Fire

Investigation summary

What happened

On the morning of 21 July 2025, a Virgin Australia Airlines Boeing 737-800, registered VH-YFY, was being operated on a scheduled air transport passenger flight from Sydney, New South Wales, to Hobart, Tasmania. About 10 minutes prior to landing in Hobart, one cabin crew member was checking the cabin was secure for landing when they identified smoke and flames coming from the top of an overhead locker. When the overhead locker was opened, a passenger’s backpack was found to be on fire. The cabin crew doused the flames with a fire extinguisher, and with the assistance of some passengers, poured water on the bag until no smoke was emitted. The aircraft landed without further incident. 

After landing, aviation rescue firefighters retrieved a burnt power bank from inside the backpack. 

What the ATSB found

The ATSB found that the lithium-ion battery in a power bank experienced a thermal runaway, resulting in a fire in the overhead locker inside a passenger’s bag. Due to the timing of the fire, when the aircraft was already close to landing, the cabin crew had limited time to complete the lithium battery firefighting procedure. 

It was also identified that, while the cabin crew attempted to use the protective breathing equipment provided by the operator, difficulties during its fitment meant that they did not find it effective in this incident. 

What has been done as a result

Following this incident, Virgin Australia Airlines reviewed its policy regarding the carriage of power banks and spare batteries. As of 1 December 2025, guidance provided to passengers stated:

• Power banks, spare and loose batteries must be carried as carry-on baggage only and must be protected against damage.
• Each battery and power bank must be individually protected to prevent short circuiting by placing it in the original retail packaging, in a separate plastic bag, a separate protective pouch or insulating the terminals by applying tape over the exposed terminals.
• Only bring batteries and power banks that are clearly labelled and made by reputable manufacturers. Unlabelled, damaged, leaking, subject to product recall, and counterfeit batteries or power banks must not be brought on board the aircraft.
• Batteries and power banks must be stowed in the seat pocket, under the seat in front, or be kept on you/in your hands. Do not store them in the overhead lockers.
• Power banks must not be used to charge other devices on board the aircraft. Even when not in use, remove all cables/USB cables connected to power banks and batteries.
• Power banks and batteries must not be recharged using the aircraft’s power supply. 

Virgin Australia Airlines also stated that batteries that were damaged, swollen, leaking, recalled, showing signs of defects, or had been repaired or modified, could not be carried in either checked or carry-on baggage. 

Safety message

Passengers often travel with multiple devices that contain lithium batteries, including laptop computers, mobile phones, headphones, and power banks. To reduce the risk associated with lithium battery fires, passengers should ensure their devices are packed safely, easily accessible in the cabin and are not carried on board an aircraft if they show signs of damage or deterioration.

The thermal runaway of a lithium battery can be difficult to manage, particularly when the aircraft is airborne. In-flight fires pose a significant risk to the safety of an aircraft if not managed quickly and appropriately. An operator’s procedure to manage battery fires is designed to limit the risk and reduce the likelihood of re-ignition of the battery until the aircraft can land. However, it requires the batteries to be out of a bag and accessible to be easily completed.

Passengers are encouraged to review their airline’s website, and check the Civil Aviation Safety Authority ‘Pack Right’ website to confirm that equipment they are planning to take on board an aircraft is permitted and packed safely.

Summary video

The investigation

The occurrence

On the morning of 21 July 2025, a Virgin Australia Airlines Boeing 737-800 aircraft, registered VH-YFY, was being operated on a scheduled air transport passenger flight from Sydney, New South Wales, to Hobart, Tasmania. There were 2 flight crew, 4 cabin crew (comprised of a cabin manager under training (‘1L’), a cabin crew trainer (‘1R’), and 2 cabin crew (‘2L’ and ‘2R’) and 149 passengers on board. The first officer was pilot flying and the captain was the pilot monitoring.[1]

At about 0901 local time, as the aircraft descended through 10,000 ft with the seatbelt sign illuminated, the cabin crew began their final checks on the cabin prior to landing at Hobart. While near the front of the cabin, the 1R heard a sound that they described in their interview with the ATSB as a popping and hissing sound. On looking, they saw white smoke, then flames, emanating from the overhead locker above row 7DEF (Figure 1). They immediately instructed the passengers seated in both sides of rows 6,7 and 8 to move away from the area and into other seating in the aircraft. The 1R then retrieved a fire extinguisher, the portable breathing equipment (PBE), and water from the forward galley.

The 1L made a call from the front galley to the other cabin crew for assistance. The 2 rear cabin crew brought more water and another fire extinguisher forward. The 1R and 2R attempted to don the PBE around the same time, however, one was unable to stretch the neck ring sufficiently to don the PBE, and the other, after donning the PBE felt it restricted their ability to see and communicate effectively so decided to remove it. 

