Key points:

• A sudden wind change during high-speed descent resulted in the airspeed suddenly increasing towards the aircraft maximum operating speed
• The captain responded by abruptly pulling back on the control column, causing autopilot to disconnect
• Subsequent sudden pitch attitude and vertical acceleration changes resulted in injuries to cabin crew members.

The actions of the captain of a Boeing 737 in response to a sudden speed increase during a high speed descent resulted in sudden pitch changes and injuries to two cabin crew members, a new ATSB report details.

The Virgin Australia-operated Boeing 737-800 was at the top of the descent 136 nautical miles south-east of Adelaide Airport conducting a scheduled passenger flight from Melbourne on 13 September 2017, with the first officer acting as pilot flying.

Air traffic control instructed the crew to perform a high-speed descent, which they commenced with the autopilot engaged with a target descent speed of 320 knots, which was higher than the normal descent speed of 280 knots.

During the descent, the first officer attempted to manage airspeed by using changes in the autopilot modes and reductions in the target airspeed. As the aircraft descended through around 17,000 feet, the tailwind affecting the aircraft decreased suddenly and significantly, which caused the indicated airspeed to increase and approach the maximum operating speed limit of 340 knots.

Highly concerned about overspeeding the aircraft, the captain responded by abruptly pulling back on the control column, causing the autopilot to disconnect. The resulting control forces caused sudden changes to the aircraft’s pitch attitude and vertical acceleration.

Two cabin crew members who were standing in the aircraft’s rear galley eating a meal received injuries during the upset, with one sustaining a broken leg.

ATSB Director Transport Safety Dr Stuart Godley said that during the occurrence, the aircraft only exceeded its maximum operating speed by one knot, which did not require any structural inspections to ensure the ongoing airworthiness of the aircraft. Instead, the safety implications associated with this event related to the actions of the captain in response to the sudden change in airspeed.

“Even though the autopilot was operating correctly, when the aircraft was approaching and exceeding the maximum operating speed, the captain’s perception was that the autopilot was not controlling the aircraft and that urgent intervention was necessary,” Dr Godley said.

“However, the captain did not follow the normal procedure for taking over control of pilot flying duties, and the large pitch control inputs made by the captain were probably influenced by a perception of urgency.”

Dr Godley said the investigation serves to remind pilots that they are entitled to decline air traffic control instructions where they do not perceive they can safely comply.

“Due to increased kinetic energy and reduced margins to placard speed limits, high-speed descents involve a higher level of risk, including increased risk of harm due to abrupt control input.”

The investigation also highlights the challenges pilots face when responding to sudden or unexpected situations, Dr Godley said.

“There will often be a reduction in safety when pilots perceive a situation is urgent and when they make decisions rapidly and reflexively. In these situations, pilots may not be able to effectively process information or make good decisions.”

The investigation also notes that it took over 90 minutes for the injured cabin crew member, who had sustained a badly broken leg, to be removed from the aircraft after its arrival at Adelaide, while the operator’s ground operations supervisor, Aviation Rescue Fire Fighting Service (ARFFS) officers and SA Ambulance officers co-ordinated the extraction.

The injured cabin crew member was not able to walk or to sit in a wheelchair, and an ambulance stretcher would not fit down the aircraft aisle, however, the ground operations supervisor declined an ARFFS request to use a catering truck, the report notes.

Instead, emergency services personnel used a slide sheet to drag the injured cabin crew member along the aisle to the front of the aircraft, then placed the injured cabin crew member on a stretcher.

Virgin Australia has subsequently updated the training and information provided to pilots about overspeed and overspeed recovery. The airline has also changed procedures for ground handling staff when responding to requests from emergency services.

Read the final report: Overspeed and pitch up resulting in cabin crew injury involving Boeing 737, VH‑VUE, 42 NM east-south-east of Adelaide Airport, South Australia, on 13 September 2017

Key points:

• Unstable atmospheric conditions resulted in UAV being unable to maintain controlled flight
• UAV’s structural limitations were exceeded, resulting in both wings fracturing at about mid-span
• Procedures ensured minimal risk to the public and environment

An Airbus Zephyr high-altitude UAV broke up in-flight after encountering unstable atmospheric conditions which resulted in a series of uncommanded rolls and an uncontrolled spiral descent over remote northern Western Australia, a new ATSB report details. 

