Safety summary

What happened

On 22 December 2019, the crew of a Cessna 172R aircraft, registered VH-YXZ and operated by Hartwig Air, was conducting aerial shark patrols. The aircraft departed Parafield, South Australia for the second flight of the day and flew along the coast to Goolwa Murray Mouth, returning along the same route.

About 2 hours into the flight, the crew started to experience symptoms typically associated with carbon monoxide (CO) poisoning, and subsequently observed a localised discolouration on the disposable CO chemical spot detector. The pilot notified air traffic control, who offered the pilot to land at Adelaide Airport. The pilot initially agreed, but as their symptoms resulted in confusion about the runways at Adelaide Airport, they subsequently decided to fly to Parafield, due to their familiarity with that airport.

The aircraft was landed safely and the three crew were taken to hospital for assessment. Blood tests confirmed all crew had mildly elevated carboxyhaemoglobin levels.

What the ATSB found

The ATSB found that, despite having only mildly elevated carboxyhaemoglobin levels, the crew’s physical symptoms and cognitive effects likely resulted from exposure to elevated CO levels in the aircraft cabin. The CO source within the aircraft could not be established. Further, the discrepancy between the low carboxyhaemoglobin levels and severity of experienced effects could not be resolved.

Safety message

Carbon monoxide is a colourless and odourless gas, and its presence may not be detected until the physical symptoms and cognitive effects are more developed. Therefore, operators and owners of piston‑engine aircraft are strongly encouraged to install a CO detector with an active warning to alert pilots to the presence of elevated levels of CO in the cabin. Should any smell or sensation of illness develop, pilots should check their CO detector, ensure cabin heat has been turned off, open all fresh air vents and windows, make prompt decisions to land as soon as possible, and use all available resources for assistance. Further information on CO poisoning and detectors can be found at the following:

Are you protected from carbon monoxide poisoning?

Carbon Monoxide: A Deadly Menace

The investigation

The occurrence

On the morning of 22 December 2019, the crew of a Cessna 172R aircraft, registered VH-YXZ and operated by Hartwig Air, was being operated on an aerial shark patrol flight under visual flight rules.^[1] The three crew on board included the pilot, a communications officer^[2] and an observer.

The morning consisted of two flights, flying the same route along the coast. At about 1000 Central Daylight-saving Time,^[3] the first flight departed Parafield Airport, South Australia, and proceeded along the coast to Goolwa Murray Mouth, before returning along the same route (Figure 1). This flight went for about 2.75 hours, which was longer than expected. This resulted in limited time for the crew to refuel the aircraft, conduct all the checks and ground runs, and have a lunch break prior to the second flight.

At about 1330, the aircraft departed Parafield Airport for the next flight. While overhead Sellicks Beach on the return leg, and about 2 hours into the flight, the communications officer became sick, followed shortly thereafter by the pilot. The crew discussed their sickness and dismissed it on the assumption that it was likely due to turbulence encountered while flying across the hills.

After passing Port Noarlunga, the pilot looked down and observed a localised discolouration on the disposable carbon monoxide (CO) chemical spot detector. The communications officer, sitting in the front right seat, verified the discolouration on the detector and all the crew confirmed they were feeling light-headed.

The crew immediately opened the windows and confirmed that the aircraft’s heating was turned off. The crew reported that, due to smoke haze in the area from the Cudlee Creek bushfire, they experienced no relief from this action and began to feel worse. The pilot noted losing periods of time, had begun to lose feeling in their legs, experienced chest pains, and had a tingling feeling in their hands.

The pilot contacted Adelaide air traffic control, notified the controller of potential CO poisoning and requested a clearance to fly direct to Parafield. The controller offered the pilot direct to Adelaide Airport for runway 30, to which the pilot initially agreed. The pilot then decided to fly to Parafield due to their familiarity with the airport, as their light-headedness had become worse and resulted in confusion about the runways at Adelaide.

The pilot continued to experience confusion for the rest of the flight, including with radio calls, however, the aircraft was landed safely at Parafield. The three crew were subsequently taken to hospital for a medical examination (refer to section titled Medical information).

Figure 1: Aircraft’s flight path (in white)

Source: Google earth, annotated by the ATSB

Context

Medical information

Physical symptoms and cognitive effects experienced

The crew all reported experiencing nausea, headaches, fatigue and light headedness. Individually, the pilot experienced memory loss, confusion, a numbness/tingling sensation in their extremities, chest pains and mildly blurred vision. The observer reported experiencing chest pains, fatigue and breathlessness, while the communications officer reported vomiting.

The crew did not experience any eye irritations and did not detect a strong smoke smell while flying. They also did not identify a significant difference in the strength of the smoke odour while on the ground, compared with in the air. Both the communications officer and the observer did not recall a smoke odour on their clothing after the flight, however, the pilot recalled a slight odour on their shirt when they got home.

General health and fitness

With respect to their health and fitness, the crew reported that:

• All crew felt well, were well-rested prior to the first flight, and were fit and healthy.
• Both the pilot and the observer had a light breakfast. The communications officer could not recall if, or what they had for breakfast. The crew all had a light lunch prior to the second flight.
• The crew were non-smokers, were not taking any medication, and did not have any pre‑existing conditions that could have contributed to the incident.
• The communications officer reported being prone to motion sickness, particularly on an empty stomach.
• The observer felt a bit more tired than usual after the first flight. The pilot felt okay after the first flight but recalled having a slight headache. The communications officer felt fine.

Dehydration

The crew reported drinking minimum amounts of water prior to the flight and only having small sips during the flight. Specifically, the pilot had some water before the flight and also sipped water during the flight. The observer had not drunk any water during the morning before the flight but took regular small sips during the flight. It was unknown if the communications officer had drunk any water prior to the flight.

In addition, the pilot and observer reported having not consumed any alcohol or drugs in the 24 hours leading up to the flight. The communications officer had a slight headache from drinking alcohol the night before but was fit to fly.

Dehydration is caused by excessive water loss. Causes include alcohol and caffeine consumption; and as both create a diuretic effect, working in the heat before flying and by not drinking enough water (Flight Safety Foundation, 2001). Symptoms of dehydration can include fatigue, nausea, elevated pulse and respiratory rate, headache, dizziness and confusion.

Medical examinations

Blood samples were taken approximately 3 hours after the crew’s initial physical symptoms and cognitive effects were detected. The results of these tests established that the crew had mildly elevated levels of carboxyhaemoglobin (COHb). Both the pilot and communications officer had levels of 1.2 per cent and the observer had 1 per cent. The crew declined the administration of oxygen while at hospital.

Carbon monoxide is an odourless, colourless and tasteless gas formed by the incomplete combustion of carbon-containing materials. When inhaled, it preferentially binds to haemoglobin, the oxygen carrying molecule in red blood cells. This creates COHb compounds and prevents oxygen from binding to the molecule and being transported, resulting in oxygen starvation.

According to Baselt (2014), normal endogenous levels of COHb are generally reported to fall within the range of 0.4-0.7 per cent. Smokers, and those living in an urban area, may have higher than average levels of COHb. Carbon monoxide has a half-life of 4-5 hours at sea level, meaning that the COHb will reduce to half its initial value within that time, after the source of CO has been removed. The CO half-life can be reduced to 80 minutes with the administration of pure oxygen.

The physical symptoms and cognitive effects of CO poisoning can worsen with an increasing level of COHb, however, different individuals’ reactions to a given COHb level can vary (Lacefield et al., 1982). Typically, COHb levels of 10-20 per cent can result in symptoms of a mild headache. Levels of 20-40 per cent can result in increasing severity of headaches, irritability, mental changes, fatigue, weakness, nausea, dizziness, visual problems and confusion (Knobeloch & Jackson, 1999; Lacefield et al., 1982). Though physical symptoms do not generally show at levels below 10 per cent, researchers have found that a person’s ability to perform complex tasks can be adversely affected at levels of 10 per cent or less (Baselt, 2014). It has also been found that the effects of CO can begin to show with the deterioration of psychomotor function at COHb levels of about 3 per cent (Hawkins, 1993).

Given the half-life of CO and elapsed time since the symptoms and effects were first detected, it was likely that the crew’s COHb levels were a maximum of approximately 2 per cent. For the crew to have obtained a saturation level of 2 per cent COHb, according to Baselt (2014), they would have been exposed to 200 parts per million (ppm)^[3] for about 2 hours, not taking into account the break between flights. The maximum exposure level, as recommended by Safe Work Australia, is 30 ppm over an 8-hour period.

Aircraft maintenance

A new engine was installed on the aircraft 10 days prior to the incident. An inspection was conducted during this process and no faults were found that would relate to a possible exhaust leak.

Immediately after the incident, an inspection was carried out on the aircraft, focusing on the exhaust system and airframe, including the firewall and door seals. No faults or exhaust gas leaks were found. The aircraft was not tested for CO leaks prior to the inspection. However, there were no reports or maintenance release entries made prior to the incident that indicated a possible exhaust leak. Further, the pilot who operated the aircraft the day before the incident reported not feeling any adverse health effects during the flight.

After the inspection, ground runs were conducted with a digital CO detector in the aircraft cabin. No indications of CO were found during the ground runs or during a subsequent check flight.

Environmental conditions

Bureau of Meteorology

The Bureau of Meteorology 1-minute observation data at Adelaide Airport, indicated the surface wind was variable, blowing to the south-west with wind speeds between 5-13 kt, and the temperature was 24 °C.

On the day of the incident, a bushfire was burning at Cudlee Creek, 16 km south-east from Parafield Airport and 40 km from the coast. The fire had grown to 25,000 hectares in size. There were also two small fires burning on Kangaroo Island to the south-west of Adelaide. However, given the wind conditions on the day, it was unlikely that these fires would have contributed to the smoke haze in Adelaide.

Throughout the flight, the crew reported the visibility was approximately 6 km due to smoke haze from the bushfire and that this remained constant. The visibility in the routine aerodrome weather report^[4] for Adelaide and Parafield were recorded as CAVOK^[5] and above 10 km respectively, throughout the day. The Adelaide Airport automatic terminal information service ^[6] reported smoke haze to the north-east of the airport.

The South Australian Environment Protection Authority recorded CO levels in the Adelaide central business district at ground level of 0.46 ppm at 1500. The average was 0.29 ppm from 1000 to 1600.

Bushfire smoke

The ATSB engaged the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Climate Science Centre who were conducting research into the effects of bushfire smoke on firefighters. CSIRO reported that CO disperses in the air and high CO concentrations of about 400 ppm are generally correlated with low visibility of only a few metres. They noted that, to have CO poisoning with the effects the crew reported after 3 hours, the crew would have been exposed to very high levels. They also advised that, given the distance to the fire and the fact that there was no strong smell of smoke experienced by the crew, the CO concentrations in the plume would not have been elevated enough to cause adverse health effects.

The ATSB also engaged the South Australian Country Fire Service to determine if any of their aircrew had experienced similar symptoms while conducting aerial firefighting on the day of the incident. They reported that none of their aircrew had experienced any CO effects during this fire or during any other fires in the past.

The possibility of other toxins in the bushfire smoke that may have potentially led to the crew’s partial incapacitation were also considered. CSIRO advised that typically, if the concentrations were high enough to cause adverse health effects, one of the main symptoms would be irritation in the eyes and throat. The crew did not report any irritations nor a strong smoke smell, therefore, it was unlikely that other toxins in the smoke led to their symptoms.

Carbon monoxide detector

The aircraft was fitted with an Aviation Supplies and Academics disposable CO chemical spot detector, attached to the centre of the instrument panel. The detector consisted of an orange‑coloured circle (spot) in the middle of the card, which was designed to change colour to grey/black following a chemical reaction with CO in the immediate vicinity. The spot then returns to normal (orange) after it has been exposed to fresh air. The chemical reaction depends on the concentration of CO in the air and the time of exposure. This detector was designed to react to a minimum of 50 ppm of CO within 30 minutes, 100 ppm within 10 minutes and 200 ppm within 4 minutes.

A limitation of this type of detector is that it does not actively alert the pilot to the presence of CO. Therefore, its effectiveness relies on the pilot regularly monitoring the detector throughout the flight. It is also dependent on the detector being easily visible and accessible, in a well-lit position. In a low ambient light environment, the discolouration of the chemical spot, from orange to a grey/black colour, can be difficult to see. 

Similar occurrences

ATSB investigation (AO-2017-118)

On 31 December 2017, the pilot and five passengers of a de Havilland Canada DHC-2 floatplane, registered VH-NOO, boarded the aircraft for a charter flight from Cottage Point to Rose Bay, New South Wales. The aircraft taxied for about 7 minutes. Shortly after take-off, the aircraft deviated from the standard flight path, stopped climbing, and entered a confined area (Jerusalem Bay) below the height of the terrain. The aircraft continued along the bay before making a very steep right turn and colliding with the water. All on board were fatally injured and the aircraft destroyed.

Toxicology results identified that the pilot and passengers had higher than normal levels of COHb in their blood. This was almost certainly due to elevated levels of CO in the aircraft cabin. The ATSB’s wreckage examination established that several pre-existing cracks in the exhaust collector ring, very likely released exhaust gas into the engine/accessory bay. This then very likely entered the cabin through holes in the main firewall where three bolts were missing from the magneto access panels.

ATSB investigation (AO-2020-055)

On 23 September 2020, the pilot of a Piper PA-28 aircraft, registered VH-TBB, departed Moree, New South Wales on a private ferry flight to Tamworth. Shortly after take-off, the pilot started to experience dizziness, breathlessness, and a warm feeling in the chest. The pilot conducted a visual scan and observed a discolouration on the disposable CO chemical spot detector that was gradually getting darker. The pilot opened the air vents and storm window and returned to Moree. The investigation is ongoing.

National Transportation Safety Board investigation (CEN17LA101)

On 2 February 2017, shortly after take-off, the pilot of a Mooney M20C aircraft became incapacitated. The aircraft continued flying until running out of fuel and then collided with terrain near Ellendale, Minnesota, United States. The pilot survived the accident but had no recollection of events between becoming incapacitated and waking up on the ground. The National Transportation Safety Board investigated the accident and concluded that the pilot’s incapacitation was due to CO poisoning.

The pilot reported using the aircraft’s heater throughout the day and having a headache and experiencing ‘butterflies’ in their stomach by the end of the first flight. The symptoms subsided after the first flight but returned after landing on the second flight. The symptoms were still present on the third flight and the last event the pilot remembered was being cleared to climb to 6,000 ft by air traffic control.

A post-accident inspection revealed several cracks in the exhaust muffler. The pilot’s COHb level, taken 4.5 hours after the accident, was 13.8 per cent. However, given the half-life of CO, the pilot’s level would have been at least 28 per cent at the time of the accident. In response to the experience, the pilot stated that:

Current technology has made portable CO detection very accurate and expensive. A high-resolution detector would have not only prevented this accident flight but may have alerted me to a comprimise [compromise] in my exhaust system many flight hours before the incedent [incident].

Analysis

Partial crew incapacitation

The observed physical symptoms reported by the crew were consistent with CO poisoning. This was supported by their blood tests, which established that they had mildly elevated levels of COHb adjusted to 2 per cent, and the positive indication on the CO detector in the aircraft’s cabin. Although, the extent of these symptoms was inconsistent with the literature and would generally be associated with COHb levels between 20-40 per cent. However, research has shown that adverse effects on cognitive functions can occur as low as 3 per cent and different individuals’ reactions to a given COHb level can vary.

While it was noted that a level of dehydration and possible motion sickness may have exacerbated the crew’s symptoms, this would not account for the elevated COHb levels.

Source of carbon monoxide

The ATSB considered the likely sources of CO, including cigarette smoke, bushfire smoke, and the aircraft. None of the crew were smokers and the reported visibility throughout the day indicated a relatively modest amount of smoke pollution. Further, as high concentrations of CO in bushfire smoke are generally associated with low visibility of only a few metres, it was unlikely that the smoke haze observed by the crew was sufficient to result in adverse health effects. This was consistent with the low CO levels recorded in Adelaide.

Therefore, the most likely source of CO was from the aircraft. There were no indications of a potential exhaust leak prior to the flight and the post-flight testing found no fault with the aircraft. Although it was possible that, by disassembling the aircraft prior to testing, an existing problem was masked. However, despite the unresolved inconsistency with measured CO levels and in the absence of other sources, it was likely that the crew were exposed to elevated levels of CO in the aircraft cabin. Therefore, it was likely that the crew’s symptoms were associated with CO poisoning.

Findings

From the evidence available, the following findings are made with respect to the partial incapacitation of the crew involving a Cessna 172R, registered VH-YXZ that occurred 44 km south of Adelaide Airport, South Australia on 22 December 2019.

Contributing factors

• It was likely that the flight crew were exposed to elevated levels of carbon monoxide in the aircraft cabin, which likely contributed to them experiencing mild incapacitating symptoms and effects.

Other findings

• The source of the carbon monoxide could not be determined.

Safety actions

Carbon monoxide education

As a result of this incident, the operator has advised the ATSB that they will:

• Install additional CO detectors in all aircraft, in both the cockpit and in the back of the cabin.
• Brief all pilots on the effects of CO poisoning, using the audio of the incident pilot’s radio calls to help demonstrate these effects.
• Instruct pilots to monitor both the instrument panel-mounted CO detector and the domestic electronic detector, with the instruction to land as soon as possible should the presence of CO be detected,
• Adjust the rosters to ensure that shark patrol flights were split into two shifts and separated by a few hours to assist in the dissipation of any CO that may have started to accumulate in the flight crew’s bodies.

Sources and submissions

Sources of information

The sources of information during the investigation included:

• the crew
• Hartwig Air
• Gulfstream Aviation (aircraft maintainer)
• Commonwealth Scientific and Industrial Research Organisation (CSIRO)
• South Australian Country Fire Service.

References

Baselt, R.C. (2014). Disposition of Toxic Drugs and Chemicals in Man (10th ed.). Seal Beach: Biomedical Publications.

Flight Safety Foundation. (2001). Dehydration Presents Unique Risks for Pilots. Human Factors and Aviation Medicine, 48(4):1-6. Retrieved from https://flightsafety.org/hf/hf_jul-aug01.pdf

Hawkins, F. H. (1993). Human Factors in Flight (2nd ed.). Aldershot, England: Ashgate Publishing.

Knobeloch, L & Jackson, R. (1999). Recognition of Chronic Carbon Monoxide Poisoning. Wisconsin Medical Journal, 98(6):26-9. Retrieved from https://www.researchgate.net/publication/12696822_Recognition_of_chronic_carbon_monoxide_poisoning

Lacefield, D. J., Roberts, P. A., & Grape, P. M. (1982). Carbon monoxide in-flight incapacitation: An occasional toxic problem in aviation (FAA-AM-82-15). Oklahoma City, Oklahoma: Federal Aviation Administration.

Safe Work Australia. (n.d.). Exposure Standard Documentation: Carbon monoxide. Retrieved from http://hcis.safeworkaustralia.gov.au/ExposureStandards/Document?exposureStandardID=111

Submissions

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

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

• the crew
• Hartwig Air
• Gulfstream Aviation.

Submissions were received from:

• the crew.

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

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2021 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

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1. Visual flight rules: a set of regulations that permit a pilot to operate an aircraft only in weather conditions generally clear enough to allow the pilot to see where the aircraft is going.
2. The communications officer’s role was to contact the police in the event a shark was spotted.
3. The concentration of CO in the air is represented as parts per million.
4. METAR: a routine aerodrome weather report issued at routine times, hourly or half-hourly.
5. CAVOK ceiling and visibility okay: visibility, cloud and present weather are better than prescribed conditions. For an aerodrome weather report, those conditions are visibility 10 km or more, no significant cloud below 5,000 ft, no cumulonimbus cloud and no other significant weather.
6. Automatic terminal information service (ATIS): continuous broadcast of recorded aeronautical information. ATIS broadcasts contain essential information, such as current weather information, active runways, available approaches, and any other information required by flight crew.

Safety summary

What happened

On 11 May 2020, a Fairchild SA227-DC Metro 23 (Metro) aircraft, registered VH-HPE and operated by Toll Aviation, was being loaded for its scheduled freight service from Townsville to Rockhampton then Brisbane, Queensland. The pilot was the only person on board.

The pilot completed a load and trim sheet, which indicated that the planned load was not within the allowable centre of gravity limits. It was agreed that 126 kg of freight would be moved from compartment three to the nose compartment. The revised load and trim sheet indicated the centre of gravity to be within the limits. During the flight to Rockhampton, the pilot observed that the aircraft felt tail heavy, but did not experience any controllability issues.

