An incident where a SAAB 340 regional airliner crossed the holding point to enter the runway when another aircraft had commenced its take-off roll illustrates the effects expectations can have on how pilots perceive information, an Australian Transport Safety Bureau investigation report notes.

The Regional Express operated SAAB 340B, with a crew of three and 30 passengers, was being prepared to operate a flight from Carnarvon to Perth on the afternoon of 31 August 2020.

When the SAAB’s first officer was outside the aircraft conducting preflight inspections and the captain was on the flight deck, they both observed a Piper PA-31 twin-engined light aircraft taxi past them, and onto runway 22 via taxiway Alpha.

Neither SAAB pilot was monitoring Carnarvon’s local common traffic advisory frequency (CTAF) yet – nor were they required to be – so they did not hear the PA-31 pilot’s taxi call.

Carnarvon’s taxiway Alpha is at the southern end of runway 22, so aircraft are required to backtrack – taxi along the runway – before turning around and beginning their take-off roll.

Once on the runway, the PA-31, which was operating a Shine Aviation service to Geraldton with a pilot and two passengers on board, began to backtrack towards the threshold.

About three minutes after the PA-31 taxied past them, the SAAB pilots contacted Melbourne centre air traffic control to advise taxi details. Melbourne centre advised them to standby.

While waiting for Melbourne centre, the captain directed the first officer to broadcast on the CTAF that they were about to taxi.

“While the pilot of the PA-31 heard the SAAB crew’s taxi call, they did not respond on the CTAF,” ATSB Director Transport Safety Dr Michael Walker said.

“The SAAB then commenced taxiing for runway 22.”

Shortly after they commenced taxiing, the SAAB pilots were advised by Melbourne centre that the PA-31 was taxiing at Carnarvon for Geraldton and had planned the same route as them at 9,000 ft.

“However, the SAAB pilots later advised the ATSB that in their experience, air traffic control will provide the same information about another aircraft until they receive a departure call from that aircraft, which can occur some time after take-off,” Dr Walker said.

“Both pilots of the SAAB believed the PA-31 had already departed by the time they were ready to taxi, later stating they estimated at least 10 minutes had elapsed since they observed it taxiing past them.”

Based on the recorded radio transmissions, the ATSB estimated only about five minutes had passed.

“The SAAB crew said their belief the PA-31 had already departed was further enforced when they did not hear a response to their CTAF call, and did not observe any traffic on their traffic collision avoidance system (TCAS).”

When the SAAB arrived at the holding point for taxiway Alpha, the captain looked left up the runway, towards where the PA-31 was preparing to commence its take-off roll. The captain stated they did not see the other aircraft on the runway.

“At about this time, Melbourne centre passed traffic information to the PA-31, and the pilot of the PA-31 broadcast on the CTAF they had lined up and were rolling on runway 22,” Dr Walker said. “The SAAB flight crew did not hear either of these transmissions, possibly because their attention was diverted to confirming the assigned transponder code.”

Additionally, the SAAB flight crew later recalled that transmissions from the PA-31 were faint and quite scratchy, and this was supported by the aerodrome reporting officer (ARO) present during the incident.

The ATSB’s review of the CTAF recording noted the PA-31’s transmissions were distinctly weak in comparison to those from the SAAB and the ARO, but they were still audible and understandable. There was also no indication that the PA-31’s transmissions to Melbourne centre were degraded in any way.

“Since they believed the runway to be clear, the first officer of the SAAB broadcast they were entering and backtracking runway 22,” Dr Walker continued.

As the SAAB passed the holding point on taxiway Alpha, the pilot of the PA-31 commenced the take-off roll. The PA-31 pilot heard and observed the SAAB enter the runway and immediately advised them they were rolling.

The PA-31 subsequently rejected their take-off, and began backtracking again. The SAAB stopped a few metres past the holding point, prior to crossing the edge of the runway.

“This runway incursion incident highlights the potential effects that expectation can have on how a flight crew perceives information,” Dr Walker said.

