain held an Air Transport Pilot Licence (Aeroplane), class 1 aviation medical certificate, and had accrued 5,921 hours total flying time, 1,480 of which were in the Airbus A320 and A321 aircraft types.

The first officer held a Commercial Pilot Licence (Aeroplane), class 1 aviation medical certificate, and had 2,212 hours total flying time, 551 of which were on the Airbus A320 and A321 aircraft types.

Fatigue

The captain reported that they felt 'moderately tired' during the go-around, likely due to the back-of-the clock[9] flight, which departed Denpasar at 0057 local time in Sydney. They also stated there was limited opportunity for controlled rest during the flight and their nap prior to the flight was disrupted due to noise at the hotel. The first officer reported feeling 'ok, somewhat fresh.’  

The flight crew also reported they had an adequate rest opportunity the evening prior to the flight and obtained around 6 hours sleep in the previous 24 hours and around 13‍–‍14 ‍hours in the previous 48 hours. Their sleep during the rest opportunity was reported to be good quality and the conditions at the hotel where they spent the night were suitable and therefore conducive to obtaining restful sleep. Biomathematical modelling[10] of the flight crew’s roster for the 2 weeks leading up to the flight indicated a low likelihood of fatigue.

The ATSB considered that fatigue was unlikely to have affected the flight crew’s performance at the time of the occurrence.

Aircraft information

General

The Airbus A321-251NX is a modern, fly-by-wire aircraft, powered by 2 CFM International LEAP-1A32 turbofan engines and had seating for 232 passengers in a single-class layout. 

All the flight controls are electronically actuated with the pilots using sidesticks to fly the aircraft in pitch and roll during manual flight. The 2 sidestick controllers are not coupled mechanically, and they send separate sets of signals to the flight control computers. 

Sidestick priority logic

Jetstar Airways A320-A321 Flight crew operating manual (FCOM) contains the following description of the aircraft sidestick priority logic: 

At all times, only one flight crewmember should fly the aircraft. However, if both flight crewmembers use their sidesticks simultaneously, their orders are algebraically added.

The flight control laws limit the combined order to the equivalent of the full deflection of one sidestick.

In this case the two green SIDE STICK PRIORITY lights on the glareshield come on and "DUAL INPUT" voice message is activated.

 A flight crewmember can deactivate the other sidestick and take full control, by pressing and keeping pressed the sidestick pb (Figure 2).

A “PRIORITY LEFT” or “PRIORITY RIGHT” audio voice message is given each time priority is taken.

Figure 2: Airbus A320/A321 captain's side sidestick and sidestick pushbutton

Source: Operator, annotated by the ATSB

Post-flight maintenance

The operator reported that there were no corrective maintenance actions that were required to be carried out in relation to the occurrence. The aircraft subsequently operated a scheduled passenger service the following day.

Meteorological information

The pre‑flight briefing package provided to the flight crew from the operator’s flight dispatcher included the aerodrome forecast[11] for Sydney Airport. The forecasted weather conditions for the scheduled time of arrival 0630 local time on 26 June indicated:

• wind direction of 240° at 15 kt with gusts up to 25 kt
• CAVOK[12]
• moderate turbulence[13] below 5,000 ft.

One-minute weather data for Sydney Airport from the Bureau of Meteorology indicated a wind direction of 255° at 17 kt with gusts up 20 kt at the time of the occurrence.

Airport information

Runway 16R at Sydney Airport is oriented on a magnetic heading of 155° and has a declared length of 3,962 metres with a width of 45 metres. A precision approach path indicator system is installed and set to 3° with a threshold crossing height of 64 ft. 

For daytime operations, the runway centreline, aiming point and touchdown zone markings provide visual references to assist pilots with approach and landing (Figure 3).

Figure 3: Sydney Airport runway 16R markings

Source: Google Earth, annotated by the ATSB

Recorded information

The aircraft’s quick access recorder data which captured the incident approach indicated that, as the aircraft descended below 1,000 ft, it maintained an appropriate speed and flightpath with no sustained exceedances of the stable approach criteria throughout the approach. 

At 0621:59, the recorded data captured the captain’s control inputs commencing concurrently with the initiation of the go-around, while the first officer was actively manipulating their sidestick control. Simultaneous control inputs lasted for a duration of 6 seconds (Figure 4), while the aircraft’s pitch attitude remained below the aircraft’s pitch limit of 11.5° until the aircraft had climbed through about 50 ft. 

The recorded data further indicated that the wind direction and speed varied following the flare manoeuvre, however the crosswind component remained well below the first officer’s operational limitation. The wind direction and speed was 315° at 13 kt with a crosswind component of 5 kt when the go-around was initiated.

Figure 4: Graphical representation of the recorded quick access data

Source: Quick access recorder from VH-OYF, annotated by the ATSB

Following the initiation of the go-around, the landing gear was retracted at 06:22:20 and 12 seconds later, the flap was retracted to the flap 2 configuration[14] at 174 kt.

Operational information

Stabilised approach criteria 

Jetstar Airways A320-A321 Flight crew operating manual (FCOM) defined a stabilised approach criteria as being established on the correct lateral and vertical flight path by 1,000 ft height above airport (HAA), configured for landing, and within the stated tolerances with the required checklists completed by 500 ft HAA. The FCOM also stated that if these criteria could not be met, or if the approach became unstable below 1,000 ft HAA, a missed approach was required. 

The crew reported the approach was stabilised against these criteria, which was consistent with the available recorded data.

Touchdown zone 

The FCOM provided the following operational information regarding the touchdown zone: 

The touchdown zone commences at 300 m (1000 ft) beyond the threshold and will not normally extend further than 600 m (2000 ft) beyond the threshold.

It is a requirement that the touchdown is planned to occur within the touchdown zone. Should it become apparent that the aircraft will touch down further than 600 m (2,000 ft) beyond the threshold, and the PIC believes that the landing is safe to continue, the PF must apply maximum reverse thrust and sufficient braking to ensure the aircraft stops within the landing distance available. If the PIC decides that a go-around is required, they will without delay, call “Go-Around”. In all cases this must be completed before the PF initiates reverse thrust.

The captain stated that runway 16R in Sydney was long enough to stop the aircraft on the runway if they had continued with the landing during the occurrence. This would have involved requesting maximum reverse and manual braking as necessary after the aircraft touched down. 

The FCOM did not specifically reference runway centreline tracking during a visual approach, however the captain stated that it was their personal expectation that a deviation from the runway centreline would lead them to calling for a go-around. 

Transfer of control  

The operator described procedures for transfer of control within the FCOM as follows:

The pilot relinquishing control of the aircraft shall say “You have control”. The pilot assuming control shall ensure that they have clear and unobstructed access to the flight controls and, when ready, say “I have control”. Only then is the pilot relinquishing control permitted to remove their hands and feet from the flight controls.

In critical phases of flight the PIC must be alert and positioned such that they can assume immediate control of the aircraft.

Following the occurrence, the captain stated the preferable method to conduct a go‑around at low level would have been to announce ‘I have control’ and initiate the go‑around themselves. They stated that their primary consideration when conducting a go‑around at low level was to avoid the risk of tail strike. 

Go-around procedure 

The FCOM defined the go-around procedure for the A320/A321, which specified the task sequence, memory-based crew actions and applicable guidance relating to techniques and navigation (Figure 5).

Figure 5: Jetstar Airway A320/A321 go‑around procedure below acceleration altitude

Source: Operator, annotated by the ATSB

Following the occurrence, the captain stated that although they could have taken over and landed, they believed that going around was considered the safest option. The first officer also stated, at about that time, that they were in the mindset of preparing to initiate a go-around themselves. 

Related occurrences

The following ATSB investigation highlights the importance of pilots maintaining their readiness for a go-around on every approach as it is typically a period of high workload requiring effective crew coordination. 

ATSB Investigation

On the morning of 18 May 2018, an Airbus A320 aircraft, registered VH-VQK, was being operated on a regular public transport flight by Jetstar Airways. The flight departed from Sydney for Ballina/Byron Gateway Airport, New South Wales.

The flight crew conducted a go-around on the first approach at Ballina because the aircraft’s flight path did not meet the operator’s stabilised approach criteria. On the second approach, at about 700 ft radio altitude, a master warning was triggered because the landing gear had not been selected DOWN. The flight crew conducted a second go‑around and landed without further incident on the third approach.

The flight crew did not follow the operator’s standard procedures during the first go‑around and subsequent visual circuit at 1,500 ft. In particular, the flaps remained at flaps 3 rather than flaps 1 during the visual circuit. This created a series of distractions leading to a non‑standard aircraft configuration for a visual circuit. Limited use of available aircraft automation added to the flight crew’s workload.

Safety analysis

During the approach to Sydney airport, with the first officer acting as the pilot flying (PF), the flight crew reported experiencing a crosswind of up to 30 kt until descending through about 500 ft above mean sea level. The crew were advised by air traffic control to expect a right crosswind component of 8 kt for landing, which was within the first officer’s operational crosswind limit of 20 kt. The captain confirmed the approach was ‘stable’ at 500 ft and the first officer continued the approach as PF.

At 50 ft, the first officer initiated the flare manoeuvre prior to landing. They recalled they ‘over flared,’ and the aircraft subsequently floated for an extended period along the runway. During this time, the first officer’s control inputs did not counteract the effect of the crosswind, and the aircraft drifted left of the centreline. After observing the lateral deviation from the centreline, the captain commanded the first officer to conduct a go‑around. 

This occurred just prior to the aircraft touching down when the flight crew would normally be focused on landing. The flight crew did not expect a go-around at the time and had to rapidly shift their focus to conducting the missed approach procedure. The captain recalled being ‘startled’ by the unexpected need to discontinue the landing, however they were more likely experiencing ‘surprise.’ Surprise is a cognitive-emotional response to something unexpected, which results from a mismatch between one’s mental expectations and perceptions (Rivera, Talone, Boesser, Jentsch, & Yeh, 2014). But their decision was consistent with the expectation that an approach be discontinued if the aircraft departed from the correct lateral flight path.

The unexpected change from landing to conducting a go-around close to the ground also resulted in the captain experiencing a sudden stress response at this time. When experiencing acute stress, people can respond quickly to a situation, but without conscious decision‑making (Wickens, Helton, Hollands, & Banbury, 2022). After the go‑around was commanded, there was a rapid increase in pitch attitude, engine thrust and airspeed, and in response the captain instinctively and inadvertently manipulated their sidestick while the first officer was flying, resulting in a dual-input alert. 

The captain reported they only realised they had manipulated their sidestick when they heard the dual input alert. Their primary consideration during the go-around was to avoid an excessive rotation rate to avoid a tail strike, which did not occur. Additionally, operator procedures directed captains to be alert and be positioned to ‘assume immediate control of the aircraft’ during critical phases of flight. 

Following the dual input alert, the captain took full control by engaging their sidestick push‑button and announced ‘I have control’, and the first officer assumed the role of pilot monitoring. A consequence of the control handover during the initial stages of the go‑around was the momentary interruption of sequential crew actions during the go‑around procedures. Interruptions typically disrupt the chain of procedure execution so abruptly that pilots turn immediately to the source of the interruption without noting the point where the procedure was suspended (Loukopoulos, Dismukes, & Barshi, 2009). 

Additionally, there was a further disruption (rapid task switching) associated with the first officer and captain exchanging pilot flying and pilot monitoring roles. As a result, some of the procedural items were completed out of sequence (flap 3 retraction occurred after gear retraction). 

Pilots are highly vulnerable to errors of omission when they must attend to multiple tasks. If one task becomes demanding, their attention is absorbed by these tasks demands and they can forget to switch their attention to other tasks (Loukopoulos, Dismukes, & Barshi, 2009). Although the flap retraction occurred out of sequence during the go-around, there were no associated flight envelope exceedances or negative effects on aircraft performance.  

