Key points:

• Mining charter flight experiences in-flight engine failure
• Pilots conduct successful forced landing with no injuries and minimal aircraft damage
• Repaired engine component contributed to compressor turbine blade fracture and subsequent engine failure

The Australian Transport Safety Bureau welcomes US Federal Aviation Administration (FAA) consideration of the adoption of an Airworthiness Directive that seeks to address the likelihood of compressor turbine blade failures in certain variants of the PT6A turbine engine fitted with repaired compressor turbine vane rings.

In August 2020 the FAA released a notice of proposed rulemaking of its consideration to issue the Airworthiness Directive (AD) which would require operators to check for, and remove specific third party‑repaired compressor turbine vane rings from Pratt & Whitney Canada PT6A‑114 and PT6A-34 series engines, which power single-engine Cessna 208B Caravan and aerial application aircraft, respectively.

The AD was first issued by Transport Canada and subsequently adopted by Australia’s Civil Aviation Safety Authority in 2019, and came in conjunction with an ATSB investigation into an engine-failure incident involving a Caravan aircraft with two pilots and 11 passengers onboard which force landed on a service road near the Solomon mine site in Western Australia on 16 November 2016.

In that incident the Caravan aircraft had departed Solomon Airport bound for Karratha when at an altitude of 4,600 feet the engine failed, with the pilots hearing a loud bang and observing smoke billowing from the exhaust.

On commencing a right turn back towards the airport, the pilots assessed that a return there would not be possible due to uncertainty over whether over they could safely avoid high terrain.

Scanning the immediate area, the pilots identified an unsealed dirt road as their planned emergency landing area. The subsequent landing was accomplished without injury to the occupants and the aircraft was undamaged apart from flat spots on the main gear tyres due to emergency braking on landing.

“A compressor turbine blade from the engine developed fatigue cracking and fractured after approximately 1.8 hours of operation, leading to the engine failure and resulting in the forced landing of the aircraft,” said ATSB Director Transport Safety Stuart Macleod.

“The compressor blade fracture in turn could be attributed to variations in the aerofoil geometry of a repaired compressor turbine vane ring. The variations likely led to increased vibratory stresses within the compressor turbine blade, and the development of fatigue cracking during operation of the engine.”

The investigation identified that the use of FAA-approved repaired compressor turbine vane rings significantly increased the likelihood of single-crystal 

compressor turbine blade fracture in PT6A-114A engines, compared to engines fitted with Pratt & Whitney Canada‑manufactured compressor turbine vane rings.

“This involved and complex investigation has resulted in significant safety actions being taken by a number of parties,” Mr Macleod said.

The compressor vane repairer, Southwest Turbine Inc, ceased conducting repairs on CT vane rings for fitment into PWC PT6A-114A engines in March 2017.

Also, in March 2017, the engine manufacturer, Pratt & Whitney Canada, released a Service Instruction Letter advising of the heightened risk of CMSX-6 single-crystal compressor turbine blade fatigue fracture when combined with a compressor turbine vane ring that had been repaired using processes that were not approved by PWC.

Then in August 2019, Transport Canada (the regulatory certifying authority for the PT6A engine) released airworthiness directive CF-2019-30, which required operators to check for, and remove, Southwest Turbine‑repaired CT vane rings from PT6A‑114 and PT6A-34 engines within a period of 9 calendar months, or 250 hours of operation.

That AD was immediately adopted by the Civil Aviation Safety Authority, requiring Australian operators to also remove Southwest Turbine-repaired compressor turbine vanes rings fitted to the PT6A-114A and PT6A‑34.

“Due to the significant safety action taken by the directly involved parties since the occurrence, including action from the engine and component manufacturers, as well as the aviation regulatory authorities, the ATSB considers that the risk of CMSX-6 single-crystal compressor turbine blade fractures in Australian‑operated PWC PT6A-114A engines has been adequately addressed,” Mr Macleod said.

“Further, the ATSB welcomes the initiation of safety action by the FAA to consider legislation of the Transport Canada AD. However, with closure of the NPRM on 1 October 2020, the ATSB notes that at the time of publication, no decision has been made whether the AD will be adopted.”