The Zephyr unmanned aerial vehicle (UAV), designed as an ultra-light high-altitude pseudo‑satellite, had launched from Wyndham Airport on 28 September 2019 for a high altitude flight.

While climbing through an altitude of 5,200 feet and about one hour after launch, the UAV encountered unstable atmospheric conditions that resulted in an uncommanded roll to the right and a track change of about 180° before self-recovery. The flight crew in the ground control station, comprising a remote pilot, a remote pilot in command, a mission planner and a flight test engineer, elected to continue the climb and directed the UAV towards the north in anticipation of smoother conditions.

However, atmospheric conditions became increasingly unstable and the UAV, as it passed through 8,700 feet, experienced a second uncommanded roll but again was able to self-correct, with the crew increasing power and directing the aircraft to calmer conditions. Wind conditions reduced groundspeed to around 1 knot, reducing its ability to move out of the unstable conditions in a timely manner, and the Zephyr descended about 1,000 feet over the next 7 minutes.

The UAV then experienced a third uncommanded roll to the right. Unable to self‑recover, the UAV entered into an uncontrolled spiral descent, during which its maximum airspeed was exceeded and the roll angle increased beyond its structural limitations, resulting in both wings fracturing at about mid-span.

ATSB acting Director Transport Safety Derek Hoffmeister noted that the solar-electric Zephyr was designed to operate in the stratosphere, above the weather and conventional air traffic, and was extremely sensitive to atmospheric instability during the climb and descent phases.

“Once the Zephyr entered an area of unstable atmospheric conditions that exceeded the aircraft's ability to remain in the flight envelope, an in-flight break-up occurred,” Mr Hoffmeister said.

A separate Zephyr UAV was involved in an accident after launching from Wyndham in March 2019. The September 2019 accident was only the second launch from Wyndham for the Zephyr program.

“At the time of the occurrence, the Zephyr program was in its early operation phase. As such, information regarding the UAV’s structural limitations and methods to forecast turbulence were still evolving,” Mr Hoffmeister said.

“However, operational and post-crash management procedures were effective in minimising risk to the public and environment.”

In response to this accident, Airbus conducted an investigation of this occurrence, which resulted in several safety recommendations being directed to the design and operational departments of the Zephyr program.

“The number of UAVs and remotely piloted aircraft in Australia, and worldwide, is increasing rapidly," Mr Hoffmeister said.

“Through reporting and investigation of UAV and remotely piloted aircraft accidents and incidents, the ATSB is able to monitor trends and identify areas for safety improvement.

“This information helps to enhance the safety of all aircraft, and the public in general, enabling this sector of the aviation industry to continue to grow and develop.”

Read the final report: In-flight break-up involving Airbus Zephyr unmanned aerial vehicle, near Wyndham Airport, Western Australia, on 28 September 2019

Key points:

• Wagons started to roll back to towards siding as freight train’s locomotives started run-around movement
• Brake pipe air taps were closed during wagon uncoupling before full application of train air brakes
• Handbrakes not applied to wagons

Thirty freight train wagons rolled away unattended for 1,425 metres from a crossing loop before slowing and coming to a stop just before the end of a siding, road and level crossing at Bordertown, South Australia on 23 November 2019, a new ATSB report details.

The Bowmans Rail-operated freight train was being moved out from the siding onto the crossing loop, where locomotive drivers involved in preparing the train for its journey to Adelaide detached the train’s two locomotives for a run-around movement to reattach the locomotives to the other end of the train’s consist.

As the runaround movement started, the unattended wagons started to roll back towards the siding. The wagons rolled over a level crossing, bounced over a derailer and continued back into the siding. A driver in the siding saw the rolling wagons and ran alongside and commenced applying the handbrake to one of the wagons before they slowed and came to a stop.