Findings

From the evidence available, the following findings are made with respect to the control issues during landing and go-around involving Airbus A321, VH-OYF, at Sydney Airport, New South Wales, on 26 June 2025.

Contributing factors

• During the landing after crossing the threshold, the first officer’s control inputs resulted in a lateral deviation from the runway centreline during a prolonged float.
• After calling for a go-around, the captain inadvertently manipulated their sidestick while the first officer was the pilot flying, which resulted in a simultaneous control input and the go-around procedure being completed out of sequence.

Sources and submissions

Sources of information

The sources of information during the investigation included:

• Jetstar Airways Pty Limited
• Bureau of Meteorology
• the flight crew
• recorded data from the quick access recorder from VH-OYF.

References

Loukopoulos, L., Dismukes, R., & Barshi, I. (2009). The perils of multitasking. AeroSafety World, 4(8), 18-23.

Rivera, J., Talone, A., Boesser, C., Jentsch, F., & Yeh, M. (2014). Startle and surprise on the flight deck: Similarities, differences, and prevalence. In Proceedings of the human factors and ergonomics society annual meeting (Vol. 58, No. 1, pp. 1047-1051). Sage CA: Los Angeles, CA: SAGE Publications.

Wickens, C. D., Helton, W. S., Hollands, J. G., & Banbury, S. (2022). Engineering psychology and human performance, 5th edn. Routledge, doi: 10.4324/9781003177616.

Submissions

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

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

• Civil Aviation Safety Authority
• the flight crew
• Jetstar Airways Pty Limited
• Bureau of Meteorology.

Submissions were received from:

• the flight crew
• Jetstar Airways Pty Limited.

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

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through:  identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. About ATSB reports ATSB investigation reports are organised with regard to international standards or instruments, as applicable, and with ATSB procedures and guidelines. Reports 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. 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 2025 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 Commonwealth Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this report is licensed under a Creative Commons Attribution 4.0 International licence. The CC BY 4.0 licence enables you to distribute, remix, adapt, and build upon our material in any medium or format, so long as attribution is given to the 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.

Investigation summary

What happened

On 15 April 2025, an Embraer ERJ 190-100, registered VH-UZD, was conducting a passenger transport flight from Sydney, New South Wales, to Launceston, Tasmania. After commencing approach to Launceston, the flight crew received multiple caution messages including a SLAT FAIL caution. The flight crew discontinued their approach and after completing the relevant checklists elected to divert to Melbourne, Victoria, as it was the longest available runway in the region. The remainder of the flight was uneventful, and the aircraft landed safely.

Post-flight troubleshooting determined that a torque tube in the left wing slat drive system had disconnected as it had been incorrectly assembled when it was last refitted.

What the ATSB found

The ATSB identified a similar occurrence with another of the operator’s Embraer ERJ 190‑100 aircraft, VH-UYB, where a torque tube in the left wing flap drive system had disconnected as it had been incorrectly assembled when it was last refitted.

The occurrences were similar in that the locking bolts that secured the torque tubes to their actuators had not been fitted correctly into the holes of the splined shafts, since the torque tubes had been incorrectly positioned during installation.

In both occurrences, those carrying out and certifying for the torque tube installations did not identify that they had been incorrectly assembled.

These errors occurred at different maintenance providers, and reportedly from January 2005–August 2011 in the worldwide fleet of Embraer 170, 175, and 190 aircraft (all sharing similar componentry), there have been 5 similar occurrences related to incorrect torque tube installation.

What has been done as a result

The operator, Alliance Airlines, issued a maintenance notice that detailed the flap torque tube disconnect affecting VH-UYB and the slat torque tube disconnect affecting VH-UZD. This notice reiterated the aircraft maintenance manual information for the correct installation of flap and slat torque tubes.

The maintenance organisation added an additional task card that is automatically issued when work is scheduled on the E190 slat system torque tubes that provides guidance in addition to the aircraft maintenance manual to mitigate the incorrect assembly of torque tubes on their splines. A similar additional task card was being developed for the E190 flap system torque tubes.

Safety message

Historical occurrence and technical information provide an opportunity to review known errors prior to commencing particular maintenance activities, thereby reducing the possibility of further errors occurring. When an error does occur, this information also provides a means to bolster the actions taken to prevent re-occurrences.

This information can be available from multiple sources including the manufacturer, national aviation authorities (such as CASA or the FAA), accident investigation authorities, and the safety management systems of operators and maintenance organisations.

The investigation

The occurrence

Previous maintenance

In November 2024, an Embraer ERJ 190-100 aircraft, registered VH-UZD and operated by Alliance Airlines, commenced a heavy maintenance[1] check by Rockhampton Aviation Maintenance in Rockhampton, Queensland. A team comprising 2 aircraft maintenance engineers (AMEs) was tasked with inspecting and lubricating the leading-edge slat drive system (see Embraer E190 slats and flaps). This involved removing, cleaning, lubricating, and refitting each slat torque tube in turn. A licensed aircraft maintenance engineer (LAME) briefed the AMEs on what was required.[2] The LAME was familiar with the task but was unaware of any historical issues with the task (see Maintenance requirements). The work was carried out in a new facility with good lighting. Access to the components was good, and a purpose-built platform allowed the work to be carried out with the relevant components at eye level.

Prior to commencing work, brakes internal to the power drive units (PDUs) (which drive the flap and slat torque tubes) were electrically released as required by the aircraft maintenance manual (AMM) procedure. The AMEs printed a copy of the relevant AMM procedure, and worked together on the torque tube driving the left-wing outboard actuator for slat number 4. The PDU brakes were also required to be released prior to installing the torque tubes, however, it could not be established whether this took place (the PDU brakes reapply when power is removed). After refitting the outboard actuator torque tube, a push-pull check was carried out to ensure it was locked in place, as required by the AMM. Unknown to the AMEs, when this torque tube was refitted, it had not been positioned far enough onto the actuator’s splined shaft for the locking bolt to secure it (Figure 1, lower right). The locking bolt was inadvertently installed beyond the end of the spline (shown in grey) rather than through the hole as required.

One AME then continued work on the left wing and the other moved to the right wing slat drive system to work alone. The remaining slat torque tubes were correctly fitted.

After this work was completed, the LAME inspected the installation of the torque tubes and their locking bolts, and a second LAME carried out an independent inspection[3] of the work. The heavy maintenance check was completed in March 2025, and the aircraft was returned to service. 

Figure 1: Aircraft maintenance manual torque tube installation illustration

Source: Embraer

Flight control event

On 15 April 2025, 50 flights after returning to service from heavy maintenance, the aircraft was being operated on a passenger transport flight from Sydney, New South Wales, to Launceston, Tasmania, by Alliance Airlines for QantasLink. After commencing approach to Launceston, the flight crew received multiple caution messages[4] on the aircraft’s engine indicating and crew alerting system (EICAS) including a SLAT FAIL caution. The flight crew discontinued the approach and requested clearance from air traffic control for vectors[5] so they could action the relevant quick reference handbook (QRH) checklists for the caution messages.

The flight crew completed the QRH checklist. As the slat failure would require landing with the slats and flaps up, the flight crew elected to divert to Melbourne Airport, Victoria, as it had the longest available runway in the region. The flight crew declared a PAN PAN[6] and commenced the diversion to Melbourne. After climbing to 19,000 ft the aircraft was flown to Melbourne at 220 kt as required by the QRH because of the slat failure. The aircraft landed at Melbourne without further incident.

Post-flight inspection

Post-flight inspection determined that the torque tube for the left wing slat number 4 outboard actuator had disconnected as the locking bolt fitted to the torque tube had not passed through the corresponding hole in the actuator’s splined shaft when it was last refitted (Figure 2).

Figure 2: VH-UZD left wing outboard actuator for slat number 4 and torque tube, shown disconnected after the occurrence flight

Source: Alliance Airlines, annotated by the ATSB

Context

Aircraft information

The Embraer ERJ 190-100 IGW (E190) is a narrow-body aircraft used for air transport operations and powered by 2 General Electric CF34-10E5 turbofan engines. VH-UZD was manufactured in Brazil in 2008 and registered in Australia on 31 January 2022.

Embraer E190 slats and flaps

The E190 is fitted with devices to increase the lift produced by its wings during take-off and landing. On the leading edges of the wings there are 8 slat panels and on the trailing edges of the wings there are 4 flap panels (Figure 3), where each set (slats/flaps) extends and retracts together.

Figure 3: Embraer E190 slats and flaps

Source: Embraer, annotated by the ATSB

Slat and flap extension and retraction is controlled from the cockpit by using the slat/flap control lever (SFCL). When the SFCL is moved from its 0 (up) position,[7] the flap and slat power drive units (PDUs) drive torque tubes which in turn drive actuators, transferring the rotary motion of the torque tubes to linear motion that extends the slats and flaps (Figure 4 and Figure 5).

Each PDU has 2 internal brakes that are engaged under spring force and released electrically, such that the brakes would re-engage when power is removed. There are 26 torque tubes in the slat drive system and 22 torque tubes in the flap drive system.

In the event of a slat or flap failure, redundant detection and protection systems prevent them operating in such a way that may compromise safety of flight.

Figure 4: Embraer E190 slat drive system

Source: Embraer, annotated by the ATSB

Figure 5: Embraer E190 flap drive system

Source: Embraer, annotated by the ATSB

Maintenance requirements

The slat and flap torque tubes are removed periodically for the actuator splines to be lubricated with grease. They may also need to be removed to replace associated components. A detailed visual inspection of the slat and flap drive system is also carried out periodically and includes a requirement to check that the torque tubes are correctly secured in place by their locking bolts. No detailed visual inspections of the slat system had been required between the heavy maintenance in November 2024 and the occurrence flight.

The procedure to remove and install the slat and flap torque tubes is detailed in the aircraft maintenance manual (AMM). As part of this procedure, the slat or flap PDU brakes are disengaged electrically to eliminate any residual torque in the system that may impede (through friction) the removal of the torque tubes. For the same reason, the brakes must also be disengaged for their installation.[8] Embraer advised the ATSB of the importance of removing residual torque for the installation.

Rockhampton Aviation Maintenance noted during its investigation into the occurrence that excessive amounts of grease on the actuator splines can produce hydraulic resistance to re-assembly of the torque tube and therefore no more than what is required to lubricate the splines should be applied. It could not be determined whether this occurred during the maintenance of VH-UZD. The installation procedures for torque tubes in the AMM requires the old grease to be removed, new grease to be applied, and any unwanted grease to be removed prior to assembly.

The torque tubes interface with other components via splined shafts and are secured by locking bolts in conjunction with castellated nuts and split pins to prevent their inadvertent disconnection. There are 24 locking bolts in the slat drive system and 18 locking bolts in the flap drive system, all with this configuration.

The AMM describes and illustrates a ‘push-pull’ check to determine the locking bolt has been correctly installed and had showed representative examples of correct and incorrect installation (Figure 1).

The torque tube locking bolts pass through holes close to the end of each actuator’s splined shaft. A correctly installed torque tube is visually apparent by less exposed splines (Figure 6). If a slat torque tube is incorrectly positioned[9] on a slat actuator the locking bolt will not capture the splined shaft and can lead to the torque tube disconnecting and slat failures.

Figure 6: Exemplar slat torque tube correctly fitted (upper image) and incorrectly fitted (lower image) to a slat actuator 

A slat actuator and torque tube were correctly and incorrectly assembled on a workbench to create these images. Source: The maintenance organisation, annotated by the ATSB

Actions taken to prevent installation errors

In 2010 the AMM was amended to include the previously mentioned illustration (Figure1) showing the correct and incorrect installation of slat and flap torque tubes along with the push-pull test. This revision also added the requirement to release the PDU brakes.