“The ATSB found that although both flight crews were aware that they were mutual traffic, they both had an incorrect understanding of the other’s position and/or intentions, which led to them not recognising the potential conflict and therefore not directly communicating with each other.”

In addition, the investigation found that the lookout conducted by the SAAB’s pilots prior to entering the runway was not effective and likely to have been influenced by their expectation that the PA-31 had already departed.

Dr Walker said it is important that flight crew remain vigilant while maintaining situational awareness to counter expectation bias.

“Pilots should not hesitate to contact another aircraft if there is any uncertainty as to their position and/or intentions.”

Read the report: Runway incursion involving a SAAB 340B, VH-ZRH, Carnarvon Airport, Western Australia, on 31 August 2020

The Australian Transport Safety Bureau (ATSB) urges operators and owners of piston-engine aircraft to know about the presence of carbon monoxide (CO) by using an active warning detector. 

CO is a colourless and odourless gas, and its presence may not be detected until the physical symptoms and cognitive effects present themselves. When inhaled, CO preferentially binds to haemoglobin, the oxygen carrying molecule in red blood cells. This creates carboxyhaemoglobin (COHb) compounds and prevents oxygen from binding to the molecule and being transported, resulting in oxygen starvation.

Symptoms can include breathlessness, confusion, disorientation and incapacitation.

Disposable chemical spot detectors, as commonly used in general aviation, may be effective in warning pilots of the presence of CO, but they have known limitations. Spot detectors are passive devices that relies on the pilot regularly monitoring it for discolouration. In addition, identifying a positive indication is also dependent on the detector being easily visible and accessible. Plus, these detectors do have a limited shelf-life when removed from their original packaging, which may be further affected by factors such as exposure to harsh direct sunlight, cleaning chemicals, and halogens. 

The ATSB highlighted its concerns regarding exposure to CO when it issued two Safety Advisory Notices arising from its investigation into the collision with water of a DHC-2 Beaver aircraft in Jerusalem Bay, north of Sydney, in which the pilot and five passengers were fatally injured. 

Toxicological testing of blood samples found the pilot and two passengers had elevated levels of CO. The levels detected were likely to have adversely affected the pilot’s ability to control the aircraft during the flight. The aircraft was fitted with a disposable chemical CO spot detector.

From the investigation, the ATSB published a Safety Advisory Notice, to piston-engine aircraft owners and pilots, reiterated the importance of the use of an active CO detector in the cabin. A second Safety Advisory Notice, to maintainers of piston-engine aircraft, highlighted the importance of the thorough inspection of exhaust systems and the timely repair or replacement of deteriorated components. 

Additionally, the Civil Aviation Safety Authority (CASA) published an Airworthiness Bulletin(Opens in a new tab/window), which encouraged operators and maintenance organisations to initiate a periodic CO detection check to measure the level of CO in the cabin at each annual or 100 hours-time in service (whichever occurs first), and each time the exhaust system or related components are disturbed.

The CO level entering the cabin must be less than 1 part in 20,000 parts of air (equivalent to 50 parts per million), derived from FAA FAR 23.83.

The ATSB's 'Know CO' campaign, launched in December 2021, encourages the use of CO detectors with an active warning. These inexpensive and widely available devices can provide pilots with the best opportunity to detect CO exposure before it adversely affects their ability to control the aircraft, or they become incapacitated.

It is worth noting that in July 2023, the UK Civil Aviation Authority (CAA) published its report into a study on how low-cost, commercial off-the-shelf, carbon monoxide CO detectors with attention-getting capabilities performed in a variety of general aviation (GA) aircraft and operating conditions.

Following a review in 2020 of accidents and incidents in the UK by the Air Accidents Investigation Board (AAIB) which identified two fatal accidents, each with two fatalities, and fifteen other events where CO may have been a causal factor over a 20-year period,  a was established to qualitatively and quantitatively investigate how low-cost active detectors perform in UK GA aircraft over a full flying season, to better understand pilot’s user experience of flying with these devices and to evaluate CO levels in a cross-section of the fleet.