In total, the wagons rolled unattended for about 1,425 metres, before stopping about 47 metres from the end of the siding, immediately before a level crossing.

“The ATSB found that while detaching the locomotives a misunderstanding between the driver in the lead locomotive and the driver uncoupling the wagons led to the brake pipe air taps being closed out of sequence and before a full application of the trains air brakes had propagated to the wagons,” said ATSB Director Transport Safety Dr Stuart Godley.

In addition, handbrakes were not applied to any wagons, the report notes. Not applying handbrakes during the run-around at Bordertown had become a common practice, as it saved time and had not caused any issues in the past.

“Once the locomotives were detached, the lack of air brakes and handbrakes allowed the wagons to roll away on the descending grade.”

Dr Godley said the occurrrence highlights how omitting a procedural step may result in over-reliance on remaining protective measures.

“The non-application of handbrakes increased the train’s reliance on the full application of wagon air brakes to prevent a runaway,” he said.

“However, a slight out of sequence implementation of the air brake process resulted in only partial application of the wagon air brakes and the subsequent runaway of unattended wagons.

“It is essential that all procedural steps are undertaken when uncoupling wagons for run-around movements.”

In response to the incident, operator Bowmans Rail has issued a safety alert requiring uncoupled wagons to have all air exhausted and handbrakes applied when left unattended.

“Additionally, the operator has communicated the findings of their investigation and their expectations to train crew, as well as consulted on improvements planned for its Bordertown shunting processes,” Dr Godley said.

The ATSB also found that the baulk installed on the Bordertown siding before the road and level crossing was only suitable for restraining runaways at speeds of up to 1.5 km/h and was unlikely to restrain the speed and momentum of a faster runaway.

The Australian Rail Track Corporation has since installed an arrestor bed on the track at the Bordertown dead end.

Read the final report: Runaway of freight train wagons, Bordertown, South Australia, on 23 November 2019

Key points:

• Level crossing protections mistakenly removed during signal upgrade work
• Isolation plans did not provide specific detail for the scope of work for each stage of the project
• Investigation highlights the importance of providing clear, concise and detailed work instructions to reduce the risk of errors

Flashing lights and boom gates were not activated at a North Geelong level crossing when an Overland passenger train passed through as protections had been inadvertently removed for planned track work.  

An ATSB investigation report into the 8 January 2019 incident found that, in preparation for signalling upgrade works, the Thompson Road level crossing was to be isolated for the broad and dual-gauge tracks only. However, the level crossing protections for the adjacent standard-gauge track were also deactivated.

“Level crossing protections for the standard-gauge track, as used by the Overland passenger train service, was to continue operating as normal until a second stage of works at the site at a later date,” said acting ATSB Director Transport Safety Kerri Hughes.

“However, the signalling tester, following the provided isolation plans, mistakenly isolated the level crossing for an upcoming second stage of works at the same time as for the initial stage of works.”

As a consequence, as the Adelaide-bound Overland service 3MA8 approached the level crossing, the train crew noticed that the flashing lights had not activated and the boom gate had not lowered. In response, they commenced braking, reduced the throttle, and sounded the horn to alert approaching road traffic.

“The train passed through the crossing at a reported speed of about 50 km/h, with the level crossing protections inactive,” said Ms Hughes.

“Although there was road traffic in the vicinity, no vehicles were on the crossing at the time the train passed through.”

The signalling upgrade work, managed by VicTrack and contracted to UGL Engineering, involved the removal, modification and installation of new signalling equipment. Stage one of the project involved the isolation of crossing protections for the V/Line-managed broad-gauge and dual-gauge tracks, with the level crossing protections for the adjacent ARTC-managed standard-gauge track to operate as normal until the start of a second stage of works.

The ATSB found that there were no supporting instructions in the plan specifically detailing the scope of work for each stage. 

“The contractor undertaking the work did not provide signalling testers with specific instructions detailing the scope of work to be conducted at each stage of a project, but rather, only provided packaged isolation plans for the entire project,” Ms Hughes said.