Figure 1: Aircraft seat plan showing the location of the overhead locker where flames and smoke were observed

Source: Virgin Australia Airlines, modified by the ATSB

When the overhead locker was opened, flames and smoke were observed emanating from a backpack. Although they could not see what was causing the fire, from their training, the cabin crew suspected it was from a portable electronic device overheating. The 1L discharged a fire extinguisher into the locker until the flames were extinguished. The 1L and 1R then poured water over the bag, with the assistance of the 2R and passengers. To reduce the risk of re‑ignition, a second fire extinguisher was discharged into the locker. The cabin crew instructed passengers to keep their heads down and cover their nose and mouth to avoid inhaling smoke. They also asked the passengers who was the owner of the bag but did not receive a response at the time.

While the other cabin crew managed the fire, the 2L called the flight deck. The captain recalled in interview that, prior to the call, they detected a smoky odour in the flight deck, which they thought was ozone. The 2L advised the captain there was a fire in an overhead locker, which was extinguished, but there was still smoke, and the 1L was dousing the bag with water. They also stated that there were still passengers standing. On ending the call, the captain asked the 2L to ensure everyone was seated for landing. 

Following receipt of this information, at 0905:17, just prior to descending through 5,100 ft, the captain made a ‘PAN PAN’[2] call to the Hobart approach air traffic control to advise of a possible fire in the cabin, and that they would require assistance on landing. The captain also asked to speak to the tower controller earlier to request clearances. The approach controller coordinated to get the tower controller on frequency. 

The captain decided to take control of the aircraft for landing due to the emergency. At 0906:00, the aircraft was cleared to land on runway 30 by the tower controller. At this time, the first officer also asked to cancel the approach they had been previously cleared for and to instead conduct a visual approach. This change was permitted. At 0906:28, air traffic control contacted the aviation rescue and firefighting service at Hobart Airport, which deployed in preparation for the aircraft landing.

The 2L then retrieved gloves and the portable electronic device fire containment bag and took it to the other cabin crew, intending for the burnt device to be placed in the bag, and the bag stored in the rear lavatory, as per procedure. The backpack was too large to fit in the fire containment bag and there was difficulty in locating the device inside the backpack. Given the short amount of time remaining before landing, the decision was made by the 1R to keep the device inside the backpack in the overhead locker above row 7. It was identified by the cabin crew that the rounded shape of the overhead locker retained the water that had been poured on the backpack, which kept the bag soaked, and would help reduce the risk of re‑ignition during landing. The cabin crew planned to keep the overhead locker open, with the 1R seated in seat 7C adjacent to the locker to monitor the device during landing, with water to use if necessary. The cabin crew also directed the passengers standing to be seated immediately, even if it required 4 passengers to be in a row.

As recalled by the captain in interview with the ATSB, the first officer contacted the 1L just prior to the aircraft turning onto the final approach. This was likely just prior to 0909, with the aircraft between 1,500 ft and 1,000 ft. The 1L confirmed the fire was out, and the passengers were seated, but that the cabin crew were still standing. They assured the first officer the cabin crew would be seated for landing. 

The 1L, 2L and 2R secured the final items for landing and seated themselves in their designated seats, except for 1L who sat in 1R’s seat to maintain better visibility of the cabin. On their way to their seat at the front, the 1L checked the overhead lockers around row 7 for heat or any developing hot spots. Once all the cabin crew were seated, the 1L signalled to the flight crew the cabin was secure. The 1L made a final announcement to passengers to ensure their seatbelts were fastened, to remain seated for landing and follow instructions of crew following the landing.

Flight data provided by Virgin Australia showed that the aircraft touched down at Hobart at 0910:29 (Figure 2). 

Figure 2: Flight path with key events

Source: Google Earth, annotated by the ATSB

The captain stopped the aircraft on the taxiway and exited the flight deck to speak to 1L and observed the cabin to determine whether an evacuation was required. As the fire appeared to be contained, the captain taxied the aircraft to the parking bay. At 0919, the aviation rescue and firefighting personnel boarded the aircraft and removed the backpack from the overhead locker. They confirmed the origin of the fire was a lithium power bank, stored in one of the backpack’s front pockets (Figure 3). 

Figure 3: Backpack containing the power bank 

Source: Airservices Australia

The passengers were cleared to disembark normally at 0927. After disembarkation, one cabin crew member (2L) was treated by paramedics. It was unknown if this was due to the effects of smoke as they had been unwell throughout the flight prior to the fire commencing. No other crew or passengers reported to the operator about seeking medical attention from the effects of the smoke. The fire caused minor damage to the overhead locker above row 7/8 DEF (see section Aircraft damage). 

Context

Cabin crew information

The flight comprised of 4 cabin crew, 2 located at the front set of aircraft doors (called ‘1L’ and ‘1R’) and 2 at the rear of the aircraft (called ‘2L’ and ‘2R’). Each cabin crew member had designated roles on the flight, based on which door they were operating. On this flight, the 1L position was filled by a trainee cabin manager who had previous experience in this role working for other airlines, but was completing their first flight as a cabin manager under training for this operator. The 1L was supervised by a cabin crew trainer in the 1R position.

Each of the cabin crew had between 1 and 17 years of experience as cabin crew. They had all completed their annual emergency procedures training between November 2024 and June 2025. This training included both theoretical information and a practical review of the lithium battery firefighting procedure. All cabin crew reported having completed simulated scenarios where the fire occurred either during cruise or on the ground, where there was plenty of time to complete the firefighting procedure, and store the damaged battery appropriately. None of the cabin crew had completed a simulated scenario involving a time‑pressured situation.  