Findings from the study suggested the risk of CO exposure remains a persistent background threat throughout the year and is somewhat elevated during cold weather operations. Anecdotal test evidence suggested that active CO detectors designed for domestic use can function reasonably at typical recreational GA altitudes (up to 5,000 feet). 

The report highlighted that while effective maintenance remains the first line of defence against CO and is the only way to avoid exposure, choosing to fly with an active CO detector is a decision pilots can make to protect themselves and their passengers from CO should maintenance fail.

With a wide range of active CO detectors on the market it has never been easier for pilots to find a device that suits their needs and budget. Active CO detectors are increasingly being built into other aviation equipment as standard, including ADS-B and headsets, making them ever more prevalent in GA aircraft. Additionally, some active CO detectors can be paired to personal electronic devices such as smartphones and smartwatches, increasing the likelihood of being alerted to elevated CO levels.

The report also highlighted the risk of CO poisoning may be known and understood by many pilots, the same cannot be said for consumers and third parties generally, who may fly in piston engine aircraft on a commercial or recreational basis. Pilots therefore should consider the significant safety benefits offered by flying with an active CO detector – it could not only save their life, but their passengers’ as well.

Read the report: CODE Trial Summary Report (caa.co.uk)(Opens in a new tab/window)
 

AOPA Real Pilot Story: Hidden Hazard

Flying his Mooney, Dan Bass was overcome by CO poisoning and lost consciousness while airborne. He recounts the dreadful accident and his miraculous survival waking up in a snow-covered field in the bitter north American February cold.

New Zealand Airline Academy sees immediate value of electronic CO detectors

In this CAA NZ article, The value of an electronic CO detector | aviation.govt.nz(Opens in a new tab/window), the Chief Flying Instructor of the New Zealand Airline Academy talks about Installing electronic CO detectors across its entire training fleet almost immediately saved two lives.

Key points:

• A train’s driver was probably distracted by unrelated thoughts when the train passed a signal instructing it to stop;
• Driver stopped the train across a junction about to be used by second train on hearing an emergency broadcast made by the signaller;
• V/Line has committed to install a Track Protection and Warning System at the signal, and further signals at Southern Cross.

Victoria’s regional rail operator will install authority-overrun protection at a signal near Southern Cross station, following a near collision between two passenger trains there last year.

On the afternoon of 23 November 2020, a loco-hauled V/Line passenger train left Melbourne’s Southern Cross station for a service to Melton.

Shortly after departure, the train passed signal SST535, under the LaTrobe Street road-over-rail bridge, at about 23 km/h, despite the signal instructing the train to stop. This is known as a signal passed at danger (SPAD) event.

The train continued for about 200 m beyond the signal, before stopping across a junction which was about to be passed through by a second passenger train.

The second train, a three car V/Line VLocity train operating a Wendouree to Southern Cross service, stopped about 100 m from the junction, following an emergency broadcast from the controlling signaller.

The subsequent investigation into the near-collision, conducted on behalf of the ATSB by Victoria’s Chief Investigator Transport Safety, determined the driver was probably distracted by task-unrelated thoughts when they passed signal SST535, and probably looked past the signal to another, further along the track, which they incorrectly believed to be the signal where they were to stop.

“Once signal SST535 had been passed, the risk control to reduce the likelihood of a collision was primarily the action of the Southern Cross signaller to respond to system alarms,” Chief Investigator Chris McKeown said.

“In this instance, the signaller responded by making an emergency broadcast to the Wendouree to Southern Cross service and this was sufficient to stop that train. The driver of the Melton train also overheard this broadcast and stopped their train.”

Some signals around the V/Line network are equipped with a Train Protection and Warning System (TPWS), which can automatically brake a train when a SPAD occurs.

While both trains were equipped to receive signals from a TPWS system, trackside TPWS transmitters were not fitted at signal SST535 at the time of the incident.

During a 2014 risk assessment to determine which signals on its network warranted TPWS functionality, V/Line did not consider a head-on or side-on collision to be a credible scenario as a result of a SPAD at signal SST535.

“Had a front-on or side-on collision been considered a credible scenario in the 2014 risk assessment, the risk rating of the signal probably would have led to the fitting of TPWS.”