Mr Macleod said the occurrence shows how subtle changes can have unintended detrimental effects.

“In this instance, geometry variations in a repaired compressor turbine vane ring likely led to rapid fatigue cracking and fracture of a compressor turbine blade, and subsequent engine failure.”

Separately, the incident also reinforces the importance of communication and effective decision-making during an emergency, Mr Macleod said.

“The pilots’ response to the engine failure and subsequent emergency landing was handled in a competent and proficient manner that reduced the risk of damage to the aircraft and injury to passengers or crew,” he said.

“Noting the rugged terrain surrounding Solomon Airport, the decision to land on the access road considerably reduced the risk of damage and injury.”

Read the report: Engine failure and forced landing involving Cessna 208B, VH-LNH, 8 km north-west of Solomon Airport, Western Australia, on 16 November 2016

Key points:

• Ballast loss from a mud hole reduced track lateral resistance
• Longitudinal compressive forces were also present in the rail due to the day’s hot conditions
• Track buckled under the dynamic load of the train, with the leading bogie of one wagon derailing

A freight train wagon’s lead bogie derailed when passing over track that buckled and deformed under the train likely due to a loss of supporting ballast due to a mud hole and compressive forces within the rails due to hot weather, a new transport safety investigation report details.

On 21 January 2019, SCT Logistics freight train 6BM9, consisting of two locomotives and 31 wagons, was travelling south from a logistics terminal in Barnawartha, Victoria to Altona in Melbourne, with temperatures expected to reach 39°C.

At 1530, the train passed through Creighton travelling at about 100 km/h. About 500 metres after crossing Creighton Siding Road, the lead bogie of the third-last wagon derailed a short distance before a small rail bridge. The driver noticed a plume of dust towards the rear of the train in the rear view mirror, and observed a loss of brake pipe pressure.

The train was brought to a stop and network control notified. The crew then inspected the train and identified the derailed wagon. An immediate site inspection by maintenance personnel from the track manager, the Australian Rail Track Corporation (ARTC), found significant lateral misalignment of the track.

A transport safety investigation into the incident conducted by the office of Victoria’s Chief Investigator, Transport Safety, which undertakes rail safety investigations in Victoria on behalf of the ATSB, established that the wagon derailed at a section of track with a  mud hole* and an associated loss of ballast, resulting in a reduction of track lateral resistance.

“The combination of reduced track lateral resistance from the mudhole and longitudinal compression within the rails due to the hot weather was sufficient for the track to misalign under the dynamic loading of the freight train, and for one wagon to derail,” said Chris McKeown, Chief Investigator, Transport Safety.

“In this case, the wagon derailment only resulted in minor track damage, however, had the wagon not derailed an XPT passenger service 80 minutes behind the freight train would have encountered the track misalignment and possibly derailed,” he said.

The mud hole had been identified and recorded in maintenance work orders for at least two years prior to the derailment, but no remedial work had been undertaken and it was not identified as a special location for the monitoring of track stability in ARTC’s Track Stability Management Plan, the investigation notes.

“The loss of ballast profile at the derailment location probably required a more significant level of response than being monitored, such as a temporary speed restriction or repair,” Mr McKeown said.

The longitudinal compressive forces were due to the hot conditions of that day, and possibly localised low stress-free-temperatures in the rails near the rail bridge, the investigation notes.

“In continuously welded rail, longitudinal compression forces occurs regularly during summer, as the rail expands longitudinally and it may buckle if there is inadequate track lateral resistance,” said Mr McKeown.

“In this instance, the rail bridge likely acted as a fixed point, with deformed track creating an ‘S’ buckle that went from the derailment site to the bridge.”

In response to the derailment, ARTC has reviewed its Track Stability Management Plan and included the affected section of track as a special location for the monitoring of track stability.

“This investigation highlights the importance of rail infrastructure managers having systems in place to identify track sections vulnerable to lateral instability during the summer period,” Mr McKeown said.

