Key points:

• Blockage in the left pitot tube prevented water escaping, obstructing air flow;
• Incorrect airspeed indications were displayed on the left PFD, triggering miscompare alerts;
• Spurious instrument readings can create a more complex scenario for pilots than a complete instrument failure

Differing airspeed indications on a PC-12 aircraft’s two primary flight displays due to a blocked pitot tube underscores the complexity of managing spurious instrument readings, an Australian Transport Safety Bureau (ATSB) investigation notes.

On the evening of 22 June 2020, a Royal Flying Doctor Service Pilatus PC-12/47E was conducting a positioning flight from Perth’s Jandakot Airport to Albany, on Western Australia’s southern coast, with a pilot, a doctor and a flight nurse on-board.

On descent to Albany while passing through flight level 180 and in icing conditions, the pilot observed an airspeed miscompare indication on the aircraft’s left primary flight display (PFD).

The pilot then compared the airspeeds displayed on the left and right PFDs with the airspeed indication on the aircraft’s standby instruments (the electronic secondary instrument system/ESIS), and determined that the left PFD was likely displaying incorrect information.

Assessing that a blocked pitot tube was likely causing erroneous data, the pilot requested clearance from air traffic control to climb to FL230 to get clear of cloud and avoid the worst of the icing conditions.

During the climb, the airspeed displayed on the left PFD exceeded the aircraft’s maximum operating speed, resulting in audible overspeed alerts, and the pilot elected to return to Jandakot rather than continue to Albany.

During the return to Jandakot, while descending the aircraft to exit icing conditions and cloud, the left PFD’s indicated airspeed reduced to zero, however, no stall warning activated. In addition, heading data on the left and right PFDs diverged, resulting in a heading miscompare indication on the left PFD, while the left PFD would also display an incorrect attitude.

Approaching Jandakot the pilot reported that all indications returned to normal until the aircraft was on short final to land when an altitude mismatch and low airspeed warning was identified on the PFDs

The aircraft landed without further incident.

Post flight, an initial aircraft examination revealed a small amount of foreign material was blocking the left pitot tube drain.

“During the flight, water entered the left pitot tube either as rain or an accumulation of moisture from flying through cloud,” said ATSB Director Transport Safety Stuart Macleod.

“The blockage meant the water was unable to escape, and this in turn obstructed the flow of air to the aircraft’s air data attitude heading reference system, resulting in an incorrect airspeed being displayed on the left PFD.”

In addition, the heading miscompare was likely caused by the aircraft’s movement through moderate to severe turbulence during the return to Jandakot, Mr Macleod noted.

About a month prior to the incident the pilot had undertaken an operational proficiency check flight under the guidance of a check and training captain, which included observing the aircraft’s performance at various engine power settings and attitude combinations.

“The pilot advised the ATSB that this check flight had given them more confidence in the assessment that it was likely a pitot tube blockage and that the right PFD and ESIS were showing the correct information,” Mr Macleod said.

“Spurious instrument readings can create a more complex scenario for pilots than a complete instrument failure.

“Unlike in this incident, erroneous overspeed readings have had serious consequences when not properly diagnosed.”

Read the final report: Unreliable Airspeed Indication involving Pilatus PC-12/47E, VH-OWI, near Albany, Western Australia, on 22 June 2020

The collision of a passenger train with the open hatch of an adjacent locomotive emphasises the need for appropriate risk controls to prevent hatches from opening during service, a safety investigation has concluded.

On the evening of 21 July 2020, a passenger train bound for Kiama collided with the air filter hatch of a stationary Pacific National NR locomotive near Loftus station, on Sydney Trains’ Illawarra line.

There were no injuries reported, but the guard’s windscreen and passenger doors on the lead carriage of the passenger train were damaged in the collision.

An investigation into the incident was undertaken by the Office of Transport Safety Investigations (OTSI), which conducts rail safety investigations in NSW on behalf of the ATSB.

It concluded the air filter hatch was likely not properly secured during recent maintenance. This was then missed during roll-by inspections, as the design of the hatch and locks meant that the hatch could appear visibly closed and locked without it being secured correctly.