V/Line has advised that funding was approved in July 2021 to install track-mounted TPWS transmitters at a number of signals in the Southern Cross area, including signal SST535. The operator plans to complete this installation in 2022.

Additionally, the investigation also found the absence of ‘flank-track’ protection increased the risk of a potential collision in this incident.

Where a train’s route is set over a junction, flank-track protection requires the tracks between a signal protecting a converging route and the junction to be clear before the signal will display a proceed aspect.

In this instance, flank-track protection could have directed signalling to instruct the driver of the VLocity train to stop when the SPAD occurred.

“V/Line signalling standards did not identify flank-track protection as a control to prevent collision because of a SPAD, and none was installed at the incident location,” Mr McKeown said.

“Flank-track protection was also not identified as a potential control to prevent collision because of a SPAD in the signalling standards, administered by the Rail Industry Safety and Standards Board (RISSB).”

RISSB has advised flank-track protection will be considered for inclusion when the signalling principles standard AS 7711 is next under review.

“This occurrence has highlighted the importance for passenger rail networks to have engineering controls in place to detect SPAD events and prevent potential consequences such as collision,” Mr McKeown concluded.

“In determining applicable SPAD risk controls, rail operators should consider all SPAD precursors, and potential collision scenarios.”

Read the final report: Signal SST535 passed at danger involving passenger train 8239 and near collision with another passenger train, Docklands, Melbourne, on 23 November 2020

A pilot did not conduct a missed approach on two separate occasions while on an approach to land during which their twin-engined Piper aircraft exceeded tracking tolerance limits and they lost the required visual reference with the runway while operating below the approach minima, an Australian Transport Safety Bureau investigation details.

In the early afternoon of 22 March 2021, a twin-engined PA-31P-350 Mojave aircraft was conducting a positioning flight from Dubbo to Bankstown operating under instrument flight rules, with a pilot and crew member on board.

During a GPS instrument approach to Bankstown Airport’s runway 11C, the tower controller advised the pilot they were 0.5 NM south of the required track. This deviation continued as the aircraft passed the final approach fix, to the point it was exceeding tracking tolerance limits for the approach.

“The tower controller instructed the pilot to conduct a missed approach, but this did not occur,” ATSB Director Transport Safety Stuart Macleod said.

The pilot initially acknowledged that instruction but then requested, and was approved by the controller, to continue the approach visually as the aircraft had descended clear of cloud.

The pilot then conducted extensive manoeuvring, including two orbits, at low altitude and below the approach minima, that were not in accordance with the approach requirements, before landing the aircraft safely on runway 11C.

“The ATSB’s investigation into the incident found that the pilot did not conduct a missed approach when the aircraft exceeded the tracking tolerance limits, resulting in the aircraft operating significantly below the minimum allowable altitude,” Mr Macleod said.

“Additionally, having descended visually below the minimum descent altitude and commencing manoeuvring to position the aircraft for a landing, the pilot did not conduct a missed approach when the aircraft exited the circling area and the required visual reference with the runway was lost.”

Such manoeuvring was contrary to the intention of a circling approach, which is normally performed within the surveyed environment of the circuit area as part of visual circling to other than the straight‑in approach runway, Mr Macloed noted.

More importantly, when compared to the straight-in approach descent profile, it resulted in reduced obstacle clearance, increased pilot workload and an increased risk of an unstable approach.

“Adherence to operational procedures ensures consistency of pilot action and aircraft operation during the approach and landing phases of flight. This, along with careful monitoring of aircraft and approach parameters, ensures instrument approaches are conducted safely,” Mr Macleod said.

“If the criteria for safe continuation of an approach are not met, the pilot should conduct a missed approach to remove the risk of colliding with obstacles or terrain.”

Read the final report: Flight below minimum safe altitude, Piper PA-31 Mojave, VH-XGW, near Bankstown Airport, New South Wales, on 22 March 2021

An incident where a police air wing AW139 helicopter flew below the lowest safe altitude in the vicinity of Mount Baw Baw, Victoria, highlights the importance of lowest safe altitude calculations, according to an Australian Transport Safety Bureau (ATSB) investigation.