* Mud holes occur when ballast becomes contaminated (or fouled) with fine materials. This can be due to poor ballast, a breakdown of the ballast material or the formation (the track base) rising up through the ballast. The fouled ballast retains water (appears like mud), prevents effective drainage, and can result in poor track geometry.

Read the report: Derailment of freight train 6BM9, at Creighton, Victoria, on 21 January 2019

Key points:

• Flight crew inadvertently lined-up and commenced take-off roll on Canberra Airport’s runway 30, rather than the assigned runway 35
• Flight crew advised they were ready for take-off before checks were complete

A Virgin Australia ATR72 inadvertently lined-up on the wrong runway at Canberra Airport for a night time departure, a new ATSB report details.

The flight crew of the 25 September 2019 flight to Sydney had elected to depart Canberra Airport’s runway 35 from intersection G (‘Golf’), based on aircraft performance considerations, environmental conditions and the short distance between their parking bay and the runway holding point.

While taxiing to the holding point at intersection Golf, the flight crew completed their departure review. Just before reaching the holding point, the flight crew advised ATC they were ready for take-off. After clearing the aircraft for take-off, ATC deactivated the stop bar and the lead-on lights were illuminated. The aircraft then crossed the holding point and started turning through the intersection and inadvertently lined-up with the centreline of runway 30, which is considerably shorter in length than runway 35.

ATC saw the aircraft moving on runway 30 and immediately instructed the flight crew to stop. At about the same time, the flight crew rejected the take-off.

A review of airport closed-circuit television and recorded flight data showed the aircraft lined-up on runway 30, paused and then briefly accelerated and braked suddenly. The aircraft then exited the runway and departed from intersection ‘N’ (November) for runway 35 as per ATC instructions, without further incident.   

Acting ATSB Director Transport Safety, Kerri Hughes said that using intersection Golf for runway 35 meant the flight crew only had about 90 seconds to complete the preparatory tasks for departure. This resulted in the flight crew advising ATC they were ready for take-off prior to completing the before take-off procedure.  

“The first officer reported being focused on the before take-off checks as they approached the holding point, while the captain was focussed on the runway lead-on lights,” Ms Hughes said.

“The challenge and response nature of the before take-off procedure would have required some of the captain’s focus. This likely resulted in the captain taxiing the aircraft through the intersection with divided attention, while the first officer’s attention was focussed inside the cockpit.”

Ms Hughes explained that intersection Golf leads to the intersection of the Canberra Airport's two runways, 12/30 and 17/35, and is listed in airport documentation as a known runway incursion hotspot due to this complex layout. There are few airports in Australia where a taxiway leads to the intersection of two runways.

Further, when the stop bar at intersection Golf was deactivated, the lead-on lights to both runway 30 and 35 were illuminated, increasing the risk of confusion.

“The complexity of some airport runway and taxiway layouts can be exacerbated by reduced visibility conditions, such as at night or in poor weather, which can easily increase flight crew confusion,” Ms Hughes said.

“This investigation highlights the need for flight crews to familiarise themselves with complex runway layouts, particularly any unique designs, and ensure effective flight crew co-ordination is employed to minimise the risk of a runway incursion.”

The investigation also found that Virgin Australia’s ATR72 before take-off procedure did not specify when the crew were to advise ATC they were ‘ready’ for take-off . Further, runway verification checks using external cues were not included in procedures for all their aircraft. 

“The ATSB notes that, while Virgin Australia no longer operate the ATR72 aircraft, they have developed a new runway verification procedure for inclusion in their Flight Crew Operating Manual for their Boeing 737 fleet.”

Read the final report: Runway incursion and take-off commenced on incorrect runway involving GIE Avions de Transport Régional ATR72, VH-VPJ, Canberra Airport, Australian Capital Territory, on 25 September 2019

Key points:

• Passenger train struck the end of a steel coil which had fallen off a freight train travelling in the opposite direction
• Coil’s securing straps likely failed due to direct contact with a supporting cradle, which was missing a rubber mat
• Two crew on the passenger train sustained minor injuries as train traversed damaged track

A passenger train had begun making an emergency braking application when it struck the tail of a steel ‘jumbo’ coil which was obstructing rail track in both directions on the Sydney-Melbourne main line near Winton, Victoria on 30 March 2018, after the coil had dislodged from a freight train, a new ATSB investigation report notes.