Open, and able to swing perpendicular to the train, the hatch exceeded the rolling stock outline*, thus becoming out of gauge. This allowed the hatch to infringe on the outline of the oncoming passenger train on the adjacent track.

The Australian Standard for Rolling Stock Outlines (AS 7507:2017) specifies external hatches should be designed such that when open they do not protrude from the kinematic envelope (i.e. outline) of the rolling stock.

“If this cannot be achieved, the Australian Standard suggests a range of secondary measures that can prevent an incident like this one occurring,” said OTSI Chief Investigator and CEO Dr Natalie Pelham.

“While not mandatory, the Standard provides industry with guidance on recommended practices that can reduce the risk of an incident occurring and improve safety for everyone using the network.

“Rail transport operators should review their rolling stock to ensure that appropriate risk controls are in place to prevent hatches from opening while in service and becoming out of gauge.”

Following the incident, Pacific National and its maintenance provider United Group Limited (UGL) conducted an assessment of the NR locomotive fleet, which identified the locomotives’ CA10 communications cabinets featured a hatch which could also exceed the rolling stock outline if not properly secured.

As a result, Pacific National and UGL have released a modification to fit a secondary latch to the air filter and CA10 hatches on all NR locomotives.

The intent of the modification is to prevent a hatch from exceeding the rolling stock outline if it was not properly secured or the lock was to fail.

Pacific National and UGL also issued a bulletin to maintenance staff in November 2020, detailing the correct procedure for securing hatches, and conducted an inspection to check the integrity of locks and hinges on air filter hatches across the NR locomotive fleet.

* The maximum permissible dimension a train must remain within to maintain acceptable clearances between rolling stock, structures and passing trains.

Read the final report: Collision between out of gauge freight train 3WB3 and passenger train C181, Loftus, New South Wales, on 21 July 2020

Key points:

• Student pilot and Instructor did not detect forecast deteriorating weather during their pre-flight briefing;
• Pilots should maintain knowledge and skills required to avoid unintentional operations in IMC;
• If a VFR-rated pilot does find themselves in marginal weather, they should seek whatever assistance is available, including contacting air traffic services.

An incident that saw a student pilot and instructor in a Piper PA-28 encounter deteriorating weather and enter instrument meteorological conditions (IMC) while operating under visual flight rules (VFR) highlights the importance of thorough pre-flight planning, an Australian Transport Safety Bureau investigation notes.

The student pilot (in the left seat) and instructor (in the right hand seat), with a second student pilot (seated in the rear) observing, were conducting a navigation training flight in the PA-28 from Melbourne’s Moorabbin Airport to Warrnambool in western Victoria and return on 25 February 2021, as part of the student’s integrated commercial pilot licence training.

After refuelling at Warrnambool the aircraft departed to return to Moorabbin in visual flight conditions, with the plan that they would return to Warrnambool if the weather deteriorated.

As the flight progressed, and as had been forecast, the weather deteriorated, and the instructor decided to divert to Cobden Airport to land and wait until the weather cleared.

However, visibility significantly reduced in rain, and the instructor, who held an instrument rating but had not conducted any instrument flying since a March 2020 proficiency check (and therefore did not meet the currency requirements for single-pilot instrument flight rules flights), took control of the aircraft and the decision was taken to return to Warrnambool.

As the aircraft approached Warrnambool, visibility continued to reduce and the cloud base began to lower. The instructor then initiated a climb into cloud and contacted air traffic control, which provided navigation assistance to an area free from cloud, issuing a heading to Avalon Airport.

The aircraft, which was certified for day and night VFR operations only, subsequently exited cloud about 10 nm south-west of Avalon Airport, with the flight then continuing to Moorabbin for an uneventful landing.

“The ATSB found that although the pilots had conducted a pre-flight briefing, they did not detect the forecast deteriorating weather in the Warrnambool area,” said ATSB Director Transport Safety Stuart Macleod.