Due to the concern of an aft centre of gravity, the additional freight loaded at Rockhampton was limited, which was still within the calculated allowable centre of gravity limits. On take-off from Rockhampton, the pilot reported that the aircraft had a strong pitch-up tendency and that strong forward pressure on the flight controls was required to maintain the correct pitch attitude. During the cruise, the autopilot would not consistently maintain level flight. The pilot disconnected the autopilot and with full nose-down trim applied, the pilot had to maintain forward pressure to control the pitch attitude of the aircraft. The aircraft continued to Brisbane and the pilot reported that no problems were experienced during the approach and landing.

What the ATSB found

The ATSB found that, the ground handlers at Townsville did not accurately weigh the freight relocated into the nose compartment, but rather, it was estimated by feel. This resulted in an inaccurate load and trim sheet, and the centre of gravity being further aft than expected. Therefore, when additional freight was loaded in Rockhampton, this unknowingly moved the centre of gravity beyond the rear limit, leading to the pitch-up tendency experienced by the pilot.

Although not contributory, the operator’s paper-based load planning tool used by ground handlers for the Metro did not account for the centre of gravity position. Rather, this was later determined by the pilot on the load and trim sheet, which was potentially completed after loading had commenced. This increased the chance of freight having to be relocated and the potential for loading errors to occur.

It was also identified that the operator’s ground handling manual did not contain sufficient procedural detail to facilitate the accurate redistribution of freight. In particular, there was no guidance on conducting last-minute changes or taking into account the centre of gravity when preparing a load plan to ensure that an aircraft would be correctly loaded.

What has been done as a result

Following the incident, the operator amended their ground handling processes and included increased direction to ensure that freight would be accurately redistributed in the event of a last-minute change. The operator has since relinquished their Civil Aviation Safety Authority’s Air Operator’s Certificate and divested their flying operations to another operator. The new Metro aircraft operator also considered the findings of this investigation, reviewed their ground handling manual and incorporated amendments to ensure that an aircraft would be correctly loaded.

Safety message

This incident demonstrates the critical nature of load control and the requirement to ensure an aircraft is correctly loaded and the centre of gravity is within the allowable limits. It also emphasises the importance of providing ground handlers with sufficient and detailed procedures to allow them to accurately conduct load control duties and minimise the potential for error.

The occurrence

Townsville–Rockhampton

On 11 May 2020, a Fairchild SA227-DC Metro 23 (Metro) aircraft, registered VH-HPE and operated by Toll Aviation, was being loaded for its scheduled freight service from Townsville to Rockhampton then Brisbane, Queensland. The pilot was the only person on board.

The pilot signed on for duty at 1700 Eastern Standard Time^[1] and shortly after commenced pre‑flight preparations of the aircraft. The loading process had already commenced by that time and was about half complete when the ground handlers provided the load plan to the pilot.

The pilot then completed a load and trim sheet and ascertained that the planned load was aft of the rear centre of gravity limit. The pilot advised the ground handlers that the load was too heavy in compartment (zone) three and that some of that freight be moved to the nose compartment.

A team of four ground handlers were loading the aircraft, none of which were designated as a supervisor. One ground handler suggested to the pilot that 126 kg could be moved from compartment three into the nose compartment, leaving 300 kg in zone three. The pilot agreed, provided this could be achieved, having noted that the nose compartment was much smaller than the remaining compartments in both size and weight limit (Figure 1).

The ground handler contacted their supervisor who was at the freight depot. The supervisor had completed and signed the load plan, and advised the ground handler to carry out the pilot’s request to move the load. The ground handler commenced loading freight into the nose compartment. The ground handler recalled that ‘the nose is small in space’ and that it will ‘only fit a certain amount of things in there’, so only loaded as many bags as they could, filling the nose to volume capacity. This freight was not weighed, but rather, estimated by feel as there were no scales available at the aircraft. The ground handler explained that the load change took place at about 1745 and that the aircraft was scheduled to depart at 1800.

The pilot asked the ground handler if the freight had been moved as requested and the ground handler confirmed it had been. Believing that the load distribution was correct as amended from the original plan, the pilot completed a new load and trim sheet, which indicated the centre of gravity to be within the limits.

Shortly after, the aircraft departed Townsville. During the flight to Rockhampton, the pilot indicated that the aircraft felt tail heavy, but did not experience any controllability issues.

Figure 1: VH-HPE freight compartment configuration and weight limits

Source: Toll Aviation, modified by the ATSB

Rockhampton–Brisbane

On arrival in Rockhampton, the pilot discussed the load with ground handlers. The ground handlers had already reviewed the load plan from Townsville and were aware that the aircraft was relatively heavy. As a result, they had transferred most of the freight to another carrier for transport.

The ground handler at Rockhampton noticed that the aircraft appeared to be sitting ‘tail heavy’, and due to the pilot’s concern regarding an aft centre of gravity, the aircraft was only loaded with 111 kg in compartment three and 3 kg in compartment five. While the pilot believed the aircraft could still be loaded with more, they both agreed to minimise additional load.

On take-off from Rockhampton, the pilot reported the aircraft had a strong pitch-up tendency and rotated without input. The pilot had to apply strong forward pressure on the flight controls to maintain the correct pitch attitude and the pressure required to do so increased with altitude. Concerned with maintaining sufficient air density^[2] to maintain control effectiveness, the pilot reduced the planned cruising altitude to flight level (FL)^[3] 130.

After establishing the aircraft in the cruise, the pilot observed that the autopilot would not consistently maintain level flight. The aircraft would ‘porpoise’ as the autopilot tried to correct the pitch-up tendency. The pilot disconnected the autopilot from controlling the pitch of the aircraft, keeping it in GPS steer mode (lateral guidance only). Full nose-down trim had already been applied and the pilot then manually controlled the pitch attitude of the aircraft.

The pilot found that constant application of forward pressure was required, though noted that the force needed was ‘only a couple of kilograms’. The pilot did not observe any other controllability issues and was satisfied that control of the aircraft could be maintained.

The aircraft continued to Brisbane and the pilot reported that no problems were experienced during the approach and landing. The pilot had contacted operations prior to arrival, explained their observations regarding pitch control, and was met on the ground by maintenance engineers.

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1. Eastern Standard Time (EST): Coordinated Universal Time (UTC) + 11.0 hours.
2. As altitude increases, air density decreases, which results in less air passing over the flight control surfaces reducing their ability to effect aircraft movement and therefore control.
3. Flight level: at altitudes above 10,000 ft in Australia, an aircraft’s height above mean sea level is referred to as a flight level (FL). FL 130 equates to 13,000 ft. 

Context

Personnel information

Pilot

The pilot held a valid Commercial Pilot Licence (Aeroplane) and multi-engine command instrument rating. The pilot had over 3,000 hours in total, with about 2,500 hours in command and about 700 hours on the Metro 23 aircraft. The majority of their flying experience was in overnight freight (single pilot operations). The pilot had been flying for Toll Aviation (Toll) for about 1 year.

Ground handler 1 (Townsville)

Ground handler 1 had been a Toll employee for a combined total of 11 years. In addition to ground handling duties, they conducted other freight related duties including deliveries via motor vehicle.

Ground handler 2 (Townsville)

Ground handler 2 had been a Toll employee for almost 10 years in a variety of roles with the last six in operational roles. Their current position was supervisory in nature and oversaw freight related duties. Mostly located in the depot, they did not normally carry out actual loading duties, but were responsible for the preparation of, and signing of load plans.

Ground handler 3 (Rockhampton)

Ground handler 3 had 13 years at Toll and was in a supervisory role similar to ground handler 2. They had about 10 years’ experience with loading the Fairchild SA227 (Metro) aircraft, and often carried out both load planning and actual loading tasks.

Organisational information

Toll Aviation was part of the Toll group of companies and provided air freight capability to Toll Express Parcels. Toll Express Parcels provided ground handling services to Toll Aviation at some of its ports but was not a full-time aviation ground handling organisation. Ground handling in Townsville and Rockhampton was undertaken by Toll Express Parcels, but Brisbane was handled by Toll Aviation.

Ground handling staff explained that they were a mix of Toll employees and contract delivery drivers who were trained in aviation ground handling duties. When not conducting aircraft related duties, the ground handlers undertook road deliveries/pickup.

Aircraft information

VH-HPE was a Fairchild SA227-DC Metro 23, twin turboprop engine regional aircraft, which had been configured for freight operations. Freight could be loaded into the nose compartment, or the main fuselage compartment, which had been divided into five zones (compartments) (Figure 1). The zones had a webbing style net for segregation of freight between compartments. Heavy, bulkier freight could be physically restrained to the compartment floor.

Table 1: VH-HPE aircraft weight limits

An aircraft must be operated within prescribed weight and balance limits. That is, it should not be loaded above the maximum weight limitations (Table 1) and the position of the aircraft load (fuel, passengers, cargo etc.) should be such that the centre of gravity is within lateral and longitudinal limits (balance). Maintaining this balance is critical to stable, controllable flight. A pilot is to use the approved loading system for the aircraft to ensure that the weight and balance is within the approved envelope, either manually (graphical) or electronically.

The approved loading system for the Metro operated by Toll utilised a graphical method (load and trim sheet) for determining the centre of gravity position. The pilot was required to complete the load and trim sheet once all the weight information (freight, fuel, passengers) had been obtained. Freight loads were provided on the load plan (Appendix A). The operator had a load and trim sheet that was specific to VH-HPE (Appendix B).

The load and trim sheet considered weight and position when graphically determining centre of gravity. Load placed closer to the front (nose compartment) or rear (compartment five) of the aircraft would have greater effect on centre of gravity than load placed near the middle of the aircraft (compartment two). Load placed in compartment two had negligible effect on the aircraft’s centre of gravity. Load placed in the nose compartment and in compartment one shifted the centre of gravity towards the front of the aircraft. Load placed in compartments three­­‑five shifted the centre of gravity towards the rear of the aircraft.

Post-incident inspection/actions

Freight reweighed

Following arrival in Brisbane, the pilot discussed the incident with the maintenance engineers. This resulted in the freight being reweighed as it was unloaded from the aircraft. When compared to the load plan used to complete the load and trim sheet, there was a significant difference in the weight distribution. Notably, only 65 kg was in the nose compartment and an extra 64 kg was in compartment three. All other compartments had more weight than planned. However, the individual compartment weights were not exceeded. The planned and actual weights are shown in Table 2, representing the load for the flight from Rockhampton to Brisbane.

The pilot subsequently completed a new load and trim sheet using the actual weights and the centre of gravity was found to be aft of the rear limit (outside of the limits) (Appendix C).

Table 2: Aircraft load (reweighed) for Rockhampton to Brisbane

The weight of the additional freight loaded at Rockhampton was subtracted to determine the actual weight and distribution of freight for the flight from Townsville to Rockhampton. The actual weights did not correspond to the load plan but did not exceed individual compartment limits. Table 3 shows the weights on the original load plan during aircraft loading and the revised plan after moving some freight from compartment three to the nose compartment, compared with the actual weights.

A load and trim sheet with the actual weights determined that the load from Townsville was still within limits but the centre of gravity was much further aft than originally calculated. The recalculated load and trim sheet also revealed that the aircraft departed Townsville about 6 kg above its maximum take-off weight (Appendix D). A lower fuel load on departure from Rockhampton meant that the aircraft was within the take-off weight limits. However, the additional freight loaded in Rockhampton shifted the centre of gravity position beyond the rear limit.

Table 3: Aircraft load for Townsville to Rockhampton

Scales at Townsville

The operator’s internal investigation report stated that the scales used in Townsville were calibrated on 27 June 2019 and were due to be recalibrated in June 2020. They also verified that these scales were reporting an accurate weight.

Flight controls inspections

To confirm the serviceability of, and their potential to have contributed to the pitch control issues, the operator replaced the pitch servo and pitch flight guidance computer. Maintenance logs showed that replacement parts were fitted and tested serviceable. There was no evidence to suggest the components were malfunctioning or contributory.

Aircraft loading process

Townsville

On the day of the incident, items for air freight began arriving at the depot around 1600 and aircraft load preparations commenced at that time. Individual freight items were weighed with smaller envelope style parcels placed in consolidation bags, to a limit of 14 kg per bag. As each item was weighed, it was allocated to an aircraft compartment. The Townsville supervisor reported that, compartment allocation was based on the size or volume of the freight item and the experience of the ground handler to get an even distribution of freight. The supervisor said it was normal to prioritise freight to compartments one and two (toward the front of aircraft), to enable later ports to add freight to the rear.

Each aircraft compartment had its own ‘barrow’ (or area in a truck) to ensure segregation and facilitation of loading onto the aircraft. All weights were written on a load sheet, which upon completion, was presented to the supervisor.

Normally, consigned items already had a weight annotated on them. However, if found to be different when weighed prior to compartment allocation, it did not appear that these items were annotated with their correct weight. Consolidation bags did not have total weights annotated on the bag, nor was there a requirement to do so.

The supervisor stated that the load was driven to the aircraft as soon as preparations had completed.

Despite not taking part in the load preparation, the supervisor completed and signed the load plan in addition to other freight paperwork. The supervisor explained that the paperwork was then delivered to the pilot by one of their staff who was not on the load team. The supervisor stated they did not have an opportunity to verify if the load matched the plan or make changes prior to the load being delivered to the aircraft. They then forwarded a copy of the load plan to the Rockhampton supervisor to enable them to begin their load preparations.

The ground handler contacted the supervisor and was advised to amend the load as directed by the pilot.

The supervisor indicated that, on this particular night the freight allocation was much bigger than normal. Further, in general, it was a rare occasion in which the pilot requested freight to be moved once the load plan had been completed.

Rockhampton

The load process at Rockhampton was described as being similar to Townsville. Due to Rockhampton being a smaller depot, a distinct difference was the supervisor being more involved in the loading process and physically participated in all aspects. The supervisor at Rockhampton also stated that it was a rare occasion for a pilot to request changes to the load plan.

Load control policy and procedures

The operator’s load control policy and procedures were contained in numerous manuals within their operations manual suite. These are described in the following sections.

Flight operations

The flight operations manual stated that:

Responsibility for load control of Toll Aviation aircraft lies with the Pilot-in-Command for the particular flight.

The Pilot-in-Command shall ensure that a load sheet is completed prior to departure of the aircraft on each stage of every flight.

The Pilot-in-Command will advise Toll Aviation Operations or the Supervisor/Load Controller of the maximum payload for the particular flight as this will allow loading to commence. During the loading and unloading of freight on company aircraft, the Pilot-in-Command shall monitor the operation and location of loading vehicles and equipment by ground handling staff to ensure the aircraft is not damaged.

The Pilot-in-Command may delegate this duty to a person identified as an employee to a client freight organisation, trained in loading procedures for the aircraft.

Before each flight, the Pilot-in-Command shall ensure that the aeroplane is loaded within the prescribed centre of gravity limits as determined by the current approved loading system specified in the AFM for that aircraft.

As stated above, the pilot was ultimately responsible for load control, despite not physically undertaking load duties. Ground handlers carried out the bulk of load control duties on behalf of the pilot.

The pilot reported that it was not possible to physically confirm the load was accurate (for example, confirming correct weights). Similarly, although present at the aircraft for part of the loading, the pilot was not able to closely supervise the process. As these tasks were delegated to ground handlers, the pilot relied on the ground handlers providing an accurate load plan, so the pilot could complete the load and trim sheet and fulfil their requirement to ensure the aircraft was loaded within the prescribed centre of gravity limits.

Ground handling operations

The operator’s ground handling manual (GHM) covered the requirements for all organisations conducting ground handling for Toll Aviation. Section 2.4.4 was titled Ready reference and stated:

This manual is intended for use by Toll Aviation employees, contractors, freight forwarders and ground handlers involved in any way with the air transport process and specifically in relation to acceptance, handling, loading, carriage or consignment of cargo on Toll Aviation aircraft.

The ATSB’s review of the load control aspect of the GHM identified that it was focused on policy and procedural inclusions that were primarily related to load plan preparation. There was no other document or manual containing procedures or work instructions relating to load control.

Allocation of responsibilities

The GHM indicated that responsibility for load control was assigned to the pilot in command, reiterating the requirements of the flight operations manuals as:

2-4-6 Pilot-in-Command

…the Pilot-in-Command shall at all times:

     b.   take all reasonable steps to ensure that the:

1. load is properly distributed and safely secured

2. aircraft weight and balance is within the calculated limits for the operating conditions.

3-1-2 Pilot-in-Command responsibilities

Responsibility for Load Control of Toll Aviation aircraft lies with the Pilot-in-Command for the particular flight.

The Pilot-in-Command shall ensure that:

a. a Load and Trim Sheet is completed prior to departure of the aircraft for each stage of every flight

3-1-24 Pilot-in-Command approval

Prior to departure, a completed Loading Plan signed by the person responsible for loading the aircraft shall be provided to and shall be approved by the Pilot-in-Command

The GHM did not specify a similar assignment of responsibility for ground handlers undertaking load duties.

Supervision

The GHM did not specify a requirement for a supervisor to be included in the load team and none of the ground handlers in the load team at Townsville were assigned as a supervisor. The supervisor at Townsville said that, as the supervisor for all depot operations, they were not always able to attend the aircraft. Furthermore, there was not a leading hand position or similar that was part of the load team.

Weighing freight

The GHM directed that:

All freight loaded at any port shall be weighed and the weight shall be measured in kilograms to the nearest kilo using calibrated scales.

Ground handlers at both Townsville and Rockhampton confirmed that, upon arrival at the depot, all freight items were weighed. However, once weighed, items were not annotated with their verified weight, nor was there a requirement to do so.

Load plan preparation

The GHM included procedures for the preparation of a load plan and a generic load plan procedure.

3-1-22 Preparing the Loading Plan

The Departure Port Supervisor/Responsible person or PIC [pilot in command] shall be responsible for preparing the Loading Plan. He/she shall:

a.  obtain the maximum payload figure from the Pilot-in-Command

b.  using the excel Loading Plan spreadsheet, freight is allocated to particular zones on the aircraft (taking into account the maximum weight for floor loading limits for the zone). This information is then transferred to a Loading Plan form.

c.  complete Loading Plan on the day departure including information at the end of the Loading Plan, REGO = Aircraft Rego, FROM = departing port, TO = NEXT port aircraft will land, DATE = Date of departure, Loaders name = Person responsible for completing Loading Plan on day of departure, Signature = of person responsible for Loading Plan

d.  provide a copy of the Loading Plan to the Loader

e.  transmit a copy of the Loading Plan to the Supervisor/responsible person at each transit port.

The load plan tool used by the operator for the Metro was a manual, paper-based tool. A diagram of each aircraft and their compartment layouts were annotated with the applicable weight limits. This tool did not account for how the position of freight may affect the resultant centre of gravity (Appendix A).

Load and trim sheet

The subsequent completion of the load and trim sheet was the only means to calculate the centre of gravity position. This was the responsibility of the pilot, since ground handlers were not required to undertake this task. To complete the load and trim sheet, the pilot was wholly reliant on the information provided on the load plan by ground handlers.

Freight loading and last-minute changes

The GHM did not provide guidance on how to distribute freight across the aircraft compartments. As previously discussed, the distribution of freight was highly dependent on the experience of the ground handler conducting the task. According to the pilot and the ground handlers, it appeared that, in most cases, the planned allocation rarely required changes to be made and the load plan was usually within the centre of gravity limits. The redistribution of freight requested by the pilot was considered a last-minute change (LMC). The GHM only referred to LMCs as follows:

Any last-minute change to the freight load shall be approved by the Pilot-in-Command

The operator stated that this scenario was trained for, and that in a situation like the incident, freight was to be returned to the depot to be reweighed before loading. This was not documented in any manual, nor was it included in the training presentations. Further, ground handlers were not able to weigh the freight at the aircraft as scales were not available to the load team at the aircraft.

Ground handler 1 at Townsville inferred that, if 10-20 kg needed to be moved then estimating the weight by feel would be sufficient. However, if 150 kg needed to be moved, this would require taking freight back to the depot to reweigh. The ground handler could not explain why the 126 kg LMC for this incident was any different.

Ground handler 3 at Rockhampton explained that, if freight needed to be moved, they would attempt to move an entire compartment allocation (a known weight) or only move items that had weights annotated. Although not explicitly stated, the ground handler inferred that, if either of those options were not feasible, then they would return to the depot to reweigh the freight.

A procedure or explanation regarding a LMC was not detailed in the GHM. However, ground handlers appeared to have been provided some training/guidance for handling an LMC. The operator advised that, returning to the depot to reweigh freight was taught but conceded this was not documented anywhere.

Ground handling training

The operator’s ground training program included several presentations covering all aspects of load control. This was supplemented by practical instruction and formal assessment. Recurrent training was required every 24 months.

Module 3 of the training covered load control and discussed its critical nature. It emphasised the requirement for accurate loading of the aircraft and that the pilot was reliant on ground handlers to provide accurate information to complete the load and trim sheet. The module provided examples of the consequences of incorrect loading to reinforce this message. The ATSB noted that this information was not explicitly included in the GHM.