Aircraft cabin information

VH-YFY was a Boeing 737-800 aircraft, with a single aisle in the cabin and seating for 182 passengers. In economy, where this fire occurred, there were 3 seats on either side of the aisle. 

The cabin on this aircraft was fitted with the Boeing 737 sky interior design. In this design, the overhead lockers lowered from the ceiling, creating a contained basket for the bags to sit in. In comparison, the doors in other locker designs would open upwards. 

Lithium batteries

Overview

There are 2 primary types of lithium batteries – lithium metal and lithium-ion. Lithium metal batteries cannot be recharged and are designed to be disposed of once their initial charge has been used, whereas lithium-ion batteries are rechargeable. Compared to lithium metal, lithium-ion batteries store a high amount of energy and are commonly found in many portable electronic devices (PEDs) such as smartphones, tablets, cameras, laptops, and power banks. 

Guidance on the safe carriage of lithium-ion batteries on board aircraft

Lithium batteries are classified by the United Nations as dangerous goods. As such, the International Civil Aviation Organization’s Technical Instructions for the Safe Transport of Dangerous Goods by Air (2025-2026 Edition) stated that lithium batteries, including power banks must be carried as carry-on baggage only.

The Civil Aviation Safety Authority stated that spare batteries and power banks should be packed in carry-on baggage only, so that trained aircrew can manage any issues quickly and safely. Their Pack right website provided safety tips when travelling with lithium batteries:

These simple steps help keep you and your fellow passengers safe:

• choose reputable suppliers when buying devices and spare batteries

• follow airline and manufacturer rules for carrying and charging lithium batteries

• keep spare batteries with you in the cabin and protect them from damage

• stop using or charging batteries that show signs of damage, overheating, or swelling

To prevent short circuits, protect spare battery terminals by:

• keeping them in original packaging

• covering terminals with tape

• placing each battery in a separate plastic bag or case.

At the time of the incident, the operator’s policy permitted power banks to be carried in the cabin only, but they could be stored inside a bag and there were no restrictions on their use on board. Advice on the carriage of power banks and other electronic devices was provided to passengers on the operator’s website and during check-in. 

Thermal runaway

Thermal runaway is a rapid and uncontrolled increase in temperature and occurs when the internal cell(s) of a lithium battery become damaged for reasons including:

• internal short circuits
• breakage from dropping or crushing
• exposure to excessive heat
• failure of the battery cell due to manufacturing defects.

The operator’s Aircrew Emergency Manual stated that crew should be alert not just for signs of smoke or fire in the cabin but also to the smell of overheating electronic devices. 

The smell of overheating may be the first sign of an impending lithium battery/PED fire. PEDs approaching a thermal runaway start initially displaying hissing, crackling sounds, as well as bubbling or blistering casings.

Once a lithium battery cell thermal runaway starts, it quickly leads to the failure of adjacent cells in a chain reaction that can produce fire, which is especially difficult to extinguish. A fire caused by lithium batteries can produce a fire burning with a temperature as high as 1,000^°C, explosions releasing toxic gases and flammable electrolytes as well as shrapnel from damaged PED casings. The manual also stated that in some cases, the explosive force of the venting gasses could be significant enough to cause spikes in cabin pressure.

Managing lithium battery fires

The operator’s Aircrew Emergency Manual stated a general risk about onboard fires was that:

Any fire, no matter how small, may rapidly become out of control if not combatted quickly. Research has shown that if left uncontained, a smoke-filled cabin can be consumed by fire in as little as 6-10 minutes. The first priority shall always be to put the fire out.

In order to manage the risk, the manual outlined 3 important principles of firefighting:

• Immediately locate the source of fire, smoke or fumes. Specific to lithium battery fires, all smoke or fire events occurring in baggage within an overhead locker should be assumed to be a PED/lithium battery fire until the source is positively confirmed.
• Aggressively attack and extinguish the fire using all available resources, which can include able bodied persons.
• Communicate to other crew and the flight crew, as soon as possible, specifying the location and source of fire.

Furthermore, the manual also guided crew that: 

It is important to protect yourself from the effects of smoke and fumes while attempting to flight a fire. In some circumstances it may be safe and thus more important to attack a fire first than fitting of PBE [portable breathing equipment]. PBE should be worn by at least one person when a team is formed to flight a fire and anytime by the primary firefighter when they are in smoke, a confined space of affected by fumes.

In regard to managing a lithium battery fire, the manual stated:

The primary method for stopping a lithium battery from thermal runaway or overheating is to cool it down by pouring water or other non-flammable liquid on the battery or device. This should be done once any flames have been extinguished and continued until the device is cooled and there is no evidence of smoke, heat, crackling or hissing sounds usually associated with an overheating lithium battery. This could take as long as 10–15 minutes. 

Another recommendation in the emergency procedures manual was a suggestion not to open any baggage if there was smoke or flames emanating from it, unless it was required to get a fire extinguisher and liquid onto an identified battery. Once the device was cooled, it could then be placed in a fire containment bag or other suitable container.