“In addition, prior to departure from Warrnambool they did not assess the aerodrome forecasts for both Moorabbin and Warrnambool to ensure they were suitable destination airports.

“This probably resulted in them selecting Warrnambool as an alternate airport, despite the forecast temporary deterioration, and the aircraft encountering poor weather during the return to Warrnambool.”

Mr Macleod said weather related incidents continue to be a significant concern in aviation safety.

“The ATSB encourages pilots of all experience levels to develop and maintain the knowledge and skills required to avoid unintentional operations in IMC,” he said.

“And if a VFR-rated pilot does find themselves in marginal weather, they should seek whatever assistance is available, including contacting air traffic services.”

Mr Macleod said the ATSB’s 'Don't push it, Don't go' safety education campaign provides further information on the risks of VFR into IMC flight.

“Don’t push it, Don’t go’ highlighted three key messages: the importance of thorough pre-flight planning and having alternate plans, that pressing on where there is the possibility of entering IMC carries a significant risk of spatial disorientation, and the value of using a ‘personal minimums’ checklist to help manage flight risks,” he said. 

“Pilots without a current instrument rating should always be prepared to amend and delay plans to fly due to poor or deteriorating weather conditions, and not to push on.

“Thorough pre-flight preparation is the best defence against flying into deteriorating weather."

Read the report: VFR into IMC involving a Piper PA-28, VH-FPS, near Warrnambool, Victoria, on 25 February 2021

A Robinson R22 helicopter which collided with terrain while mustering showed evidence of a wirestrike, the ATSB’s preliminary report from its on-going investigation into the 26 May 2021 accident details.

The pilot, the sole occupant on board, was mustering cattle along a fence line on a property 75 km west of Hay, NSW, and had landed to open a gate at the entrance to a yard. Shortly after, a witness heard the helicopter take-off and, very soon after, a loud bang.

Suspecting an accident, the witness drove to the site and found the helicopter on its side, substantially damaged. First aid was rendered to the pilot, however they had sustained fatal injuries.

Subsequent analysis of recorded flight data by ATSB transport safety investigators indicated that after taking off after the pilot had opened the gate, the helicopter flew south towards another gate, at between 20 and 30 feet (6 to 9 metres) above ground level, and at a speed of up to 27 knots. The track then turned slightly towards the second gate which was required to be opened to allow the cattle through.

This gate was adjacent to the accident site, which was about 27 metres from a single wire earth return (SWER) powerline which ran across the yards with a minimum height between spans of 24 feet (7 metres).

Examination of the helicopter’s flight controls, engine and structure did not identify any pre-existing defects. However, there was evidence of wirestrike marks on the front of the helicopter’s left skid.

Director Transport Safety Stuart Macleod noted that the ATSB’s preliminary report does not include any safety findings or analysis, which will be detailed in the investigation’s final report.

“As the investigation progresses, the ATSB will continue to analyse recorded data, the aircraft’s maintenance documentation and operational records, weather information, and assess visibility of the powerline, accident survivability and the pilot’s qualifications and experience,” he said.

A final report will be released at the conclusion of the investigation.

“However, should a critical safety issue be identified at any time during the investigation, the ATSB will immediately notify relevant parties so appropriate and timely safety action can be taken.”

Read the preliminary report: Wirestrike and collision with terrain involving Robinson R22, VH-KLY, 75 km west-north-west of Hay, New South Wales, on 26 May 2021

An Australian Transport Safety Bureau (ATSB) investigation into a depressurisation incident involving a Cessna 441 Conquest has resulted in a new ultrasonic bond inspection procedure for the aircraft’s emergency exit door.   

During a 22 July 2020 charter flight from Broome to Browns Range, Western Australia, with two pilots and six passengers on board, a Skippers Aviation operated Cessna 441 experienced a rapid depressurisation shortly after reaching its planned cruising altitude of flight level 270 (approximately 27,000 ft). In response the pilots and passengers donned their oxygen masks and the pilots performed an emergency descent.