Embraer communicated these changes by publishing a service newsletter SNL 190‑27‑0050 noting reports of incorrect slat or flap torque tube installation, advising that the AMM had been revised to mitigate future occurrences, and provided an overview of the revisions. This information was also published in Embraer’s safety magazine[10] (available to operators of E190s) and was contained in a document[11] published by the National Civil Aviation Agency of Brazil.

In October 2017 Embraer published an update on the issue in a document[12] that reiterated the previous actions taken to mitigate these occurrences. This document noted that from January 2005–August 2011 in the worldwide fleet of Embraer ERJ170, 175, 190, and 195 aircraft[13] there were 483 reports of slat or flap system failures. Of these, 5 were occurrences related to incorrect torque tube installation. Additionally, the document stated that the subject of incorrect torque tube installation was presented to civil aviation authorities in Europe and the Americas. It was concluded that no additional actions were required, as there were a small number of exposed aircraft, and there had been no reported events since the AMM was revised in 2010, and the manufacturer considered the issue closed.

Related occurrences

Incorrect flap torque tube installation

In late 2024, an Embraer ERJ 190-100 aircraft, registered VH-UYB and operated by Alliance Airlines for QantasLink, commenced a heavy maintenance check at a facility in Singapore. The torque tube driving the left wing flap actuator number 2 (see Embraer E190 slats and flaps) was removed to carry out flap actuator torque limiter checks. When fitted, the torque tube had not been positioned far enough onto the actuator’s splined shaft for the locking bolt to secure it.

On 10 November 2024, 35 flights after returning to service from heavy maintenance, the aircraft departed for a passenger transport flight. After take-off, the flight crew received a FLAP FAIL caution on the EICAS as the flaps were retracting. The flight crew initiated a turnback and the aircraft landed safely.

Engineering personnel later found that the locking bolt for the left wing flap actuator number 2 torque tube had not passed through the corresponding hole in the actuator splined shaft when it was last refitted (Figure 7).

Figure 7: VH-UYB left wing flap actuator 2 and torque tube

Source: Alliance Airlines, annotated by the ATSB

Other flight control event involving VH-UZD

On 18 April 2025, VH-UZD was operating from Adelaide, South Australia, to Canberra, Australian Capital Territory. When flaps were selected down, the slats began to extend but the flaps did not deploy, and the crew received multiple failure warnings. The flight crew diverted to Melbourne. Post-flight troubleshooting determined that the flap power drive unit (PDU) torque limiter had tripped, which is a problem unrelated to the investigation occurrence or the recent heavy maintenance check.

Safety analysis

Incorrect fitment of actuator torque tubes

When the torque tube for the left wing slat number 4 outboard actuator was refitted to VH-UZD in November 2024, it had not been positioned far enough onto the actuator’s splined shaft for the locking bolt to secure it in place. After re-entering service and conducting 50 flights, the torque tube disengaged from the actuator, and the slat system failed. Protection systems ensured the safety of flight was minimally affected.

Similarly, when another E190, VH-UYB, was under heavy maintenance at a different facility at around the same time, the torque tube driving the left wing flap actuator number 2 was incorrectly assembled in that the locking bolt had not passed through the hole in the actuator’s splined shaft. The torque tube disengaged 35 flights after the aircraft re-entered service and the flap system failed. 

Non-detection of the error

The 2 AMEs who fitted the torque tube in VH-UZD did not identify that the torque tube had been incorrectly fitted. Further, the LAME checking this work and the second LAME carrying out the independent inspection of this work did not identify that it had been incorrectly assembled. The similar error affecting VH‑UYB also apparently remained undetected by those carrying out and certifying for the work.

As far as could be established, there were no physical or environmental factors that may have influenced the incorrect assembly of the torque tube. The work on VH-UZD was carried out in a new facility with good lighting, and access to the work area was good and could be carried out with the relevant components at eye level.

Ultimately, it is likely that not knowing the subtle difference in appearance of an incorrectly assembled slat torque tube (that is, as little as about 6.35 mm more of the actuator spline visible) contributed to the error not being detected by the 2 AMEs and the 2 LAMEs involved. Further, the remaining torque tubes in the slat drive system were correctly assembled, however their subtly different appearance did not trigger recognition that the original torque tube had been incorrectly assembled.

Available relevant information

Installation of the slat and flap drive system torque tubes is a simple task, but errors have occurred. Embraer noted that from January 2005–August 2011 in the worldwide fleet of Embraer 170, 175, 190 aircraft (all sharing similar componentry) there were 5 occurrences related to incorrect torque tube installation. The Embraer 190 has 24 locking bolts in the slat drive system and 18 in the flap drive system representing a total of 42 opportunities to incorrectly secure the torque tubes.

In 2010, Embraer made amendments to the aircraft maintenance manual to reduce the possibility of assembly errors. These were intended to remove any residual torque loads during removal and installation (by releasing the PDU brake), highlight the possibility of error with an illustration, and through the addition of the push-pull check, provide a means to detect an installation error.

These changes were communicated in multiple documents, such as a service newsletter, that were available to operators and maintainers of E190s. Review of such documents can assist in highlighting known issues and thereby prevent reoccurrence.

Findings

From the evidence available, the following findings are made with respect to the flight control event involving Embraer E190, VH-UZD, 29 km south-east of Launceston Airport, Tasmania, on 15 April 2025. 

Contributing factors

• During scheduled maintenance, the locking bolt for the left outboard slat torque tube was not passed through the hole in the actuator’s splined shaft as the torque tube had been incorrectly positioned. The aircraft was released from maintenance, and 50 flights later, the torque tube disconnected, causing the slat system to fail.
• Both licensed aircraft maintenance engineers inspecting the left outboard slat torque tube did not identify that it had been incorrectly assembled.

Safety actions

Safety action taken by Alliance Airlines

On 17 April 2025, Alliance Airlines issued a maintenance notice that detailed the flap torque tube disconnect affecting VH-UYB on 11 November 2024 and the slat torque tube disconnect affecting VH-UZD on 15 April 2025. This notice reiterated the aircraft maintenance manual information for the correct installation of flap and slat torque tubes.

Safety action taken by Rockhampton Aviation Maintenance

The maintenance organisation added an additional task card that is automatically issued when work is scheduled on the E190 slat system torque tubes. This task card provides guidance in addition to the aircraft maintenance manual to highlight the possibility of hydraulic lock caused by lubricant and the importance of releasing the PDU brake. Additionally, this task details a dimensional check to confirm the correct installation of torque tubes on their splined shafts. A similar additional task card was being developed for the E190 flap system torque tubes.

Sources and submissions

Sources of information

The sources of information during the investigation included:

• Alliance Airlines
• Centro de Investigação e Prevenção de Acidentes Aeronáuticos (Brazil)
• Civil Aviation Safety Authority
• Embraer
• Rockhampton Aviation Maintenance
• licenced aircraft maintenance engineer that made the final certification of the work
• both aircraft maintenance engineers.

Submissions

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

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

• Alliance Airlines
• Centro de Investigação e Prevenção de Acidentes Aeronáuticos (Brazil)
• Civil Aviation Safety Authority
• Embraer
• Rockhampton Aviation Maintenance
• licenced aircraft maintenance engineer that made the final certification of the work
• both aircraft maintenance engineers.

Submissions were received from:

• Embraer
• Rockhampton Aviation Maintenance.

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

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through:  identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. About ATSB reports ATSB investigation reports are organised with regard to international standards or instruments, as applicable, and with ATSB procedures and guidelines. Reports 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. 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 2025  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 Commonwealth Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this report is licensed under a Creative Commons Attribution 4.0 International licence. The CC BY 4.0 licence enables you to distribute, remix, adapt, and build upon our material in any medium or format, so long as attribution is given to the 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.

Investigation summary

What happened

At 1021 on 7 April 2025, a Bankstown Helicopters Robinson R44 helicopter, registered VH‑EWM (EWM), with a pilot and 2 passengers on board, departed from Bankstown Airport, New South Wales, for a local scenic flight around Sydney Harbour. Shortly after 1028, as EWM was entering the Parramatta River helicopter lane behind an EC120 helicopter, the occupants of EWM experienced a sudden onset of turbulence followed by an uncontrolled descent. 

In response, the pilot applied full collective, which resulted in a low rotor speed condition as the helicopter descended towards the water. The pilot was able to manoeuvre the helicopter and complete a forced landing on the river shoreline.

What the ATSB found

The ATSB found that it is likely that EWM entered the rotor wake from a preceding heavier EC120 helicopter, which resulted in the control difficulties, an uncontrolled descent, low rotor speed warning and the forced landing. 

What has been done as a result

Following review of the draft report, the Civil Aviation Safety Authority undertook proactive safety action to improve existing guidance about helicopter wake vortices in Advisory Circular 91-16. The updated advisory circular was released on 17 July 2025 and can be found at the link: AC 91-16 v1.2 - Wake turbulence.

Safety message

Flight tests have demonstrated that helicopter wake turbulence is comparatively larger and less predictable in its behaviour than for aeroplanes of the same weight. Helicopter rotor vortices can descend, remain level or climb, and the duration of their persistence can increase significantly in conducive weather conditions. The United States Helicopter Safety Team website recommends remaining 3 rotor disks clear of a hovering or taxiing helicopter and allowing 3 NM and/or 2 minutes for the rotor wake from a preceding helicopter to dissipate.

The investigation

The occurrence

At 1021 local time on 7 April 2025, a Bankstown Helicopters Robinson R44 Raven 1 helicopter, registered VH‑EWM (EWM), with a pilot and 2 passengers on board, departed from Bankstown Airport, New South Wales for a local scenic flight around Sydney Harbour. Bankstown Tower air traffic control (TWR) cleared EWM to depart via ‘Choppers West’, which was a standard procedure for helicopters departing to the north when runway 29 was active at Bankstown. 

The pilot reported that they climbed to about 1,000 ft above mean sea level.[1] The pilot’s plan was to join the Parramatta River on the west side of the Ryde Bridge and descend to 500 ft to follow the helicopter lane[2] along the south side of the river to Sydney Harbour (Figure 1).

Figure 1: Key locations

Source: Google Earth, annotated by the ATSB

About 1 minute after EWM departed, an Airbus EC120B helicopter departed Bankstown, also following the Choppers West departure. Shortly after the EC120 departed, TWR advised the EC120 pilot that there was ‘R44 traffic 1 NM ahead’, to which the EC120 pilot reported that they had the traffic sighted. Bankstown TWR then advised the pilot of EWM that they were not receiving their transponder data, which the pilot acknowledged. The pilot of EWM then turned their transponder off and on in an attempt to transmit transponder information, but no data was received from it throughout the incident flight.

As the 2 helicopters tracked north towards the Parramatta River, the EC120 flew to the west of EWM and passed it before reaching the river. The EC120 then turned right to join the Parramatta River helicopter lane, tracking towards the Ryde Bridge and Sydney Harbour, and passed over the Ryde Bridge at a recorded radar altitude of 600 ft. 

The pilot of EWM reported that they descended the helicopter to 500 ft as they approached the river. Just before the pilot turned EWM right to join the helicopter lane, another larger helicopter (the EC120) suddenly appeared in front of them (Figure 2). The pilot of EWM estimated the EC120 was about 500‍–‍600 ft (150‍–‍180 m) in front of them and about 100 ft above them. While there was no recorded altitude for EWM, primary radar data indicated that EWM entered the lane about 9 seconds behind the EC120.[3] Primary radar data for EWM was lost about 10 seconds later, just after 1028, indicating it had descended below radar coverage.