“The absence of these instructions increased the risk of the works being incorrectly implemented.”

This investigation highlights the importance of providing clear, concise, and detailed work instructions to reduce the risk of errors during critical safety work, Ms Hughes noted

“Work instructions are step-by-step guides on how to perform a specific task or activity, in support of a process or procedure. They are important defences within a safety system for ensuring work is performed safely and as intended.”

In response to the incident, VicTrack now includes specific work instructions for each task associated with level crossing isolation plans.

Read the final report: Level crossing irregularity involving passenger train 3MA8, North Geelong, Victoria, on 8 January 2019

Key points:

• Cloud and low visibility almost certainly precluded the pilot from navigating by ground reference
• The aircraft collided with terrain in level flight, under power
• ATSB remains concerned about the frequency of accidents, many fatal, which involve pilots flying with reduced visual cues

Low cloud and reduced visibility almost certainly resulted in the pilot of a Cessna 182 losing visual reference with the ground before the aircraft collided with rising terrain.

The aircraft had departed Mount Garnet, far north Queensland for a 20-minute flight under visual flight rules (VFR) to Atherton, with the pilot the sole occupant. The forecast weather for the 8 April 2019 flight included low cloud extending to the ground in areas of higher terrain, and low visibility in cloud and showers of rain.

The ATSB’s investigation into the accident found that cloud and low visibility almost certainly precluded the pilot from navigating by ground reference, and changes in aircraft direction and altitude, as recorded by the aircraft’s GPS unit, were indicative of the pilot manually flying the aeroplane rather than having the autopilot engaged.

“Changes in track were consistent with what would be expected if attempting to avoid weather,” said ATSB Director Transport Safety Dr Stuart Godley.

As the aircraft approached the Herberton Range it climbed to an altitude about 400 feet higher than the highest terrain in the area, but this was very likely not above the cloud tops, the investigation notes. It could not be known whether the pilot then descended in an attempt to get under the cloud, having lost visual reference with the ground, or due to geographical disorientation, having assessed the aircraft was beyond the range and closer to Atherton.

“Low cloud and reduced visibility obscured rising terrain, and this almost certainly resulted in the pilot losing visual reference with the ground and the aircraft colliding with terrain in level flight, and under power and pilot control.”

The aircraft impacted the tree canopy and terrain, and the pilot sustained fatal injuries. The 130 metre-long wreckage trail was consistent with significant forward speed at impact. No pilot radio calls were recorded.

“This tragic accident highlights that any pilot, no matter their level of experience, is at risk of experiencing disorientation and a loss of spatial awareness due to reduced visual cues if pressing on into instrument meteorological conditions (IMC) without a current instrument rating and in a suitably-equipped aircraft,” said Dr Godley.

Accidents involving visual flight rules pilots in Instrument Meteorological Conditions

The ATSB remains concerned about the frequency of accidents which involve pilots flying with reduced visual cues, as highlighted by its ‘Don’t push it, DON’T GO' – know your limits before flight’ safety campaign.

“The risks associated with operating under visual flight rules in adverse weather should not be under-estimated,” Dr Godley said.

“Understanding weather-related hazards and how to assess and mitigate them are vital skills for pilots, particularly those who fly in challenging environments like mountainous terrain.

“During flight, it is critical that pilots continuously assess the weather, and if conditions deteriorate make timely decisions to turn back, divert or hold in an area of good weather. Don’t push it, don’t go. Know your limits before taking off.”

The ATSB continues to encourage VFR pilots to use a ‘personal minimums’ checklist to help control and manage flight risks through identifying risk factors that include marginal weather conditions, and only fly in environments that do not exceed their capabilities.

“As a personal ‘go/no-go’ checklist they can help take the stress out of difficult decisions both before and during flight, and act as a safety buffer between the demands of the situation and the extent of a pilot’s skill,” Dr Godley said.

Short case studies of ATSB investigations into accidents involving VFR pilots encountering IMC are published in the ATSB’s recently-updated Accidents involving pilots in Instrument Meteorological Conditions publication.