The operator advised that ground handlers were taught that freight was to be returned to the depot to be reweighed in the event of LMCs such as this incident. They acknowledged that this was not documented in any manual (it was also not in module 3 of the training).

The operator also reported that, about 3 years prior, several issues covering the delivery of, and management of ground handling training had been identified. As a result, the operator received board approval for additional resources to revise their training structure and improve those issues. They advised that, at the time of this incident, remedial action was in progress to amend training documentation and provide greater scrutiny over training activity.

The supervisor at Townsville was the designated trainer, but had not completed recurrent training. The supervisor explained that, training had been deficient for about 4 years since the branch manager had left the organisation. The supervisor also reported that significant catch-up had been required to get all staff up-to-date. Rockhampton did not appear to have such training issues.

The ATSB reviewed training as a possible contributing factor to the incident. However, when considering the lack of procedural guidance for load control duties, the ATSB assessed that effective training could not take place without robust documented procedures to train for, therefore did not consider training aspects any further.

Similar occurrence

ATSB investigation (AO-2013-044)

On 30 January 2013, a Toll Fairchild SA-227AC Metro aircraft, registered VH-UUO, departed Melbourne Airport, Victoria for Launceston Airport, Tasmania on a scheduled freight flight. The pilot was the only person on board.

During the take-off, the pilot reported that they needed more forward elevator trim than usual to climb out at a 10° nose-up attitude. The pilot noticed that, in straight-and-level flight, the aircraft had full nose-down trim, but flying at a 5° nose-up attitude. When the autopilot was engaged, the pilot stated that the autopilot struggled to maintain straight-and-level flight, explaining that the aircraft ‘porpoised’. The pilot conducted a normal landing at Launceston.

The operator determined that, although the loading plan for the aircraft indicated 100 kg of freight in the nose locker, one of the loaders had removed about 70 kg of freight from the nose locker and moved it to the rear of the aircraft. The operator identified that there was no formalised approach to the loading and unloading of the aircraft.

In addition, as the freight for the aircraft was not reweighed at Launceston, it was not possible to determine the exact centre of gravity that existed at the time of take-off from Melbourne. However, the flight characteristics of the aircraft suggested that it was either at the most rearward centre of gravity position, or just outside the rear centre of gravity limit.

The operator identified a lack of formal training for ground handlers and a lack of general procedures for them to follow. They also noted that there was insufficient oversight of the loading process and that the load plan for the Metro did not take centre of gravity position into account. Actions proposed by the operator included a review of, and publishing revisions to the GHM and the development of a ground handling training manual.

Operator comments

The operator’s investigation for this incident also identified that there was a lack of procedural guidance in the ground handling manual to support ground handlers in their duties. They stated that:

The Ground Handling Manual provides limited information on practical application of safe loading procedures for the Metro Aircraft and instead relies on input from the Pilot in Command.

The ATSB noted similarities between the two occurrences (albeit 8 years apart) and sought additional information regarding the status of safety actions from the 2013 incident. The operator’s safety manager was not able to provide any additional information relating to the previous occurrence as it was before their tenure and there was no record within their safety management system. Therefore, the ATSB was unable to explore any potential links between the two occurrences.

Safety analysis

Introduction

During the dedicated freight flight from Townsville to Rockhampton, Queensland, the pilot of VH‑HPE noted that the aircraft felt tail heavy, but did not experience any controllability issues. On the subsequent flight from Rockhampton to Brisbane, the aircraft had a strong pitch-up tendency, and the pilot was required to apply strong forward pressure on the flight controls to maintain the correct pitch attitude. The aircraft continued to Brisbane and the pilot reported that no problems were experienced during the approach and landing.

This analysis will examine the planned and actual load distribution and corresponding centre of gravity position for the flights from Townsville to Rockhampton and then to Brisbane. It will further discuss the operator’s load planning tool and ground handling procedures regarding the redistribution of freight.

Inaccurate load

After receiving the load plan from the ground handlers at Townsville, the pilot completed the load and trim sheet, and identified that the aircraft’s centre of gravity was aft of the rear limit. Consequently, it was agreed that 126 kg of freight was to be relocated to the nose compartment.

As there were no scales available at the aircraft, the ground handler estimated the amount of freight to be moved based on feel. However, the reweigh of the load post-incident established that the aircraft was not loaded in accordance with the revised load plan. Therefore, the completed load and trim sheet did not reflect the actual load distribution. Although the load distribution was not as planned, it was still within centre of gravity limits, albeit more toward the rear than expected. As this was not known, any additional load would not have been accurately reflected on the load and trim sheet and was potentially out of limits.

Centre of gravity out of limits

At Rockhampton, additional freight was loaded based on the load and trim sheet prepared at Townsville. However, since the load and trim sheet did not accurately reflect the actual load distribution, the additional freight moved the centre of gravity rearward, beyond the rear limit. As a result, the aircraft was operated outside of its centre of gravity limitations.

The centre of gravity envelope is established to provide a pilot with the allowable distribution of weight, within which the aircraft will have longitudinal stability and allow the pilot to have full control of the aircraft. Although the aircraft was still controllable in this case, the pilot had used full nose‑down trim and the auto pilot was not able to maintain level flight. This required the pilot to apply constant forward pressure to manually control pitch and reduced the options available to the pilot to maintain full control of the aircraft.

Load plan did not account for centre of gravity position

The paper-based load planning tool utilised by Toll Aviation (Toll) for its Metro aircraft only accounted for compartment weight limits and did not provide information on the resultant centre of gravity position. This was later determined on completion of the load and trim sheet, which was a pilot responsibility. Ground handlers were not trained to, nor were they required to, complete the load and trim sheet. Further, there was no documented guidance for the distribution of freight within the aircraft and it was dependent upon an individual ground handler and/or supervisor’s training, experience and knowledge of the aircraft.

Loading was often commenced prior to the pilot being able to complete the load and trim sheet. Consequently, loading may be quite advanced if not already completed by the time the pilot has determined that the load plan was not within limits. While in this case and for the 2013 incident, the loading error occurred due to the freight not being weighed, this could necessitate additional workload and delay. As there was no ability to weigh freight at the aircraft and no documented procedure to guide such a reasonably foreseeable situation, this increased the chance of freight having to be relocated, thereby creating opportunities for errors to occur.

Ground handling procedures

According to the operator’s flight operations and ground handling manuals (GHM), the pilot was ultimately responsible for load control. However, practically, a significant portion of the load process was delegated to the ground handlers. The GHM detailed the requirements for conducting ground handling operations, including the loading of freight. However, the procedures were primarily related to the preparation of a load plan, with no other routine tasks or reasonably expected contingency tasks included. Further, there was no other documents or manuals that contained work instructions for ground handling operations.

Specifically, the GHM did not provide details on how to take centre of gravity into account when preparing a load plan, to minimise the potential for last-minutes changes. Also, the GHM did not include any instructions for the conduct of last-minute changes to ensure the aircraft was loaded correctly. For such situations, ground handlers were taught that the freight was to be returned to the depot to be reweighed, however, this instruction was not documented. The operator also identified that there was limited information in the manual regarding safe loading procedures.

In this incident, the ground handlers involved had different views on what was required when faced with a similar situation. Ground handler 1 at Townsville displayed an understanding of what should have occurred with regard to moving the freight, specifically mentioning that an amount of 150 kg would require return to the depot for reweigh, although they could not answer why 126 kg was different. Ground handler 3 at Rockhampton displayed a higher understanding and had numerous options available to consider when redistributing freight, none of which were documented in the GHM.

In the absence of clear, documented procedures, ground handlers were effectively put into situations where they had to rely on their own judgement and experience, and possibly utilise other procedures, which may not necessarily be appropriate for the task. Robust documented procedures create predictable standards and expectations and provide a solid foundation for training. This will enable staff to undertake tasks, identify errors and ensure consistent, safe outcomes.

Load awareness

The ground handler’s recognition that the aircraft was relatively heavy on arrival at Rockhampton and the decision to make alternative arrangements for freight to minimise the additional load demonstrated a high level of situational awareness. While they were not to know that the aircraft was incorrectly loaded and that additional load would result in the centre of gravity being out of limits, their actions limited the potential severity of the situation.

Findings

From the evidence available, the following findings are made with respect to the aircraft loading and in-flight controllability issue involving Fairchild SA227, VH-HPE, Rockhampton Airport, Queensland, on 11 May 2020.

Contributing factors

• Ground handlers did not accurately weigh the freight relocated to the nose compartment at Townsville. This resulted in an inaccurate load record on the load and trim sheet, with the centre for gravity further aft, though still within limits.
• Additional freight was loaded in Rockhampton as per the load and trim sheet. However, due to inaccuracies in the load and trim sheet (ex. Townsville), the additional load unknowingly moved the centre of gravity aft of the rear limit (out of limits). This resulted in the aircraft exhibiting a strong pitch-up tendency, requiring the pilot to apply constant forward pressure to maintain aircraft control.

Other factors that increased risk

• The load planning tool used by the operator for the SA227-DC Metro 23 aircraft did not account for the centre of gravity position. This increased the chance of freight having to be relocated once the pilot completed the load and trim sheet and increased the potential for loading errors to occur.
• The operator's ground handling manual did not contain detailed procedural guidance for facilitating accurate redistribution of freight to ensure that an aircraft would be correctly loaded. (Safety Issue)

Other findings

• Ground handlers at Rockhampton assessed the aircraft as relatively heavy and took action to minimise additional load. On arrival, it was agreed with the pilot to limit the additional freight. These actions reduced the severity of the centre of gravity being out of limits.

Safety issues and actions

Guidance in the ground handling manual

Safety issue number: AO-2020-027-SI-02 

Safety issue description: The operator's ground handling manual did not contain detailed procedural guidance for facilitating accurate redistribution of freight and ensure that an aircraft would be correctly loaded.

Safety action not associated with an identified safety issue

Additional safety action Toll Aviation

Soon after the incident, Toll Aviation advised that:

• An outcome discussion was conducted with all ground handlers regarding the actions taken on the day of the incident and their responsibilities under the ground handling manual.
• Human Factors for Ground Handlers training had been finalised and was being implemented in stages across Toll Air Express.
• An electronic load tool (Excel) had been devised for the Metro aircraft, to provide the ground handlers with a guide for the position of the index units when determining freights loaded into each compartment. This tool was in the stage of testing and quality review prior to formal change management process and implementation.
• A weight and balance review of VH-HPE was conducted by the weight control officer. The load and trim sheet has been revised and was undergoing testing and quality review prior to formal change management process and implementation.

Glossary

EST                  Eastern standard time

FL                    Flight level

GHM                Ground handling manual

GPS                 Global positioning system

LMC                 Last-minute change

Sources and submissions

Sources of information

The sources of information during the investigation included the:

• the pilot
• the ground handlers (Toll Express Parcels)
• the operator (Toll Aviation).

Submissions

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

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

• the pilot
• the ground handlers (Toll Express Parcels)
• the operator (Toll Aviation)
• the Civil Aviation Safety Authority.

Submissions were received from:

• the pilot
• the ground handlers (Toll Express Parcels)
• the operator (Toll Aviation)
• the Civil Aviation Safety Authority.

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

Appendices

Appendix A – Metro 3/23 load plan

 

Source: Toll Aviation

Appendix B – VH-HPE load and trim sheet

Source: Toll Aviation

Appendix C – Centre of gravity (CoG) position (Rockhampton to Brisbane)

Source: Toll Aviation, annotated by the ATSB

Appendix D – Centre of gravity (CoG) position (Townsville to Rockhampton)

Source: Toll Aviation, annotated by the ATSB

Purpose of safety investigations & publishing information

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2021 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

Overview of the investigation

The occurrence

On 28 April 2020, the ATSB commenced a transport safety investigation into a near collision involving 3 aircraft near Bankstown Airport, New South Wales on 15 April 2020. At that time, all 3 aircraft were converging on the Paramatta checkpoint within the Bankstown Airport lane of entry (LOE),^[1] which was in non-controlled Class G airspace.

VH-SEW

At about 1315 Eastern Standard Time,^[2] the pilot of a Piper PA-28-151 aircraft, registered VH-SEW (SEW), departed Camden Airport on a private flight under visual flight rules (VFR).^[3] The purpose of the flight was to complete the ‘Victor 1 South’^[4] VFR coastal route and then return to Camden. After take-off, the pilot tracked to Prospect Reservoir at 2,300 ft. Upon reaching Prospect Reservoir, the pilot changed their radio to the Bankstown Tower frequency to monitor traffic inbound to Bankstown Airport. They then turned towards the Parramatta central business district^[5] to join the LOE northbound. The pilot changed their radio to the Sydney Centre frequency after passing Parramatta.

VH-JBC

Shortly after SEW took off, the instructor and student pilot of a Cessna 172S aircraft, registered VH-JBC (JBC), also departed Camden on a navigation check flight to Cessnock Airport. JBC was also tracking northbound via Prospect Reservoir to join the LOE at Parramatta. When about 3 NM (6 km) south of Prospect Reservoir, the student pilot turned the aircraft towards Parramatta. The student pilot had set Bankstown Tower on their primary radio and was monitoring Sydney Centre on their secondary radio.

VH-BMS

At about 1328, the instructor and student pilot of a Cessna 182 aircraft, registered VH-BMS (BMS), departed Bankstown Airport on a pre-commercial flight test to Remlap Park Airport via the LOE. BMS joined the LOE northbound at the perimeter of the Bankstown control zone and tracked to Parramatta. The crew were monitoring the Sydney Centre frequency.

Figure 1 shows the approximate tracks of the 3 aircraft.

The incident

At about 1330, the instructor in JBC identified traffic (being SEW) in the 9 o’clock^[6] position and confirmed this with the student pilot. Shortly after, the instructor observed SEW descend ‘rather sharply’ and they lost sight of the aircraft in the urban background. The student pilot slowed the aircraft before the instructor observed SEW climb from the left and in front of JBC in close proximity. The instructor took control of the aircraft and manoeuvred to avoid SEW. The pilot of SEW reported that they had not seen any other aircraft operating in the area at that time. Air traffic control radar data showed that SEW and JBC were both at 1,900 ft, with a minimum horizontal separation of 0.2 NM (0.4 km).

As BMS approached Parramatta, the student verbally indicated that they had sighted 2 aircraft ahead (SEW and JBC). The student elected to maintain 1,700 ft. They continued up the LOE and commenced overtaking JBC. However, the manoeuvre made by JBC to avoid SEW put JBC in close proximity to BMS. At about 1331, the radar data showed a minimum vertical separation of 200 ft and horizontal separation of 0.2 NM (0.4 km) between JBC and BMS. The instructor of JBC then requested flight following^[7] from Sydney Centre to assist with their awareness of other traffic.

No broadcasts were made by either of the pilots when approaching and transiting the LOE.

Figure 1: Approximate aircraft flight paths

Source: Airservices Australia, annotated by the ATSB

Investigation activities

During the investigation, the ATSB:

• interviewed the pilot in command of each aircraft
• reviewed air traffic control recordings
• reviewed ATSB occurrence data of similar events
• consulted several flying schools and aero clubs
• reviewed the guidance available to pilots operating within the vicinity of Bankstown Airport and the LOE.

ATSB observation

The ATSB found that the pilots were relying on unalerted see-and-avoid principles for identifying other aircraft. This limited their situational awareness when converging on the Paramatta checkpoint in the Bankstown Airport lane of entry and resulted in the aircraft coming into close proximity.

Safety message

The practice of see-and-avoid has long been recognised as the primary method for minimising the risk of collision when flying in visual meteorological conditions;^[8] it is considered a crucial element of a pilot’s situation awareness. The effective use of such is particularly crucial in Class G airspace, where aircraft separation is the pilot’s responsibility.

An ATSB research report titled Limitations of the See-and-Avoid Principle, showed that, when searching for traffic, alerted see-and-avoid (when a radio is used in combination with a visual lookout) is 8 times more effective than unalerted see-and-avoid (when no radio is used). However, pilots should be mindful that the absence of a traffic broadcast does not necessarily mean the absence of traffic. Pilots should remain vigilant and employ both unalerted and alerted see‑and‑avoid principles to ensure the greatest level of traffic awareness is achieved.

Reasons for the discontinuation

Based on a review of the available evidence, the ATSB considered it was unlikely that further investigation would identify any systemic safety issues or important safety lessons. Consequently, the ATSB has discontinued this investigation.

The evidence collected during this investigation remains available to be used in future investigations or safety studies. The ATSB will also monitor for any similar occurrences that may indicate a need to undertake a further safety investigation.

The ATSB has briefed the Civil Aviation Safety Authority about some of its observations and potential learnings. However, it considered that broader communication of this information would not be of significant benefit to other parties.

__________

1. Lane/s of entry (LOE): a lane or lanes established to permit passage to and from specified Class D control zones (CTR) such as Bankstown Airport, without entering an adjacent Class C or military CTR. The vertical limits provide separation from overlying control or restricted areas. The Bankstown Airport LOE was a fairly narrow corridor between Sydney CTR to the east and the Richmond CTR to the west.
2. Eastern Standard Time (EST): Coordinated Universal Time (UTC) + 10 hours.
3. Visual flight rules (VFR): a set of regulations that permit a pilot to operate an aircraft only in weather conditions generally clear enough to allow the pilot to see where the aircraft is going.
4. Victor One is a VFR coastal route east of the Sydney control zone between Long Reef and Jibbon Point. The Sydney CTR and the Victor 1 route are depicted on the Sydney visual terminal chart.
5. Parramatta was a check point within the LOE northbound.
6. O’clock: the clock code is used to denote the direction of an aircraft or surface feature relative to the current heading of the observer’s aircraft, expressed in terms of position on an analogue clock face. Twelve o’clock is ahead while an aircraft observed abeam to the left would be said to be at 9 o’clock.
7. Flight following: the provision of an ongoing surveillance information service.
8. Visual meteorological conditions (VMC): an aviation flight category in which VFR flight is permitted – that is, conditions in which pilots have sufficient visibility to fly the aircraft while maintaining visual separation from terrain and other aircraft.

Safety summary

What happened

On the morning of 2 April 2020, a road coach operated by Sandringham Charter Coaches was providing a V/Line train replacement service between Melbourne and Waurn Ponds in Geelong. At about 1049, the coach departed North Shore station in Norlane (Geelong) bound for North Geelong Railway Station. There was one passenger aboard the bus.

The coach travelled along Station Street and was veering left to cross the Station Street level crossing when the crossing warning system activated in response to an approaching freight train. The driver of the coach immediately applied the brakes, and the coach was stopped, but within the crossing.

A short time later as the train approached the crossing, the train crew observed the coach. The locomotive driver made an emergency brake application and the co-driver began to sound the horn. The coach driver heard the train horn and attempted, unsuccessfully, to reverse the coach.

The train was unable to stop and impacted the front-left corner of the coach at about 1050. The coach driver and the sole passenger were injured in the collision and were taken to hospital. The coach driver was released from hospital the same day, and the passenger the next day.

What the ATSB found

The ATSB found that the coach had stopped past the boom barrier with the front-left corner of the coach foul of the western standard-gauge track. The coach driver reported that they had stopped in response to the crossing warning signals and was reluctant to proceed across the crossing because of fear of a complaint. The acute road-to-rail track angle may have influenced the driver’s perception of the crossing and the position of the left-front corner of the bus relative to the track. The driver also reported not expecting a train because they were operating a train-replacement service.

Had the driver not stopped the coach, there was adequate time to complete the crossing prior to the arrival of the freight train.

What has been done as a result

Westernport Road Lines issued a safety alert to their drivers, reminding drivers that level crossings must be regarded as live, even if they are providing rail replacement services.

Safety message

Motorists need to be aware that in situations where passenger train services are not operating, freight trains may be operating, and normal safety precautions should be observed.

The occurrence

Prior to the collision

On 2 April 2020, a Sandringham Charter Coaches (SCC) road coach was to operate train replacement services for V/Line[1] passengers travelling between Southern Cross Station and Waurn Ponds Station (Figure 1). The coach driver arrived at the company depot in Moorabbin, in south east Melbourne, at about 0400^[2] that morning and prepared the coach.

The coach departed the Moorabbin depot at 0440 and travelled ‘out of service’ to Waurn Ponds. At 0638, the coach commenced its first scheduled passenger service, departing Waurn Ponds for Southern Cross.

Figure 1: Train replacement coach route between Southern Cross and Waurn Ponds

Source: Google maps data © 2020 with annotations by Chief Investigator Transport Safety

The coach arrived at Southern Cross at 0841 and at 0930 commenced a service back to Waurn Ponds. There were no passengers on board at departure. The coach ran via Little River to Lara Station, where one passenger boarded. From there the coach proceeded to Corio and North Shore stations, with no passengers boarding or alighting.