On the morning of 4 March 2021, the crew of a Victoria Police Air Wing AW139 was re-assigned from an aerial search near Coldstream, Victoria to a search and rescue task near Orbost. Due to cloud en route, the pilot upgraded the flight from visual to instrument flight rules.

While transiting to Bairnsdale at a cruising altitude of 5,000 ft, the helicopter entered cloud and shortly after the enhanced ground proximity warning system (EGPWS) activated with a ‘caution terrain’ alert. The pilot initiated a climbing left turn to avoid Mount Baw Baw, which has a maximum elevation of 5,138 ft.

At the time of the EGPWS alert, the helicopter was about 1.8 NM (3.3 km) horizontally from and 200 ft above terrain. A few moments later during the left turn, a second EGPWS alert activated, while the helicopter was at 5,150 ft and within 0.8 NM (1.5 km) horizontally and 350 ft above terrain.

The helicopter exited cloud to the north of Mount Baw Baw and the pilot contacted air traffic control to request a climb to 6,000 ft. The flight continued to Bairnsdale without further incident.

“Lowest safe altitudes are published on aeronautical charts and in publications to ensure a minimum 1,000 ft obstacle clearance when aircraft are operating under instrument flight rules,” ATSB Director Transport Safety Dr Stuart Godley explained.

“In this incident the helicopter was below the lowest safe altitude as, based on their estimate of height above the cloud tops, the pilot had incorrectly assessed the in-flight conditions as visual meteorological conditions after the helicopter reached 5,000 ft in the vicinity of Coldstream,” he said.

“As a result, the pilot elected to remain at 5,000 ft instead of recalculating the lowest safe altitude as the flight progressed.”

Day visual meteorological conditions are an acceptable reason to operate below lowest safe altitude. As the flight progressed the pilot observed the cloud tops beginning to rise, but initially believed they would pass just over the cloud tops. However, the helicopter entered cloud just below the cloud tops while the pilot was continuing attempts to contact East Sale air traffic control.

The ATSB’s investigation found that the operator did not have a procedure for pilots for upgrading from visual to instrument flight rules when in flight.

Particularly in single-pilot operations, this would reduce the likelihood of an error when replanning in-flight, which the operator reported to be an infrequent and higher-than-normal workload task.

“Our investigation highlights the importance of lowest safe altitude calculations and to recalculate the lowest safe altitude appropriate for the area of operations,” Dr Godley said.

“Operators should also review their operations manual to ensure they have procedures in place to adequately capture their operating procedures in order to minimise the likelihood of decision‑making errors.”

Following the incident, the Victoria Police Air Wing developed an instrument flight rules upgrade procedure for inclusion in its operations manual. This procedure includes the acceptable methods for calculating lowest safe altitude and was circulated to all their pilots.

Read the final report: Flight below lowest safe altitude and ground proximity alert involving Leonardo Helicopters AW139, VH-PVO, 44 km north-north-west of Latrobe Regional Airport, Victoria, on 4 March 2021

The Australian Transport Safety Bureau (ATSB) is alerting owners and operators of Vulcanair/Partenavia P.68 aircraft of a European Union Aviation Safety Agency (EASA) proposal to issue an airworthiness directive (PAD) to mandate an inspection of the aircraft’s upper rudder hinge.

The proposed AD, which was issued in October, would mandate inspections of the hinge in accordance with Service letter 23, revision 2, dated 29 September 2021(Opens in a new tab/window) and the aircraft’s maintenance manual.

It follows the ATSB’s publication of an Occurrence Brief report into a flight control system failure involving a Vulcanair P.68C near Brisbane, Queensland, on 11 April 2021. As the aircraft taxied to the apron after the flight, the pilot had difficulty controlling the aircraft’s direction and advised that the rudder seemed jammed.

A post-flight inspection revealed that the top rudder hinge had failed.

The PAD is applicable to all P.68 Victor, P.68B Victor, P.68R Victor, P.68C, P.68C-TC, P.68 Observer, P.68 Observer 2 and P.68TC Observer aircraft.