“Weather-related general aviation accidents remain one of the ATSB’s most significant causes for concern in aviation safety,” Dr Godley said.

“The ATSB encourages VFR pilots to learn from the experiences of others, to help build a robust understanding of the risks of flying into IMC and just how rapidly such accidents can happen.”

Read the final report: Controlled flight into terrain involving Cessna 182, VH-DJN, 14 km south-south-west of Atherton Airport, Queensland, on 8 April 2019

Read the Accidents involving Visual Flight Rules pilots in Instrument Meteorological Conditions publication.

Key points:

• Uncommanded engine shutdown due to bearing fracture
• On the day before the flight, metal debris was detected on the engine chip detector
• Crew were unable to feather the propeller and it continued to rotate at low speed, in a coarse pitch condition

Confusing and ambiguous procedures probably led to maintenance personnel releasing to service a DHC-8 (Dash 8) aircraft which subsequently experienced an uncommanded in-flight engine shut down after metal debris had been detected on the engine’s chip detector, a new ATSB report details.

The QantasLink-operated DHC-8-400’s right engine, a Pratt & Whitney Canada PW150A, shut down uncommanded as the aircraft approached the top of the descent north of Brisbane Airport when operating a scheduled passenger flight from Mackay on 26 June 2018. The crew actioned the engine shutdown checklist but the propeller did not feather and continued to rotate at low speed in a coarse pitch position. The crew actioned the ‘Non-Normal’ checklist and continued to Brisbane for a safe landing.

“Examination of the affected engine at Pratt & Whitney’s facility in Canada found that the uncommanded shutdown occurred as a result of a bearing fracture in the tower shaft for the accessory gearbox that runs the main engine oil pump and fuel-metering unit,” ATSB Director Transport Safety Mr Stuart Macleod said.

However, consistent with previous similar occurrences, due to the extent of the damage it was not possible to establish the cause of the bearing fracture, the ATSB investigation notes.

Mr Macleod said the investigation found that maintainers missed an opportunity to ground the aircraft when, on the day before the flight, metal debris was detected on the engine’s chip detector.

“Procedures in the aircraft maintenance manual were confusing and ambiguous and this probably led to a misunderstanding which allowed the aircraft to be released to service.”

The investigation found that following the detection of debris on the chip detector and the oil filter, maintenance personnel discussed a previous detection of debris but incorrectly concluded that it did not need to be considered. This resulted in the aircraft being released to service with a 20 flight-hour limitation.

In response to the incident Pratt & Whitney Canada have standardised the wording relating to debris analysis guidance in the aircraft maintenance manual.

“The ATSB acknowledges the improvement this will make, but still considers there is ambiguity and the potential for confusion in the procedure and has asked Pratt & Whitney to take further action to improve the clarity of the chip detector debris analysis section of the manual,” Mr Macleod said.

In addition, QantasLink have introduced a system to monitor metallic debris found on chip detectors to assist in trend identification, and have issued an airworthiness standing order to all certifiers within the approved maintenance organisation to introduce a single certification statement standard for all maintenance.

“Clear and unambiguous procedures are very important to avoid misinterpretation and error when performing safety‑critical tasks like aircraft maintenance,” Mr Macleod said.

“This occurrence also illustrates that the high reliability of modern aircraft maintenance depends on accurate record keeping of all performed tasks to both communicate what has been done and assist in trend identification.”

QantasLink have also issued a technical advisory bulletin to DHC-8-400 pilots advising them of the incident and warning that propellers may not always feather as practiced in the simulator.

Despite detailed technical examination, the reason the propeller did not feather could not be established.

However, the propeller did go to a ‘safe coarse’ condition due to the counterweights in the propeller system, as it would if there was no oil in the propeller system, and QantasLink identified that the one engine inoperative performance reduction between a counter‑weight coarsened propeller and a fully feathered propeller was only 0.5–0.9 per cent.