Aircraft firefighting equipment

Overview

The operator fitted the Boeing 737 aircraft with firefighting equipment. In addition to this designated equipment, the cabin crew were taught to use other equipment available on board as required, such as drinks used in the cabin service as well as wet blankets and pillows to smother a fire.

Fire extinguishers

The aircraft had 4 bromochlorodifluoromethane (BCF)/halon fire extinguishers. These fire extinguishers are designed to be used on all types of fires by discharging a colourless, odourless, non-corrosive, liquified gas. This gas is not cooling, meaning that further steps are required in fighting a lithium battery fire.

Fire protection gloves

Fire protection gloves were designed to protect the wearer’s hands when fighting fires, including lithium battery incidents. The emergency procedures also suggested that crew should use gloves whenever fighting fires, including using oven gloves if the fire protection gloves were not available.

The L2 retrieved the fire protection gloves from the galley with the intention to move the power bank once the fire was suppressed, but the gloves were not used during the firefighting process.

Portable breathing equipment

Portable breathing equipment (PBE), commonly referred to as a smoke hood, was provided for each cabin crew member on board. The PBE supplied was designed to protect the wearer from fumes and smoke by forming a secure seal using an elastic neoprene neck ring (Figure 4). An oxygen generator on the nape provided oxygen to the wearer. 

Figure 4: Exemplar PBE, showing how to open the neck ring (left) and when donned (right)

Source: Virgin Australia Airlines, modified by the ATSB

Operator procedures recommend PBE should be used by at least one person involved in firefighting, or when one person was fighting a fire in an enclosed environment. Although, consideration was given that the first person to a fire might need to immediately attend to the fire while others gathered and donned the PBE. 

The 2 cabin crew who attempted to use the PBE stated that the equipment provided in training was much easier to don as the neck ring was stretched from repeated usage.

In October 2025, the Airbus Safety First magazine contained an article about PBE, reviewing a case study where 7 cabin crew had difficulties using the PBE provided. The analysis indicated that, similar to this incident, despite having regular training in the use of PBE, the cabin crew found it difficult to use the PBE in a real emergency. The article recommended that ‘dummy’ PBE used in training may not represent the equipment found on board.

Fire containment bags

There were 2 sizes of fire containment bags carried on the operator’s Boeing 737 aircraft. The smaller sized bag, designed to fit an iPad, was carried in the flight deck in the event of a thermal runaway involving one of the flight crew’s electronic flight bags.

A larger bag, designed to fit a device the size of a laptop, was carried in the aircraft cabin (Figure 5). The purpose of this bag was to place the device in after it was cooled post‑fire, so that it could be stored in a water filled container in a secure place.

Figure 5: Fire containment bag

Source: Virgin Australia Airlines

Damage to the power bank

The power bank was inspected by the aviation rescue firefighters after being removed from the aircraft. 

The power bank had a rated output of 37 watt hours and had both USB‑A and USB‑C charging ports. It was not charging a device when the fire started, but there was a cable plugged into the USB‑A charging port. When orientated with the manufacturer’s label facing up, most of the damage was observed along the top and right side of the power bank. The damaged right end contained the USB-C charging port. External observations suggest that the power bank contained 2 internal cells, of which only 1 was affected by the thermal runaway by the time the fire was extinguished (Figure 6). The power bank was not protected from short circuits as it did not appear to have the terminals covered and was not separated from other items in the bag by being placed in a protective pouch or the original packaging. The backpack was reported by the operator to be substantially damaged by the fire.

The owner of the power bank advised the operator that it was purchased in 2024 and:

• it had no pre-existing damage
• was fully charged the day prior to the incident, and there were no previous issues during charging or use
• it was not dropped, exposed to moisture or heat prior to the incident. 

Figure 6: Power bank showing damage from the back (left) and side view (right)

Source: Airservices Australia (left) and Virgin Australia Airlines (right)

Aircraft damage

An inspection of the aircraft found fire damage in the panels above and behind the overhead locker above row 7 and 8 DEF. The passenger service unit containing the reading lights, call bell and information signals under this locker also sustained fire and water damage. The overhead locker needed to be replaced post-fire (Figure 7). 

Figure 7: Overhead locker above row 7DEF where the smoke and flames were observed (left) and area behind the overhead locker showing fire damage (right)

Source: Airservices Australia (left) and Virgin Australia Airlines (right)

Related occurrences

Australian data

This incident was the first reported power bank-related in-flight fire either in Australia or on an Australian‑registered aircraft. A review of the ATSB’s occurrence database identified 3 previous incidents where smoke was reported emanating from a power bank in the aircraft’s cabin, but no fire occurred:

• OA2025-01608: On 20 January 2025, a Boeing 737 aircraft was being operated on a flight from Brisbane, Queensland, to Melbourne, Victoria. During cruise, a power bank overheated in the cabin, and smoke was observed emanating from the attached charging cable. The power bank and cable were placed in a container and stowed in the rear lavatory for the remainder of the flight.
• OA2019-04325: On 28 May 2019, an Airbus A330 aircraft was being operated on a flight from Melbourne, Victoria, to Hong Kong. During cruise, smoke was detected emanating from a passenger's power bank.
• OA2019-02629: On 15 April 2019, an Airbus A330 aircraft was being operated on a flight from Hong Kong to Melbourne, Victoria. During passenger disembarkation, smoke was observed emanating from a passenger's power bank. The crew doused the power bank in water.