That same morning, a Pacific National (PN) freight train No. 5KQ7 was travelling from Murtoa (in Victoria) to Werris Creek (in New South Wales), via North Geelong and Melbourne. After passing North Geelong, the train stopped at Anakie Loop^[3] (about 3 km from the Station Street level crossing in Norlane) for a crew change (locomotive driver and co-driver). At about 1045,^[4] it resumed travelling towards Melbourne.

The collision

At about 1049, the road coach was stopped at North Shore Railway Station bus stop on Station Street. The level crossing was 70 m ahead and was visible from the bus stop. The flashing lights installation^[5] in the centre of the road was also visible (Figure 2).^[6]

Figure 2: View of the level crossing from the North Shore Station bus stop
 

Source: Chief Investigator Transport Safety

No passengers boarded or alighted, and the coach departed the North Shore Station bus stop with the one passenger, bound for North Geelong Station. It was running to schedule. The coach was driven south in the bus lane, before moving across into the centre traffic lane of Station Street as it approached the level crossing at the junction with North Shore Road. The driver intended to travel in the right-hand lane across the level crossing and enter the roundabout on the right lane for an exit onto Corio Quay Road (Figure 3).

Figure 3: Intended route of coach from Station Street towards North Geelong station
 

Source: Google maps data © 2020 with annotations by Chief Investigator Transport Safety

On approaching the crossing, the driver slowed the coach in preparation to cross. The driver reported that the coach had just crossed the level crossing stop line road marking when they heard the level crossing warning bells and stopped the coach. In the stopped position, the coach was foul of the first track (Figure 4).

The driver also indicated that, at the time, he was under the impression that trains were not operating that day.

The freight train was about 580 m (and 39 s) from the crossing when the active protection at the crossing was activated. Due to the curvature in the track and trackside obstructions, the train was not yet visible from the crossing, and the crossing was not yet visible to the train crew. The train crew stated that they sounded the horn when the train passed the whistle board, about 400 m prior to the crossing.^[7]

After stopping, the coach driver placed the bus transmission in neutral, engaged the park brake, removed their seatbelt and stood up. The driver recalled there were no vehicles ahead or behind  the coach. The right-hand level crossing boom barrier then descended onto the roof of the coach. The driver was aware of the boom but did not attempt to reverse the coach concerned at possible damage.

As the train came around the curve and when the train was about 100 m from the level crossing, the coach’s position on the crossing came into view. The train was travelling at about 53 km/h. The train crew identified that the coach was foul of the crossing and made an emergency brake application and commenced continuous sounding of the train horn.

The coach driver was alerted to the train’s presence by the train horn. The driver recalled attempting to reverse the coach, but the coach did not move. The driver reported that they had forgotten to release the park brake.

About 39 seconds after the crossing warning had activated, the leading locomotive entered the crossing travelling at a speed of about 50 km/h. The train then collided with the front left-hand quarter of the coach.

Figure 4: The estimated position of the coach on the crossing and the approaching train
 

Source: Google maps data © 2020 with annotations by Chief Investigator Transport Safety

Consequence of the collision

The coach driver and passenger suffered injuries requiring treatment at a local hospital. The driver was discharged the same day and the passenger was discharged the next day. The locomotive crew were not injured.

The front section of the coach was substantially damaged and the locomotive sustained minor front-end damage and a shattered windscreen (front cover).

The impact pushed the coach into the near side flashing light assembly and boom barrier causing substantial damage to infrastructure (Figure 5).

Figure 5: Damaged flashing signal and boom barrier assembly
 

Source: Chief Investigator Transport Safety

_____________________

1. V/Line is a government-owned corporation that operates regional passenger train and coach services in Victoria.
2.  All times are in Australian Eastern Daylight Time (UTC+11).
3. The ‘Anakie crossing loop’ is located near Thompson Road, North Geelong. It is not associated with the town of the same name.
4. Train logger times have been adjusted to align with GPS time.
5. The installation was a pedestal onto which warning signage, flashing lights, bells and boom barrier were mounted.
6. From the coach stop, the left-hand (or ‘near’) side signal assembly was partly obscured by vegetation and roadside infrastructure.
7. The train recorder fitted to this locomotive was not fitted to record the activation of the train horn.

Context

Station Street level crossing

The Station Street level crossing is about 67 km from Melbourne on the Werribee – Geelong section of the rail corridor (Figure 6).

Figure 6: Aerial view of the Station Street level crossing and its key features
 

The aerial photograph shows the layout of four rail tracks crossing five lanes of road traffic. The photograph was taken prior to the pedestrian crossing being re-aligned (its alignment at the time of the incident is shown as dotted lines).

Source: Google maps data © 2020 with annotations by Chief Investigator Transport Safety.

At this crossing, four bi-directional rail tracks crossed five lanes of road traffic. The western-most track on which the coach impinged was a standard-gauge track managed by the Australian Rail Track Corporation (ARTC). The middle two tracks were main line broad-gauge tracks managed by V/Line and the track furthest from the coach was a dual-gauge track leading to an industrial siding.

The road comprised two lanes for traffic travelling south-east and three lanes travelling north-west. The distance through the crossing, between opposing boom-barriers, was about 40 m.

A CCTV camera provided partial surveillance of the crossing. However, in this instance, the point at which the coach stopped was outside the camera’s field-of-view.

Level crossing protection

The level crossing was fitted with active protection that included flashing lights, bells and boom barriers protecting the inbound-side of each carriageway. Operation of the equipment was triggered by a level crossing predictor system.^[8] The system was configured to activate the initial crossing warnings of flashing lights and bells about 35 seconds prior to the arrival of a train. The boom barriers would commence lowering about 7 seconds after the initial warning.

Level crossing event logger

The level crossing was fitted with an event logger. The logger was designed to record the time when the crossing activated and the time when a train entered the crossing but was not equipped to record the time when the boom barriers commenced descending and when they were at the horizontal.

Environmental conditions at location

At the time of the occurrence, the sky was overcast, and the road was wet from previous rainfall. There was no evidence to suggest that the environmental conditions at the incident location contributed to the occurrence.

Road and rail approaches to the level crossing

Approaching by road along Station Street

The train replacement bus stop for the North Shore Railway Station was located on Station Street, about 70 m from the level crossing. Along this stretch of road, the sign-posted maximum speed was 60 km/h and it is probable the coach was travelling significantly below this.

Approaching the crossing, the road and crossing configuration meant that traffic was required to pass the road intersection with North Shore Road and then veer to the left to enter the crossing. Drivers of road vehicles would have a view of the stop line road marking, crossing signage and both the left-hand^[9] and the central^[10] flashing light assemblies (Figure 7).

Figure 7: Road approach to level crossing including signage and protection equipment flashing light and boom barrier assembly
 

Source: Chief Investigator Transport Safety

Rail traffic approach

The rail approach to the level crossing (travelling towards Melbourne) was on a left-hand curve with a radius of about 550 m. The curve commenced about 200 m prior to the crossing and was preceded by a curve board indicating a permitted speed of 80 km/h. The train was travelling at 53 km/h prior to the emergency brake application and was therefore significantly below this speed.

Due to the track curvature and the visual obstructions along the left-hand side of the rail corridor, the train crew could not observe the crossing until clear of the obstructions (Figure 8). It is estimated that the coach was not in the view of the locomotive drivers until the train was within about 100 m of the crossing.

Figure 8: The rail approach to the Station Street level crossing

The “direction of travel” arrow is placed over the track on which the train was travelling.

Source: Google maps data © 2020 with annotations by Chief Investigator Transport Safety

Management and maintenance of the level crossing

Safety Interface Agreement

The level crossing involved the interface of infrastructure owned and maintained by several organisations. A Safety Interface Agreement^[11] (SIA) established the shared understanding of safety responsibilities of each party for the crossing and its components. The parties to the SIA were the Australian Rail Track Corporation (ARTC),^[12] V/Line, VicRoads,^[13] and the Greater Geelong City Council.

ARTC and V/Line were the rail infrastructure managers for their track passing through the crossing. ARTC was identified as being the initial point of contact and responsible for maintenance of the level crossing infrastructure and equipment.

VicRoads was the primary road manager, responsible for road signage and markings and Greater Geelong Council was the footpath manager.

Infrastructure inspection and maintenance

Infrastructure service maintenance was carried out by ARTC as per the following schedule:

• HXP3 crossing predictor maintenance service scheduled every 180 days with 27 days planning latitude, completed on 27 February 2020.
• Level 1: check and inspection of the crossing active warnings to be carried out every 90 days with 18 days latitude, completed on 27 February 2020
• Level 2: a more in-depth examination of the crossing active warnings every 360 days with 54 days latitude, completed on 7 January 2020

Post-occurrence inspection of the level crossing found that the stop line marking was approximately 1.8 metres from the boom barrier^[14] when measured along the inner edge (or near side) of the street; AS1742.7 requires a minimum of 3 m.

ALCAM Survey

The level crossing had previously been assessed using the risk-based Australian Level Crossing Assessment Model (ALCAM).^[15] The most recent ALCAM survey of the Station Street level crossing was in September 2009 at which time the survey found that traffic controls at the crossing were observable from a safe stopping distance and that there was no vehicle queueing issues at the crossing.

Yellow box marking

Yellow box road markings are used to highlight the hazard zone of level crossings for road users. AS1742.7 specifies that they are only used to discourage traffic queuing on a crossing where the other treatments such as grade separation cannot be used.

Figure 9: Yellow box marking

Source: Australian Standards AS 1742.7:2016

Additionally, the VicRoads Supplement to AS 1742.7:2016 – Edition 1 states:

It is important to limit the use of yellow box markings in order to maintain the effectiveness in attracting drivers’ attention and improve the level of compliance with road rule 123(e). As such, yellow box marking shall not be used generally to denote the limits of railway level crossings, as the overuse of such markings may leave the impression that it is permissible to remain stationary within a level crossing where there is no yellow box marking.

The train replacement service

Contractual arrangements

V/Line contracted the management of train replacement coach services to Wangaratta Coaches that in turn sub-contracted a number of routes to Dineen Group. Sandringham Charter Coaches was part of this group and had been allocated the Southern Cross to Waurn Ponds route for a block of work that included the day of the occurrence.

Sandringham Charter Coaches

Sandringham Charter Coaches, incorporating Brighton Coaches, was an accredited Melbourne-based private charter bus company servicing the bayside, eastern and south-eastern suburbs of Melbourne. The company had been operating since 1925 and was part of the Dineen Group that operated charter coach and bus services in New South Wales and Victoria.

Coach information

The road coach was built in 2011 with a Scania K320 chassis and a Higer A30 body. It was about 12-metre-long and could seat 54 passengers (Figure 10). The coach was acquired by Sandringham Charter Coaches in April 2019 and was used predominantly for charter services. At the time of the occurrence, the coach was registered in Victoria. Its service regime was up-to-date and there were no known safety defects. The coach was fitted with seat belts.

Figure 10: Photograph of a similar coach

Source: Sandringham Charter Coaches

The coach driver

The coach driver had about 36 years’ experience driving similar coaches, mainly within the greater Melbourne region and had joined Sandringham Charter Coaches as a charter coach driver in December 2018. At the time of the occurrence, his licence was current. The driver wore spectacles when driving and reported that he was wearing them at the time of the incident.

In August 2019, the driver was suspended from driving duties for about two weeks due to passenger complaints of careless driving and an incident involving collision with a low-hanging tree branch.

In the days prior to the incident, the driver attended route-familiarisation training for the route between Melbourne and Waurn Ponds on 30 March and completed a four-hour shift within the Melbourne region on 31 March. The driver’s first shift on the new route was on 1 April, commencing at 0430 and finishing at about 1530 (two round trips). On each trip, the incident level crossing was traversed without it operating. That evening the driver went to bed at about 1930. There were no indicators to suggest fatigue may have contributed to the occurrence.

On the morning of 2 April, the driver woke at about 0330 and after having breakfast arrived at the depot at about 0400. On the first round-trip that morning (coach depot to Waurn Ponds to Southern Cross), the driver travelled across Station Street level crossing each way, without encountering a train.

Safety management of drivers

With regard to safety management, the company monitored the currency of driver licenses and driver accreditation certificates issued in accordance with State and National regulations for coach drivers. In addition, drivers were required to complete a ‘fitness to drive’ declaration on their daily pre-start check.

The company had also introduced a clearance for work document, which was used if a driver had an extended period of absence for medical issues or if they became aware that the driver may be suffering from a medical condition that may affect their ability to drive.

As required by their safety management system, the company conducted route familiarisation training and/or provided route maps to assist the drivers whenever a new route was allocated.

Driver route-familiarisation training

This was the first time Sandringham Charter Coaches had been allocated a charter outside the Melbourne area. As a result, the company arranged route-familiarisation training for their drivers.

Driver route-familiarisation training was facilitated by the Dineen Group (the parent company) and delivered by Panorama Coaches,^[16] using the V/Line Driver Training Manual prepared by Roscar.^[17] The manual provided information on the location of rail replacement coach stops, preferred routes between stations/coach stops and parking/layover bays for coaches; and reporting requirements for drivers. The training manual did not address normal road rules, which licensed drivers were expected to know.

Panorama Coaches advised that the routes described in the manual were not mandatory. Drivers could use their discretion when selecting a particular route between stops. With reference to this occurrence, the training manual suggested that the coach take a right turn at the Station Street level crossing and travel along North Shore Road to North Geelong Station (Figure 11), whereas the trainer recommended turning left and crossing the tracks to follow Corio Quay Road (Figure 3) as it was shorter.

Figure 11: Training manual recommended route

Source: Sandringham Charter Coaches with annotations by Chief Investigator Transport Safety

As part of the training, the drivers were provided with a route map and taken on a route-familiarisation observer trip from Southern Cross to Waurn Ponds and back. On each leg they drove across Station Street level crossing, unimpeded. Whether trains would be operating at this time was not discussed in the training.

Road rules, entering and leaving a level crossing

Section 123 ‘Entering a level crossing when a train or tram is approaching etc.’ of the Road Safety Road Rules 2017 (Vic) states:

A driver must not enter a level crossing if— 

(a) warning lights (for example, twin red lights or rotating red lights) are operating or warning bells are ringing; or 

(b) a gate, boom or barrier at the crossing is closed or is opening or closing; or

(e) the crossing or the road beyond the crossing is blocked.

and Section 124 of the Rules ‘Leaving a level crossing’ states:

A driver who enters a level crossing must leave the level crossing as soon as the driver can do so safely.

Freight train operation

Train information

Train 5KQ7 was a Pacific National freight service from Murtoa, Victoria to Werris Creek (in the Hunter Valley NSW), travelling via North Geelong and Melbourne. It consisted of Locomotives 8161 (cover photo) and BL31 with a trailing load of 40 grain-laden wagons. The total length of the consist was about 639 m. The locomotives were equipped with Hasler recorders.^[18]

Locomotive crew information

Both locomotive crew were based in Geelong.

The driver running the train at the time of the collision joined Pacific National in November 2013 and qualified as a locomotive driver in February 2020. At the time of the occurrence, their certification and medicals were current. On 1 April, he completed his shift at 1600 and joined train 5KQ7 on 2 April at 0945.

The co-driver joined Pacific National in October 2015 and qualified as a locomotive driver in October 2018. At the time of the occurrence, his certification and medicals were current. He had a rostered day off on 1 April and also joined train 5KQ7 on 2 April at 0945.

Previous incidents

Data received from the Office of the National Rail Safety Regulator (ONRSR) indicates that since May 2014 and prior to this occurrence, there had been 20 instances of damage to the boom spanning the left lane at Station Street level crossing. In five instances, a road vehicle was seen to collide with the barrier. The other 15 instances were not witnessed, but it is presumed that a road vehicle caused the damage. None of those instances resulted in a ‘near-miss’ incident with a train being reported.

_____________ 

8. A level crossing predictor system measures the train’s approach speed in order to predict the arrival time of the train at the crossing. This information is then used to adjust the commencement of the level crossing warning so as to achieve a consistent and efficient warning time for road traffic.
9. Visible when about 55 m from the crossing.
10. Visible from the North Shore Railway Station bus stop on Station Street.
11. A requirement of the Rail Safety National Law Application Act 2013 (Vic).
12. ARTC is Government of Australia owned and manages the Australian defined inter-state rail network (DIRN).
13. The primary road manager under the SIA was VicRoads. VicRoads became a part of the Department of Transport (DoT), on 1 July 2019.
14. 1.80 m when measured along the inside radius of the road. When measured along the centre of the lane, the distance was about 5.5 m.
15. Australian Level Crossing Assessment Model (ALCAM) is an assessment tool used to identify risks at level crossings and to assist in the prioritisation of crossings for upgrades.
16. Also a part of the Dineen Group.
17. Roscar Australia Group Pty Ltd is a Melbourne based major event transport and logistics specialist, handling events requiring specialised transport arrangements.
18. Developed by Hasler Rail, Switzerland, the Hasler electro-mechanical speedometer incorporates a waxed chart-strip on which several basic operational parameters were recorded.

Safety analysis

The Incident

The driver recalled having just crossed the stop line when the level crossing warnings commenced. He immediately stopped the coach but was within the crossing zone.^[19] At this point, the train was probably still about 35 seconds away from the crossing. To clear the crossing width of 40 m^[20] at a nominal speed^[21] of 15 km/h would have taken the coach about 12.5 seconds. Had the coach not stopped but continued through the crossing it would have cleared the crossing safely.

When the boom lowered on the coach a short time later, the driver took no action. The driver advised that he was concerned that moving the coach with the boom resting on its roof may cause damage.

The train crew approaching the level crossing around a curve had limited vision of the Station Street side of the crossing. On observing the coach foul of the track, the locomotive driver made an Emergency brake application and the co-driver began to sound the train horn continuously. It was estimated from the Hasler recording that this brake application was initiated about 80m from the crossing.

Alerted to the presence of the train about 5 seconds before collision, the coach driver recalled attempting to reverse the coach, but the coach would not move. It is probable that the driver forgot to release the park brake before attempting to reverse.

The locomotive subsequently collided with the left-front corner of the coach. The train was travelling at a speed of about 50 km/h and stopped about 200 m from the point of the application of the emergency brake. This was consistent with the expected braking performance for this train.

Factors influencing coach driver actions

The driver’s response to the activation of the warning lights and bell was to immediately apply the brakes bringing the coach to a stop as he thought was required. Possible factors that influenced the driver’s initial action in stopping the coach and subsequent actions are:

Concern of reprimand

In August the previous year, the driver had been suspended following passenger complaints. At interview, the driver indicated that he did not continue over the crossing as he did not want to be reported for crossing with the bells ringing.

Expectancy

The driver indicated at interview that he was surprised when the crossing was activated. He knew that V/Line trains were not running because he was driving the train replacement service. Also, during familiarisation training and his previous service trips, he had not encountered a train at the crossing. The coach driver also reported that when the level crossing warnings activated, he had thought that the activation may have been due to maintenance work.

Crossing complexity

The stop line in Station Street marked the beginning of the level crossing zone, and the intersection with North Shore Road (green triangle in Figure 12). Both the road intersection and level crossing overlap with no clear delineation between the two. The lack of clear delineation between the road intersection and the level crossing may have influenced the driver’s perception of the crossing (shown in red in Figure 12).

The crossing itself was four tracks wide (40 m). This is greater than most crossings and may have influenced the decision of the driver not to proceed. The geometry of the crossing also meant it may not have been immediately apparent to the driver that the left-front corner of the coach had fouled the track.

Figure 12: Road intersection and level crossing layout

Source: Google maps data © 2020 with annotations by the Australian Transport Safety Bureau.

While there were no identified queueing issues that may have triggered applying yellow box markings,^[22] such markings at this complex crossing may have assisted with identification by the driver of the crossing limits and the hazardous zone.

Road rules for level crossings

Once the crossing was activated, the driver was probably focussed on the requirement to stop prior to the crossing (Rule 123) and may not have appreciated that having already entered the crossing, or unaware that he would not be able to stop prior to the crossing, that the requirement then was to leave the crossing as soon as could be done safely (Rule 124). Improved delineation of the boundary of the level crossing itself may have assisted with this.

Previous incidents

Although probably not directly related to this incident, in the previous six years, there had been 20 occurrences of the boom barrier strikes by road vehicles on the inside lane of the Station Street approach. This suggests that the crossing configuration is probably conducive to driver error on that approach, and that additional risk controls may be warranted.

A report completed by the Australian Rail Research Board (ARRB) for VicRoads found that compliance by motorists was better at railway crossings provided with traffic lights in addition to flashing lights and boom barriers, compared to sites with flashing lights and boom barriers only.^[23]

____________________

19. Section 124 of the Road Safety Road Rules require a driver who enters a level crossing to leave the level crossing as soon as the driver can do so safely.
20. Clearing the crossing would require travel of about 52 m, comprising the 40 width of the crossing and the 12 m length of the bus.
21. Estimated speed for negotiating the turn.
22. AS1742.7 specifies that yellow box markings be used to discourage traffic queuing on a crossing.
23. Carney P, Bennett P, and Green D, Compliance with traffic signals at railway level crossings, ARRB Research Report No VC7 3922-1 August 2009.