Figure 2: Primary radar return (left) and loss of primary radar return (right) for VH‑EWM

Source: Airservices Australia, annotated by the ATSB

The pilot of EWM made a radio broadcast that they were entering the helicopter lane as they crossed the Ryde Bridge behind the EC120. They then experienced what they described as very strong turbulence from a vertical motion in the atmosphere. A passenger later described it as ‘like heavy turbulence … rolling left and right’ followed by ‘diving towards the water’.

The pilot noted that the helicopter was descending through 400 ft and responded by raising the collective lever.[4] However, the helicopter continued descending towards the water as it tracked behind and below the EC120. A passenger recalled the pilot announced ‘brace for impact’ as the helicopter approached the water. The pilot applied full collective to avoid the water, which caused the rotor speed to decay sufficiently for the low rotor speed warning horn to activate. They also reported feeling that they could not escape what they believed to be the rotor wake from the EC120. The pilot then sighted a suitable forced landing area at Cabarita Park and, using the helicopter’s remaining airspeed and rotor speed, manoeuvred the helicopter to the shoreline for a landing.

Following the landing, the pilot rolled the engine throttle back to idle and proceeded through their after‑start checks and confirmed normal operations on the ground. The pilot then conducted a hover check and again confirmed normal operations. The pilot attempted radio contact with their operations base but received no reply. They then conducted a return flight to Bankstown without further incident. 

Context

Pilot information

The pilot held a commercial helicopter pilot licence, issued on 26 November 2024, with a single‑engine helicopter class rating and low‑level rating. The pilot held a class 1 aviation medical certificate with no restrictions and expiration date of 30 May 2025. The pilot had accumulated about 112 hours flying experience and the incident flight was the pilot’s first commercial flight.

Helicopter information

The incident helicopter, EWM, was a piston‑engine 2‑bladed Robinson Helicopter Company R44 Raven 1 with a maximum take‑off weight of 1,089 kg. The weight and balance data provided by the operator indicated it was within limits for the flight. 

The Airbus EC120B was a turbine-engine 3‑bladed helicopter with a maximum take‑off weight of 1,715 kg. Therefore, the EC120 was about 57% heavier than EWM at their respective maximum take‑off weights.

The maintenance release for EWM indicated the helicopter was operated by Bankstown Helicopters in the operational category of Part 133 Air Transport. The maintenance release current at the time of the incident was issued on 3 April 2025 at 4,349 hours total time in service with an expiry date of 3 April 2026 or 4,400 hours. A maintenance test flight was certified on the maintenance release as conducted on 3 April with ‘nil defects evident.’ 

After the incident, the operator’s maintenance organisation inspected the helicopter and found no defects. As the flight hours remaining on the helicopter were close to the next overhaul, the operator elected to remove the helicopter from service and have the maintenance organisation complete the overhaul. 

Meteorological information

The METAR[5] recordings for Bankstown Airport at 1000 and 1030 indicated that the wind was westerly at a speed of 9 kt at 1000 and 7 kt at 1030. No cloud was detected. These conditions were consistent with the Bankstown Airport forecast for 8 kt westerly winds. The pilot reported their assessment of the weather was 5 kt of variable wind and CAVOK[6] conditions, but when they encountered the turbulence over the Ryde Bridge it felt like 40 kt of wind.

Rotor wake turbulence

In 1996, the United States Federal Aviation Administration (FAA) produced a report on the subject of Flight test investigation of rotorcraft wake vortices in forward flight. They used a laser doppler velocimeter to measure the vortices and small probe aircraft to test the actual flying conditions. Smoke generation was used to visualise the wake vortices for the probe aircraft. Their investigation concluded that:

• The measured vortex circulation diminished with decreasing airspeed for helicopter airspeeds below 40 knots. At these lower speeds, the wake vortex structure begins to break down and changes to a distinct downwash.
• Vortex duration depends strongly on ambient weather conditions and a variance of 300% was observed on those days most conducive[7] to vortex persistence and duration compared with those observed on typical days.
• Typically, helicopters with higher gross weight, larger rotor diameters, and larger numbers of rotor blades generated vortices of larger core diameters.
• Probe tests revealed that helicopter vortices did not descend in the same predictable manner as for fixed‑wing aircraft. Some vortices descended; some remained level; and some initially descended, levelled off, and then ascended above the altitude of the generating helicopter.

Figure 3: Rotor wake vortices visualised with smoke generators

Visualisation of the wake vortices behind an S‑76A helicopter in forward flight with smoke generators from the FAA (1996) flight tests. Source: Reddit

Meiris (n.d.) provided an article for the United States Helicopter Safety Team website, on the subject of Avoiding helicopter wake turbulence. The article referenced the FAA 1996 flight test report and provided the following recommendations:

As a result of these findings and the studies conducted regarding helicopter downwash in a hover, a few guidelines have been developed to increase awareness around helicopter wake turbulence:

• For hovering flight or a hover taxi, stay three rotor diameters away.

• For forward flight, a minimum of 3 nm [NM] separation is recommended, especially from larger helicopters. The investigation we discussed previously discovered that even at 3nm [NM], the planes encountered uncommanded pitch and roll oscillations.

• Leave 2 minutes for the rotor vortices to dissipate behind a helicopter in forward flight.

Related occurrences

The French Bureau of Enquiry and Analysis for Civil Aviation Safety investigation BEA2019-0234, Accident to a paraglider involving the Airbus - EC135 - T2 PLUS registered F-HTIN, examined a fatal paraglider accident in 2019. The paraglider’s wing collapsed after encountering the rotor wake from an Airbus EC135 helicopter, which drifted with the wind from the helicopter’s flightpath onto the paraglider (Figure 4).

Figure 4: Simulation of rotor wake drifting onto the paraglider

Source: YouTube – Bureau of Enquiry and Analysis for Civil Aviation Safety, annotated by ATSB

The 2022 United States National Transportation Safety Board investigation WPR22LA072 found that the pilot of a Cessna 120 attempted a go‑around about 20 seconds behind the passage of a Bell UH‑1H helicopter. During the go‑around the Cessna encountered wake turbulence, resulting in a loss of control and collision with terrain (Figure 5). The report indicated light wind conditions of 4 kt at the airport.

Figure 5: Loss of control accident from rotor wake

Source: YouTube – Aviation Safety Network, annotated by ATSB

Safety analysis

Primary radar data and the pilot’s report indicated that EWM entered the Parramatta River helicopter lane and passed over the Ryde Bridge about 9 seconds behind and slightly below the EC120 helicopter. At this point, EWM encountered heavy turbulence, an uncontrolled descent and a low rotor speed when the pilot applied full collective to avoid a collision with the water.

The uncontrolled descent and low rotor speed condition resulted in the pilot conducting a forced landing on the shoreline of the Parramatta River. 

The incident occurred under relatively calm wind conditions and EWM operated in a serviceable condition for the return flight. Subsequent maintenance inspections of the helicopter found no fault. Furthermore, EWM passed overhead the Ryde Bridge in sufficient proximity to a preceding heavier 3‑bladed helicopter to be subject to a rotor wake induced upset. Therefore, the ATSB concluded that the sudden onset of turbulence and uncontrolled descent were likely the result of EWM encountering rotor wake turbulence from a preceding EC120 helicopter. 

Findings

From the evidence available, the following findings are made with respect to the wake turbulence encounter and forced landing involving Robinson R44, VH-EWM, about 15 km north‑east of Bankstown Airport, New South Wales, on 7 April 2025. 

Contributing factors

• It is likely that the incident helicopter entered the rotor wake from a preceding heavier helicopter, which resulted in control difficulties, an uncontrolled descent, low rotor speed warning and a forced landing.

Safety actions

Safety action by the Civil Aviation Safety Authority

Following review of the draft report, the Civil Aviation Safety Authority undertook proactive safety action to improve existing guidance about helicopter wake vortices in Advisory Circular 91-16. The updated version of the advisory circular was released on 17 July 2025 and can be found at the link: AC 91-16 v1.2 - Wake turbulence.

Sources and submissions

Sources of information

The sources of information during the investigation included:

• Airservices Australia
• Civil Aviation Safety Authority
• the operator and maintenance organisation for VH-EWM
• the pilot and passengers of the incident flight

References

Bureau of Enquiry and Analysis for Civil Aviation Safety. (2021). Accident to a paraglider involving the Airbus - EC135 - T2 PLUS registered F-HTIN on 11 May 2019 at Le Conquet (Finistère). https://bea.aero/fileadmin/user_upload/BEA2019-0234.en.pdf

Federal Aviation Administration. (2023). Aeronautical information manual. http://www.faa.gov/air_traffic/publications

Federal Aviation Administration. (1996). Flight test investigation of wake vortices generated by rotorcraft in forward flight (DOT/FAA/CT-94/117). https://apps.dtic.mil/sti/tr/pdf/ADA318103.pdf

Meiris, J. (n.d.). Avoiding helicopter wake turbulence. https://ushst.org/avoiding-helicopter-wake-turbulence/

National Transportation Safety Board. (2022). Aviation investigation final report (WPR22LA072). Investigation docket https://data.ntsb.gov/Docket?ProjectID=104480

Submissions

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

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

• Civil Aviation Safety Authority
• the maintenance organisation for VH-EWM
• the operator and pilot of the incident flight.

No submissions were received.

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 2025   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 Commonwealth Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this report is licensed under a Creative Commons Attribution 4.0 International licence. The CC BY 4.0 licence enables you to distribute, remix, adapt, and build upon our material in any medium or format, so long as attribution is given to the 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.

Executive summary

What happened

On the morning of 23 April 2023, a Saab 340A, registered VH-KDK and owned by Pel-Air Aviation, was being operated by Regional Express Airlines (Rex) for a non-revenue flight from Wagga Wagga, New South Wales, to Charleville, Queensland. While in cruise at 22,000 ft and passing to the east of Cobar, New South Wales, the flight crew received a cargo smoke indication on the central warning panel. As a precaution, the crew fitted their oxygen masks and smoke goggles. Shortly after, the cockpit filled with smoke.

The captain commenced a diversion to Cobar while the first officer made a PAN-PAN[1] call to Melbourne Centre. Thick smoke then filled the flight deck preventing the crew from effectively seeing external visual references or the aircraft’s flight instruments. While completing the emergency checklists, the crew received further warnings for avionics smoke, followed by a cabin depressurisation, and then a right engine fire detection fail indication. The crew landed at Cobar and elected to stop on the runway and evacuate the aircraft.

Shortly after landing, Fire and Rescue New South Wales personnel arrived from the Cobar station and located a heat source at the air cycle machine and in the associated wiring. After gaining access to the cabin underfloor area, the source of the heat was doused with water. An internal inspection of the aircraft found fire damage in the area around the right recirculating fan. The aircraft was substantially damaged, and the crew were not injured.

What the ATSB found

The ATSB found that a likely failure of the right recirculating fan electronic box sub-assembly resulted in an in-flight fire under the cabin floor. The fire filled the cabin with smoke, which then entered the flight deck due to a smoke barrier curtain not being fitted in place and the flight deck door being open. 

When the crew fitted their oxygen masks, it was found that the first officer’s mask microphone was not working correctly, which delayed emergency checklists being actioned. The fire also caused substantial structural damage and led to a breach of the fuselage, resulting in a depressurisation of the aircraft. 

It was also found that the Rex flight crew had not been trained or had knowledge of the differences in the cargo‑configured Saab 340 aircraft, leading to them having no familiarity with specific systems fitted. This prevented them from completing some of the required steps in the emergency checklists. 