Read the final report: Uncommanded engine shutdown involving De Havilland Aircraft of Canada DHC-8, VH-LQD, 77 km north-north-west of Brisbane Airport, Queensland, on 26 June 2018

Key points:

• The primary protection against thunderstorm-related turbulence is avoidance
• 10 nautical miles was not enough separation to ensure safe passage from a thunderstorm
• Incident occurred two years after two pilots were fatally injured in an in-flight breakup of another Cessna 210, which had encountered severe turbulence

Despite attempting to avoid a thunderstorm while flying in the Top End during the build-up, the pilot of a single-engine Cessna encountered sudden and sustained severe turbulence, resulting in a loss of control for an extended period and minor injuries to passengers.

The Cessna 210M, registered VH-SJW and operated by Mistar Holdings, was conducting a passenger charter flight with a pilot and four passengers on board from Darwin to Tindal, Northern Territory, on 25 November 2019. Soon after departure, the pilot diverted five nautical miles right of the planned track to avoid a large storm cell that was five nautical miles left of track.

While maintaining 3,500 feet, the aircraft encountered sudden and sustained severe turbulence. Control of the aircraft was lost for over three minutes, with the pilot having no control over bank angle, height or heading for extended periods. Radar at Darwin recorded the aircraft’s highest groundspeed as 210 knots, and rate of descent at one point to be 5,000 feet per minute with a lowest altitude of 1,200 feet.

Three of the passengers sustained minor injuries.

After landing safely at Tindal, the pilot inspected the Cessna for potential damage, before flying the aircraft for over an hour to Millingimbi to pick up four more passengers for a charter flight to Galiwin’ku (Elcho Island).

That evening, the pilot reported the incident to the operator who, upon receiving notification of the turbulence encounter, grounded the aircraft at Galiwin’ku, pending an engineering inspection.

This serious incident occurred just seven months after the ATSB published the final report from its investigation into the in-flight break up of another Cessna 210, which claimed the lives of two young pilots on 23 October 2017. The pilots had encountered severe turbulence while attempting to avoid thunderstorm activity to the east of Darwin during a flight to Galiwin’ku.

That investigation found a combination of airspeed, turbulence and control inputs probably led to excessive loading on the aircraft’s wings, which separated from the fuselage in-flight.

“These two investigations highlight the importance of recognising and avoiding tropical weather conditions that present significant hazards to flight,” ATSB Director Transport Safety Dr Mike Walker said.

“Identifying an appropriate distance to keep from thunderstorms, which comes through experience in operating in the tropics, can be particularly challenging for pilots.

“In many cases, deviations of 10 nautical miles may not be enough for an aircraft to remain safely clear of the turbulent and powerful forces associated with storms.”

The ATSB’s investigation into the 2019 occurrence also found that the operator did not have guidance to direct pilots to seek advice or peer support following abnormal events.

“Following the turbulence encounter, the inspection carried out by the pilot was not sufficient to ensure the airworthiness of the aircraft beyond doubt,” Dr Walker said.

“Flying another charter flight without an inspection by a qualified maintenance engineer exposed the operator, the pilot and the passengers to elevated risk.”

The investigation also highlights that the primary protection against thunderstorm related turbulence is avoidance, Dr Walker said.

“Operators, pilots and passengers can work together to avoid flying in adverse weather. For instance, by starting a day’s flying early it can be completed before weather becomes a problem typically in the afternoon.”

The investigation report notes that a pilot with the best intentions may make a suboptimal decision after experiencing an abnormal event.

“Operators can provide guidance to assist pilots to make good decisions in these situations, by providing peer support and emphasising the importance of reporting abnormal events in a timely manner,” Dr Walker said.

“Early reporting reduces pressure in operations, allowing ample time to make alternative arrangements.”

In October 2019, an ATSB Senior Transport Safety Investigator joined Aviation Safety Advisers from the Civil Aviation Safety Authority (CASA) in Darwin and Cairns to discuss with local pilots how to make more informed and rational decisions when managing the hazards associated with flying across the Top End during the build-up and wet seasons.