ATSB records showed that, in the past 10 years, there were 4 in-flight fires resulting from mobile phones, 3 of which occurred after the mobile phone was crushed in the seat mechanism, damaging the lithium battery contained inside. The reason for the fourth fire was unknown.

International incidents

While this was the first reported incident in Australia, there have been a number of significant fires resulting from power banks, including: 

• In January 2025, an Air Busan A321 aircraft was preparing for flight at Busan, South Korea. Prior to taxi, a power bank fire started in an overhead locker. The fire spread, resulting in an evacuation. The aircraft was destroyed.
• In March 2025, a Hong Kong Airlines A320 aircraft diverted after a power bank experienced a thermal runaway. The fire was extinguished.
• In October 2025, an Air China A321 aircraft had to divert after a battery caught fire in an overhead locker. 

The United States Federal Aviation Administration recorded 8 in‑flight fire incidents involving power banks occurring in the past 10 years. 

Safety analysis

Power bank thermal runaway

For unknown reasons, one of the cells in a lithium-ion power bank stored in an overhead locker failed during the descent into Hobart. In this case, there was no reported pre‑existing damage, or any other identified problems with this power bank prior to flight. However, the power bank was stored with a cable in it and the ports uncovered, both factors which can increase the risk of a fault.

Inspection of the power bank post-flight, combined with the cabin crew reports of sounds they were trained to expect in the event of a lithium battery fire, suggested that the fire was characteristic of a thermal runaway. As the temperature of the power bank continued to increase, smoke, followed by flames resulted.

Completion of firefighting procedures

As described in the operator’s procedures, fires on board aircraft can spread quickly. As the aircraft was already on descent when the smoke was initially observed, there was limited time for the cabin crew to manage the power bank fire by completing all the procedures they were trained to do in response to an in-flight fire. In addition, they had the responsibility to ensure the cabin was secure for landing. 

In less than 8 minutes, the cabin crew worked together to identify a fire, gather the required equipment, and aggressively fight the fire to a point where the fire appeared suppressed. In addition, they communicated the problem with the flight crew and managed moving passengers to alternative seating. 

While the cabin crew had received emergency procedures training, they had never trained for a lithium battery fire in a compressed time. They completed as many of the procedures as they were able to in the available time, but by the time the fire was considered controlled, there was only around 90 seconds for the cabin crew to clear up the cabin and be seated for landing. Besides the logistics and risk that would result from handling the power bank to remove it from the backpack and place it in a fire containment bag, there was no time available. 

The cabin crew identified an alternate solution to moving the burnt power bank. While the overhead locker held the water poured on the backpack, there was no assurance that the power bank was going to remain fully submerged for landing, in accordance with the operator’s procedures, or isolated from other lithium battery devices. Although there was no consequence as a result of the power bank remaining in the overhead locker, there was an increased risk of cabin occupant injury and aircraft damage if the power bank re‑ignited due to further exposure to fire and smoke. 

Protective breathing equipment

Protective breathing equipment (PBE) was available for cabin crew to use if deemed necessary in preparation to fight a fire, and all crew were trained in their use. Two of the cabin crew attempted to use the PBE, but did not find it effective due to fitment and communication/visibility issues. As the cabin crew were unable to use the PBE, they had no protection from the smoke and were placed at an increased risk of smoke inhalation. While these cabin crew did not experience any residual effects from the smoke, any protective equipment provided should be efficient to don and wear continuously while managing an emergency situation.

Findings

From the evidence available, the following findings are made with respect to the in-flight fire involving Boeing 737, VH-YFY, 56 km north‑north‑east of Hobart Airport, Tasmania, on 21 July 2025. 

Contributing factors

• During the descent, a passenger's lithium-ion power bank, located in the overhead locker, overheated due to thermal runaway and began to emit flames and smoke.

Other factors that increased risk

• Due to the timing of the fire starting on descent, the cabin crew had limited time to complete the procedure for managing a lithium battery fire.
• The cabin crew attempted to use the protective breathing equipment provided by the operator but did not find it effective when managing the lithium battery fire.

Safety actions

Safety action by Virgin Australia Airlines

Virgin Australia Airlines advised it has reviewed its policy regarding the carriage of power banks in the cabin. As of 1 December 2025, guidance provided to passengers stated:

• Power banks, spare and loose batteries must be carried as carry-on baggage only and must be protected against damage.
• Each battery and power bank must be individually protected to prevent short circuiting by placing it in the original retail packaging, in a separate plastic bag, a separate protective pouch or insulating the terminals by applying tape over the exposed terminals.
• Only bring batteries and power banks that are clearly labelled and made by reputable manufacturers. Unlabelled, damaged, leaking, subject to product recall, and counterfeit batteries or power banks must not be brought on board the aircraft.
• Batteries and power banks must be stowed in the seat pocket, under the seat in front, or be kept on you/in your hands. Do not store them in the overhead lockers.
• Power banks must not be used to charge other devices on board the aircraft. Even when not in use, remove all cables/USB cables connected to power banks and batteries.
• Power banks and batteries must not be recharged using the aircraft’s power supply. 