The flight crew did not receive training on the cargo‑configured aircraft differences prior to conducting freight operations. Further, the operator’s flight crew operating manuals did not reflect the differences in the cargo‑configured aircraft interior checklists, which may have alerted the flight crew to these differences during pre-flight preparation. Additionally, the manufacturer did not have any specific pre-flight check for correct fitment of the smoke barrier curtain for cargo‑configured aircraft preparation. 

What has been done as a result

On 13 May 2023, Rex issued an Operations Notice to all pilots, highlighting the guidance on the cross-valve handle as outlined in the Saab Aircraft Operating Manual (AOM). Furthermore, this guidance has been incorporated into the Rex Flight Crew Operating Manual (FCOM). 

On 13 November 2024, Rex amended the internal inspection checklist that is contained in their Saab 340 FCOM. The amendment now requires flight crews verify the position of the cross‑valve handle during the pre-flight checks.

Rex have also updated the training information delivered in their ground school to include the cross-valve system for the cargo‑configured Saab 340 aircraft into the training syllabus.

Rex indicated they are implementing a fleetwide inspection of the recirculating fan assemblies at the next aircraft heavy maintenance cycle, with a focus on the electronic sub-assembly module.

Pel-Air have included a revision to their flight crew operating manual with a caution that the smoke barrier curtain must be installed whenever combustible material is carried in the cargo compartment. Due to contract completion, Pel-Air have ceased conducting freight operations using the Saab 340 aircraft and have since sold the aircraft. 

Saab has revised their preparatory and walk-around pre-flight checklists to include the fitting of the smoke barrier curtain when carrying cargo in the cargo‑configured aircraft. 

Safety message

It is essential for operators to ensure that flight crew are conversant with differences in aircraft configurations when required to conduct operations on aircraft they may be unfamiliar with. It is important that information is readily available and accessible and be delivered in a manner to inform flight crews on the operational requirements of the aircraft. 

Operator flight crew operating manuals need to be relevant for the aircraft configuration being utilised. Further, manufacturer checklists for pre-flight inspections are required to cover the modifications fitted, so that this is available to operators to enable them to write the appropriate documentation for their flight crews.

The occurrence

History of the flight

On the morning of 23 April 2023, a Pel-Air Aviation cargo‑configured Saab 340A, registered VH‑KDK and operated by Regional Express Airlines (Rex), was being prepared for the first stage of a non-revenue freight flight from Wagga Wagga, New South Wales, to Charleville, Queensland. The purpose of the flight was to pre‑position a Rex Saab 340 engine to Cairns, Queensland, utilising a Rex crew, consisting of a captain and first officer (FO), and operating under the Part 91 flight rules. 

The crew had flown the aircraft from Cairns the previous day, and were tasked to fly the return leg, including a refuelling stop at Charleville. The flight crew arrived at the aircraft at about 0830 local time and conducted their pre-flight checks. The captain performed the interior checks while the exterior walk around checks were conducted by the FO. The aircraft departed Wagga Wagga at about 0949, tracking for Charleville, and cruising at FL 220.[1] The captain was the pilot flying (PF), and the FO was pilot monitoring (PM).[2]

In-flight fire and diversion

At about 1052, the crew was alerted by a cargo smoke detection warning[3] on the central warning panel. They began to manage the warning by identifying and cancelling the indication. The crew then donned their oxygen masks and smoke goggles. However, once fitted, the crew had difficulty communicating due to the FO’s mask microphone not functioning correctly and being very faint. A review of the cockpit voice recorder (CVR) recording showed it took another 57 seconds for the crew to establish effective communications with each other before they could commence the emergency checks.

At 1055 the crew received a right (engine) fire detection fail caution light, followed shortly after by an air conditioner caution light. This was due to the detection of a right distribution duct over temperature which automatically closed the right engine low pressure bleed valve. The crew initially detected no smoke or fumes, however within about 60 seconds, thick black smoke began filling the cockpit.

During the process of establishing the nature of the warnings, the flight crew discussed which airport would best suit their needs for the emergency, and opted to divert to Cobar, New South Wales (Figure 1). The captain had flown to this airport on several previous occasions and was familiar with it, and from their position, they could conduct a direct approach with minimal manoeuvring.

Figure 1: VH-KDK flight overview

Source: Google Earth and Flightradar24, annotated by the ATSB

At 1056, the FO gave a PAN PAN[4] radio call and advised air traffic control (ATC) that they were diverting to Cobar. ATC arranged for emergency services to meet the aircraft upon arrival into Cobar. Due to the radio coverage in the Cobar area, ATC utilised an overflying aircraft to relay communications as the diversion progressed.

While descending through FL 160, the crew received a cabin pressure failure warning, indicating that the aircraft had lost pressurisation. This occurred 4 minutes after the initial warning of the cabin smoke. The cabin depressurisation led to the crew increasing their rate of descent to get below FL 100. 

At approximately 1058, they commenced the ‘cargo compartment smoke’ emergency checklist. The CVR indicated the crew completed the first checklist item, which called for the left bleed valve to be closed. The checklist then called for closing the cross-valve handle, however the crew was unable to locate it, with the CVR recording indicating the crew tried to find it for 61 seconds before resuming the checklist flow without actioning the cross-valve handle closure. The crew completed the cargo compartment smoke checklist as visibility on the flight deck reduced to less than 10 cm. The captain recalled sliding their seat forward to enable them to see the instrument panel through the thick smoke.

Five minutes after the PAN PAN call, the crew commenced the checklist for ‘avionic or electrical smoke or fire’.[5] The crew then conducted the ‘smoke removal’ checklist to clear the smoke from the flight deck. 

One requirement of the smoke removal checklist called for aircraft speed reduction to below 160 kt, and to open a crew hatch to aid in smoke removal. Due to the unknown severity of the on‑board fire, the crew decided to maintain their speed and not complete all the checklist items as required, enabling them to expedite their landing.

As the crew continued their approach, the volume of smoke in the flight deck began to dissipate. This allowed them to navigate using external visual cues and conduct a visual approach for the landing. Because of the unknown source of the fire, upon arrival in Cobar, the crew elected to stop the aircraft on the runway and evacuate the aircraft. 

As part of the emergency evacuation procedure, the crew activated the fire extinguisher system[6] on both engines after shutting down, and then exited the aircraft. The incident had taken 22 minutes from the first smoke warning to landing.

After evacuation, the crew noted smoke to be coming from the vicinity of the right air cycle machine at the right wing root. Shortly after landing, Fire and Rescue New South Wales personnel arrived from the Cobar station and assessed the aircraft. After gaining access to the cabin underfloor area, an electrical harness was initially found melted and smoking. Consequently, the area was doused with water. 

Further inspection of the aircraft found significant fire damage concentrated in the area around the right recirculating fan. The right recirculating fan was also significantly fire damaged. An assessment of the right engine found no evidence of a fire. The aircraft underfloor structure was substantially damaged, and the crew were not injured.

Context

Aircraft information

The Saab 340A[7] is a twin-engine turboprop aircraft designed and initially produced by Saab and Fairchild Aircraft. It is designed to seat 30‍–‍36 passengers in standard configuration and is powered by 2 General Electric CT7-5A2 turboprop engines.

VH-KDK was manufactured in Sweden in 1984 and first registered in Australia in February 1985. It was operated in passenger configuration by Regional Express Airlines (Rex), before being modified to cargo configuration in 2009. VH-KDK was then owned and operated by Pel‑Air Aviation.[8] 

At the time of the accident,[9] VH-KDK had accrued a total time in service of 48,130.6 hours and 60,046 landings and had flown 13.5 hours since the last maintenance. 

Flight crew information

Captain

The captain held an air transport pilot licence (ATPL) (Aeroplane), and a valid Class 1 aviation medical certificate. They reported a total flying time of 7,579 hours with about 5,070 of those being on the Saab 340. They had flown for the operator for about 10 years, and previously had flown for another regional airline and had operated into Cobar airport on numerous occasions. 

The captain had previously flown the Saab 340A in a passenger configuration but had not flown either the Saab 340A or B variant in a cargo configuration.

First officer

The first officer (FO) held an ATPL (Aeroplane), and a valid Class 1 aviation medical certificate with a restriction for vision correction. They had reported a total flying time of about 18,297 hours, having flown about 1,480.9 in the Saab 340B. The FO had not previously flown any Saab 340 variants in a cargo configuration.

Meteorological conditions

Graphical area forecasts provided by the Bureau of Meteorology (BoM) stated that generally good weather conditions, with little cloud, and visibility greater than 10 km existed during the flight. The terminal area forecast for Cobar indicated light winds from the east at about 10 kt with the flight crew reporting CAVOK[10] conditions existing for the time of the diversion.

Cargo configuration

VH-KDK cargo conversion

The cargo conversion modification was carried out in accordance with Saab service bulletin (SB) 340-25-280. As an overview, the SB involved removal of the passenger fit‑out and replacing it with an interior cargo liner, blanked over windows, additional cargo barrier nets, and a floor roller system (Figure 2). In conjunction with this SB, other SBs were incorporated on the cargo version, which modified the air conditioning system. This was done by removing the left recirculating fan and introducing a cross-valve handle. 

A removable smoke barrier curtain was added at the forward section of the cargo compartment. The fire extinguishing system for the passenger cargo area at the rear of the cabin (zones C1 and C2) was also removed, and additional smoke detectors were added to the cabin.

Figure 2: Cargo configuration modification

Source: Saab, annotated by the ATSB

Smoke curtain

A removable smoke barrier curtain was designed to be installed between compartment A and the front-left fuselage (Figure 2). The purpose of the curtain was to provide containment of smoke and fire within the cargo compartment in the event of an on-board fire and prevent smoke ingress to the flight deck (Figure 3). The aircraft carried a placard at the top of the entrance stairs which stated: 

Smoke barrier must be installed for all cargo operation flights.

The smoke barrier was constructed of a fibreglass impregnated vinyl which was secured in place by a Velcro perimeter and metal press studs. The aircraft owner stated that the standard procedure was that it would be left attached by the left side attachment points and secured in place by the freight handlers after loading of cargo. It was then to be checked by the FO prior to flight. 

During interview, the flight crew stated that they were not aware of the use of the smoke barrier, and that it had been located after the incident in compartment A of the cargo area, and that it was not in place on the left of the cabin. The ATSB did not determine why the engineers who loaded the engine into VH-KDK had not secured the smoke curtain.

Figure 3: Smoke barrier curtain location in exemplar aircraft

Source: Saab, annotated by the ATSB

Air conditioning system 

In passenger configuration, the Saab 340 air conditioning system is comprised of a left and right air conditioning pack (ACP) which is supplied by bleed air from its respective engine. Each ACP is mounted externally under a fairing on the lower fuselage near the rear of each wing. The system has 2 recirculating fans under the adjacent cabin floor, ducting for the cabin and flight deck conditioned air supply and return, temperature sensors and controls, and cabin and flight deck air outlets. 

The left and right ACPs supply conditioned air to the cabin, and a portion of the right ACP conditioned air is supplied to the flight deck. The left recirculating fan returns the air to the left ACP from the aircraft cabin, while the right fan extracted air from the flight deck. The avionics fan draws air for cooling the avionics from the cabin conditioned air supply. The air is then expelled under floor. 

As part of the modification from passenger to cargo configuration, the left recirculating fan and ducting were removed. This resulted in limited extraction and recirculation of any contaminated air from the cabin interior, while the right recirculating fan would extract and recirculate air solely from the flight deck. 

Cross-valve handle

In the cargo configuration, a cross-valve and handle were added to the air conditioning system ducting between the left and right ACP (Figure 4), with the manual operating handle being located at floor level, next to the FO seat. Closing of the left bleed valve and cross-valve in accordance with the emergency checklist would isolate the supply of air to the cabin in the event of cargo smoke or fire, and the right ACP would supply only to the flight deck. As part of the emergency checklist for ‘cargo compartment smoke’, the left ACP would also be isolated from supplying the cabin. 