Later this evening [15 September 2020], CASA and the Bureau of Meteorology are holding a safety seminar in Darwin to again highlight the dangers of flying near thunderstorms for both general aviation and commercial pilots.

“Pilots should regularly review operational documents and industry advice to build on their experience and to develop a comprehensive understanding of the challenges of flying in the Top End, and the strategies available to reduce risk,” Dr Walker said.

Following this serious incident, the operator developed case studies for pilots, emphasising weather avoidance and management of abnormal events. These have been integrated into proficiency checks to ensure solid understanding of theory, and practical application of weather avoidance, escape and post encounter management.

Read the final report: Severe turbulence and loss of control involving a Cessna 210M, VH-SJW, 30 km south of Darwin Airport, Northern Territory, on 25 November 2019

Key points:

• Electrical power lost when the auxiliary generators shut down due to overheating cooling water
• Blackout resulted in a loss of propulsion and steering control
• Bridge communications were ineffective and the pilots were not informed of the machinery problems prior to the blackout

A bulk carrier ran aground in a channel during its departure from Dampier, Western Australia when it lost steering and propulsion due to a total electrical blackout from a failed generator.

The ATSB investigation into the 11 March 2018 grounding found that the 298 metre, Panamanian-flagged Bulk India had lost all steering control and propulsion when shortly after the main engine was increased to full ahead, the ship’s auxiliary diesel generator engines shut down after the cooling water temperature controller failed, resulting in overheated cooling water.  

In addition, when the ship’s emergency generator started in response to the blackout, it also shut down from overheating as a radiator fan belt that had failed several months earlier had not been replaced.

As a result, control of the Bulk India, which at the time had one tug in attendance and two pilots on-board, was lost and the rudder remained fixed at 20° to port. The ship turned to port and contacted the channel side, running aground.

The ship was recovered into the channel with the aid of tugs, before being taken out the channel to anchor. A subsequent dive inspection of the hull found evidence of contact with the bottom but no significant damage.

“The ATSB investigation found that the ship’s engineers did not immediately identify the problem and were unable to manually operate the cooling water temperature control valve in time to prevent the blackout,” said ATSB Director Transport Safety Mr Stuart Macleod.

“The investigation also found that while the problems in the engine room started about 13 minutes before the blackout, the two pilots on board were not informed of the situation. This removed the opportunity for the pilots to prepare for the loss of control, and delayed actions that may have assisted in a more timely or more effective response.”

The ship operator’s lack of adequate procedures to ensure that critical spares were identified and maintained in inventory to guarantee availability when required on board also contributed to the grounding, the investigation notes.

“This investigation highlights that ship operators and crewmembers should ensure that systems, machinery and equipment critical to the continued safe operation of the ship are thoroughly understood, as well as appropriately maintained and tested,” said Mr Macleod.

Subsequent to the grounding, the ship’s operator made improvement to their safety management and operating systems, as well as staff education and training processes.

Separately, Rio Tinto have revised escort towage arrangements for ships departing their facilities in Dampier following extensive simulation exercises and a review of existing risk assessments. As a result, a second tug remains in attendance with bulk carriers for further along the channel. Further, a comprehensive guidance manual for ship towage operations in Dampier and Port Walcott was developed.

Read the final report: Grounding of bulk carrier Bulk India, Dampier, Western Australia, on 11 March 2018

Key points:

• Pedal breaks, jams following small control input
• Failure likely due to a pre-existing fatigue crack, undetected at previous 100-hourly inspection
• Maintenance organisation to conduct magnetic particle inspection of pedal assembly at 2,200-hourly major overhauls

A Robinson R22 helicopter’s right tail rotor pedal failed due to fatigue cracking during mustering operations, an ATSB investigation details.

The R22 was conducting mustering at Kutchera Station in far north Queensland on 22 June 2019, when the pilot applied a small amount of right pedal to turn the helicopter, and the pedal cracked, bent forward and became stuck. The pilot was unable to dislodge the pedal and prepared for an immediate landing in accordance with the stuck pedal procedure. However, just prior to landing, the helicopter struck a tree and became uncontrollable, impacting the ground. While the helicopter was substantially damaged, the pilot was uninjured.