Virgin Australia Airlines also stated that batteries that are damaged, swollen, leaking, recalled, showing signs of defects, or have been repaired or modified, cannot be carried in either checked or carry-on baggage. 

It has updated the cabin crew’s pre-flight announcement and website to inform passengers of the revised policy.

Virgin Australian Airlines has also acknowledged that, while it made changes to its policy, there are challenges in monitoring passengers’ compliance with these measures. It also stated that greater awareness about the risks of travelling with lithium batteries should be delivered by all airlines and airports.

Sources and submissions

Sources of information

The sources of information during the investigation included:

• the cabin crew
• the captain
• Virgin Australia Airlines
• Airservices Australia
• Civil Aviation Safety Authority.

References

Airbus. (2025). Focus on protective breathing equipment. https://safetyfirst.airbus.com/focus-on-protective-breathing-equipment/   

Civil Aviation Safety Authority. (n.d.). Lithium batteries. Retrieved 25 July 2025, from https://www.casa.gov.au/packright/lithium-batteries

International Civil Aviation Organization (2025). Technical instructions for the safe transport of dangerous good by air 2025-2026. https://www.icao.int/Dangerous-Goods/Technical-Instructions 

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 cabin crew
• the flight crew
• Virgin Australia Airlines
• Airservices Australia
• Civil Aviation Safety Authority.

Submissions were received from:

• Virgin Australia Airlines
• 2 cabin crew members
• Civil Aviation Safety Authority.

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. About ATSB reports ATSB investigation reports are organised with regard to international standards or instruments, as applicable, and with ATSB procedures and guidelines. Reports 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. 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 2025   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 Commonwealth Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this report is licensed under a Creative Commons Attribution 4.0 International licence. The CC BY 4.0 licence enables you to distribute, remix, adapt, and build upon our material in any medium or format, so long as attribution is given to the 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.

Executive summary

What happened

On the morning of 23 April 2023, a Saab 340A, registered VH-KDK and owned by Pel-Air Aviation, was being operated by Regional Express Airlines (Rex) for a non-revenue flight from Wagga Wagga, New South Wales, to Charleville, Queensland. While in cruise at 22,000 ft and passing to the east of Cobar, New South Wales, the flight crew received a cargo smoke indication on the central warning panel. As a precaution, the crew fitted their oxygen masks and smoke goggles. Shortly after, the cockpit filled with smoke.

The captain commenced a diversion to Cobar while the first officer made a PAN-PAN[1] call to Melbourne Centre. Thick smoke then filled the flight deck preventing the crew from effectively seeing external visual references or the aircraft’s flight instruments. While completing the emergency checklists, the crew received further warnings for avionics smoke, followed by a cabin depressurisation, and then a right engine fire detection fail indication. The crew landed at Cobar and elected to stop on the runway and evacuate the aircraft.

Shortly after landing, Fire and Rescue New South Wales personnel arrived from the Cobar station and located a heat source at the air cycle machine and in the associated wiring. After gaining access to the cabin underfloor area, the source of the heat was doused with water. An internal inspection of the aircraft found fire damage in the area around the right recirculating fan. The aircraft was substantially damaged, and the crew were not injured.

What the ATSB found

The ATSB found that a likely failure of the right recirculating fan electronic box sub-assembly resulted in an in-flight fire under the cabin floor. The fire filled the cabin with smoke, which then entered the flight deck due to a smoke barrier curtain not being fitted in place and the flight deck door being open. 

When the crew fitted their oxygen masks, it was found that the first officer’s mask microphone was not working correctly, which delayed emergency checklists being actioned. The fire also caused substantial structural damage and led to a breach of the fuselage, resulting in a depressurisation of the aircraft. 

It was also found that the Rex flight crew had not been trained or had knowledge of the differences in the cargo‑configured Saab 340 aircraft, leading to them having no familiarity with specific systems fitted. This prevented them from completing some of the required steps in the emergency checklists. 

The flight crew did not receive training on the cargo‑configured aircraft differences prior to conducting freight operations. Further, the operator’s flight crew operating manuals did not reflect the differences in the cargo‑configured aircraft interior checklists, which may have alerted the flight crew to these differences during pre-flight preparation. Additionally, the manufacturer did not have any specific pre-flight check for correct fitment of the smoke barrier curtain for cargo‑configured aircraft preparation. 

What has been done as a result

On 13 May 2023, Rex issued an Operations Notice to all pilots, highlighting the guidance on the cross-valve handle as outlined in the Saab Aircraft Operating Manual (AOM). Furthermore, this guidance has been incorporated into the Rex Flight Crew Operating Manual (FCOM). 