The Melbourne to Albury V/Line passenger train service was travelling at about 110 km/h when it struck the unrolled tail of the 1.9 metre diameter, 16 tonne coil of rolled steel.

The coil had fallen from the 35th wagon of a Pacific National freight train, which was travelling from Port Kembla to Melbourne with a consignment of steel products from Blue Scope Steel, after passing the Seven Mile Creek Bridge near Winton. After falling from the wagon, the coil impacted ballast between the tracks at least twice, misaligning the east and west tracks, and damaging 39 trailing wagons (including damage to steps, handbrakes, brake cylinders and bearing caps), before coming to rest between the two tracks.

About 10 minutes later, the V/Line passenger service, which was travelling in the opposite direction, impacted the unravelled tail of the coil and entered the damaged track, but did not derail.

Two train crew members standing in the buffet car were thrown sideways as the train traversed the damaged tracks, sustaining minor injuries. The train’s locomotive received superficial damage.  

“While no injuries to passengers were reported, this investigation highlights the importance of robust load restraint systems to protect against movement of loads during transport, which is particularly important for heavy loads,” said ATSB Director Transport Safety Dr Stuart Godley.

“Should heavy loads like jumbo coils fall from train wagons they pose a significant risk to the safety of passengers and train crew of other rail vehicles.”

After striking the coil, the driver brought the passenger train to a stop, and advised train control that they had struck a steel coil. After applying signal blocks to both tracks, train control requested the drivers of the freight train to stop and inspect their train.

The subsequent ATSB investigation into the incident found that the coil had likely fallen from the wagon due to the absence of a rubber mat from one of the two faces of the cradle that supported the coil. The mat’s absence meant some of the coil’s metal unitising securing straps were in direct metal-to-metal contact with the cradle, increasing the risk of the straps failing, and allowing the coil centre to telescope (where the inner rolls of the coil move laterally relative to the outer layers). This reduced the coil’s lateral stability, and increased the risk of it falling from the cradle.

While it could not be conclusively determined when the straps broke it was likely that at least some broke during transit, reducing the ability of the remaining straps to maintain the coil as a unit. Subsequently, the remaining straps either also broke due to the forces imposed on them or were insufficient to prevent the coil from telescoping. Two broken steel straps were found either side of the track where the coil had fallen from the train.

Photographic evidence showed that the mat had been missing from the wagon's cradle since at least June 2017.

“The missing mat resulted in steel-on-steel contact between the coil and the cradle,” said Dr Godley.

“This increased the likelihood of wear on the coil’s securing straps, particularly if the radial straps were positioned within the contact area, which was permitted by the operator’s loading rules. Consequently, the risk of securing straps breaking during the journey was increased.”

Since the incident, a number of actions have been taken to reduce the risk of a similar occurrence, the ATSB investigation report notes. These include Pacific National updating their freight loading manual to require the use of a minimum of two radial and two circumferential straps to secure coils. The operator also updated its wagon maintenance manual to include a requirement to 'consider the condition of load mats during inspection and maintenance', and to repair or replace as required.

However, the ATSB has identified two safety issues from the investigation that remain unaddressed, and so has issued two formal safety recommendations to Pacific National. The first recommendation concerns the risk presented by continuing to allow the loading of jumbo coils in such a way that radial securing straps can contact the wagon’s support cradle. The second concerns ensuring that cradles sufficiently restrain jumbo coils against lateral accelerations to prevent their moving and falling during transit.

“Load restraint systems should include assessments and documentation that demonstrate appropriate load cases, design requirements, operational and loading requirements have been met, to ensure that the safety of the load restraint is maintained over time,” said Dr Godley.