Following the accident, the helicopter’s maintenance organisation identified a significant fracture in the right tail rotor pedal assembly at a right angle weld join between two sections of tube.

The right pedal was then sent to the ATSB’s technical facilities in Canberra. Examination and testing determined that the pedal fracture was a result of a pre-existing fatigue failure, which had initiated at the highest stress part of the welded joint and had opened up following the control input applied by the pilot.

While it was considered likely that the developing crack was present at the time of a recent 100-hourly maintenance inspection, it was not detected, likely due to the location of the weld making it difficult to identify in-situ. The developing crack would have initially presented as a hairline feature, and it was located on a matte black surface, at a change in section slightly below the level of the cabin floor.

“The location of the fatigue crack in this accident highlighted the need to be vigilant when performing inspections in difficult or hard to reach places,” said acting Director Transport Safety Kerri Hughes.

“In the case of the tail rotor pedal, the inspection was made difficult due to the location, and required a torch and mirror to inspect the pedal assembly, which featured a matte black surface.”

While not required as part of the routine inspections, the helicopter’s maintenance organisation has added the tail rotor pedals to the list of components that undergo magnetic particle inspection at each 2,200‑hour overall for the R22.

The investigation also notes the pilot’s positive actions likely contributed to their avoiding any injuries.

“The quick thinking actions of the pilot following the failure resulted in a good outcome, with no injuries sustained,” Ms Hughes said.

Read the final report: Tail rotor pedal failure and collision with terrain involving Robinson R22, VH-HHQ, near Kutchera Station, Queensland, on 22 June 2019

The fuselage of a Dash 8 turboprop aircraft was penetrated in two places when a propeller blade collar separated shortly after take-off from Darwin.

The DHC-8-202 (Dash 8) aircraft had departed Darwin Airport for aerial work on 3 December 2019 when during the early stages of the climb, the flight crew heard a loud bang. Based on the observations by one crewmember the noise was assumed to be due to a birdstrike. With no issues with controllability and all systems functioning normally, the crew elected to continue the flight, which was undertaken without further incident.

On the ground, a subsequent engineering inspection found that the number 2 blade collar on the right propeller was missing and there was damage to the right propeller and ice shield on the right side of the aircraft fuselage. Removal of the shield revealed the fuselage had been penetrated in two places.

An ATSB investigation identified that the propeller blade collars on the number 2 and number 3 blades had previously undergone field repairs, after having been found loose. Examination of both blades showed evidence of inadequate cleaning and surface reparation on the number 2 blade shank, and that the collar on the number 3 blade was loose due to the presence of adhesive from the field repair.

“It is likely that surface preparation issues from the field repairs resulted in a lack of adhesion between the number 2 blade and its collar, leading to its separation in-flight,” said ATSB Director Transport Safety Stuart Macleod.

“The blade collar then struck the number 1 blade, accelerating the fragments of the collar forcefully into the aircraft's fuselage.”

“This investigation reminds operators and maintenance personnel that due to constraints on equipment, time, and experience, field repairs can be a source of added risk to an aircraft,” said Mr Macleod.

“To minimise risk, maintenance manuals should be closely followed when conducting field repairs and operators should consider alternatives such as replacement over repair whenever practical.”

In response to this incident, the aircraft operator, Cobham Aviation Services Australia, has released an engineering notice requiring the entire blade assembly to be replaced in the event of a loose or cracked blade collar and that if a serviceable blade assembly was not available, collars were to be replaced in consultation with a Technical Services Engineer, and in strict accordance with the component maintenance manual.

Mr Macleod noted that the incident also serves to remind pilots that damage to their aircraft may not always be apparent.

“This occurrence highlights that in‑flight damage may not always be readily apparent to flight crews, and in instances of abnormal noises and vibrations they should seriously consider terminating the flight,” he said.

Read the final report: Propeller blade collar failure involving de Havilland DHC-8, VH-ZZA, near Darwin, Northern Territory, on 3 December 2019