Consultation on the PAD closed on 18 November, but any follow-up enquiries regarding the proposed directive can be referred to EASA’s Safety Information Section, Certification Directorate via email ads@easa.europa.eu.

Read the Occurrence Brief (AB-2021-013): Flight control system failure, Vulcanair P.68C, near Brisbane, Queensland, on 11 April 2021

Key points:

• During a low-level geophysical survey flight, an overstress fracture due to a fatigue crack in a Cessna 210’s wing carry-through spar structure resulted in the separation of the right wing;
• Relevant Cessna 210 aircraft have since been subject to eddy inspection requirements to assess for fatigue and the application of a corrosion preventative coating, however the ATSB is recommending further safety action be taken;
• Cyclic loads induced by the low-level survey flight profile are significantly greater than those associated with the higher-level flight profile originally intended for the aircraft type.

The Australian Transport Safety Bureau has made a formal recommendation to the manufacturer of the Cessna 210 aircraft to further address the risk of fatigue cracking within the aircraft’s carry-through structure.

The safety recommendation forms part of the ATSB’s final report from its investigation into the 26 May 2019 collision with terrain of a Cessna T210M which was conducting low-level geophysical survey work about 25 km north‑east of Mount Isa, Queensland.

The aircraft, with a pilot and observer on-board, was operating at a height of 193 ft above ground level and a speed of 147 kt when its right wing separated in flight, leading to a rapid loss of control. The aircraft collided with the ground, and both crewmembers were fatally injured.

Relevant components of the aircraft were subject to detailed examination at the ATSB’s technical facilities in Canberra where it was found that relatively minor corrosion near a highly-stressed location on the lower surface of the wing spar carry-through had progressed into the aluminium alloy structure, initiating a fatigue crack. The crack propagated to a critical size resulting in an overstress fracture of the remaining wing carry-through structure material and separation of the right wing.

This information was immediately communicated to the aircraft manufacturer, Textron Aviation (which now owns Cessna), and Australian and US aviation regulators, and resulted in a number of initial safety actions.

These included Textron issuing service bulletins to owners of relevant Cessna 210 and Cessna 177 aircraft on 24 June 2019 requiring a one-off inspection of the carry‑through structure and communication of inspection findings to the manufacturer, and a US Federal Aviation Administration (FAA) Airworthiness Directive issued on 21 February 2020 requiring the visual and eddy current inspections of the carry-through spar lower cap along with the application of a corrosion preventative coating of certain model Cessna 210 aircraft.

At the time of finalising the ATSB’s investigation report, the FAA and Textron Aviation had received 1,119 reports from Cessna 210 owners/operators who had undertaken the visual and eddy current inspections of the carry-through spar on their aircraft. Of these, 499 reported corrosion and 68 carry‑through structures were removed from service.

Textron has advised the ATSB that it would be undertaking a fatigue analysis of the C210 wing spar carry-through in its original configuration to determine whether a modified inspection program or life limit is necessary. Textron has also advised the ATSB that it is working on a certification program to install a new spar in the C210 with an updated configuration and material.

“The ATSB acknowledges the significant safety actions taken to date by the manufacturer and regulators as a result of this accident and the ATSB’s investigation, and notes that these measures have addressed the short-term risk of further similar failures,” said ATSB Chief Commissioner Angus Mitchell.

“Further, the ATSB welcomes Textron’s ongoing efforts to address the risk of cracking in wing spar carry-through structure of Cessna 210 aircraft used for low-level geophysical survey operations. However, the ATSB remains concerned by the indefinite nature of the manufacturer’s proposed analysis and certification program and recommends that further action be taken to address this safety issue.”

In 1992, Cessna had introduced a continued airworthiness program for the Cessna 210 which included repetitive eddy current inspection for cracking of the carry-through structure. This flight-hours based inspection was more stringent for aircraft being used for low-level surveys.

Eddy current inspection is a form of non-destructive testing which can detect flaws in the internal consistency of certain types of metals.

However, following an assessment of historical data in 2011, Cessna replaced this inspection with a visual corrosion inspection, on a three-yearly frequency for all operation types, irrespective of hours flown.