Read the final report: Track obstruction due to loss of freight involving train 6WM2 and subsequent impact of passenger train 8615 with track obstruction, near Winton, Victoria, on 30 March 2018

Key points:

• Boeing 787 experienced uncommanded right engine shutdown
• A blocked inlet filter in a fuel metering valve servo assembly resulted in the electronic engine control being unable to control flow of fuel to the engine, resulting in the shut down
• Replacement of fuel pump and hydro-mechanical unit now required in event of maintenance messages indicating lack of FMV control

A Boeing 787 experienced an uncommanded shutdown of its right Rolls-Royce Trent 1000 engine while the aircraft was on descent into Perth Airport due to a blocked inlet filter in a fuel metering valve servo assembly, an ATSB investigation report details.

Operated by Scoot Airways, the Boeing 787-9, registered 9V-OJE, departed Singapore on 11 October 2018 on a regular scheduled flight to Perth, with 11 crew members and 356 passengers on board. About 2 hours into the flight the fight crew received status messages indicating abnormalities with the right engine, and later told the ATSB that the engine was slow to respond to commanded inputs and that engine performance continued to decline. At 9,000 ft, severe thrust asymmetry developed, and the autopilot made a rudder input. Shortly after, the right engine shutdown uncommanded.

The flight crew issued a PAN and air traffic control provided a clearance to level-off at 5,000 ft and vectored the aircraft off the approach to allow time for the completion of the quick reference handbook checklist, which required the crew to decide whether they should attempt to relight the engine. With the close proximity of Perth Airport and the aircraft’s capability to land safely with one engine, the flight crew decided not to attempt an engine restart. They then completed their landing performance calculations and advised air traffic control they were ready to land. The aircraft subsequently landed safely at 1909 local time and passengers disembarked as normal.  

ATSB Director Transport Safety Stuart Macleod, said the investigation highlights the importance of flight crews being familiar with their emergency procedures.

“In this case the flight crew worked effectively to assess the situation and took appropriate action to minimise risk in line with the operator’s flight crew manual,” said Mr Macleod.

To determine the cause of the uncommanded engine shut down engine manufacturer Rolls-Royce conducted a review of flight data information from the electronic engine controller (EEC), the report explains.

“A series of maintenance messages were found indicating a gap between the commanded and actual position of the fuel metering valve (FMV) – part of the hydro-mechanical unit (HMU) used to control the supply of fuel to the engine – that increased until the engine shut down,” Mr Macleod said.

“The first message showed that the flight metering valve was taking longer than needed to reach the position as specified by the EEC, subsequent data showed that after a later commanded declaration the FMV moved below the idle position as directed and did not move back as directed reducing fuel to the engine and it shutting down.”

Before the aircraft’s non-revenue flight to return to Singapore for further maintenance the right engine’s HMU was replaced. Similar maintenance messages were generated during a later flight but without an in-flight engine shutdown.

“Examination of the two HMUs showed evidence of a blocked inlet filter in the FMV servo assembly from worn journal bearings the engine’s secondary high pressure fuel pump, limited the EEC’s ability to effectively manipulate the FMV position and therefore the flow of fuel to the engine,” said Mr Macleod.

In response to the incident Rolls-Royce have updated its Fault Isolation Manual to include the removal of the fuel pump and HMU in the event of maintenance messages indicating the FMV not moving as commanded position.

In addition, when on 1 November 2018, another Scoot Boeing 787 generated maintenance messages related to the HMU during start-up, the engine was inspected, and some wear was found on some journal bearings. To search for similar maintenance messages, Rolls-Royce examined all maintenance data across the fleet of Trent 1000 Package B and Package C engines and monitored ongoing flights. Six other events were found, five with Scoot-operated aircraft, but none resulted in an in-flight shutdown. The majority occurred between late 2018 and early 2019.

The report notes Rolls-Royce considered a number of factors to explain the incidences of journal bear wear on Scoot operating aircraft but due to the number of variables they were unable to identify a dominant factor that could explain their susceptibility to pump bearing wear; however, Rolls-Royce identified and implemented a number of interim measures such as engine data monitoring to address the risk from low life wear of bearings.

“This occurrence highlights that positively identifying all factors that contribute to technical failures can be difficult and time consuming but that it is possible for manufacturers and operators to implement interim risk mitigation measures as done in this case,” said Mr Macleod.