When at 10,000 feet, the pilots removed their oxygen masks, instructed the passengers to do the same and confirmed they were all responsive and uninjured. After communications with the operator’s senior base pilot, the pilots continued their flight with the aircraft depressurised to Browns Range, where the aircraft landed without further incident.

During their walk-around of the aircraft both pilots noticed the lower aft section of the emergency exit door skin had disbonded.

“A structural fatigue investigation concluded that the emergency exit door progressively disbonded between the inner and outer skin, likely due to the age of the aircraft, facilitated by a combination of corrosion, moisture, and flight cycles,” said ATSB Director Transport Safety Dr Stuart Godley.

“This weakened the structure, which resulted in an accelerated failure of the bondline and rapid depressurisation of the cabin when the aircraft reached flight level 270.”

The incident aircraft was manufactured in 1978 and had accumulated over 27,000 flight hours and was operating under a supplementary type certificate (STC) life extension program developed by West Star Aviation. As a result of this incident and the subsequent discovery of two further disbonded doors in two other Cessna 441s operating under the life extension STC, it was concluded that the STC’s existing visual inspection procedures for the emergency exit door bondline were inadequate.

In January 2021 Textron Aviation (the type certificate holder for Cessna aircraft) released a service letter for the Model 441 Conquest/Conquest II introducing an ultrasonic bond inspection of the the aircraft’s emergency exit door to verify the integrity of the emergency exit door bondline.

Separately, the operator is seeking a design advice response from the Civil Aviation Safey Authority for the modification of its Conquest aircraft with the installation of rivets through the bondline and subjecting the door to additional inspection requirements.

The investigation also notes that the incident aircraft returned to Broome with the pilots applying the minimum equipment list for the pressurisation system.

As a result, the special flight permit process to recover the aircraft for repair was not followed, which removed the opportunity for an independent assessment that the flight could be conducted in a safe manner.

“After landing at Browns Range and discovering the disbonded door skin, the pilots elected to continue with the return flight to Broome with the pressurisation system inoperative, which was consistent with the initial advice they received from their company,” said Dr Godley.

“However, whenever new information about an abnormal situation becomes available, decisions may need to be re-evaluated, as the initial reasoning may no longer be valid. In addition, for the scenario of a structural failure, the special flight permit process should be followed to manage the potential risks associated with a damaged aircraft.”

Read the final report: Door failure and depressurisation involving a Cessna 441, VH-LBY, near Broome, Western Australia, on 22 July 2020

The Australian Transport Safety Bureau Commission acknowledges the retirement of Greg Hood as Chief Commissioner and Chief Executive Officer, and sincerely thanks him for his leadership, professionalism, guidance and compassion in leading the ATSB from 1 July 2016 to 30 June 2021.

Mr Hood retires from the Bureau at the completion of his five-year term, in which time he drove an innovation and transformation agenda at the ATSB, which saw the introduction of world-leading practices like a multi-modal teams approach to investigations, new recruitment practices, a tertiary partnership with RMIT University, and new technologies to support investigations such as remotely piloted aircraft and 3D modelling. All have helped to further establish the ATSB as a global leader in transport safety investigation.

During his tenure Mr Hood, with the other members of the ATSB Commission, approved more than 530 aviation, rail and maritime investigation reports for public release to improve transport safety for all Australians.

In addition, under Mr Hood’s leadership, the ATSB developed a strategic property plan that included the establishment of a Melbourne office and increases in staffing in the agency’s Brisbane and Perth offices, and introduced a replacement program for all enterprise IT systems, including the procurement of a new investigation information management system.

Mr Hood also served a two-year term as Chair of the International Transportation Safety Association (ITSA), the network of the heads of 18 independent transport safety investigation authorities, at a time when the world was navigating the COVID-19 pandemic, and when safe and efficient transport networks were needed like never before.

He also oversaw a partnership agreement with the Defence Flight Safety Bureau (DFSB) to align accident investigator skillsets and to participate in each other’s investigation activities, and further strengthened the ATSB’s close working relationships with New South Wales’ Office of Transport Safety Investigations (OTSI) and Victoria’s Chief Investigator, Transport Safety (CITS).