Figure 4: Schematic of modified air conditioning system

Source: Saab, annotated by the ATSB

Recirculating fan

The right recirculating fan was a centrifugal impeller type fan and was driven by an AC motor. The fan had an in‑built inverter, supplied by 28-volt DC. The majority of the electronics for the fan unit were contained in the box sub-assembly. This included the inverter, an electromagnetic interference (EMI) filter unit and the electronic card sub-assembly. The box sub-assembly controlled the fan operation, including the thermal control. Each electric motor was equipped with:

• a thermal switch[11] located in the cooler which guarded against an abnormal temperature increase. This switch would cut off the power if the motor temperature exceeded 110°C +/− 5° (230°F +/− 41°). The fan would start again when the temperature decreased to 65°C +/− 5° (149°F +/− 41°)
• a speed sensor which guarded against an abnormal decrease of nominal speed. If the speed fell below 80% of nominal speed for more than 17 seconds, the fan would be stopped.

In 1987, Saab released a service bulletin which gave operators the option to install an upgraded recirculating fan. The original fan was a brush type motor which required regular maintenance, including brush replacement when they had worn from use. Saab had received reports of smoke and burning smells which were attributed to brushes that were incorrectly installed. The brushless fans were introduced to help eliminate this issue and also required less maintenance. 

The fan installed in VH-KDK was the new brushless fan, manufactured in 1990 and fitted in April 1996. The fan history prior to installation was unknown by the operator. The fan accrued 27,585 hours while fitted to VH-KDK. 

Recirculating fan examination

Fire damage was found in the area around the right recirculating fan and on the fan itself (Figure 5). There were no other components in the vicinity of the fan with significant fire damage. As such, it is likely the right recirculating fan was the source of the fire.

Figure 5: Damaged recirculating fan

Source: ATSB 

An examination of the recirculating fan was conducted at the ATSB’s technical facilities in Canberra. The examination found that the fire damage was most significant at the external box sub‑assembly which housed the EMI filter, the resistor support plates and electronic card sub‑assembly. The aluminium cover of the box sub-assembly had melted, the electrical wiring was damaged, and some terminals had disconnected as a result of the fire damage. There was heavy soot and melting of solder in the cooler assembly.

The electronic card sub-assembly was made up 3 circuit boards, mounted to the resistor support plate. The function of the circuit boards was for motor speed detection, timer control, and a logic card. The damage exhibited on the circuit boards showed significant burning, consistent with the other components within the aluminium cover.  

The electromagnetic interference (EMI) filter sub-assembly had considerable damage to the filter itself and to the mounting plate with signs of melting and heat tinting of the steel plate structure, indicating a significant heat source. The heat tint was indicative of temperatures of approximately 310° to 330°C. 

Of note, the fire did not appear to be associated with the motor and there was no indication of damage to the internal components of the fan and was able to rotate freely. There was carbon and soot observed on the external surface on the motor. The crew stated that there had been no circuit breakers tripped that would be associated with the failure of the electronic card sub‑assembly.

The ATSB examination of the recirculating fan could not determine the cause of the failure of the electronic components attached to the assembly. 

Pressurisation system

The Saab 340 cabin is pressurised by the 2 air conditioning packs. The pressurisation system uses bleed air drawn from each engine and was either automatically controlled by a pressurisation controller, or manually controlled by a control valve operated by the flight crew from the flight deck. 

Pressure is able to be regulated by the opening and closing of 2 outflow valves, located in the empennage. The primary outflow valve is electro-pneumatically operated by the pressurisation controller, while the secondary outflow valve is pneumatically controlled from the cockpit and used as a manual standby system.

When emergency pressure relief is required, the primary outflow valve is able to be opened with the emergency pressure dump switch. When the crew of VH-KDK experienced the smoke in the cabin and flight deck, dumping cabin pressure as stated in the ‘smoke removal’ emergency checklist was the method used to assist in rapid removal of the smoke.

Aircraft depressurisation

The severity of the fire resulted in significant damage to the surrounding underfloor furnishings, ducting and airframe structure. The damage was then sufficient to rupture the skin (Figure 6) and caused a subsequent depressurisation of the aircraft. 

Figure 6: Underfloor fire damage showing fuselage hole

Source: Operator, annotated by the ATSB 

Checklists

The pre-flight procedures for the Saab 340A aircraft, including cargo configuration aircraft, were covered by the Aircraft Operations Manual (AOM) normal procedures, produced by the aircraft manufacturer. The AOM pre-flight normal checklist contained a check of the cross-valve handle position prior to flight but did not include a specific check for correct fitment of the smoke barrier curtain. 

A flight crew operating manual (FCOM) was carried on board VH-KDK which was developed by Pel-Air, based on the aircraft manufacturer’s AOM. Unlike the aircraft manufacturer's AOM, the pre-flight checks in the operator's FCOM did not contain any reference to the cross-valve handle. Consistent with the aircraft manufacturer’s AOM, the operator’s FCOM also did not include a specific pre-flight check for correct fitment of the smoke barrier curtain. The weight and balance chapter of the FCOM did show a diagram of the smoke curtain fitted but did not include a requirement to ensure the smoke curtain was in place.

The manufacturer had an airplane flight manual supplement in place, implemented as part of the cargo configuration SB, which included fitting the smoke barrier as a limitation (Figure 7 left). There were no identified interior checks in this supplement, which included the checking of the cross-valve handle prior to flight.

The aircraft manufacturer did have emergency checklists specific to cargo‑configured aircraft. These were compiled into the quick reference handbook (QRH) which was available to flight crew in the aircraft (Figure 7 right). 

Figure 7: Flight manual supplement (left) highlighting smoke curtain use and QRH checklist (right) highlighting cargo cross-valve handle and cockpit door 

Source: Saab, annotated by the ATSB

Flight deck door

The Pel-Air FCOM stated in the Operating Limitations section that during flight, the flight deck door must be kept closed and locked at all times. It is further listed in the engine start checklist that all doors are closed before engine start. 

Evidence from the accident flight, however, shows that before the fire, the crew were operating with the cockpit door open. During interview, the flight crew indicated they closed the door, whilst performing the cargo compartment smoke checklist. This was further supported by the CVR review, where the crew were heard to state the door was to be closed as per the checklist steps, which was followed by the sound of the door shutting. 

Flight crew training

Rex conducted a ground school, including simulator training, for their new Saab 340 flight crew. Under a commercial agreement, Pel-Air flight crews were also trained by Rex. The ground school covered the 340 variants of A, B and B WT. The aim of the ground school was to provide pilots from both operators with the necessary knowledge to gain a Saab 340 type rating. The type rating covered all Saab 340 aircraft and did not distinguish between any variant or configuration of the aircraft.

Following the Rex ground school, Pel-Air then conducted further training through its line training program for its flight crews allocated to freight operations. Delivery of this training was in a practical environment, with pilots learning the systems and differences of the cargo‑configured Saab 340. This included the use of the smoke barrier and the operation of the cross-valve handle. 

The ATSB asked what the process was for Rex pilots to receive this training and knowledge. Pel‑Air advised that a pilot employed by Rex would only receive this if they were to transition to freight operations with Pel-Air in a permanent role. 

Crew familiarity of cargo aircraft

The flight crew operating VH-KDK were both Rex pilots, who were normally rostered for passenger operations. The night before the flight to Wagga Wagga, they were rostered to fly the cargo‑configured 340A. The captain recalled asking the scheduler if they needed a briefing for flying the cargo 340A, and was told that they did not, but it could be arranged if needed. 

The captain decided to speak to a Rex colleague who had flown the cargo‑configured 340A several times previously. They were told there were no differences other than the removal of the seats and a freight interior being fitted and that there were no special procedures to be aware of. 

Both Rex and Pel-Air advised that their respective operations could roster a crew to fly either operator’s aircraft if it was available. Crewing arrangements were such that there was never any mixing of crew, that is that the flight crew would consist of either 2 Rex or 2 Pel-Air flight crew on any flight.

Oxygen mask

The flight crew fitted their oxygen masks and smoke goggles shortly after receiving the cargo smoke warning and smelling the smoke. The FO conducted the functional tests after fitment and found their microphone was barely readable by the captain. The cockpit voice recorder (CVR) indicated that, although muffled, the speech from the FO was recorded and they were also able to be heard by air traffic control (ATC) throughout the emergency.  

The pre-flight checks relating to the crew oxygen system were conducted as part of the interior checklist. The FCOM detailed the checks as: 

RIGHT OXYGEN MASK .................................................................................CHECKED

Check flight crew oxygen mask and microphone in accordance with the following: 

•  …, 

•  set audio panel BOOM - MASK switch to MASK, 

•  increase INT/SPKR volume and knock on mask, 

•  speaker noise indicates proper microphone function, 

•  set BOOM - MASK switch back to the BOOM position, ….

The check on the left oxygen mask was to be performed in the same manner. Although not detected on the CVR, the captain advised the masks were both tested prior to departure. 

Aircraft damage

The damage caused by the underfloor fire was substantial. The fire had damaged underfloor air conditioning ducting and electrical wiring (Figure 8).

Figure 8: Underfloor fire damage

Source: Operator, annotated by the ATSB

Structural components in the surrounding area had been distorted by the extreme heat, including the floor panels, which had collapsed when fire crews entered the aircraft and inadvertently walked over the affected area. The seat track support structure had distorted, and the fuselage was weakened by the fire which breached the outer skin, preventing the aircraft from remaining pressurised (Figure 9).

Figure 9: Fuselage skin breach

Source: Operator, annotated by the ATSB

The fuselage in the immediate area above and below the cabin floor was buckled and delaminated. The heat from the fire most likely travelled between the interior panels and freight lining, leading to the damage observed (Figure 10). Following an engineering inspection of the fire damage, the aircraft was withdrawn from service and not repaired.

Figure 10: Right side delamination on fuselage

Source: Operator, annotated by the ATSB

Recorded data

The ATSB was supplied raw data by the operator from the flight data recorder (FDR). This data was analysed and was found to include the previous 4 flights. 

The recorded data from the occurrence flight showed that at about 59 minutes after becoming airborne at Wagga Wagga, the FDR stopped recording. The recording stopped at about the same time as the initial smoke indication. This was most likely due to fire damage to the electrical wiring which controlled the FDR. 

Flight track information was also obtained from FlightRadar24, which showed the entire flight, including the diversion and landing at Cobar (Figure 11).

Figure 11: VH-KDK flight track and diversion

 Source: Google Earth and Flightradar24, annotated by the ATSB based on CVR recordings

The CVR was removed and sent to the ATSB technical facilities in Canberra. The CVR data was downloaded, with the recovery of 4 channels of audio data of about 120 minutes duration which included the in-flight fire event. Reviewing the recorded CVR data also revealed that coincidentally, just prior to the indication of the cargo smoke caution, the flight crew had been discussing alternate airports in the area, and which one they would select if they had a need to divert. 

The recording contained information from the end of the previous flight, and from the day of incident. It included the:

• flight crew’s initial reaction to the caution warning for the smoke in the cabin
• conduct of the emergency checklists
• additional warnings as they occurred
• crew intercom and communications with Melbourne Centre
• landing at Cobar and subsequent exiting of the aircraft.

The recording also revealed that while conducting the emergency checklist for ‘cargo compartment smoke’ the crew closed the cockpit door as a loud bang was heard, indicating it was open during the flight.  