“Rolls-Royce have advised the ATSB they will continue to monitor maintenance messages and the condition of unserviceable fuel pumps and are investigating the possibility of using flight data to detect fuel pump journal wear before its effects on valve operation becomes apparent.”

Read the final report: Engine failure involving Boeing 787, 9V-OJE, Perth Airport, Western Australia, on 11 October 2018

Key points:

• Aircraft stalled and entered a spin while overflying a rural property’s landing area
• The pilot was unable to recover control of the aircraft before it impacted terrain
• Accident highlights the need for pilots to minimise the risk of stalling, particularly when in proximity to the ground

A Liberty XL-2 two-seat light aircraft likely stalled at low speed and at a height that limited an effective recovery before it collided with the ground at a rural property near Braidwood, NSW on 4 August 2019, fatally injuring the pilot, an ATSB investigation has found.

The Liberty had flown from Moruya to the property in company (i.e. following but not in formation) with a second light aircraft with the view to landing at the property, or if the landing area was deemed unsuitable, continuing on to Camden. The pilot of the other aircraft, a recreational category aircraft better suited to operating from unprepared landing strips due to its landing gear configuration and higher propeller clearance, successfully landed at the property, but then called the Liberty pilot via mobile phone to advise that the runway was not suitable for their aircraft.

Recorded data from a flight planning app on the Liberty pilot’s iPad showed that the aircraft approached the landing area from the south-east, overflew the homestead before turning left to circle the landing area with a slowing airspeed.

On a second orbit of the strip, at about 400 ft above ground level, and after crossing the marked end of the landing area, witnesses observed the left wing drop and the aircraft enter a steep rotating descent. The pilot was unable to recover control of the aircraft before it impacted terrain.

“The ATSB investigation found that the aircraft departed controlled flight after slowing and turning downwind with no flap selected,” said ATSB Director Transport Safety Dr Mike Walker.

“The left wing stalled, and this resulted in the aircraft entering into an upright spin at an altitude that limited an effective recovery.”

The ATSB has investigated a number of accidents where light aircraft have stalled and impacted terrain. A stall/spin will result in a steep pitch down and rotation towards the stalled wing. Recovery takes a considerable amount of height, the magnitude of which is dependent on the reaction time of the pilot, and the use of appropriate recovery technique.

“This investigation highlights the need for pilots to minimise the risk of stalling, particularly when in proximity to the ground, such as during take-off and landing,” Dr Walker said.

“Turning manoeuvres at or close to the aircraft’s critical angle of attack, if mishandled, can lead to a stall that may result in the aircraft entering a spin.

“Pilots can limit their risk of losing control in flight by maintaining situational awareness of the aircraft state while conducting turns, maintaining adequate airspeed through appropriate power application during increased bank angles, and by selecting altitudes to operate at that provide sufficient height to recognise and recover from a stall.”

The investigation established that the aircraft’s stall warning system, which was designed to provide aural warning of impending stall conditions about 5 kt above the expected stall speed, was most likely functional at the time of the accident. However, it is unknown if and for how long this warning may have sounded. How the pilot reacted to the warning before the aircraft stalled is also unknown.

Separately, the investigation found that the aircraft’s maintenance release was invalid due to an airworthiness directive (AD) requiring inspection of the muffler having not being acted upon. Dr Walker noted that the overdue maintenance did not contribute to the accident, however, the invalid maintenance release should have precluded further flight in the aircraft until the AD was addressed.

Read the final report: Collision with terrain involving Liberty Aerospace XL-2, VH-XLK, 9 km north-east of Braidwood, New South Wales, on 6 August 2019

Key points:

• Shortly after take-off at about 500 ft AGL engine power reduced to below idle
• Power loss probably due to undetected water contamination in fuel
• Chemical hopper was used as a ferry fuel tank without approved or documented engineering process

A Piper PA-36 aerial application aircraft forced landed in a paddock shortly after take-off after experiencing an engine power loss that was probably the result of water-contaminated fuel, an ATSB investigation has found.

The Piper PA-36-300 Pawnee Brave aircraft, which had been fitted with a PT6A turbine engine, had just departed Latrobe Regional Airport, Victoria on 12 August 2019 on the first leg of a ferry flight on delivery to a new owner in New Zealand.