The Commission thanks Greg Hood for his service, and wishes him the very best for his well-earned retirement.  

ATSB Chief Operating Officer Colin McNamara will act as Chief Commissioner and Chief Executive Officer pending the appointment of Mr Hood’s successor.

Key points

• Pilot incorrectly believed they had been provided a landing clearance;
• Runway incursions remain one of the most significant risks to safe aviation;
• Pilots are strongly encouraged to identify potential conflicts or runway incursions that may develop during circuits early;
• Flight training schools reinforce training regarding occupied runways and go‑arounds to students.

The student pilot of a Sling 2 aircraft which conducted a touch and go landing at Moorabbin Airport above a PA-28 aircraft that was lined up at the displaced threshold of the same runway incorrectly believed they had been provided a landing clearance, an ATSB investigation into the July 2020 incident has found.   

The PA-28 was lined up on the displaced threshold for Moorabbin Airport’s runway 17 Left awaiting take-off clearance while the Sling 2 was conducting a circuit for a touch and go landing on the same runway. Although the Sling 2’s pilot saw the PA-28 lined-up, they continued their approach, believing that air traffic control had provided a clearance for a touch and go. The Sling subsequently passed above the PA-28 and conducted the touch and go.

The pilot of the Sling, not believing any incident had occurred, continued conducting circuits, while the instructor pilot in the PA-28 reported the incident after completing their training flight.

“The runway incursion by the Sling aircraft removed the required runway separation between their aircraft and the PA-28,” said ATSB Director Transport Safety Stuart Macleod.

“Runway incursions remain one of the most significant risks to safe aviation operations and a key global safety priority.”

The investigation found the student pilot of the Sling had sighted the PA-28 but decided to conduct the touch and go landing due to an incorrect belief that the controller had provided a landing clearance.

Further, the ATSB identified that the student pilot’s training had not been effective in conveying that a go‑around must be initiated if the runway is occupied.

Subsequent to the incident, the student’s flying training organisation introduced changes to its training program and updated student and instructor educational materials, procedural guidance and exam content.

“Pilots are strongly encouraged to identify potential conflicts or runway incursions that may develop during circuits early and to attend carefully to air traffic control communications,” said Mr Macleod.

“It is important that flight training schools reinforce training regarding occupied runways and go‑arounds to students.”

The investigation also found that the Moorabbin air traffic controller did not identify the developing conflict or recall the Sling passing above the PA-28 and conducting a touch and go landing.

“This investigation also serves to remind air traffic controllers of the importance of monitoring all aircraft and providing clear and unambiguous instructions to pilots to avoid runway incursions and related occurrences.”

Read the final report: Runway incursion involving Sling 2, VH-ZSD, Moorabbin Airport, Victoria, on 23 July 2020

The structural failure of a wagon during the operation of a rail freight service was due to an existing fatigue crack at a weld in the wagon’s underframe, which was likely detectable during routine inspections, a transport safety investigation has found.

The incident shows the importance of properly managing ageing assets to ensure continued safe operation, the investigation notes.

On the morning of 6 January 2021, a contractor working near the rail line near Kiacatoo, in central New South Wales, noticed one of the wagons of passing Pacific National freight train 3YN2 was broken and dragging along the track.

This was promptly referred to the train controller at Junee, who in turn notified the train’s crew. Upon stopping, the crew inspected the 977-metre long train and found the broken wagon with its air tank resting on the rail.

It was loaded with two containers carrying zinc concentrate, which remained secured.

The investigation into the incident, undertaken by the Office of Transport Safety Investigations (OTSI), which conducts rail safety investigations in NSW on behalf of the ATSB, found the wagon had dragged along the track for at least 11 kilometres, with superficial scrape marks identified on the rail and at three level crossings.

Outside of the damage to the track and wagon, no further damage and no injuries were reported.

The investigation concluded it likely an existing crack in the wagon’s underframe had worsened between the train’s departure earlier that morning from Broken Hill, causing the centre of the wagon to sag and make contact with the track.