“Had the previous flight-hour based eddy current inspection schedule remained in place, it is almost certain that the fatigue crack within the wing spar carry-through would have been detected before this accident occurred,” Mr Mitchell said.

The accident aircraft had accumulated 6,241 flight hours in the six years leading up to the accident, and had been operated exclusively as a geophysical survey aircraft during that time. In total the aircraft had accumulated 12,175 flight hours.

As part of the investigation the ATSB, in cooperation with the operator, undertook data gathering using an instrumented Cessna 210N to determine in-flight loads associated with the geophysical survey flight profile. Data from 95 flights over a period of 10 weeks during autumn in 2020 was sampled and analysed.

“The ATSB’s analysis showed that cyclic loads induced by the low-level survey flight profile were significantly greater than those associated with the higher-level flight profile originally intended for the aircraft type, and this probably increased the risk of a fatigue-related structural failure,” Mr Mitchell said.

“Even when flying within operational limits, if an aircraft is operated in a flight profile for which it was not originally intended, its structure can fatigue more rapidly.

“The ATSB cautions all geophysical survey aircraft operators that the terrain following flight profile may significantly increase aircraft fatigue damage accumulation.”

The investigation also determined that the airframe and system modifications incorporated into the accident aircraft did not significantly increase the fatigue damage accumulated by the wing spar carry-through structure.

Read the final report: In-flight break-up involving Cessna T210M, VH-SUX, 25 km north-east of Mount Isa Airport, Queensland, on 26 May 2019 | ATSB

Key Points:

• Two of five landing gear downlock pins were not removed after a Boeing 787 was towed to the gate and prior to departure;
• Pins were also not identified during subsequent pre-flight inspections
• Flight crew were unable to raise landing gear and the aircraft returned to Sydney;
• ‘Remove before flight’ streamers are visual reminders to remove covers and lockout devices prior to flight, but can be subject to varying environmental conditions that can reduce their visibility

Two downlock pins that had not been removed from a Boeing 787’s main landing gear following towing, nor identified during subsequent pre-flight inspections, prevented the aircraft’s main landing gear from retracting after take-off, an Australian Transport Safety Bureau investigation report outlines.

On 21 June 2021, the Qantas Boeing 787-9 departed Sydney for Perth with 106 passengers and 13 crew on board.

During the initial climb, when the flight crew selected UP on the aircraft’s landing gear lever, they received a warning indicating that neither main landing gear had retracted to the ‘up and locked’ position.

Actioning the aircraft’s electronic checklist did not resolve the issue.

The flight crew then selected the landing gear lever to DOWN, resulting in a positive gear extension indication, and the aircraft was returned to Sydney for an uneventful landing.

Subsequent inspections identified that two of the aircraft’s five landing gear downlock pins had not been removed after it had been towed to the domestic terminal aircraft bay in preparation for the flight.

The pins prevented the main landing gear from retracting after take-off.

“Pins are inserted into the nose and main landing gear when the aircraft is on the ground to prevent inadvertent gear retraction during maintenance or towing,” ATSB Director Transport Safety Stuart Macleod explained.

“In this case two of the pins – one of the two for each main landing gear – had not been removed after towing and prior to the flight. In addition, subsequent preflight inspections by the flight and dispatch crew did not identify that the pins remained in place prior to departure.”

Attached to each pin was a red ‘remove before flight’ streamer. One streamer on each main landing gear was visible in CCTV footage of the aircraft being towed to its bay prior to the flight.

The pins attached to these two streamers were removed before departure, while the second gear pin on each main landing gear was missed. The missed gear pin streamers may have been stuck on the gear, from a combination of grime and the recent wet and windy conditions.

Post-incident inspection found all four main gear pins’ streamers to be in place, but dull and frayed. Their condition prior to the flight could not be conclusively determined.

“‘Remove before flight’ streamers are visual reminders to remove covers and lockout devices prior to flight, but can be subject to varying environmental conditions that can reduce their visibility,” Mr Macleod said.