The day before the accident flight the pilot had detected water in the fuel in the chemical hopper – which, consistent with common industry practice, was being used as a ferry fuel tank. The pilot drained and refuelled the hopper before conducting a second fuel drain check. Then on the day of the accident flight, the pilot’s pre-flight inspection included a fuel drain check, checking the fuel by sight and smell, with no water detected.

The aircraft subsequently departed Latrobe Airport’s runway 21, turning to the north and staying below overcast cloud at around 500 feet AGL. As take-off flap was raised and departure course was set, engine power unexpectedly reduced to below idle.

With the aircraft unable to maintain height, the pilot elected to conduct a forced landing in a paddock. During approach, the pilot detected power lines and elected to fly below them but the aircraft struck and cut a smaller unseen power line running beneath the main power lines. The pilot then intentionally conducted a hard landing to avoid hitting a fence in the middle of the paddock while airborne.

During landing, the right wing struck a fence post resulting in the separation of the outboard wing section, while the undercarriage was removed after striking several tree stumps. The pilot sustained minor injuries in the impact.

ATSB Director Transport Safety Stuart Macleod said the loss of engine power was probably due to water‑contaminated fuel.

“A significant quantity of water was found in the aircraft’s fuel system, including the airframe fuel bowl, fuel pump and the fuel control unit, while an off-white jelly substance in the fuel section of the fuel control unit may have also hindered fuel flow to the engine,” Mr Macleod said.

While the pilot had conducted a fuel drain check pre-flight, the ATSB notes that using an opaque fuel sampling container and relying on sight and smell to determine fuel quality can be unreliable.

“Checking for water in fuel using an opaque sampling container to sight and smell the fuel is not in accordance with Civil Aviation Safety Authority and US Federal Aviation Administration guidance for pre-flight testing, and does not assure that there is no suspended water droplets, which is a particular risk for turbine fuel,” Mr Macleod said.

“Instead, there are a number of methods to positively check for the presence of water, such as using water-detecting paper or paste.” 

The ATSB’s investigation also found that that the use of the chemical hopper as a ferry fuel tank was contrary to the aircraft manufacturer’s recommendation, and that no approved technical data was available for the modification.

“Using approved and documented engineering processes to make changes to safety-critical aircraft systems ensures the modification complies with applicable airworthiness standards or an equivalent level of safety,” Mr Macleod noted.  

The accident also illustrated the importance of being mentally prepared for an emergency, particularly an engine failure or a power loss in a single-engine aircraft, Mr Macleod explained.

“In this case, the pilot had secured the four-point harness over their flying suit prior to take-off, and had conducted a pre-take-off brief and so was prepared to take immediate action in the event of an engine power loss.”

Read the final report: Engine power loss involving Piper Aircraft Inc. PA-36, VH-TVU, near Latrobe Valley Airport, Victoria, on 12 August 2019

Key points:

• Coal train wagon derailed due to through-axle failure of an axle
• Derailed wheelset travelled 2.6 km before train came to a stop
• Operator conducted non-destructive testing of affected axles

Rail infrastructure including 4,350 sleepers were damaged when the wheelset of a wagon of a fully loaded coal train derailed near Moss Vale due to fatigue cracking, a new transport safety investigation report says.   

The coal train TM94, consisting of three locomotives and 45 wagons, had departed Tahmoor Colliery for Port Kembla in the early hours of 28 June 2019. As the train approached the Suttor Road level crossing the 14^th wagon’s L1 axle bearing journal separated from the rest of the axle, resulting in the wagon’s R2 wheel derailing. As there was no loss of brake pressure the train continued, with the train crew initially unaware that a derailment had occurred.

As the front of the train passed through the Suttor Road crossing at 12:42 am, a rail enthusiast who was filming the train saw sparks and heard a loud noise coming from the wheelset and contacted the Network Control Centre South at Junee. At 12:44 am, the Junee area controller requested the train crew to stop and check the train. The train came to a stop minutes later, about 2.6 kilometres past the point of derailment, by which point approximately 4,350 concrete sleepers and the concrete pad at the Suttor Road crossing had been damaged.