On 13 November 2024, Rex amended the internal inspection checklist that is contained in their Saab 340 FCOM. The amendment now requires flight crews verify the position of the cross‑valve handle during the pre-flight checks.

Rex have also updated the training information delivered in their ground school to include the cross-valve system for the cargo‑configured Saab 340 aircraft into the training syllabus.

Rex indicated they are implementing a fleetwide inspection of the recirculating fan assemblies at the next aircraft heavy maintenance cycle, with a focus on the electronic sub-assembly module.

Pel-Air have included a revision to their flight crew operating manual with a caution that the smoke barrier curtain must be installed whenever combustible material is carried in the cargo compartment. Due to contract completion, Pel-Air have ceased conducting freight operations using the Saab 340 aircraft and have since sold the aircraft. 

Saab has revised their preparatory and walk-around pre-flight checklists to include the fitting of the smoke barrier curtain when carrying cargo in the cargo‑configured aircraft. 

Safety message

It is essential for operators to ensure that flight crew are conversant with differences in aircraft configurations when required to conduct operations on aircraft they may be unfamiliar with. It is important that information is readily available and accessible and be delivered in a manner to inform flight crews on the operational requirements of the aircraft. 

Operator flight crew operating manuals need to be relevant for the aircraft configuration being utilised. Further, manufacturer checklists for pre-flight inspections are required to cover the modifications fitted, so that this is available to operators to enable them to write the appropriate documentation for their flight crews.

The occurrence

History of the flight

On the morning of 23 April 2023, a Pel-Air Aviation cargo‑configured Saab 340A, registered VH‑KDK and operated by Regional Express Airlines (Rex), was being prepared for the first stage of a non-revenue freight flight from Wagga Wagga, New South Wales, to Charleville, Queensland. The purpose of the flight was to pre‑position a Rex Saab 340 engine to Cairns, Queensland, utilising a Rex crew, consisting of a captain and first officer (FO), and operating under the Part 91 flight rules. 

The crew had flown the aircraft from Cairns the previous day, and were tasked to fly the return leg, including a refuelling stop at Charleville. The flight crew arrived at the aircraft at about 0830 local time and conducted their pre-flight checks. The captain performed the interior checks while the exterior walk around checks were conducted by the FO. The aircraft departed Wagga Wagga at about 0949, tracking for Charleville, and cruising at FL 220.[1] The captain was the pilot flying (PF), and the FO was pilot monitoring (PM).[2]

In-flight fire and diversion

At about 1052, the crew was alerted by a cargo smoke detection warning[3] on the central warning panel. They began to manage the warning by identifying and cancelling the indication. The crew then donned their oxygen masks and smoke goggles. However, once fitted, the crew had difficulty communicating due to the FO’s mask microphone not functioning correctly and being very faint. A review of the cockpit voice recorder (CVR) recording showed it took another 57 seconds for the crew to establish effective communications with each other before they could commence the emergency checks.

At 1055 the crew received a right (engine) fire detection fail caution light, followed shortly after by an air conditioner caution light. This was due to the detection of a right distribution duct over temperature which automatically closed the right engine low pressure bleed valve. The crew initially detected no smoke or fumes, however within about 60 seconds, thick black smoke began filling the cockpit.

During the process of establishing the nature of the warnings, the flight crew discussed which airport would best suit their needs for the emergency, and opted to divert to Cobar, New South Wales (Figure 1). The captain had flown to this airport on several previous occasions and was familiar with it, and from their position, they could conduct a direct approach with minimal manoeuvring.

Figure 1: VH-KDK flight overview

Source: Google Earth and Flightradar24, annotated by the ATSB

At 1056, the FO gave a PAN PAN[4] radio call and advised air traffic control (ATC) that they were diverting to Cobar. ATC arranged for emergency services to meet the aircraft upon arrival into Cobar. Due to the radio coverage in the Cobar area, ATC utilised an overflying aircraft to relay communications as the diversion progressed.

While descending through FL 160, the crew received a cabin pressure failure warning, indicating that the aircraft had lost pressurisation. This occurred 4 minutes after the initial warning of the cabin smoke. The cabin depressurisation led to the crew increasing their rate of descent to get below FL 100. 

At approximately 1058, they commenced the ‘cargo compartment smoke’ emergency checklist. The CVR indicated the crew completed the first checklist item, which called for the left bleed valve to be closed. The checklist then called for closing the cross-valve handle, however the crew was unable to locate it, with the CVR recording indicating the crew tried to find it for 61 seconds before resuming the checklist flow without actioning the cross-valve handle closure. The crew completed the cargo compartment smoke checklist as visibility on the flight deck reduced to less than 10 cm. The captain recalled sliding their seat forward to enable them to see the instrument panel through the thick smoke.

Five minutes after the PAN PAN call, the crew commenced the checklist for ‘avionic or electrical smoke or fire’.[5] The crew then conducted the ‘smoke removal’ checklist to clear the smoke from the flight deck. 

One requirement of the smoke removal checklist called for aircraft speed reduction to below 160 kt, and to open a crew hatch to aid in smoke removal. Due to the unknown severity of the on‑board fire, the crew decided to maintain their speed and not complete all the checklist items as required, enabling them to expedite their landing.