Findings

From the evidence available, the following findings are made with respect to the level crossing collision between freight train 5KQ7 and Sandringham Charter Coaches coach at the Station Street level crossing in Norlane, Victoria on 2 April 2020.

Contributing factors

• The driver stopped the coach past the boom barrier and with the front left corner foul of the standard gauge track.
• On hearing the horn of the approaching train, the driver was unsuccessful in reversing the road coach clear of the track, probably as a result of not releasing the vehicle’s park brake.

Other findings

• The boom barrier protecting the inner lane of Station Street has been damaged by vehicles 20 times in the previous six years.

Safety actions

Proactive safety action taken by Dineen Group

Dineen Group through its subsidiary Westernport Road Lines issued a safety alert to their drivers in regards to level crossing safety, reminding drivers that level crossings must be regarded as live, even if they are providing a rail replacement service. Additionally, all drivers providing rail replacement for Geelong were contacted individually by the site manager and informed of the accident.

Sources and submissions

Sources of information

The sources of information during the investigation included:

• Dineen Group, for Sandringham Charter Coaches
• Coach driver
• Australian Rail Track Corporation
• Pacific National
• Train drivers
• Office of the National Rail Safety Regulator
• Flight Medical Systems

References

Carney P, Bennett P, and Green D, Compliance with traffic signals at railway level crossings, ARRB Research Report No VC7 3922-1 August 2009

Chief Parliamentary Council of Victoria 2020, Road Safety Road Rules Act 2017, Authorised Version No.008 incorporating amendments as at 1 January 2020.

Roscar Australia Group Pty Ltd 2017, Driver Training Manual, v3.1, April 2017.

SAI Global 2016, Manual of uniform traffic control devices Part 7: Railway crossings, AS 1742.7:2016 incorporating Amendment No.1, 21 March 2016.

Submissions

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

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

• Dineen Group
• Pacific National
• The Australian Rail Track Corporation
• V/Line Pty Ltd
• Office of the National Rail Safety Regulator
• Transport Safety Victoria
• Department of Transport (Victoria)
• The coach driver and passenger
• The locomotive crew

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

Purpose of safety investigations & publishing information

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2021 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

Safety summary

What happened

On 22 April 2020, a Bell 206L1-C30P helicopter, registered VH-NBR, was being operated by Nautilus Aviation on a passenger charter flight from Kubin Airport, Queensland, to Banks Peak, on Moa Island. On board were the pilot and two passengers.

While manoeuvring at the helicopter landing site (HLS), the helicopter’s tail rotor contacted trees. The helicopter then rotated rapidly to the right, collided with terrain, and was destroyed. The passengers were seriously injured, and the pilot sustained a minor injury.

What the ATSB found

The ATSB found that the design and maintenance schedule of the HLS made it susceptible to overgrowth. Vegetation had overgrown the site, obscuring the edges and surface of the helipad. The helipad was elevated above the ground, which made positioning of the helicopter on the helipad vital for the safe conduct of a landing.

It was also found that the pilot’s use of a flight helmet very likely reduced the severity of the pilot’s injuries.  

What has been done as a result

The operator amended its helicopter landing site template to include a grading system for site assessment by the chief pilot/deputy chief pilot prior to tasking pilots. It also developed a risk assessment template for landing at non-surveyed sites. In addition, the operator sent an alert to all the operator’s pilots to reinforce the go-around procedure as stated in its operations manual, and this procedure was performed on all remote area check flights. All cross-hired aircraft were migrated to the operator’s flight following system, which allowed the ability to track these aircraft in real time while on task.  

The Department of Home Affairs, as owner of the HLS, conducted a formal risk assessment of Banks Peak and other higher-risk HLSs throughout the Torres Strait. It also ceased flying operations to landing sites deemed to have unacceptable risks until sufficient control measures had been implemented. In addition, it is developing a detailed HLS brief for aircraft operators and is considering the most appropriate mechanisms for systematic engagement with other users of the sites. 

Safety message

The design and ongoing maintenance of helicopter landing sites and helipads in a tropical environment is an important function. The frequency of the maintenance schedule must be sufficient to account for the rapid plant growth to enable safe use of the site.

Helicopter landing site owners are encouraged to add touchdown/positioning markings to their facilities. Pilots can choose natural features in lieu of human-made markers where markers are absent. Additionally, if a landing cannot be conducted as planned, pilots should reject the landing and re-evaluate their options from a safe position.

The wearing of helmets is an important safety consideration when performing utility aerial work. The survivability in the event of an accident is greatly increased, as highlighted by this accident.

The investigation

The occurrence

On 22 April 2020, at about 0756 Eastern Standard Time,^[1] a Bell 206L1-C30P LongRanger helicopter, registered VH‑NBR and operated by Nautilus Aviation, departed Kubin Airport, Queensland. The passenger charter flight was transporting workers and equipment to a communications tower on Banks Peak, a mountain on the north-east side of Moa Island in the Torres Strait. On board were a pilot, and two passengers seated in the rear seats.

Overhead Banks Peak, the pilot conducted an aerial reconnaissance circuit of the helicopter landing site (HLS). The pilot then approached the site from the north, for landing. Closer to the ground, the pilot had difficulty locating the helipad. Grass had grown across the helipad and its edges (Figure 1).

Figure 1: Helipad as viewed during aerial reconnaissance circuit

Source: Passenger photo, annotated by the ATSB

At 0808, the pilot manoeuvred over the top of the helipad and using rotor downwash to push the grass and reveal the edges of the helipad. During this process, the tail rotor contacted trees 9 m from the helipad on the eastern side. A video taken by one of the passengers showed that, as the helicopter was turning to the right, a buzzing sound was heard, followed by a crack. Immediately after this sound, the helicopter spun rapidly to the right before rolling left. The helicopter collided with terrain and was destroyed (Figure 2).

Figure 2: VH-NBR accident site showing overgrown helipad
 

Source: Operator, annotated by the ATSB

The two passengers were restrained by lap belts. The passenger video showed that, during the sequence, the left rear door opened. The spinning and rolling forced the rear left passenger’s legs out of the door and the passenger’s legs were trapped under the helicopter, resulting in serious injuries. The right rear passenger sustained a serious injury to one hand.

The main rotor blades contacted and destroyed the forward fuselage structure. During the accident sequence, the pilot’s helmet impacted the aircraft’s structure, resulting in a loss of consciousness for a brief period. The pilot was restrained by a four-point safety harness, including a lap belt and shoulder harness.

The pilot and passengers were subsequently evacuated for medical attention.

Context

Pilot information

The pilot held a valid Commercial Pilot Licence (Helicopter), and a current Class 1 Aviation Medical Certificate. The pilot was also a qualified helicopter flight instructor and had previously flown in Papua New Guinea, as well as conducting a number of years of remote flying in Australia. At the time of the accident, they had a total of 6,807.4 hours of which 3,836.4 hours was on the Bell 206. The pilot completed their last helicopter flight proficiency check in September 2019. Their most recent ridge and pinnacle training was carried out in June 2019.

The pilot had flown to Banks Peak a number of times prior to the helipad construction. In 2016, they conducted 29 trips to the site during construction of the concrete helipad, slinging materials in for the work. They had not flown to Banks Peak since the construction work.

Aircraft information

The Bell 206 LongRanger is a seven seat, single engine helicopter used in passenger and utility roles. It is primarily all metal construction with a two-blade main and tail rotor system.

The helicopter involved in this accident, serial number 45232, was manufactured in 1979 and had 8,166.4 hours total time in service. The day before the accident, a periodic (100 hourly) inspection was performed on Horn Island. This was a standard inspection with no additional work carried out, and there were no rectifications that would have contributed to the accident.

Due to the regulatory requirements in place at the time of the helicopter’s manufacture, the seatbelts fitted to the rear passenger seats consisted of lap belts only. Civil Aviation Safety Regulation (CASR) 90.115 (Occupant restraints–helicopters) required all helicopters manufactured after September 1992 to have seatbelts with upper torso restraints fitted to all passenger seats.

Banks Peak helicopter landing site

The helicopter landing site (HLS) was located on Banks Peak on the north-east side of Moa Island, Queensland. It was about 1,220 ft above sea level, confined within a steep-sloping, irregularly-shaped cleared area, and about 30 m by 35 m in size. The up-slope area to the west of the HLS contained small structures and two communication towers. The closest guy wire anchor point was 8 m to the west of the helipad. 

The helipad was constructed in 2016. The final approach and take off area^[2] (FATO) was about 21 m. The touchdown and lift-off area (TLOF) was a 4 m square. It was constructed as a box, consisting of a concrete border about 500 mm wide with a compacted gravel centre. The raised helipad meant precise positioning was required. Covering the sloping ground surrounding the helipad were numerous large rocks.

Prior to construction of this helipad, maintenance workers would utilise another helipad, downhill of Banks Peak, about 270 m west of the towers. The Banks Peak site was accessed for annual tower maintenance and the biannual site maintenance.  

Helicopter landing site guidance

Civil Aviation Regulation (CAR) 92 (Use of aerodromes) stated that an aircraft shall not land at or take off from any place unless it was:

…suitable for use as an aerodrome for the purposes of the landing and taking-off … having regard to all the circumstances of the proposed landing or take-off.

Civil Aviation Advisory Publication (CAAP) 92‑2(2) (Guidelines for the establishment of on-shore Helicopter Landing Sites (HLS)) provided detailed guidelines for the establishment and use of a HLS. The CAAP provided guidance for the design of basic and secondary HLSs:

BASIC HLS – a place that may be used as an aerodrome for infrequent, opportunity and short-term operations, other than Regular Public Transport (RPT), by day under helicopter Visual Meteorological Conditions (VMC).

SECONDARY HLS – a place suitable for use as an aerodrome for helicopter operations by day or night that does not conform fully to the standards for a heliport set out in Volume II of Annex 14 to the Chicago Convention

Due to the terrain and construction of the Banks Peak HLS, it was consistent with the stated requirements for a basic HLS.

A secondary HLS had a higher level of requirements, which incorporated the use of touchdown/positioning markings (TD/PM). CAAP 92-2 (2) described the TD/PM requirement as:

…essential where it is necessary for a helicopter to touchdown or be accurately placed in a specific position…. A TD/PM provides the visual cues that permit a helicopter to be placed in a specific position and, when necessary, orientated such that, when the pilot’s seat is above the marking, the undercarriage will be inside the load-bearing area and all parts of the helicopter will be clear of any obstacles by a safe margin.

There were no markings at the Banks Peak HLS to indicate the landing point to assist a pilot to line up for landing.

Without markings, a well-accepted and taught technique for confined areas is to use lead-in features. These features are commonly particular trees or rocks positioned around the selected landing site. The pilot can reference their position from these markers to ensure the helicopter is in the correct place. The helicopter operator’s HLS register for Banks Peak stated that pilots should conduct the approach into the prevailing wind (either towards the south-east or towards the north-west). There were no markers for lead-in features annotated on the register.

On this occasion, the pilot reported aiming for the centre of the grassed area and then the helipad. They did not use any lead-in features.  

Site maintenance

The Department of Home Affairs was responsible for the management of the Banks Peak HLS. The HLS and the area surrounding the structures had a flexible biannual preventative maintenance schedule. As part of this schedule, clearing of vegetation around the site and structures was conducted. The last maintenance, 4 months prior to the occurrence, was performed in December 2019. This included the use of chainsaws for trimming of small trees and branches from the HLS and its surrounds and utilising brush cutters and weed killer to control grass growth.

On the day of the accident, long grass obscured the helipad. Although the outline was apparent to the pilot during the aerial reconnaissance circuit of the site, when the helicopter was closer to the ground the pilot reported that the helipad became difficult to see. In the months following the December maintenance, there had been about 1,000 mm of rain recorded at nearby Horn Island.

Tail rotor strike

The tail rotor blades fitted to VH-NBR were manufactured by Van Horn Aviation and installed under a supplemental type certificate^[3]. The blade construction was a carbon fibre skin over a foam core. They were a direct replacement for the original manufacturer’s blades and were the same length, with a lighter weight.

Several branches of up to 45 mm thick were struck by the tail rotor, leading to fracturing of both blades about two-thirds of the way along their respective span. This led to bending of the leading-edge protection and splintering of the carbon fibre skins.

A detailed examination of the tail rotor blades was conducted by the ATSB. This examination found that blade A (Figure 3) had sustained bending about the leading-edge strip, opposite to the direction of its rotation. That damage was consistent with an impact under power. It also had numerous deposits of woody fibrous material throughout the inner structure. The leading edge of blade B showed the surfaces were contaminated with a quantity of dirt throughout the fractured sections and internal structure. This was most likely due to ground contact during the accident sequence.

Figure 3: Tail rotor damage showing fibrous material and dirt within the blade structure

Source: ATSB

Flight helmet

The pilot was wearing a helmet at the time of the accident, which was approved for helicopter operations. The helmet was damaged from impact with the aircraft structure, and a 25 mm split was noted in the helmet outer shell. Paint transfer on the pilot’s helmet was of a colour matching the interior paint of the cabin (Figure 4).

Passengers reported that the pilot was initially unconscious post-impact, but regained consciousness after a short time, and the pilot then freed themselves of their harness and exited the wreckage.

Figure 4: Pilot helmet showing contact with cabin interior

Source: Operator, annotated by the ATSB

Safety analysis

Helicopter landing site design and maintenance

Due to the helicopter landing site’s sloping ground, a level small 4 m square helipad was elevated above the ground, which meant precise positioning was required to prevent helicopter rollover on landing. Although a precise landing was required, there was no touchdown/positioning marking (TD/PM) at the site to assist with positioning. The application of TD/PM provides the pilot with a visual reference to align the helicopter with the correct landing position and ensures the helicopter will be clear of any obstacles.  

The compacted gravel centre of the helipad provided a surface for grass to grow over the helipad. The extended time and significant rainfall since the last maintenance, 4 months earlier, allowed that grass to grow to a length that obscured the whole helipad from view of the pilot during the approach. The obscured pad increased the complexity of the operation and increased the workload on the pilot during a critical phase of flight.

The high rainfall and tropical environment of Moa Island generated a high rate of vegetation growth. The rate of scheduled maintenance conducted at the helicopter landing site was too low to prevent the helipad becoming overgrown, effectively camouflaging the helipad during the approach.

Manoeuvring at the helipad

As already noted, there were no TD/PM markings at the site, and the pilot stated that they could not see the helipad. While manoeuvring the helicopter in the confined area, the pilot was most likely directing a reasonable amount of their attention towards identifying the helipad, and the anticipated touchdown point.

A small change in position at the front of the helicopter can be associated with a large change at the tail end. Unless changes are being observed while taking place, there is a good chance that small changes in a visual scene will not be identified (Wickens and McCarley 2008). This likely led to a difference between the pilot’s understanding of the helicopter’s position in space, and the helicopter’s actual position, leading to a tail rotor strike.

Tail rotor damage

The passenger video recording had distinct audio of a buzzing sound and then a crack, immediately prior to the loss of control. ATSB examination of the tail rotor showed no evidence of pre-existing damage. The damage on both blades was consistent with impact under power.

A detailed examination identified numerous deposits of woody fibrous material throughout the inner structure. The video evidence and the presence of the fibrous material indicated that it was likely the blade had impacted a tree or branch, immediately prior to the loss of control.

Flight helmet and restraints

The pilot was wearing an approved flight helmet. During the accident sequence, the helmet was struck by the internal structure after the structure was impacted by the main rotor system. This resulted in minor damage to the helmet, and the pilot was unconscious for a short period of time. It is very likely that had the pilot not worn the helmet, the severity of their injuries would have significantly increased.

A substantial amount of research has consistently shown that seatbelts in small aircraft that include an upper torso restraint (UTR) significantly reduce the risk of injury compared to lap belts only. This helicopter was not fitted with UTRs in the rear seats, nor were they required at the time the helicopter was manufactured.

With the rapid rotation of the helicopter, the flailing of the passengers’ limbs led to the rear left passenger’s arms and legs being thrown to the left out the open door and the rear right passenger’s hand to be injured on damaged aircraft structure. There was insufficient evidence in this case to conclude that UTRs would have reduced the severity of the passenger injuries. Nevertheless, the ATSB has previously issued a safety advisory notice to encourage all owners and operators of small aircraft to fit UTRs of all passenger seats to minimise injury risk.

Findings

From the evidence available, the following findings are made with respect to the collision with terrain involving a Bell 206L1-C30P, VH-NBR, at Banks Peak, Moa Island, Queensland on 22 April 2020.

Contributing factors

• The helipad maintenance schedule was not sufficient to prevent the gravel helipad from being overgrown. This enabled vegetation to grow out from the centre of the helipad, obscuring its edges and making its borders difficult to identify during landing.
• While the pilot was manoeuvring in the confined area, the tail rotor contacted a tree. This led to a tail rotor failure, resulting in rapid rotation and collision with terrain.

Other findings

• The helmet worn by the pilot very likely prevented a more serious head injury.

Safety actions

Safety action taken by Nautilus Aviation

Following the accident, the operator reported that it had taken or was taking the following safety actions:  

• amended its helicopter landing site template to include a grading system for site assessment by the chief pilot/deputy chief pilot prior to tasking pilots
• developed a risk assessment template for landing at non-surveyed sites
• sent an alert to all company pilots to reinforce the go-around procedure as stated in the operations manual and ensured this procedure was performed on all remote area check flights
• migrated all its cross-hired aircraft to the operator’s flight following system, which allowed the ability to track these aircraft in real time while on task.

Safety action taken by the Department of Home Affairs

The helicopter landing site owner reported that it had taken or was taking the following safety actions: 

• conducted a formal risk assessment of the helicopter landing site (HLS) at Banks Peak and other higher-risk sites in the Torres Strait.
• engaged an independent specialist to appraise the higher risk HLSs used by the department
• ceased flying operations to HLSs with unacceptable risks until sufficient control measures had been implemented
• identified vegetation growth as a significant risk factor for helicopter landings at Banks Peak, with a regular maintenance regime in place to manage ongoing clearance operations
• developing a detailed HLS brief for aircraft operators, which will include photos and relevant local risk factors
• considering the most appropriate mechanisms for systematic engagement with other site users, including how relevant information may be shared amongst stakeholders.

Sources and submissions

Sources of information

The sources of information during the investigation included the:

• pilot and passengers of the accident flight
• Nautilus Aviation
• Telstra and the organisation conducting maintenance on the communication towers
• Department of Home Affairs (organisation responsible for the maintenance of the HLS)
• Queensland Police Service
• video footage of the accident flight and other photographs taken on the day of the accident.

References

Wickens CD & McCarley JS, 2008, Applied Attention Theory, CRC Press, Boca Raton.

Submissions

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

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

• the pilot
• Nautilus Aviation
• the Department of Home Affairs
• the Civil Aviation Safety Authority.

A submission (with safety action only) was received from the Department of Home Affairs. The submission was reviewed and, where considered appropriate, the text of the report was amended accordingly.

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2021 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

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1. Eastern Standard Time: Coordinated Universal Time (UTC) +10 hours.
2. Final approach and take-off area (FATO): an area of land or water over which the final phase of the approach to a hover or landing is completed and from which the take-off manoeuvre is commenced
3. Supplemental Type Certificate, STC: Authorizes alteration to aircraft, engine or other item operating under approved type certificate.

Safety summary

What happened

On 3 April 2020, light rail vehicles (LRV) 053/054 were stabled at the light rail depot in Randwick, New South Wales. At approximately 0249, workers heard a loud noise and on investigating found a battery enclosure cover on the ground between two other LRVs. The cover was identified as originating from LRV 053.

Closed-circuit television cameras within the light rail depot captured the ejection of the cover from LRV 053. The cover was ejected with a flash visible followed by a plume of smoke or vapour and the cover landed approximately 6 m away.

There was significant damage to the battery compartment and batteries on LRV 053 and also minor damage to two other vehicles. There were no reported injuries.

What the ATSB found

The software controlling the battery charging likely corrupted during the uploading process which went undetected. The fault with the software resulted in overcharging the batteries on multiple LRVs, including LRV 053. The overcharging of batteries was not detected prior to the occurrence through Alstom’s validation or fault monitoring processes.

The overcharging of LRV 053 batteries generated excessive hydrogen within the batteries. The battery enclosure on LRV 053 ruptured when flammable gases were released into the enclosure in the presence of an ignition source. The risk of explosion had been identified although relied on risk controls that were ineffective at preventing the escalation in this instance.

What has been done as a result

Alstom made changes to the management of train fault data to generate automatic alerts for battery over temperature faults. A new fault code was created within the train control monitoring system to monitor the battery charging temperature and alert the driver if any of the defined thresholds were exceeded.