Oxidation (rust) on the bottom portion of the fracture suggested the existing crack had been there for some time, while the remaining fracture face was fresh, and likely progressed quickly during operation.

Given the oxidation, the investigation concluded the crack was likely detectable during numerous general examinations and roll-by inspections, including those undertaken in the hours prior to the incident.

The wagon was an ICX class wagon with a butt weld at the midpoint of its load-bearing centre sill, a location of known risk. ICX class wagons were manufactured from around 1968 onwards.

“This incident highlights the importance of managing ageing assets to ensure continued safe operation through the lifecycle of the asset,” said OTSI Chief Investigator and CEO Dr Natalie Pelham.

“Rolling stock operators should ensure that their maintenance and inspection regimes effectively monitor and detect conditions that might escalate and contribute to accidents.”

Following the incident, Pacific National released a rolling stock safety notice detailing the failure and requiring an inspection of all affected wagons within the class.

The operator has also said it plans to develop a lifecycle asset management strategy for the affected class of wagons with a butt weld, and complete a risk assessment to assess the limitations of those wagons for ongoing use.

Pacific National has committed to review its wagon maintenance manual to include all necessary details for ICX wagons, and to review and adjust its current non-destructive inspection strategy across its full fleet of wagons.

Read the final report: Rolling stock irregularity on train 3YN2, near Kiacatoo, New South Wales, on 6 January 2021

Key points

• During approach to the airport in darkness, the aircraft was not maintained within the required navigational tolerance;
• Adherence to procedures and careful monitoring of aircraft and approach parameters provides assurance that an instrument approach can be safely completed;
• If the criteria for safe continuation of an approach are not met, pilots should conduct a missed approach. 

A Fairchild SA227 Metro aircraft was not maintained within the required navigational tolerances while conducting an ILS approach to land at night at Melbourne Airport, an ATSB investigation has found.

The aircraft, conducting a night freight flight from Launceston on the evening of 18 January 2021 with a single pilot on board, was being positioned to commence a night-time Instrument Landing System approach to runway 27 at Melbourne. While joining the approach, a turn was not commenced until after the aircraft crossed the localiser track.

After crossing the localiser track and while descending along the approach glideslope, the aircraft descended clear of cloud and the pilot sighted the runway, the investigation notes. At that time, the aircraft was positioned slightly less than full-scale on the course deviation indicator (CDI) to the right of, and tracking away from, the localiser track. From this position, the pilot elected to continue the approach visually.

However, exacerbated by a prevailing southerly wind, the aircraft continued tracking away from the localiser and, shortly after, proceeded beyond the full scale of the CDI, requiring that a missed approach be initiated. However, the pilot assessed that the visual approach could be continued.

The aircraft continued to deviate from the localiser track and at 2135, reached a maximum lateral deviation of 0.55 nautical miles. The pilot then turned the aircraft further to track toward the localiser while continuing to descend. At about the same time, the Melbourne Tower air traffic controller noticed the deviation and contacted the pilot.

At 2136, at about 980 ft above mean sea level (about 583 ft above ground level), the aircraft was re‑established within full-scale CDI deflection and landed shortly after.

“The ATSB found that during approach to the airport in darkness, the aircraft was not maintained within the required navigational tolerance,” said ATSB Director Transport Safety Stuart Macleod.

“While that should have resulted in the conduct of a missed approach, the approach was continued with the aircraft manoeuvring significantly below the minimum safe altitude.”

Mr Macleod noted that operational procedures are designed to ensure consistency of pilot action and aircraft operation during the approach and landing phases of flight.

“Adherence to procedures and careful monitoring of aircraft and approach parameters provides assurance that an instrument approach can be safely completed,” he said.

“Most importantly, if the criteria for safe continuation of an approach are not met, pilots should conduct a missed approach to negate the risk of colliding with obstacles or terrain.”

Read the final report: Flight below the minimum safe altitude involving Fairchild SA227, VH-OZV, 9 km east of Melbourne Airport, Victoria, on 18 January 2021