Safety analysis

Introduction

On 23 April 2023, the Regional Express (Rex) Airlines flight crew operating a Pel-Air Aviation Saab 340A, registered VH-KDK were conducting an internal revenue cargo flight from Wagga Wagga, New South Wales, to Charleville, Queensland. About 1 hour into the flight, the crew experienced an in-flight fire and diverted to Cobar, New South Wales. After experiencing thick smoke on the flight deck and then a cabin depressurisation, the crew performed a safe landing at Cobar. The aircraft was substantially damaged, and the flight crew were not injured. 

This analysis will explore:

• origin of the in-flight fire
• aircraft preparation for the flight
• oxygen mask use and technical problem of the microphone
• cabin depressurisation
• flight crew knowledge of aircraft systems
• flight crew operating with the cockpit door open
• Pel-Air and Rex flight crew operating manual information deficiencies
• training of Rex flight crews
• Saab pre-flight inspection checklists
• Rex crew familiarity of cargo aircraft. 

Origin of the in-flight fire

The source of the in-flight fire was traced to the right recirculating fan assembly. Although the fan was not damaged internally, the fire damage was most significant at the box sub-assembly, which was mounted external to the fan and housed the electrical control circuit boards. It is likely that an electrical component or components within the box sub-assembly failed, resulting in the underfloor fire. The fire damaged underfloor insulation and plastic air conditioning ducting components, which led to thick smoke filling the cabin and cockpit and aircraft structural damage. 

The avionics warning received by the crew during the diversion was most likely associated with the avionics cooling air that was being drawn from the now smoke-filled cabin. This was also stated in the ‘cargo compartment smoke’ checklist. 

The ATSB examination of the recirculating fan could not determine a cause for the failure in the electronic control cards which led to the fire. 

When the crew received the air conditioning system right duct over temperature caution light, it was most likely due to the distribution duct over temperature being affected by the fire and the melting which occurred as a result. When the over temperature was sensed, the right bleed valve closed automatically as a function of system logic for over temperature protection.    

Smoke barrier curtain

Cargo operations can have a greater fire risk than passenger operations due to the carriage of cargo that could be the source of a fire and the lack of cabin crew available to fight a fire. As such, additional protection was available to minimise flight crew exposure to cabin smoke in the form of additional smoke detectors and a smoke curtain. 

However, the smoke curtain was not installed into position by anyone involved in the flight preparation. The flight crew, who normally operated the same aircraft type but in a passenger configuration, did not notice there was a placard at the aircraft entrance stating the smoke curtain was to be fitted for all cargo flights. The flight crew remained unaware of the smoke barrier curtain and its use for cargo operations. Further, the engine being transported was positioned in the cargo area of VH-KDK, on both occasions, by Rex engineers. As the curtain was usually installed by freight handlers during normal cargo operations, it is possible the Rex engineers were also unaware of its requirement to be fitted.  

In this accident, the source of the fire was an aircraft component rather than the cargo being carried. If a similar fire occurs in a passenger‑configured Saab 340 aircraft, then the smoke curtain would not be in place. However, the smoke curtain was available and was required for use for this flight, so its non-use increased risk for this event.

The flight deck door was not closed during flight as prescribed in the operator’s FCOM operating limitations and checklists. Having the door closed would have likely prevented the smoke being able to flow into the flight deck. 

The result of not having the smoke barrier fitted and the flight deck door closed as part of the aircraft pre-flight preparation was that smoke from the fire was not contained to the cabin area and was able to move forwards toward the flight deck. 

Oxygen mask fault

The flight crew fitted their oxygen masks and smoke goggles when alerted of the presence of smoke by the central warning panel. This decision may have prevented the crew from being overcome by smoke and fumes in the cockpit in the next several minutes. However, once fitted, the crew had difficulty communicating with each other, as a result of the mask microphone being very faint and difficult for the captain to hear the first officer (FO). This appeared to be an internal fault only, as the cockpit voice recording (CVR) showed that the FO was able to be adequately heard by ATC. 

This breakdown of communication delayed the crew by 57 seconds, in which emergency checks were not initiated due to the breakdown of communication. It created confusion and distraction between the crew while trying to execute the emergency checklist. 

A review of the CVR captured prior to flight could not positively determine if the pre-flight check action in relation to the oxygen mask was performed. This is an important check of the emergency communication system whilst on oxygen and was designated as a mandatory check item for a daily inspection as required by the Rex and Pel-Air FCOM.

Cross-valve handle

While the flight crew were conducting the emergency checklist items for cargo compartment smoke, they were unable to locate the cross-valve handle. This was due to the combination of the thick smoke obscuring their vision and their lack of knowledge of the differences in the cargo‑configured aircraft. 

Had the location and function of the cross-valve handle been known by the flight crew, the time taken to identify it during completion of the emergency checklist would have been minimised, which would have limited the delay of smoke removal from the flight deck. 

In this case, the subsequent depressurisation resulted in the smoke dissipating even in the absence of the cross-valve.     

Cabin depressurisation

The weakening of the fuselage structure due to the underfloor fire resulted in a breach of the fuselage skin, which led to a subsequent depressurisation of the aircraft during the descent. Although adding to another caution alert indication for the flight crew and subsequent checklist to be conducted, it also benefited in the removal of smoke from the cabin and flight deck. 

At the time of the depressurisation, VH-KDK was at FL 160 and descending. The crew, when alerted to the depressurisation, increased the rate of descent to below 10,000 ft. The cabin depressurisation occurred 4 minutes after the initial smoke warning occurred.

Due to the size of the hole created, the smoke removal most likely occurred at a greater rate than using the aircraft pressurisation outflow valves alone. The resulting fortuitous reduction in the amount of smoke in the flight deck improved visibility and allowed the crew to carry out a safe landing into Cobar.

Crew familiarity of cargo‑configured aircraft

The flight crew had not flown or had any prior training on the cargo‑configured Saab 340 and were not familiar with the differences of the passenger configuration. The captain chose to liaise with a colleague to gain information on the cargo‑configured aircraft instead of accepting the company offer for a briefing. 

This non-formal approach to understanding the differences between the 2 aircraft types ultimately did not pass on the required operational differences and potential safety aspects of the change of aircraft configuration.

Rex and Pel-Air manuals

Both operators (Rex and Pel-Air) manuals, which were designed to provide essential information to flight crews, did not include the required information to enable the pre-flight checks to be conducted adequately. While the weight and balance chapter of the FCOM showed the smoke barrier curtain location, there was no information on its importance to cargo operations, and as the crew had not been informed of any differences, they would not have been expecting that this section contained this information. The smoke barrier curtain installation information that was contained in the Saab service bulletin and flight manual supplement was not included in the pre‑flight checklists. As a result, the flight crew did not have awareness of its use. 

The operators' manuals also did not have a check to verify the position of the cross-valve handle. As discussed above, when the checklist called for the crew to use this handle when the aircraft was already filling with smoke, the crew could not locate it.

Flight crew training

The Rex ground school provided type rating training on the Saab 340 series aircraft to both Rex and Pel-Air pilots. This training was based on the passenger‑configured aircraft. Pel-Air pilots undertook further training which gave them the knowledge and skills for the cargo‑configured aircraft. 

In scheduling their flight crews to operate the cargo‑configured Saab 340, Rex did not have a process to ensure that the additional training or knowledge sharing for their crews in the differences applicable to aircraft operated by Pel-Air was delivered.

Saab pre-flight checklists

As discussed above, both operators’ manuals had no inclusion of a pre-flight interior check for the smoke barrier curtain or the cross-valve handle. Likewise, there was no pre-flight interior check for these items in the manufacturer’s documentation. Saab confirmed that there were no checks in the pre-flight checklist for the crew to specifically verify that the smoke barrier curtain was correctly fitted.

The result of the manufacturer’s pre-flight and interior checklists not detailing information for the smoke curtain was that the operator did not detail these in their own FCOM. This information was not available for the flight crew who, even without prior knowledge of the cargo‑configured variant, would have been alerted to these changes while conducting these pre-flight checks in accordance with the FCOM. 

Findings

From the evidence available, the following findings are made with respect to the in-flight fire and cabin smoke involving a Saab 340A, VH‑KDK, 114 km east-north-east of Cobar, New South Wales, on 23 April 2023. 

Contributing factors

• It was likely that an electrical component of a control circuit board on the recirculating fan failed, resulting in an in‑flight fire under the cabin floor.
• The smoke curtain was not fitted as required for the cargo configuration, and the flight deck door was open, which allowed smoke from the in‑flight fire to enter the flight deck.
• The underfloor fire caused weakening of the fuselage structure, which led to a subsequent depressurisation of the aircraft during the descent. However, the depressurisation aided in the removal of enough smoke from the flight deck on approach to allow an unhindered visual approach at Cobar.
• Crew were not familiar with the cargo configuration and were unaware of the smoke curtain requirements and location of the cross-valve handle.
• The Pel-Air and Rex Saab 340 flight crew operating manuals did not include reference to the location and operation of the cross-valve handle or the operation and use of the smoke curtain. (Safety issue)
• Rex did not ensure its flight crews received training in the differences between passenger and freight‑configured Saab 340 aircraft, prior to being scheduled to fly freight operations. (Safety issue)
• Saab did not include the smoke curtain fitment in pre-flight documentation for the cargo‑configured Saab 340 aircraft to inform flight crew of this difference from the passenger-configured version. (Safety issue)

Other factors that increased risk

• When the flight crew donned their oxygen masks, the first officer's oxygen mask microphone did not function correctly. This led to difficulty in communication between the flight crew and a delay in responding to the emergency.
• Due to the combination of the smoke density and lack of prior knowledge, the flight crew were unable to locate the cross-valve handle during the emergency, therefore delaying the removal of smoke from the flight deck.

Safety issues and actions

Saab documentation for cargo configured aircraft

Safety issue number: AO-2023-020-SI-01

Safety issue description: Saab did not include the smoke curtain fitment in pre-flight documentation for the cargo‑configured Saab 340 aircraft to inform flight crew of this difference from the passenger‑configured version.

Operator documentation and crew familiarity

Safety issue number: AO-2023-020-SI-02

Safety issue description: The Pel-Air and Rex Saab 340 flight crew operating manuals did not include reference to the location and operation of the cross-valve handle or smoke curtain.

No formal company training

Safety issue number: AO-2023-020-SI-03

Safety issue description: Rex did not ensure its flight crews received training in the differences between passenger and freight‑configured Saab 340 aircraft, prior to being scheduled to fly freight operations.

Safety action not associated with an identified safety issue

Additional safety action by Regional Express

Rex advised that it is implementing a fleet‑wide inspection of the flight deck and passenger compartment recirculation fans at the next aircraft heavy maintenance visit. The inspection will be focused on the electronic sub-assembly module of the recirculation fan due to this component being identified to have the most significant fire damage on the fan assembly removed from VH‑KDK.

Glossary

Sources and submissions

Sources of information

The sources of information during the investigation included:

• the crew of VH-KDK
• Regional Express Airlines
• the chief pilot of Pel-Air Aviation
• the manager training and checking and head of operations for Regional Express Airlines
• Civil Aviation Safety Authority
• Bureau of Meteorology
• Fire and Rescue New South Wales
• Saab
• Airservices Australia
• the cockpit voice recorder and flight data recorder
• recorded data from Flightradar24. 

References

Australian Government 2023, Part 91 (General Operating and Flight Rules) Manual of Standards 2020, Civil Aviation Safety Authority, Canberra, ACT, viewed 30 April 2024, <Federal Register of Legislation - Part 91 (General Operating and Flight Rules) Manual of Standards 2020> 

Submissions

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

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

• Civil Aviation Safety Authority
• Airservices Australia
• Crew of VH-KDK
• Regional Express Aviation
• Pel-Air Aviation
• Swedish Accident Investigation Authority (SHK)
• Bureau of Enquiry and Analysis for Civil Aviation Safety (BEA).