Additionally, further software validation and testing will be conducted by the battery charger software supplier, as well as during software acceptance testing and following uploading of revised software by the maintainer.

Safety message

The introduction and commissioning of new assets must ensure that design requirements and risk controls are tested and validated as functional. Additionally, fault monitoring and maintenance regimes must monitor asset condition, so as to avoid conditions that might escalate and contribute to accidents.

The occurrence

On the evening of 2 April 2020, light rail vehicles (LRV) 053/054 arrived at the light rail Randwick Depot, New South Wales. The vehicles were stabled towards the back of road 3 along with other vehicles. A worker completed a pre-service inspection of LRV 053/054 around midnight with no abnormalities identified.

On 3 April 2020 at approximately 0249,^[1] workers in the stabling yard heard a loud noise. On investigating the source of the noise, they located a roof-mounted battery enclosure cover on the ground between two other vehicles on road 1 and 2. Further investigation identified LRV 053 as missing a battery enclosure cover.

Closed-circuit television (CCTV) cameras in the stabling yard showed a flash coming from the battery enclosure of LRV 053 as the enclosure cover was ejected from the LRV (Figure 1). The cover struck the overhead contact wire, then struck LRV 005 and 058 before falling between the two vehicles (Figure 2). The cover was airborne for approximately 4.12 seconds^[2] from being ejected to striking LRV 005. There was substantial damage to the battery enclosure on LRV 053 and minor damage to LRV 005 and 058. There were no reported injuries.

Figure 1: Randwick yard CCTV footage

The figure shows stills taken from the CCTV at 0248:50 with a flash visible and at 0248:57 showing smoke or vapour emanating from the battery enclosure of LRV 053. The ejected panel struck the overhead contact wire and landed to the left of LRV 053 out of view of camera CM03DR.

Source: Transdev, modified and annotated by OTSI

Figure 2: Battery enclosure cover landing and on the ground

The figure shows stills from the external CCTV from LRV 005. The ejected cover from LRV 053 struck LRV 005 and 058 and fell between the two vehicles.

Source: Transdev and OTSI, modified and annotated by OTSI

Post-occurrence events

Immediately following the occurrence, Alstom reviewed the available data and identified numerous battery over temperature faults had been recorded on LRV 053 and 054.

In addition, LRV 023 was identified as recording battery over temperature faults. LRV 023 was in service and was terminated, before returning to Randwick depot for inspection at approximately 0920 on 3 April. An initial visual inspection did not detect any obvious abnormalities with the batteries on LRV 023.

__________

1. Times shown in 24 hour time as Australian Eastern Daylight Savings Time (AEDT).
2. The CCTV frame rate was 25 frames per seconds, time + 0.04 seconds.

Context

Environment

The Bureau of Meteorology (BOM) automatic weather station at Observation Hill,^[3] recorded the temperature as 18.7 °C at 0300 on 3 April 2020.

The temperature was recorded between 17.8 °C and 24.8 °C in the days leading up to 3 April. The mean temperature for March 2020 was 25.3 °C with a maximum of 37.6 °C.

Location

The light rail depot was located in Randwick, New South Wales (NSW). The depot was built as part of the Sydney Light Rail project and operates as a light maintenance and stabling yard.

There were a total of 13 stabling roads and the yard had the capacity to store the entire fleet of 60 LRVs. LRV 053/054 were stabled on road 3 at the time with LRV 005 on road 2 and LRV 058 on road 1.

Sydney Light Rail

The Sydney Light Rail (SLR) project was awarded to Altrac Light Rail Partnership as a consortium including Acciona, Alstom and Transdev (Figure 3).

Figure 3: Sydney Light Rail structure

Source: Altrac, modified and annotated OTSI

The SLR project included:

• design and construction of the CBD South East Light Rail (CSELR)
• design, construction and commissioning of the LRVs for the CSELR
• operation and maintenance of the CSELR and operation of the existing Inner West Light Rail (IWLR) Line 1.

The CSELR consists of two new rail lines, with Line 2 running between Circular Quay and Randwick and Line 3 between Circular Quay and Juniors Kingsford.

Testing and commissioning for the Line 2 LRVs commenced in Sydney in late 2018 and continued up until December 2019. Public passenger services commenced on Line 2 on 14 December 2019 and Line 3 on 3 April 2020.

Light rail vehicle information

Vehicle 053

LRV 053 was manufactured in Spain and was delivered to Sydney in October 2019. The LRV underwent final commissioning and entered service in November 2019.

As of 2 April 2020, LRV 053 had travelled 18297 km and there were no known faults with the LRV.

General

The SLR vehicles are variant of Alstom Citadis X05 (305)^[4] range designed for city environments. The LRVs operate with either a conventional pantograph or on catenary-free sections utilising the Aesthetic Power Supply (APS) system. Both systems provide 750 V DC for traction power and to the auxiliary converter for auxiliary loads and battery charging. Within the stabling yard, the LRV is powered by the pantograph and overhead contact wire.

Each LRV set consist of five vehicles with drivers cabs at each end (Figure 4). In service the LRVs operate with two sets coupled together, in this case LRV 053 and 054.

Figure 4: Light rail vehicle details

Source: Altrac, annotated by OTSI

Battery system

The LRVs are fitted with batteries to provide power to the LRVs auxiliary equipment. The battery enclosure and batteries were supplied by Hoppecke to meet Alstom’s functional requirements. The battery enclosure was mounted on the roof of the M1 vehicle and the batteries were charged by the auxiliary converter fitted to the M2 vehicle.

Battery cells

The battery cells were vented nickel cadmium (NiCd) designed for rail applications. The battery cell consists of two stacks of positive and negative fibre nickel cadmium (FNC) plates submerged in an electrolyte (Figure 5). The electrolyte used was a mixture potassium hydroxide (KOH) with an addition of lithium hydroxide (LiOH) and distilled water.

The battery model was a Hoppecke FNC 235 R3 (235AH) and the cell casings were manufactured from flame retardant polypropylene (PP-VO).

The nominal cell weight when filled with electrolyte was 11.1 kg + 3% (10.77 to 11.43 kg). The volume of electrolyte between the minimum and maximum level was 810 mL.

Figure 5: Battery cell structure

Source: Hoppecke, 2019. D62109-300-en08_Manual_Alstom_X05_NAT, modified by OTSI

Battery enclosure

The battery enclosure consists of two compartments to house the battery cells and electrical compartment for electrical connections and to facilitate current, voltage and temperature monitoring. The battery enclosure design is a standard product and can house a number of different battery cell configurations. The SLR LRVs used 19 battery cells to form the battery bank.

The battery enclosure was manufactured from stainless steel and the covers for both compartments were secured with four latches each. The battery compartment had two vents positioned on the cover to provide ventilation. The covers for both compartments were also fitted with sun shields to provide some thermal protection.

The battery cells were numbered from 1 to 19, starting with battery 1 at the positive battery terminal. Each cell was connected with a metal cell connector strap and a vent / water filling hose. The battery vent / water filling hose connected to each battery cell and vented to atmosphere through a flame arrestor for backfire protection (Figure 6).

The temperature probe was fitted on top of the battery cells between cells 5, 6, 9 and 10 and reported the temperature to the auxiliary converter.

Figure 6: Battery compartment components

Source: Hoppecke (2019). D62109-300-en08_Manual_Alstom_X05_NAT, modified and annotated by OTSI

Maintenance requirements

The technical maintenance plans (TMP) specified a number of tasks to be completed relating to the batteries when the LRV reached 75,000 km (annual inspection). These tasks required the following:

• inspection and cleaning of the battery enclosure
• checking electrolyte level and topping-up as required
• testing the battery insulation resistance
• measuring charging voltage of the battery.

LRV 053 had not travelled 75,000 km, neither had any other LRV and was not due these inspections.

Auxiliary converter

The auxiliary converter which contained the battery charger was supplied by Centum Adetel Transportation Solution (Adetel). Alstom as the design integrator communicated the requirements from Hoppecke and Alstom to Adetel to provide a suitable auxiliary converter.

The auxiliary converter functions to invert the 750 V DC power supplied by the overhead contact wire or APS to lower voltages:

• 400 V AC heating and ventilation air conditioning (HVAC)
• 230 V AC general
• 24 V DC low voltage auxiliary equipment and battery charging.

Battery charging

The battery charger was designed to supply voltage and current to the batteries. Hoppecke specified that the battery charging must supply a float voltage of 27.93 V DC at 20 °C and be temperature compensated by -3 mV/°C per cell.^[5] The charging voltage should increase for temperatures below 20 °C and decrease for temperatures above 20 °C (Figure 9). The auxiliary converter software controlled the battery charging voltage and temperature compensation.

Software version

The SLR fleet was supplied with auxiliary converter software version B09. This version of software had been designed and validated as meeting the Hoppecke and Alstom’s requirements. This software version was also supplied to Alstom’s X05 fleet of LRVs in Nice, France.

In November 2019, Adetel released a revised software version B11. The change was deemed minimal and was approved for use by Alstom.

The software update to B11 for the SLR fleet commenced in December 2019. There were six LRVs outstanding as of 3 April 2020, these were LRV 023/024, 045/046 and 053/054.

Fault monitoring and management

When the battery temperature reached ≥ 60 °C for more than five seconds a battery over temperature fault (F_MVS_BatOverTempFail) was recorded within the train control monitoring system (TCMS). The maximum charging voltage was also limited to 24.3 V when the battery temperature reached 60 °C.

This fault was available for review within the maintenance menu on the drivers display unit (DDU), although would not generate an alert to the driver. Remote monitoring of the LRV fault data was also possible through the use of Alstom’s HealthHub.^[6]

Battery temperature faults

Review of the battery temperature faults for the 30 days prior to the occurrence showed a number of LRVs had recorded over temperature faults. LRV 053 and 054 accounted for most of the detected faults with 971 and 74 faults respectively, closely followed by LRV 023 with 68 faults (Figure 7).

Figure 7: Battery temperature faults

Source: Alstom, modified by OTSI

Hazards associated with batteries

There are a number of hazards associated with batteries that must be managed to ensure batteries perform their intended function safely.

Flammable gases

These vented battery cells produce hydrogen and oxygen during charging. The production of hydrogen gas mostly occurs once the battery has achieved 95 per cent charge, or during any boost charging or overcharging the battery.^[7],^[8] The hydrogen and oxygen are the result of the decomposition of water in the electrolyte, with hydrogen forming on the negative plates and oxygen on the positive plates.

Hydrogen forms flammable mixtures in air at concentrations between 4 per cent and 75 per cent. These limits are referred to as the lower flammable limit (LFL) and upper flammable limit (UFL) respectively and represent the concentrations where vapours will ignite when exposed to an ignitions source of sufficient energy.^[9]

Hydrogen requires minimal energy for ignition (0.02mJ)^[10] and must be kept away from all potential sources of ignition such as:^[11]

• open flames or fire
• sparks, electrical (fuses or switches) or mechanical (sparks from grinding)
• hot surfaces were the temperature is above 300 °C
• electrostatic discharge.

Combustion of flammable mixtures are defined as either deflagrations or detonations, depending on the velocity of the flame front propagation through the fuel-air mixture.^[12]

Combustion of hydrogen and air mixtures will typically result in a deflagration but can transition to a detonation. There are a number of factors that can influence a deflagration or detonations including, hydrogen percentage, enclosure design and strength of ignition source. Detonation of hydrogen and air mixtures is possible at a narrower concentration between approximately 18 per cent and 59 per cent.^[13]

Deflagrations usually produce fairly low pressure and generally do not pulverize, but can cause serious structural damage. Detonations are more destructive than deflagrations and produce shock waves and very high pressures.^[14]

Chemical

The electrolyte within batteries is caustic and can cause severe burns and eye damage in the event of exposure. The battery cells used on the SLR also contained cadmium which is a toxic substance and a carcinogen.

Vented battery cells are typically safe providing they are handled, stored, maintained and charged in accordance with the manufactures guidelines. In the event of a cell casing failure, mishandling or uncontained battery failure, the battery contents can be released or exposed.

Electrical

Battery cells store energy and terminals are always live. Care must be taken when working on batteries to prevent electrical shocks or short circuits. High currents can be delivered by a single cell or battery bank if there is a short circuit.

The batteries must also be installed with the correct polarity.

Similar occurrences

A review of available records was unable to identify similar occurrences relating to batteries on light rail vehicles, passenger, or freight trains locally or internationally.

There have been two previous incidents investigated where a train component was ejected from a train while in service. Both incidents involved the failure of capacitors associated with traction systems.

• The Office of Transport Safety Investigations (OTSI NSW) investigated the partial volume deflagration on Waratah carriage N5508 on 20 March 2017. A number of factors contributed to production of flammable gases within the roof mounted traction inverter module. The force of the deflagration ejected a total of four hatches across platforms 3 and 5 at Burwood. (OTSI Investigation - 04770).
• The Rail Accident Investigations Branch (RAIB UK) investigated the explosions inside an underframe equipment case at Guilford on 7 July 2017. It was found that a manufacturing defect resulted in the capacitor producing flammable gases. The gas ignited with the force ejecting debris across the adjacent platform and up to 70 m away. (RAIB Investigation - 052018).

__________

3. Bureau of Meteorology recordings were taken from the weather station at Observation Hill at Millers Point. This is approximately 5.8 km north north west from Randwick.
4. The Citadis X05 range was Alstom’s fifth generation vehicle and were available in different configurations. The X05 fleet consisted of the 205, 305 and 405.
5. Hoppecke, 2014. FNC R, Railway cells, TD-R-Cells_300, V3.0
6. HealthHub – an Alstom remote condition based monitoring product.
7. Australian Standard (2020). AS 2676.1:2020 Installation, maintenance, testing and replacement of secondary batteries in buildings Vented cells.
8. Australian Standard (2019). AS 3011.1:2019 Electrical installations - Secondary batteries installed in buildings Vented cells.
9. Brown, William J., et al., (1997). Safety Standard for Hydrogen and Hydrogen Systems: Guidelines for Hydrogen System Design, Materials Selection, Operations, Storage, and Transportation. Office of Safety and Mission Assurance, National Aeronautics and Space Administration.
10. Hydrogen requires considerably less energy to ignite than other flammable gases or liquids such as petrol (0.24mJ) or methane (0.29mJ).
11. Hoppecke (2019). Alstom Citadis X05, FNC rail battery system operating and installation manual, D62109-300-en08_Manual_Alstom_X05_NAT.
12. National Fire Protection Agency (2020). NFPA 921 Guide for Fire and Explosion Investigations 2021.
13. Brown, William J., et al., (1997).
14. DeHaan, John D., et al., (2012). Kirk’s fire investigation, 7th ed.

Safety analysis

Battery charging

Design and validation

Alstom as the design integrator used DOORS^[15] to manage and validate the various engineering requirements for the design and construction of the SLR fleet.

Alstom provided evidence demonstrating that the requirements from Hoppecke and Alstom had been communicated to Adetel during the design phase. Adetel in turn provided validation test results demonstrating that the auxiliary converter and software met the requirements and functioned correctly within the design environment.

Auxiliary converter software

Prior to acceptance of software version B09 for installation across the SLR fleet, high level functional testing was conducted on LRVs 027/028. Given all the parameters of software version B09 had been validated by Adetel (charging management, temperature curve, etc), Alstom’s software change processes did not require full functional testing. This high level functional testing did not detect any faults and was approved for installation across the entire SLR fleet.

Software version B09 consisted of a number of separate files that needed to be uploaded. The parameters for the temperature compensation and charger management were contained within the configuration script file. Post incident analysis detected that the temperature compensation law on some LRV’s with software B09 was incorrect. For reasons that could not be determined, it was believed that the configuration file was likely corrupted during the uploading process on some LRVs. This was not detected at the time of uploading the software, during the validation testing or prior to the occurrence. Later it was found that the software on LRV 027 had corrupted during the uploading prior to the acceptance testing.

Adetel provided a revised auxiliary converter software version B11 in November 2019. The release notes for this version of software did not detail any known issue with the temperature compensation for software B09. It was communicated that the only known changes to software B11, was the removal of files associated with B10^[16] and changes to the uploading process.^[17] The process for uploading software version B11 was different to B09 and did not require separate files to be uploaded. The parameters for the charging management and temperature compensation were now imbedded within software B11 and appeared to upload correctly.

At the time of the software revision (B11), the project was transitioning from design and construction to operate and maintain. The change was deemed minor and approved for use by Alstom with B11 forming the standard configuration for the SLR fleet. This change occurred after the transition and was not subjected to the full configuration control board (CCB) review as required.

Temperature compensation

Recorded data from LRV 053 showed that the batteries were charging at approximately 28 V for most of 2 April 2020 (Figure 8). During the same period the battery temperature fluctuated between 50 °C and 60 °C and the charging voltage of 28.11 V was higher than the specified temperature compensated value (Figure 9). At these temperatures the charging voltage should have reduced to between 26.22 V and 25.65 V which did not occur. The batteries were also charging at a high current (17 A) which increased from 2100 and was recorded at 33 A at the time of the occurrence.

Data from LRV 054 showed the batteries were charging at around 28 V on 2 April 2020. The charging voltage of 28.43 V at the time of the occurrence was also higher than that specified by the temperature compensation. The charging current (3 A) and battery temperature (39 °C) were however lower than that of LRV 053.

The batteries on both LRV 053/054 were overcharging in the lead up to the occurrence, while in service and within the stabling yard. The overcharging likely increased the production of hydrogen and oxygen within the battery cells and depleted the electrolyte. The high current recorded on LRV 053 was very likely a result of the battery condition and effects of overcharging.

The recorded battery temperature on LRV 053 was more than 40 °C above the ambient temperature, so ambient temperature was not a factor in the elevated battery temperature.

Figure 8: LRV 053/054 battery charging data from 2 and 3 April 2020

Source: Alstom, modified and annotated by OTSI

Figure 9: LRV 053/054 charging voltage vs electrolyte temperature

Source: Hoppecke (2019). D62109-300-en08_Manual_Alstom_X05_NAT and Alstom, modified and annotated by OTSI

Temperature probe

The temperature probe was mounted to a post and positioned above batteries 5, 6, 9 and 10. The probe on LRV 053 was found to be sitting up and was not in contact with the top of the battery cells (Figure 11). This was probably the result of the forces created during the occurrence as the temperature probe post allowed the probe to sit on top of the batteries post incident.

The Hoppecke temperature compensation refers to compensating the charging voltage based on the electrolyte temperature (Figure 9). The location of the probe would not provide a direct temperature of the electrolyte but rather the case temperature at the top of the battery cells. Testing conducted post incident determined that the probe measured within approximately 1 °C of the electrolyte temperature.

The difference between the electrolyte temperature and case temperature under normal circumstances would probably be negligible. However, low electrolyte levels would decrease the effectiveness of the temperature probe as the distance between the electrolyte and probe increases.

Survey of battery electrolyte

Post incident Alstom undertook a survey to inspect the battery compartments on the SLR fleet including checking the battery electrolyte levels.

Low electrolyte levels were identified on a total 28 LRVs, including 023, 041, 046 and 54 which had reported battery over temperature faults. The battery banks on the 28 LRVs required between 0.2 and 26 L of distilled water to restore the electrolyte to the correct level. Refer to Appendix A – Electrolyte survey results.

The low electrolyte had not been detected prior to the fleet survey as the LRVs had not reached the 75,000 km maintenance interval and the over temperature faults had not been monitored.

Alstom also undertook the same survey across the global X05 fleets and advised that low electrolyte levels were also identified in the fleet of LRVs in Nice, France.

Uncontained battery failure

The initial inspection conducted on 3 April 2020 identified the battery compartment had ruptured and there was evidence of heat (browning) between a number of cells. Most the battery filler plugs were lifted and a number of battery cell casing had cracked outwards (Figure 10 and Figure 11). The vents on the ejected cover appeared to be unobstructed.

Figure 10: LRV 053 ruptured battery compartment

Source: OTSI

Figure 11: LRV 053 battery cells and temperature probe

The image shows a close up view of signs of heat between battery cells 9 and 10 and between cells 10, 11, 12 and 13. The temperature probe can also be seen to be sitting up and not in direct contact with the top of the battery cells.

Source: OTSI

Two further inspections of the battery compartment were conducted at the Randwick light rail depot on 15 April and 30 April 2020. These inspections were undertaken with representatives from Alstom, ATSB and representatives on behalf of Hoppecke. Observations from these inspections are recorded in Appendix B – Battery cell assessment.

There was no evidence of high resistance joints within the battery or electrical compartments and all electrical connections were secure with witness markings intact. The temperature probe was tested and functioned as expected.