“Expectation can also affect your ability to identify these warning devices. If you are not expecting to see a ‘remove before flight’ streamer, you are significantly less likely to detect one that is present.

“The same principle can also prevent the discovery of damaged and/or missing components.”

The 787 has five landing gear pin locations: one in its nose gear, and two in each of its main landing gear, whereas other types in the Qantas fleet such as the A330 and 737 have three pins: one in the nose gear, and just one in each of the main landing gears.

The two members of the tow crew who had removed three of the five gear pins – one from the nose gear, and one each from the left and right main landing gear – had not towed a 787 prior to the occurrence.

Moreover, once removed, on the A330 and 737 the gear pins are stored on the flight deck, whereas on the 787 they are stored in the aircraft’s electrical equipment centre (EEC), just aft of the nose gear.

When stowing the three removed gear pins in this incident, the tow crew team member reached up from a ladder below, and so was unable to see inside the stowage compartment, where there were receptacles for five gear pins in total.

After the occurrence, Qantas advised it was working to relocate the gear pin stowage on its 787s to the flight deck, to bring them in line with other aircraft in its fleet, and to enable ease of access to verify pin stowage.

The operator also distributed a memo to its engineering, flight and ramp staff to highlight the quantity and location of the gear pins on the Boeing 787, and the importance of following the documented ramp, pre-flight and dispatch procedures.

The memo also emphasised the importance of checking the pin locations, rather than relying on ‘remove before flight’ streamers for identification of pins, after towing.

Read the final report: Landing gear retraction deactivation and return involving a Boeing 787, VH-ZNH, near Sydney Airport, New South Wales, on 21 June 2021

Key points

• Fracture of the propeller bolts was likely related to a loss of bolt tension
• Emergency training practice and recurrence increases the likelihood of pilots achieving a safe outcome
• The incident highlights the importance of pilots remaining vigilant to transient or persistent changes to the normal operation of their aircraft.

The propeller of a Jabiru aircraft separated in-flight due to fractured propeller bolts likely due to a loss of bolt tension, an ATSB investigation has found.  

A student pilot had departed on a training area solo flight in the Jabiru J170-C aircraft from Muchea Greenside airfield, north of Perth, on 22 December 2021. On return to the airfield, during the downwind leg of the circuit, the pilot commenced configuring the aircraft for landing when a vibration from the engine was felt.

The engine gauges read as normal and the vibration reduced with throttle reduction.

Shortly after, while on final approach, the pilot observed emus crossing the runway around the normal touchdown point and conducted a go-around. While on climb at around 800 feet, there was a loud ‘bang’ and the pilot observed that the propeller had separated from the aircraft.

The pilot elected to land ahead and conducted an uneventful forced landing in a paddock, approximately 2.5 km from the end of the runway. The aircraft suffered minor damage during the landing, and the pilot was uninjured.

“The ATSB’s investigation found that the propeller separated as a result of fracture of the propeller bolts that was likely related to a loss of bolt tension,” said ATSB Director Transport Safety Dr Stuart Godley.

“However, as the propeller was not able to be found, the mechanism for the loss of bolt tension was not determined.”

The investigation also noted that the student pilot’s actions were positively influenced by having recently undertaken several hours’ worth of flight emergency training, contributing to the safe outcome.

“When faced with an in-flight emergency, emergency training practice and recurrence will increase the likelihood of pilots achieving a safe outcome,” Dr Godley said.

The incident also highlights the importance of pilots remaining vigilant to transient or persistent changes to the normal operation of their aircraft, which may be indicative of an impending failure of a critical component or system.

“Landing as soon as practicable and having the aircraft inspected is a prudent course of action.”

Dr Godley noted that the ATSB did not typically investigate incidents and accidents involving recreational category aircraft. However, as Australia is the state of design and state of manufacture for the Jabiru aircraft, and the same aircraft model are registered with CASA and is also operated internationally, the ATSB conducted the investigation to determine if there were broader lessons for the aircraft type.

Read the final report: In-flight propeller loss involving Jabiru J170, 24-7496, near Muchea/Greenside ALA, Western Australia, on 22 December 2021