A transport safety investigation into the incident conducted on behalf of the ATSB by the New South Wales Office of Transport Safety Investigations (OTSI) found that the derailment was due to a through-axle fracture at the start of a radius transition, about 250 mm from the end of the axle.

The report notes that although no clear initiation point for the fatigue crack was visible, a discoloured area, extending 16 mm into the cross section, was the likely the initiation point and that cracking was likely present at the time of two separate wheelset maintenance activities in January and November 2016 and would have been detected had non-destructive testing been carried out on the wheelset.

There was no evidence to suggest that the actions of the train crew contributed to the derailment.

“This investigation highlights the need for rolling stock operators and maintainers to ensure that axle maintenance and inspection procedures include non-destructive testing of known defect areas are as part of their regular maintenance program,” said OTSI CEO and Chief Investigator Mick Quinn.

“Records of these inspections also need to be kept within their asset management system for the life of the asset.”  

To ensure that no axles pose an immediate risk of failure, the operator has completed a program in-situ of non-destructive testing of axles, including ultrasonic testing of all 7E5S axles.

The operator has also issued a Rolling Stock Notice to their wheel set overhaul contractors reinforcing the requirement to inspect and test the fillet radius for all axles where bearing removal is mandated.

Read the final report: Derailment of loaded Pacific National coal service TM94, near Moss Vale, New South Wales, on 28 June 2019

Key points:

• Duty controller granted track access to maintenance electrician during shunting
• Required protection flags were not placed on the train
• Elements of the operator’s safety management system had little scope to recover once human or procedural error occurred

A maintenance electrician was inadvertently briefly beneath a moving train wagon during a shunting operation at the Skitube Alpine Railway’s Bullocks Flat Terminal, a new ATSB investigation report details.

The electrician was uninjured during the 3 July 2019 incident, which occurred during a scheduled de-coupling of a four carriage Skitube train set into two two-carriage sets at the Bullocks Flat Terminal, New South Wales. Just before the carriage started moving the electrician heard the brakes release and moved against the wall under the platform, clear of the train, the report details.

The transport safety investigation into the incident, which was classified as a ‘near miss’, was carried out by the Office of Transport Safety Investigations (OTSI), which conducts rail incident investigations in New South Wales on behalf of the ATSB, found that the duty controller had granted access to the electrician during shunting activity on the track. 

“It is likely that the duty controller did not connect that the shunting operation and the electrician accessing the track was occurring at the same time, due to other activities occurring in the control room, including the visit of an off-duty controller,” noted acting OTSI Chief Investigator, Mick Quinn.

“In addition, the electrician did not apply the required protection flags to the train set to indicate that work was being conducted on the train.”

The investigation also found that Skitube’s safety management system was reliant on procedures being followed to manage safety risks and that there was little scope for the system to recover once there had been a human or procedural error.

“In this instance, the operator’s safety management system did consider the likelihood of the duty controller making an error and provided two secondary layers of control, the control room logbook and the temporary access track form, however these did not provide any greater awareness of a pending conflict for the controller,” Mr Quinn continued.

“Also, the placement of protection flags does not ensure energy to a train is isolated and that the train cannot be moved while it is being worked on.” 

The investigation highlights the importance of workers ensuring they are protected and that they follow safety procedures before entering the danger zone or when interacting with trains, Mr Quinn said.

“Safety management systems also need to identify when conflicting activities take place that increase the risk to workers, and organisations should assess their risk controls to ensure their safety systems are error-tolerant and have a second line of defence to protect workers,” he said.

Since the near miss, Skitube updated its temporary track access procedures. That included its red flag procedure – including lowering the pantograph, applying the brakes, removing keys and locking the driver’s cab, and placing a “Do Not Operate” tag on all driver’s cabs when a person is required to be in close proximity to a stationary train – which was formalised and documented as a discrete procedure.

Read the final report: Near miss with maintenance worker on Skitube Alpine Railway, Bullocks Flat, New South Wales, on 3 July 2019