Submissions were received from: 

• the captain of the crew
• Regional Express Aviation
• Pel-Air Aviation
• Swedish Accident Investigation Authority (SHK)
• Bureau of Enquiry and Analysis for Civil Aviation Safety (BEA).

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

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through:  identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2024   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 Commonwealth Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this report is licensed under a Creative Commons Attribution 4.0 International licence. The CC BY 4.0 licence enables you to distribute, remix, adapt, and build upon our material in any medium or format, so long as attribution is given to the Australian Transport Safety Bureau.  Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

Safety summary

What happened

On the morning of 18 December 2017, a Jetstar Airways Airbus A320 aircraft, registered VH‑VQG was on final approach for Gold Coast Airport, Queensland. The aircraft was operating as a scheduled passenger flight, from Adelaide, South Australia.

After a normal descent and touchdown, the captain selected both engine thrust reversers. The left engine thrust reverser did not activate. The aircraft decelerated using normal braking and taxied to the gate without further incident. There was no damage to the aircraft, or injuries as a result of the incident, and the captain reported the thrust reverser issue for investigation.

What the ATSB found

During overnight maintenance in Adelaide, the left engine thrust reverser lockout pin had been installed. However, the pin was not removed after the maintenance, resulting in the aircraft returning to service with the thrust reverser deactivated.

The lockout pin was located at the top of the engine and its 1 m red warning flag was difficult to see in the prevailing low‑light conditions. This probably led to the engineer not seeing the flag and removing the pin.

Further, the lockout pin was not booked out of the tool store nor was its installation recorded in the technical log. As a result, the checks that these procedures provided to ensure the pin's removal were missed.

What's been done as a result

The aircraft’s maintenance organisation, Qantas, advised that it is taking safety action that includes the following:

• Highlighting the importance of the aircraft maintenance manual precautions to maintenance staff at Adelaide.
• Lengthening all thrust reverser lockout pin warning flags to hang past the closed engine cowls. The pin will also have a warning notice attached for placement on the engine thrust reverser controls during maintenance.

The aircraft manufacturer, Airbus, advised that the August 2019 revision of the aircraft maintenance manual introduced an operational test of the thrust reverser system to confirm its re‑activation after maintenance tasks.

Safety message

This investigation highlights the importance of considering the environmental conditions in which equipment and tools will potentially be used, as well as the importance of following procedures that in this instance should have resulted in detecting the error.

When considering the effectiveness of equipment, tooling and procedures that aim to minimise the likelihood and/or consequences of an error, an engineered solution is generally more effective than relying on procedural compliance. Further, a functional check is generally more effective within procedural compliance than a self-check of work. See the ATSB research report, An overview of human factors in aviation maintenance (AR-2008-055), available from the ATSB website.

The occurrence

What happened

On the morning of 18 December 2017, a Jetstar Airways (Jetstar) Airbus A320 aircraft, registered VH‑VQG (VQG) was on final approach to Gold Coast Airport, Queensland. The aircraft was operating as a scheduled passenger flight, from Adelaide, South Australia, with two flight crew, four cabin crew, and 140 passengers.

At about 0845 Eastern Standard Time,^[1] air traffic control cleared VQG to land. After a normal descent and touchdown, the captain (pilot flying) selected both engine thrust reversers.^[2] The right engine thrust reverser activated but the left engine reverser did not, and the flight crew received a ‘reverse fault’ alert. They continued with the landing and the aircraft decelerated to a taxi speed using normal braking. The captain moved the thrust reverser controls to the stowed position, the aircraft was taxied to the gate without further incident and the passengers disembarked.

While taxiing, the captain cycled the thrust reverser levers and the alert extinguished. Nevertheless, the captain reported the thrust reverser issue for investigation by engineering personnel.

The subsequent engineering inspection found the left engine thrust reverser lockout pin installed, effectively deactivating the reverser. The lockout pin was removed, the thrust reverser confirmed to be operating normally and the aircraft returned to service.

There was no damage to the aircraft, or injuries as a result of the incident.

Overnight maintenance

Maintenance on the aircraft’s left engine was carried out in Adelaide during the night before the incident flight. Two A320 licensed maintenance engineers had carried out that maintenance.

One of the engineers (engineer 1) began his scheduled night shift at about 1900 on 17 December, and he described the weather that evening as hot and humid. He initially thought he was the only engineer on that shift to carry out maintenance certification on four A320 aircraft, and stated that he felt ‘stressed’ and under pressure. The other engineer (engineer 2) had been called in to work overtime that evening. He started his shift at 1830, carrying out other tasks before being assigned to assist engineer 1 with VQG later that evening.

At about 2300, after completing their other tasks, the engineers commenced maintenance on VQG. This maintenance was unscheduled and involved investigating an engine bleed air issue. Jetstar had not provided paperwork for this task. Engineer 2 began collecting the consumables required for the task. Engineer 1 went to the tarmac tool store to get a lockout pin, required to be installed on the engine to prevent inadvertent activation of the thrust reverser.

After locating the lockout pin with some difficulty, engineer 1 hurried back to the aircraft without booking out the pin on the store’s computer system. He opened the left engine cowling and, using a stand to access the top of the engine, installed the pin. Procedures required the pin’s installation to be entered in the aircraft’s technical log. The log was located in the line office, and the engineer decided to record it in the log later.

A couple of hours later, the engineers completed investigating the bleed air issue. By this time, it had started raining. Engineer 1 made a visual inspection around the engine in preparation to close the cowling. The available lighting had reduced as half the tarmac lights automatically turn off at midnight. Engineer 1 missed seeing the lockout pin and its 1 m long red warning flag, and closed the cowling (Figure 1). The flag was shorter than those on the pins in the hangar tool store at Adelaide, which had been lengthened to 4 m after a previous incident to make them more obvious. Additionally, the stand that engineer 1 had used to install the pin, and which may have reminded him about it, had been removed for another task.

The aircraft maintenance manual thrust reverser de-activation procedure also required the use of specific warning labels in the cockpit, stating that ‘thrust reverser HCU [hydraulic control unit] is de-activated’. This procedure was not used during this maintenance task.

Figure 1: Photograph of a thrust reverser lockout pin and warning flag (non-reflective)

Source: Operator, annotated by the ATSB

Shortly after 0230 on 18 December, the engineers completed the maintenance on VQG, and went to the line office to complete the paperwork. The engineers recorded different parts of the completed maintenance, but neither entered the installation of the lockout pin in the technical log.

At the release to service of VQG, a tooling inventory check was conducted. As the pin was not booked out on the store’s computer, it did not show up during the check.

The aircraft was released to service with the lockout pin installed.

Similar occurrences

AO-2018-064^[3]

In September 2018, the engine thrust reversers on a Jetstar A320 aircraft did not activate when landing at Sydney Airport, New South Wales. The ATSB investigation into that occurrence found that the thrust reverser lockout pins on both engines were not removed after maintenance at the Brisbane Airport, Queensland facility before the flight.

In that case, the aircraft maintenance lockout pins (fitted with warning flags) were substituted with in-service pins without flags. Further, the functional check of the thrust reversers following reactivation as per the operator’s task card for that planned maintenance was not carried out. The investigation also found that operational pressure to expedite the maintenance probably influenced the deviation from procedures.

January 2017

In January 2017, the right engine thrust reverser on a Jetstar A320 aircraft did not activate when landing at Melbourne Airport, Victoria. The operator’s investigation found that the thrust reverser lockout pin was not removed after maintenance at Adelaide before the flight.

In that case, the aircraft maintenance lockout pin also had a 1 m red warning flag and was not booked out on the store’s computer system.

Safety analysis

The left engine thrust reverser did not activate when VH‑VQG landed at the Gold Coast Airport because its lockout pin was installed. Engineers had installed the pin during maintenance in Adelaide before the flight, but missed removing it due to a number of reasons.

The maintenance in Adelaide was carried out in the night under artificial lighting on the tarmac. The lighting significantly reduced at midnight when the tarmac lights automatically dimmed (half extinguished). In addition, it was raining when engineer 1 carried out a visual inspection before closing the engine cowling. These conditions made it difficult to see the lockout pin’s red warning flag.

The red colour of the flag was also harder to see in the artificial lighting,^[4] and the flag was not fitted with reflective material. The lockout pin was located at the top of the engine, where its 1 m flag was not as conspicuous as other longer flags, which would have hung below the engine to the tarmac. Further, the stand used to install the pin, which might have served as a reminder, had been removed. The combination of these factors probably led to the pin not being removed.

Procedures aimed at ensuring the lockout pin’s removal were not followed. These procedures included booking items out on the tool store’s computer system. As the pin was not booked out, its return to the store could not be checked. Further, the pin’s installation was not recorded in the technical log, which meant its removal went unnoticed and unrecorded.

Finally, the required cockpit warnings associated with thrust reverser deactivation were not used, thereby removing an opportunity to identify that the pin had not been removed before the aircraft was returned to service.

Findings

These findings should not be read as apportioning blame or liability to any particular organisation or individual.

• The lockout pin on the left engine thrust reverser was not removed after maintenance, resulting in the aircraft returning to service with the thrust reverser deactivated.
• The location of the thrust reverser lockout pin at the top of the engine meant that its 1 m red warning flag was difficult to see in the prevailing low‑light conditions. This probably led to the engineer not seeing the flag and removing the pin.
• The lockout pin was not booked out of the tool store nor was its installation recorded in the technical log. As a result, the checks that these procedures provided to ensure the pin's removal were missed. Additionally, the required cockpit warnings associated with thrust reverser deactivation were not used, removing an opportunity to identify that the thrust reverser was disabled.

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.

Qantas

The aircraft maintenance organisation, Qantas, has advised the ATSB that it is taking the following safety actions:

• Highlighting the importance of the aircraft maintenance manual precautions, and the limitations of human performance on the stages of maintenance, to maintenance staff at Adelaide.
• Lengthening all thrust reverser lockout pin flags to hang past the closed cowls. The pin will also have a warning notice attached for placement on the engine thrust reverser controls during maintenance.
• Focused audits on work practices for tooling and documenting maintenance activities.
• Reiterating the responsibilities of engineers to those involved in this incident.

Airbus

The aircraft manufacturer, Airbus, advised that the August 2019 revision of the aircraft maintenance manual introduced an operational test of the thrust reverser system to confirm its re‑activation after maintenance tasks.

 

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 2019 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. Eastern Standard Time (EST): Coordinated Universal Time (UTC) + 10 hours.
2. The purpose of the engine thrust reversers is to decelerate the aircraft on the ground, either routinely or during an emergency.
3. Available at www.atsb.gov.au
4. An effect known as the Purkinje shift, red will appear darker relative to other colours as light levels decrease.

During the take-off run on runway 34 the first officer, who was flying the aircraft, called "failure" at approximately 120 knots. This was below V1, and the captain rejected the take-off. The Master Caution Air Conditioning lights were illuminated. The auxiliary power unit bleed air was supplying the left pack which was running in high mode. The pack tripped off as a result of high temperatures.

Autobrake was used in the rejected take-off selection and operated until down to a slow speed in the deceleration. The outboard left main wheel tyre deflated due to overheating. Both left main gear wheels and the left outboard brake unit were subsequently changed. Take-off should not be rejected from high speed for a Master Caution. However, when the first officer responded by calling "failure" the captain was obliged to reject the take-off.

Significant Factors

1. Master Caution Air Conditioning lights illuminated during the take-off roll.

2. The first officer incorrectly called "failure" for the caution light illumination.

3. The captain was obliged to reject the take off on the basis of the first officers call.