All cells except cell 15 showed signs of damage or the filler plug was lifted. Battery cells 9, 10, 11, 12 and 13 all showed signs of heat with the cell casings melted (Figure 12). Cell 12 had also short circuited. The damage to the cell casings indicates that the actual temperature far exceeded the recorded temperature of 60 °C as the cell casing begin to melt at 120 °C.

There was no visible electrolyte within the cells when inspected and all battery cells were below the minimum electrolyte level. Cell 19 which was missing a portion of the cell casing appeared to have approximately 20 to 30 mm^[18] of electrolyte in the bottom of the cell.

The battery cells weighed between 1.5 and 1.9 kg less than the nominal weight of 11.1 kg. Some cells were missing sections of the cell casing although the low electrolyte would be the greatest contributor to the reduced cell weight.

Figure 12: Battery cells 9 to 13

The image shows the damage to the cell casings for batteries 9 to 13. Cell casings for batteries 11 and 12 were fused and required mechanical separation to remove from the battery compartment.

Source: OTSI

The batteries on LRV 053 recorded frequent over temperature alerts in the 30 days leading up to the occurrence. During this time the batteries were overcharging. Most of the electrolyte probably evolved into hydrogen and oxygen due to overcharging and vented to atmosphere via the filler plugs.

The battery compartment ruptured due to pressure caused by the deflagration of flammable gases containing hydrogen. The flammable gases were probably released into the enclosure by a combination of the melted battery cells and an internal deflagration within the battery cells.

The exact source of ignition was not able to be determined. Hydrogen requires minimal energy for ignition and it is possible that the gases could have been ignited by one of the following:

• a short circuit in cell 12
• heat produced as a result of increased current and cell degradation.

Management of light rail vehicle faults

The battery temperature fault management characteristic for the X05 fleet were based on the similar logic used for Alstom’s Citadis X02 fleet. The over temperature fault had not been determined to be critical providing the temperature compensation and charging logic functioned as designed.

On each occasion the batteries on LRV 053 reached 60 °C a battery over temperature fault would be recorded. Charging continued in excess of the designed maximum charging voltage of 24.3 V at 60 °C.

The over temperature faults, charging voltage and current were all recorded, however, there were no systems in place to monitor fault conditions and alerts. Consequently, the ability to identify and monitor potential defects that might escalate and contribute to accidents was limited.

Enclosure design

The risk of explosion was known to both Alstom and Hoppecke and had been assessed with the following risk controls and recommendations:^[19],^[20],^[21],^[22]

• temperature compensated charging
• appropriate ventilation
• maintenance inspection (including electrolyte level, charging voltage and vents for obstruction).

Projection of materials had also been assessed as a known risk in the event of an explosion.

In order to prevent the build-up of flammable gases the battery enclosure was vented. Ventilation had been calculated in accordance with EN 50272 – 2, Safety requirements for secondary batteries and battery installations. Stationary batteries. This specified that the production of hydrogen within the battery enclosure must not exceed 4% (LFL). The following boundary conditions were used to calculate the required ventilation:^[23]

• Temperature: 20 °C
• Cell type: FNC 235 R3 (235AH)
• Batteries are fully charged
• Batteries are charged with a constant voltage charger with current limit
• Train [LRV] is not moving
• The ventilation will be calculated for float charging conditions of the battery
• We also assume that electrical precaution against charger malfunction will be provided
• Factor of safety of 5, to accommodate faulty cells in a battery string and an aged battery this safety factor also compensates for a temperature increase up to approximately 44 °C.

The calculated minimum ventilation requirement was 43 cm2. The battery enclosure cover for the SLR fleet was supplied with two 75 cm2 mushroom style vents (inlet and outlet). The ventilation exceeded the requirements of EN 50272-2 and permitted the use of a standard cover across the various X05 fleets.

Under normal circumstances hydrogen and oxygen produced during charging would be vented externally to the enclosure through the vent / water filler hose and flame arrestor.

The battery enclosure on LRV 053 ruptured as a result of forces created by internal pressure when a flammable concentration above the LFL was ignited. The cover and debris were ejected from the LRV as there was no means of either venting the forces or containing projectiles. The four latches that secured the cover all failed in a similar manner with the lock pin failing.

The ejected cover weighed 20 kg and was airborne for approximately 4.12 seconds in which time it struck the overhead contact wire likely slowing the ascent. The cover landed approximately 6 m away from LRV 053 and posed a significant risk to any persons in the area. The chemical hazards could also have caused burns or eye damage if released when the enclosure ruptured.

The addition of deflagration venting such as frangible panels and/or secondary restraints to prevent projections from the roof of the LRV, may have reduced the potential consequences. These measures could however introduce new or different risks and would require assessment.

__________

15. DOORS - an IBM proprietary software program used for the management of engineering requirements to track the communication, documentation and validation of the requirements.
16. Software version B10 was not supplied to the SLR fleet.
17. Alstom (2020). X05-SNY-LRV53-LV BATTERY Static converter SW.
18. Euro Power Australia (2020). Battery Inspection Report, V1.1
19. Alstom (2017). Sydney Light Rail - Preliminary Hazard Analysis, RS-PHA-SLR-ALS-D80-RST-SPE-000020_PHA_E_Ap1.
20. Hoppecke (2016). Citadis X05, LVPS FNC, Sub System Hazard Analysis, D62109-210 ALSTOM Citadis X05_Hazard Analysis.
21. Hoppecke (2016). Fault tree analysis, LVPS FNC 22,8V / 24V CITADIS X05, D63041-220 ALSTOM X05 FTA_global_NAT_R002.
22. Hoppecke (2016). Safety recommendations, LVPS FNC 22,8V / 24V CITADIS X05, 62109 ALSTOM X05 Safety recommendations_R003.
23. Hoppecke (2015). Citadis X05, Technical Offer, spsh-f104514-alstom-citadis-xo5-305aps-rev007.

Findings

From the evidence available, the following findings are made with respect to the uncontained battery failure and ejection of the battery compartment cover on LRV 053 on 3 April 2020.

Contributing factors

• Data corruption likely occurred during the uploading of the auxiliary converter software configuration file (version B09) on some light rail vehicles, including for LRV 053. The fault rendered the battery temperature compensation ineffective, resulting in overcharging of the battery system.
• Overcharging of the battery system depleted the battery cell electrolyte levels and generated excessive hydrogen within the batteries. Overcharging also generated excessive heat within the cells, resulting in the failure of some cell casing.
• Flammable gases consisting of hydrogen, were released into battery enclosure in the presence of an ignition source. The gases ignited with the force of the expanding gases rupturing the battery enclosure and ejecting the cover from the roof of LRV 053.
• Neither Alstom’s validation processes nor fault monitoring processes were sufficient to detect the overcharging of batteries prior to the event. [Safety issue]

Other factors that increased risk

• The battery enclosure while vented was not designed to vent the forces of a deflagration or contain projectiles, resulting in the ejection of the cover.

Safety issues and actions

Alstom's validation and fault monitoring processes

Safety issue number: RO-2020-005-SI-01

Safety issue description: Neither Alstom’s validation processes nor fault monitoring processes were sufficient to detect the overcharging of batteries prior to the event.

Train details

Train 1 details

Train 2 details

Train 3 details

Sources and submissions

Sources of information

The sources of information during the investigation included the:

• Alstom Limited Australia
• Altrac Light Rail
• Centum Adetel Transportation Solution
• Euro Power Australia
• Hoppecke
• Office of the National Rail Safety Regulator
• Transdev
• Transport for NSW.

References

Alstom (2017). Sydney Light Rail - Preliminary Hazard Analysis, RS-PHA-SLR-ALS-D80-RST-SPE-000020_PHA_E_Ap1.

Alstom (2020). X05-SNY-LRV53-LV BATTERY Static converter SW, 10 June 2020.

Australian Standard (2019). AS 3011.1:2019 Electrical installations - Secondary batteries installed in buildings Vented cells.

Australian Standard (2020). AS 2676.1:2020 Installation, maintenance, testing and replacement of secondary batteries in buildings Vented cells.

Brown, William J., et al., (1997). Safety Standard for Hydrogen and Hydrogen Systems: Guidelines for Hydrogen System Design, Materials Selection, Operations, Storage, and Transportation. Office of Safety and Mission Assurance, National Aeronautics and Space Administration. Accessed at: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19970033338.pdf

DeHaan, John D., et al., (2012). Kirk’s fire investigation, 7th ed, p.28, 525 – 529.

European Standards. EN 50272 – 2, Safety requirements for secondary batteries and battery installations. Stationary batteries.

Euro Power Australia (2020). Battery Inspection Report, V1.1.

Hoppecke (2014). FNC R, Railway cells, TD-R-Cells_300, V3.0.

Hoppecke (2015). Citadis X05, Technical Offer, spsh-f104514-alstom-citadis-xo5-305aps-rev007.

Hoppecke (2016). Citadis X05, LVPS FNC, Sub System Hazard Analysis, D62109-210 ALSTOM Citadis X05_Hazard Analysis Battery_global_NAT_R002.

Hoppecke (2016). Fault tree analysis, LVPS FNC 22,8V / 24V CITADIS X05, D63041-220 ALSTOM X05 FTA_global_NAT_R002.

Hoppecke (2016). Safety recommendations, LVPS FNC 22,8V / 24V CITADIS X05, 62109 ALSTOM X05 Safety recommendations_R003.

Hoppecke (2019). Alstom Citadis X05, FNC rail battery system operating and installation manual, D62109-300-en08_Manual_Alstom_X05_NAT.

National Fire Protection Agency (2019). NFPA Glossary of terms.

National Fire Protection Agency (2020). NFPA 921 Guide for Fire and Explosion Investigations 2021, p.247 – 270.

Rail Industry Safety and Standards Board (2020). Glossary of Terms. Accessed at: www.rissb.com.au/glossary/

Submissions

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

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

• Altrac Light Rail
• Office of the National Rail Safety Regulator
• Transport for NSW.

Submissions were received from:

• Altrac Light Rail
• Office of the National Rail Safety Regulator.

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

Glossary of terms

Aesthetic Power Supply (APS) system – The APS system provides power through a ground based system with contact shoes under the intermediate car (IC) that transfers power to the vehicle. The system functions similarly to a third rail, however, the sections imbedded within the ground are only live when the vehicle crosses over that section.

Alternating current (AC) – Electrical current that reverses direction periodically.

Auxiliary converter – A auxiliary converter functions to invert direct current to alternating current. In this case the direct current supply from the overhead contact wire or APS to alternating current for use on the vehicle, as well as a DC output for battery charging.

Battery cell – A functional battery containing an assembly of electrodes, electrolyte, container, terminals and usually separators, that is a source of electric energy obtained by direct conversation of chemical energy.

Battery enclosure – a cabinet or box that provides protection against electrical contact or damage to the battery.

Catenary – In overhead electrification, the uppermost of the two overhead wires mounted above the track and supporting the contact wire.

Contact wire – A bare solid conductor being the lowest of the two overhead wires mounted directly above the track centreline. The pantographs of electric trains press against the underside of this wire and collect the current required by the train.

Combustion – A chemical process of oxidation that occurs at a rate fast enough to produce heat and usually light in the form of either a glow or a flame.

Decomposition – The transformation of a substance into simpler substances or basic elements brought about by exposure to heat, light, or chemical or biological activity.

Deflagration – Propagation of a combustion zone at a velocity that is less than the speed of sound in the unreacted medium.

Detonation - Propagation of a combustion zone at a velocity that is greater than the speed of sound in the unreacted medium.

Direct current (DC) – Electrical current that flows in one direction only.

Drivers display unit (DDU) – The display unit within the drivers compartment to display critical information to the driver.

Explosion – The sudden conversion of potential energy (chemical or mechanical) into kinetic energy with the production and release of gases under pressure, or the release of gas under pressure. These high-pressure gases then do mechanical work such as moving, changing, or shattering nearby materials.

Flammable – A combustible that is capable of easily being ignited and rapidly consumed by fire. Flammables may be solids, liquids, or gases exhibiting these qualities.

Float charging – The period of charging after a battery has fully charged and designed to maintain the battery charge.

Fibre nickel cadmium (FNC) – Hoppecke proprietary technology that refers to the metallised fibre structure within the battery cell electrode.

Frangible panels – A sacrificial panel designed to rupture or open to vent forces created through the combustion process to prevent damage to an enclosure or structure.

Light Rail Vehicle (LRV) – A vehicle used on a light rail system.

Lower flammable limit (LFL) – The lowest concentration of a combustible substance in an oxidizing medium that will propagate a flame.

Joule – The preferred international standard (SI) unit of heat, energy, or work. A joule is the heat produced when one ampere is passed through a resistance of one ohm for one second, or it is the work required to move a distance of one meter against a force of one newton.

Nickel cadmium battery (NiCd) – Storage battery which has an alkaline electrolyte, with nickel oxide as the positive element and cadmium as the negative, this type being used especially as a rechargeable battery.

Pantograph – An apparatus fixed to the roof of electric traction vehicles to draw current from the overhead supply.

Polypropylene (PP-VO) – A plastic polymer of propylene, in this instance with flame retardant characteristics.

Upper flammable limit (UFL) - The highest concentration of a combustible substance in a gaseous oxidizer that will propagate a flame.

Volts (V) – The derived SI unit of electric potential or electromotive force, defined as the difference of electric potential between two points of a conducting wire carrying a constant current of one ampere, when the power dissipated between these points is one watt.

Appendices

Appendix A – Electrolyte survey results

Appendix B – Battery cell assessment

Purpose of safety investigations & publishing information

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2020 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

Safety summary

What happened

On 22 March 2020, a Cessna 172 aircraft, registered VH-CBB, took off from a private airfield in Canyonleigh, New South Wales, on a local private flight with the pilot and one passenger on board. Shortly after take-off, due to turbulent weather, the pilot decided to terminate the flight and return to land at the airfield. During the approach, while the aircraft was lower than the pilot had intended, it encountered turbulence. This resulted in the aircraft pitching up steeply. After the pilot corrected the aircraft’s pitch attitude, the landing gear contacted the tree canopy of a steep forested escarpment on the approach path and below the level of the runway threshold. Uncertain if the aircraft could climb above the canopy, the pilot elected to reduce power immediately and land in the trees. The pilot and passenger sustained serious injuries as a result, and the aircraft was substantially damaged.

What the ATSB found

The ATSB determined that the aircraft was on a relatively shallow approach and was at a low height above the terrain when it encountered turbulence. After recovering from the turbulence, the pilot assessed that the aircraft could not reach the runway over the steep terrain, and decided to land in trees.

Safety message

This accident highlights the importance of adopting an approach profile that mitigates the effects of gusty/turbulent conditions and being prepared to go around if the approach becomes unstable. The Flight Safety Foundation Approach-and-landing Accident Reduction briefing note 6.1 emphasises the need to be ‘go-around-prepared’ or ‘go‑around-minded’ because it is not a manoeuvre that pilots execute regularly.

The investigation

The occurrence

On the afternoon of 22 March 2020, the pilot of a Cessna 172A aircraft, registered VH-CBB, planned to conduct a local private flight from a private airfield at Canyonleigh, New South Wales, with one passenger on board. The pilot noted that the wind speed and direction were as forecast, which were 20 kt and west‑south‑westerly, and therefore selected runway 27^[1] for take-off.

Shortly after take-off, the aircraft experienced some turbulence. The pilot and passenger assessed it was ‘not going to be a relaxing time to go for a fly’, and decided to terminate the flight. The pilot confirmed via the windsock that the wind direction had not changed since take‑off, and elected to continue onto a downwind leg of the circuit for runway 27.

When the aircraft was 1 NM from the threshold, and approximately 400 ft above aerodrome level, the pilot completed the turn onto final approach. The pilot reported having selected one stage of flap for the approach and landing. The aircraft was on approach over steep forested terrain when the pilot noticed that the approach profile was shallower than intended and that the aircraft was ‘a bit low’. In response, the pilot increased the power.

The pilot reported that the turbulence then became ‘very severe’ and the aircraft pitched up steeply. The pilot initially decided to conduct a go-around manoeuvre, but after correcting the pitch attitude, realised that the aircraft was far lower than expected, and no longer aligned with the runway. The aircraft’s wheels reportedly brushed the tree canopy on the escarpment downhill from the runway threshold. Uncertain whether the aircraft would be able to climb over the canopy to the runway, the pilot elected to reduce power and land in the trees. The aircraft came to rest approximately 50 metres short of the threshold and to the left of the runway.

Both the pilot and passenger sustained serious injuries, but they were able to exit the aircraft and contact emergency services. The aircraft was substantially damaged.

Context

Recorded data and airfield geography

OzRunways^[2] information for the flight was obtained, with the final approach shown in Figure 1. A review of the flight data identified that during the second half of the approach, the aircraft’s altitude remained relatively level (highlighted segment), but the terrain beneath falls away into a deep gully then climbs towards the airfield.

Figure 1: VH-CBB approach to Canyonleigh airfield, runway 27

The recorded data rounded the aircraft’s altitude down to 100 ft increments, giving a low approximation of VH-CBB’s actual approach. Due to sudden changes in attitude and altitude, the last few data points were considered unreliable and were therefore not included in the image.
Source: Google Earth, annotated by the ATSB

Pilot’s experience at Canyonleigh

The pilot had landed at Canyonleigh airfield about 50 times prior to the occurrence, all in VH-CBB. During previous landings on runway 27, the pilot reported sometimes making high/steep approaches and extending full flaps to ‘increase the safety margin’ while flying over the steep, heavily forested terrain. On the day of the occurrence, the pilot believed a high approach would not be necessary.

The pilot assessed that the severe turbulence encountered prior to landing was caused by rotors—a specific type of turbulence produced by mountain waves.^[3] This kind of turbulence had reportedly been encountered by both the accident pilot and, to a lesser degree, the airfield owner, during previous landings on runway 27.

Meteorological information

The Bureau of Meteorology provided the following assessment of the likely weather conditions at Canyonleigh on the day of the accident:

While winds gusting to 26 knots were observed at [the nearby weather station], it is possible that the winds higher in the atmosphere were a little stronger, possibly reaching 30 knots at times. With 20 to 30 knots of wind over elevated terrain, light to moderate mechanical turbulence is likely.

With regard to the possible formation of rotors beyond the threshold of runway 27, the Bureau of Meteorology stated:

While the atmospheric conditions did not strongly favour mountain wave and rotor turbulence and no evidence of waves could be seen on satellite imagery, the presence of a temperature inversion above the ridge top with moderate winds blowing perpendicular to the ridge means that small scale waves and rotors cannot be ruled out. The terrain downstream from the threshold, sloping sharply downwards towards the valley, could cause an acceleration of the winds close to the ground, thus increasing the possibility of downward air motion as well as rotor formation. There are, however, no observations to confirm that this occurred.

Safety analysis

While on approach to runway 27, the pilot noticed the glideslope was shallower than intended and that the aircraft was low, so increased power. The aircraft then encountered turbulence, resulting in it pitching upward. The exact nature of the turbulence could not be determined, but rotors or downward air motion over the escarpment may have been present at the time.

Once the aircraft’s attitude was corrected, the pilot assessed that the aircraft was too low and close to the terrain to climb out of the valley to the runway and decided to land immediately in the trees below.

Findings

From the evidence available, the following findings are made with respect to the collision with terrain involving Cessna 172, VH-CBB, on 22 March 2020.

Contributing factors

• During a shallow approach, the aircraft encountered significant turbulence that affected the aircraft’s pitch attitude and flight profile. As a result, the pilot assessed the aircraft was too low to reach the runway and elected to land in trees.

Sources and submissions

Sources of information

The sources of information during the investigation included the:

• pilot
• passenger
• airfield owner
• New South Wales Police Force
• Bureau of Meteorology
• OzRunways.

Submissions

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

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

• the pilot
• the airfield owner
• the Bureau of Meteorology.

No submissions were received.

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2020 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

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1. Runways are numbered in relation to their magnetic direction rounded off to the nearest 10°. This is the runway designation. Runway 27 at Canyonleigh has a runway direction of 269° magnetic
2. OzRunways is an electronic flight bag application that provides navigation, weather, area briefings and other flight planning information.
3. Mountain waves are a weather phenomenon involving winds flowing over mountain ranges.

Safety summary

What happened

On the morning of 17 March 2020, a QantasLink Bombardier Dash-8-402, registered VH-LQJ (LQJ), was being taxied for a scheduled flight from Gladstone Airport, Queensland to Brisbane Airport, Queensland. There were two flight crew, two cabin crew and 34 passengers on board. At the same time, an ATEC Faeta 321, registered 24-8279 (Faeta 8279), with one instructor and student on board, was conducting circuit training at Gladstone Airport.  

At about 0645, as Faeta 8279 was on approach to conduct a touch-and-go on runway 10, LQJ entered and taxied along the runway in front of Faeta 8279. The instructor on board Faeta 8279 conducted a go-around to avoid an incident on the occupied runway.

What the ATSB found

The ATSB found that the flight crew of LQJ set the incorrect common traffic advisory frequency and did not select the appropriate traffic collision avoidance system/transponder mode during the before start checks. These errors were likely influenced by increased workload and time pressures experienced during before start preparations.

The errors went undetected during the taxi phase of flight. As a result, the flight crew’s situational awareness was significantly degraded and caused the captain and first officer to form the shared belief that no other traffic was operating in the vicinity of Gladstone Airport. This shared incorrect mental model likely impacted the efficacy of the visual scan conducted prior to entering the runway, with neither flight crew member sighting the approaching aircraft.  

What has been done as a result

Following this incident, QantasLink undertook a review of operating procedures at non-controlled airports. The procedural review included transponder activation and introduced a requirement to contact Air Traffic Control prior to entering the runway. QantasLink also provided internal communications to flight crew detailing the importance of standard operating procedures and threat management when dealing with distractions and workload.

Safety message

This incident illustrates the human factors implications associated with the combination of increased workload and time pressures. Flight crews can guard against similar outcomes by applying effective threat and error management strategies that recognise when such threats may arise and set in place suitable actions that minimise error potential. These actions include strict adherence to standard operating procedures and increased cross-checking of system inputs and mode changes.

The investigation

The occurrence

At about 0600 Eastern Standard Time,^[1] on 17 March 2020, the crew of a QantasLink Bombardier Dash-8-402 aircraft, registered VH-LQJ (LQJ), commenced pre-flight preparations for a scheduled regular public transport flight from Gladstone Airport, Queensland to Brisbane Airport, Queensland. The crew comprised the captain, first officer (FO) and two cabin crew.

It was the first flight of the day for LQJ and the scheduled departure at 0645 meant that the crew had about 45 minutes to prepare the aircraft. Shortly after arriving at the aircraft, the captain started the auxiliary power unit (APU),^[2]while the FO conducted the aircraft walk around. The captain then commenced the ‘originating’ and ‘before start’ checks, which included selecting APU bleed air ‘ON’ to provide air-conditioning to the cabin. At this point the APU failed, so the captain completed the automatic APU shutdown actions.

At about 0610 during the walk around, the FO noticed a small aircraft taxi behind LQJ. This aircraft was an ATEC Faeta 321, registered 24-8279 (Faeta 8279), that was being taxied for circuit training with one instructor and one student on board. The FO made a mental note of the taxiing aircraft, finalised the walk around, and returned to the flight deck to complete the remainder of the pre-flight preparations.

The captain and FO then restarted the APU, but it failed for a second time when APU bleed air was selected ‘ON’. At about the same time, a ground crew member attended the flight deck to inform the captain and FO that a ‘person in custody’^[3]and their police escort would be travelling on the flight. The captain left the flight deck to review the person in custody paperwork and brief the cabin crew on the custody arrangements. The person in custody and their escort then boarded the aircraft, with the remainder of the flight’s 34 passengers boarding a short time later.

At about 0622, Faeta 8279 commenced circuit training using runway 28. The occupants of Faeta 8279 made regular positional broadcasts on the Gladstone Airport common traffic advisory frequency (CTAF) ^[4]throughout the training activity.

Meanwhile, on board LQJ, the captain returned to the flight deck and elected to apply the Minimum Equipment List (MEL)^[5] to the APU system. The captain and FO then actioned the procedures required to apply the MEL with remote support provided by QantasLink maintenance engineers. Completing this task took the crew 5-10 minutes.

Once the MEL had been finalised, the captain and FO undertook the remainder of the before start checks, but omitted to set the traffic collision avoidance system (TCAS)^[6]/transponder^[7] to ‘ON ALT’ and to select the Gladstone CTAF in VHF COM 2.^[8]The CTAF omission was identified by the FO during the departure briefing and subsequently addressed. However, the FO entered the incorrect frequency of 126.7 MHz instead of 118.8 MHz, which was the correct frequency for the Gladstone CTAF.

At 0643, a pilot in Faeta 8279 made a CTAF broadcast advising traffic that the aircraft would be changing runway direction for a touch-and-go on runway 10. The captain and FO of LQJ did not receive this broadcast as they were monitoring the incorrect frequency.

The weather at the time was reported as being a wind from 201 degrees magnetic at 6 knots, no cloud, and a visibility of 43 km. As the wind did not favour either runway, the flight crew of LQJ elected to use runway 28 to avoid departing towards the rising sun. This required a short taxi from bay 3 to the A5 intersection, and a right turn to enter and backtrack runway 28 (Figure 1 and Figure 2).

 Figure 1: Overview of VH-LQJ taxi routing

Source: Google Earth, annotated by the ATSB

Figure 2: Gladstone aerodrome chart

Source: Airservices Australia, annotated by ATSB

At 0643:38, the FO made a broadcast on the incorrect CTAF using VHF COM 2 and LQJ was taxied from its parked position on bay 3.

At 0644:23, the FO made a second broadcast on the incorrect CTAF as the aircraft taxied towards the A5 intersection.

At 0644:29, a pilot in Faeta 8279 made a broadcast on the Gladstone CTAF advising traffic that the aircraft was on short final for a touch-and-go on runway 10. The flight crew of LQJ did not receive this broadcast either.

The captain and FO conducted a visual scan as LQJ neared the A5 intersection, but neither flight crew sighted Faeta 8279 on approach for runway 10. At about 0645, LQJ was taxied onto the runway in front of the approaching Faeta 8279. In response, the instructor on board Faeta 8279 commenced a go-around and attempted, unsuccessfully, to contact LQJ on the Gladstone CTAF. 

At 0645:02, as LQJ backtracked along the runway, the FO made a taxi report to Brisbane Centre^[9] using VHF COM 1. A secondary surveillance radar transponder code^[10] was provided to LQJ and the captain entered it into the transponder. Shortly afterwards, the captain identified that the TCAS/transponder was not appropriately set and selected it to ‘ON ALT’.

At 0645:42, the TCAS presented the flight crew with a traffic advisory^[11] indicating climbing traffic above LQJ. The traffic – Faeta 8279 – was subsequently sighted by the captain and FO climbing in an easterly direction overhead the airport.

The captain and FO checked the frequency set in VHF COM 2 and identified the incorrect frequency selection. The frequency was changed to the correct frequency of 118.8 MHz and the FO made a broadcast at 0646:29 advising that LQJ was ‘entering and backtracking’ runway 28.

At about 0646:36, a pilot in Faeta 8279 replied to LQJs broadcast, but the flight crew of LQJ did not respond to Faeta 8279’s transmission. A short time later, the instructor in Faeta 8279 broadcast the intention to manoeuvre for runway 28 to allow LQJ to depart. At about 0648, LQJ commenced its take-off from runway 28.

Context

Air Traffic Control communications

The captain and FO elected to delay the taxi report to Brisbane Centre until LQJ had entered the runway. This was due to the shared understanding that the Gladstone Airport terminal buildings shield VHF transmissions and prevent contact being made with Brisbane Centre when parked on bay 3. QantasLink procedures permit an aircraft to be moved to an alternate location when communications with air traffic services are not possible on the bay.

Human factors

The same crew had flown LQJ into Gladstone Airport the evening prior, arriving at about 1900 on 16 March 2020. The crew then stayed overnight in local hotel accommodation. Both the captain and FO reported no fatigue issues associated with the overnight stay, and an assessment of the flight crew’s previous 14-day roster did not identify any significant fatigue risk factors.

During pre-flight preparations, the captain and FO encountered a number of unanticipated events and distractions, including two APU failures, boarding of a person in custody, and application of a MEL to the APU system. The additional actions, due to these events, increased their workload.

On the morning of the incident, neither the captain nor the FO recalled listening for an aerodrome frequency response unit (AFRU)^[12] reply to the two broadcasts made on the incorrect frequency. The first broadcast took place when both flight crew members recall increased workload associated with the turn off bay 3. The second CTAF broadcast was made mid-way through the short taxi to the runway intersection.

Prior to entering the runway, the captain recalled believing there was no other aircraft in the vicinity of Gladstone Airport as the crew had not heard any broadcasts on VHF COM 2 and there was no traffic indicating on the TCAS display. The FO recalls making reference to the small aircraft that had been sighted during the walk around checks. However, given the elapsed time since the sighting, combined with the lack of transmissions received on VHF COM 2, the FO concluded that the traffic was no longer in the vicinity of the airport.

Safety analysis

This was the first flight of the day for LQJ and the crew had about 45 minutes to complete all pre‑flight preparations prior to the scheduled departure time of 0645. During this period, the captain and FO encountered several unanticipated events and distractions, including the APU failure and person in custody paperwork, that required additional actions to be performed within the allocated timeframe. These interruptions and additional actions within a defined time period added workload and time pressures.

The combination of increased workload and time pressures is known to result in degraded information processing, increased errors, the tunnelling of attention, and an increased reliance on familiar strategies or actions (Staal, 2004). This response to workload and time pressures likely resulted in the flight crew’s omission of the two ‘before start’ checklist items and the selection of the incorrect frequency in VHF COM 2.

The frequency selection error was further compounded by the flight crew not recognising an absence of AFRU reply when making radio calls on the incorrect frequency. As a result, the captain and FO were not aware that they were monitoring and broadcasting on the incorrect CTAF.

The flight crew’s inadvertent omission of the TCAS/transponder selection resulted in the captain and FO incorrectly believing the TCAS would alert them to the presence of any transponder equipped aircraft that were operating in the vicinity of Gladstone Airport.

As a result of the frequency selection and TCAS/transponder errors, the flight crew’s situational awareness was significantly degraded resulting in the captain and FO forming the shared belief that no other traffic was operating in the vicinity of Gladstone Airport. This shared incorrect mental model likely impacted the efficacy of the visual scan conducted by the flight crew as they neared the A5 intersection. Consequently, neither flight crew member identified the approaching aircraft and LQJ was taxied onto the runway in front of Faeta 8279. The instructor on board Faeta 8279 conducted a go-around to avoid an incident on the occupied runway.

Findings

From the evidence available, the following findings are made with respect to the runway incursion involving Bombardier Dash-8-402, registered VH-LQJ, at Gladstone Airport, Queensland, on 17 March 2020.

Contributing factors

• The flight crew of VH-LQJ were not aware that light aircraft 24-8279 was on approach and taxied onto the runway in front of it. Consequently, the pilot of 24-8279 had to conduct a go‑around.
• The visual scan by the flight crew of VH-LQJ before entering the runway did not identify the approaching 24-8279, probably because of their degraded situational awareness.
• Increased workload and distractions while preparing VH-LQJ for departure led to the crew not setting the correct radio frequency and the appropriate mode on the traffic collision avoidance system/transponder. Without these essential aids to situational awareness, neither pilot developed an accurate mental model of the traffic.

Safety actions

Safety action by QantasLink

Following this incident, QantasLink undertook a review of operating procedures at non-controlled airports. The procedural review included transponder activation and introduced a requirement to contact Air Traffic Control prior to entering the runway. QantasLink also provided internal communications to flight crew detailing the importance of standard operating procedures and threat management when dealing with distractions and workload.

Sources and submissions

Sources of information

The sources of information during the investigation included:

• the flight crew of VH-LQJ
• the pilot in command of 24-8279
• QantasLink
• Avdata
• Civil Aviation Safety Authority
• Airservices Australia.

References

Staal MA 2004, Stress, cognition, and human performance: A literature review and conceptual framework, National Aeronautics and Space Administration Technical Memorandum NASA/TM-2004-212824.

Submissions

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

A draft of this report was provided to the crew of VH-LQJ, the pilot in command of 24-8279, QantasLink, and the Civil Aviation Safety Authority.

Submissions were received from QantasLink and the captain of VH-LQJ.

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

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2021 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

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1. Eastern Standard Time (EST): Coordinated Universal Time (UTC) + 10 hours.
2.  An auxiliary power unit is a small turbine engine that is normally located in the tail of an aircraft and supplies power to aircraft systems independently of ground support equipment.
3.  A ‘person in custody’ is a person who is in custody under an Act of Parliament, including a law of a State or Territory, that needs to travel by air.
4.  A common traffic advisory frequency is a designated frequency on which pilots make positional broadcasts when operating in the vicinity of a non-controlled aerodrome or within a broadcast area.
5.  A Minimum Equipment List (MEL) allows the continued operation of aircraft with certain equipment inoperative, subject to specified conditions.
6.  A traffic collation avoidance system (TCAS) monitors the airspace around an aircraft for other traffic equipped with a corresponding active transponder and gives warning of possible collision risks.
7.  A transponder is a receiver/transmitter fitted to an aircraft which will generate a reply signal upon proper interrogation; the interrogation and reply being on different frequencies..
8.  The VHF COM 2 is one of two VHF transceivers available on the aircraft.
9.  Brisbane Centre is the air traffic control area control centre responsible for the flight information region within which Gladstone Airport is located.
10.  The number assigned to a particular multiple-pulse reply signal transmitted by a transponder in Mode A or Mode C.
11.  A traffic advisory is an indication given to the flight crew that a certain intruder is a potential threat.
12.  An Aerodrome Frequency Response Unit (AFRU) is a device installed at non-controlled aerodromes that will provide an automatic response when pilots transmit on the CTAF for the aerodrome at which it is installed.

Safety summary

What happened

On the afternoon of 5 March 2020, an Airbus A320, registered VH-VFL and operated by Jetstar Airways landed at Proserpine, Queensland, on a scheduled passenger service from Sydney, New South Wales. On the walk around after landing, damage was found to the nose gear landing light and the left main landing gear, including a pierced hydraulic brake line.

Fluid was subsequently found in the landing gear wheel well. No evidence of a strike or foreign object debris was found on the runway at Proserpine or Sydney. There was no indication that the aircraft had been struck by ground support equipment prior to departure from Sydney, and no recent maintenance had been performed on the left main landing gear.

What the ATSB found

The ATSB determined that the nose gear landing light was probably struck and damaged during departure from Sydney. However, the source of the damage could not be determined. The glass lens from the nose gear landing light most likely struck the main landing gear, resulting in the pierced hydraulic brake line.

Safety message

Visual inspections play an important role in maintaining the safety of an aircraft. In this case, a vigilant flight crew identified damage that could have otherwise impacted on the safety of future flights. Flight crew are encouraged to be attentive in their post-flight inspections, even when the flight has been completed without incident.

The investigation

The occurrence

At 1308 Eastern Standard Time^[1]on 5 March 2020, a Jetstar Airways (Jetstar) Airbus A320‑232 registered VH-VFL, completed a scheduled passenger flight from Sydney, New South Wales to Proserpine, Queensland. During the subsequent walk around the flight crew noticed damage to the aircraft’s undercarriage, specifically:

• the nose gear landing light was damaged
• the left main landing gear (MLG) brake hydraulics were pierced, with fluid visible on the apron, tyres and gear assembly
• a metal conduit carrying wiring for the left MLG was deformed.

After the damage was found, a member of the cabin crew recalled hearing a ‘deflation noise’ while on descent into Proserpine. There was no visible biological evidence that might indicate a wildlife strike. Therefore, given the extent and nature of the damage, Jetstar reported that a remotely piloted aircraft (RPA) may have collided with the aircraft.

Runway inspections were subsequently conducted at Sydney and Proserpine, however no debris or any evidence of an impact could be found at either location. Jetstar reviewed the flight data but could not identify anything that might indicate a strike had occurred. The flight data did not record the condition of the landing light or the level of hydraulic fluid in the MLG brake line.

Context

Aircraft damage description

Figure 1 shows the damage to the nose gear landing light at the time of the post‑flight walk around. Most of the lamp was missing, with a small fragment still attached to the socket. In the background of the image, the damaged left MLG can be seen. The broken nose gear landing light was inspected by the manufacturer, but there was no comment made regarding possible reasons for the damage.

Figure 1: Damaged nose gear landing light

Source: Jetstar Airways, annotated by the ATSB

Figure 2 shows the damage found on the left-hand MLG wiring conduit and the adjacent brake hydraulic line. Fluid can be seen on the apron as well as the tyres. A subsequent inspection of the aircraft found more fluid in the wheel well of the left main landing gear.

Figure 2: Main landing gear damage

Source: Jetstar Airways, modified by the ATSB

Ground handling and maintenance

The maintenance history of VH-VFL was reviewed to determine if some or all of the landing gear damage could have been due to some earlier maintenance activity, or if tooling might have been left in the wheel well, resulting in the damage to the MLG observed. However, prior to the occurrence, the aircraft had completed 35 scheduled flights since any maintenance was performed on the landing gear.

There were no reported incidents of damage from ground support equipment prior to departure from Sydney, but there was there was no CCTV footage available to confirm this.

Landing gear design and operation

The nose gear landing light used a halogen lamp. The lens was made of glass, but it included a polycarbonate lens cover described by the manufacturer as very resistant to thermal shocks and mechanical impacts. An undamaged halogen lamp, installed on an A320, is shown in Figure 3.

Figure 3: Undamaged nose gear landing light with polycarbonate cover

Source: Jetstar Airways

The damaged main landing gear hydraulic line was responsible for actuating the wheel brakes. The line would pressurise when the brakes were applied via pilot input or the automatic brake system. One function of the automatic brake system was to apply the brakes during landing gear retraction, to prevent wheel rotation.

Hydraulic line examination

The pierced hydraulic line was sent to the ATSB for examination. The line was confirmed to be a titanium-aluminium alloy, per the manufacturer’s specifications. The damage observed was consistent with a concentrated external force resulting in the puncture.

Scanning electron microscopy, including backscattered electron imagery^[2] and energy-dispersive X-ray spectroscopy^[3] was conducted on the damaged section of line. Figure 4 shows a foreign material identified around the damaged area.

Figure 4: Backscattered electron image of the hydraulic line damage

The darker regions indicate a foreign material is present, consisting of lighter elements than the titanium-aluminium line.

Source: ATSB

Energy dispersive X-ray spectroscopy identified the foreign material as a combination of silicon and oxygen. At higher magnifications, the foreign material appeared to have a granular, crystalline structure. The structure and composition of the foreign material indicated that it was most likely silica, otherwise known as silicon dioxide. Silica is the primary ingredient in most forms of glass.

Safety analysis

The polycarbonate cover on the nose gear landing light would likely have prevented it from disintegrating due to thermal stress, such as from a blown bulb. Therefore, the damage to the light indicated by the recovered bulb fragments was probably the result of an impact. The bulb fragmented despite the presence of the polycarbonate cover, indicating that the light was struck with considerable force. Given their proximity to each other and the nature of the damage, the punctured hydraulic line and deformed metal wiring conduit were also considered to be the result of an impact.

Examination of the damaged hydraulic line identified traces of what was most likely glass. The most probable source of the damage to the hydraulic line and wiring conduit was the glass lens of the nose gear landing light. Other potential sources of damage, such as ground support equipment or foreign object debris could not be ruled out, however there was no evidence found to support these.

Both impacts most likely occurred during the flight between Sydney and Proserpine, since no damage was reported following the previous flight, or during pre-flight inspections in Sydney. Fluid found in the main landing gear (MLG) wheel well likely came from the punctured hydraulic line. The fluid was probably discharged into the well when the crew raised the landing gear during departure from Sydney, as the line would have been pressurised, and the gear was not retracted. 

again prior to the damage being found. It is therefore likely that the MLG damage occurred during departure from Sydney, rather than via a remotely piloted aircraft (RPA) while on descent into Proserpine, since damage on descent would not explain the fluid found in the wheel well. As such, the noise heard by the cabin crew member was probably unrelated to the occurrence.

The source of the impact to the nose gear landing light could not be determined. It is possible the aircraft struck a bird or an RPA during departure from Sydney, or foreign object debris during its take-off roll. It should be noted, however, that no debris was found during runway inspections at Sydney Airport and there was no visible biological evidence of a wildlife strike.

Findings

From the evidence available, the following findings are made with respect to the landing gear damage involving Airbus A320 VH-VHL, on 5 March 2020.

Contributing factors

• On departure from Sydney, the nose gear landing light was probably struck and damaged by an unknown object. Consequently, part of the nose gear landing light lens likely impacted and damaged the main landing gear.

Sources and submissions

Sources of information

The sources of information during the investigation included:

• Jetstar Airways
• the nose gear landing light manufacturer.

Submissions

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

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

• Jetstar Airways
• Airbus
• the nose gear landing light manufacturer
• French Bureau of Enquiry and Analysis for Civil Aviation Safety (BEA).

A submission was received from:

• Jetstar Airways.

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

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2021 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

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1. Eastern Standard Time (EST): Coordinated Universal Time (UTC) +10 hours.
2. Backscattered electron imagery involves firing an electron gun at a subject and detecting electrons that scatter off its surface. Heavy elements scatter more electrons than light ones, so appear brighter.
3. Energy-dispersive X-ray spectroscopy identifies the chemical elements within a sample by measuring how the elements interact with X-rays.