As the crew continued their approach, the volume of smoke in the flight deck began to dissipate. This allowed them to navigate using external visual cues and conduct a visual approach for the landing. Because of the unknown source of the fire, upon arrival in Cobar, the crew elected to stop the aircraft on the runway and evacuate the aircraft. 

As part of the emergency evacuation procedure, the crew activated the fire extinguisher system[6] on both engines after shutting down, and then exited the aircraft. The incident had taken 22 minutes from the first smoke warning to landing.

After evacuation, the crew noted smoke to be coming from the vicinity of the right air cycle machine at the right wing root. Shortly after landing, Fire and Rescue New South Wales personnel arrived from the Cobar station and assessed the aircraft. After gaining access to the cabin underfloor area, an electrical harness was initially found melted and smoking. Consequently, the area was doused with water. 

Further inspection of the aircraft found significant fire damage concentrated in the area around the right recirculating fan. The right recirculating fan was also significantly fire damaged. An assessment of the right engine found no evidence of a fire. The aircraft underfloor structure was substantially damaged, and the crew were not injured.

Context

Aircraft information

The Saab 340A[7] is a twin-engine turboprop aircraft designed and initially produced by Saab and Fairchild Aircraft. It is designed to seat 30‍–‍36 passengers in standard configuration and is powered by 2 General Electric CT7-5A2 turboprop engines.

VH-KDK was manufactured in Sweden in 1984 and first registered in Australia in February 1985. It was operated in passenger configuration by Regional Express Airlines (Rex), before being modified to cargo configuration in 2009. VH-KDK was then owned and operated by Pel‑Air Aviation.[8] 

At the time of the accident,[9] VH-KDK had accrued a total time in service of 48,130.6 hours and 60,046 landings and had flown 13.5 hours since the last maintenance. 

Flight crew information

Captain

The captain held an air transport pilot licence (ATPL) (Aeroplane), and a valid Class 1 aviation medical certificate. They reported a total flying time of 7,579 hours with about 5,070 of those being on the Saab 340. They had flown for the operator for about 10 years, and previously had flown for another regional airline and had operated into Cobar airport on numerous occasions. 

The captain had previously flown the Saab 340A in a passenger configuration but had not flown either the Saab 340A or B variant in a cargo configuration.

First officer

The first officer (FO) held an ATPL (Aeroplane), and a valid Class 1 aviation medical certificate with a restriction for vision correction. They had reported a total flying time of about 18,297 hours, having flown about 1,480.9 in the Saab 340B. The FO had not previously flown any Saab 340 variants in a cargo configuration.

Meteorological conditions

Graphical area forecasts provided by the Bureau of Meteorology (BoM) stated that generally good weather conditions, with little cloud, and visibility greater than 10 km existed during the flight. The terminal area forecast for Cobar indicated light winds from the east at about 10 kt with the flight crew reporting CAVOK[10] conditions existing for the time of the diversion.

Cargo configuration

VH-KDK cargo conversion

The cargo conversion modification was carried out in accordance with Saab service bulletin (SB) 340-25-280. As an overview, the SB involved removal of the passenger fit‑out and replacing it with an interior cargo liner, blanked over windows, additional cargo barrier nets, and a floor roller system (Figure 2). In conjunction with this SB, other SBs were incorporated on the cargo version, which modified the air conditioning system. This was done by removing the left recirculating fan and introducing a cross-valve handle. 

A removable smoke barrier curtain was added at the forward section of the cargo compartment. The fire extinguishing system for the passenger cargo area at the rear of the cabin (zones C1 and C2) was also removed, and additional smoke detectors were added to the cabin.

Figure 2: Cargo configuration modification

Source: Saab, annotated by the ATSB

Smoke curtain

A removable smoke barrier curtain was designed to be installed between compartment A and the front-left fuselage (Figure 2). The purpose of the curtain was to provide containment of smoke and fire within the cargo compartment in the event of an on-board fire and prevent smoke ingress to the flight deck (Figure 3). The aircraft carried a placard at the top of the entrance stairs which stated: 

Smoke barrier must be installed for all cargo operation flights.

The smoke barrier was constructed of a fibreglass impregnated vinyl which was secured in place by a Velcro perimeter and metal press studs. The aircraft owner stated that the standard procedure was that it would be left attached by the left side attachment points and secured in place by the freight handlers after loading of cargo. It was then to be checked by the FO prior to flight. 

During interview, the flight crew stated that they were not aware of the use of the smoke barrier, and that it had been located after the incident in compartment A of the cargo area, and that it was not in place on the left of the cabin. The ATSB did not determine why the engineers who loaded the engine into VH-KDK had not secured the smoke curtain.

Figure 3: Smoke barrier curtain location in exemplar aircraft

Source: Saab, annotated by the ATSB

Air conditioning system 

In passenger configuration, the Saab 340 air conditioning system is comprised of a left and right air conditioning pack (ACP) which is supplied by bleed air from its respective engine. Each ACP is mounted externally under a fairing on the lower fuselage near the rear of each wing. The system has 2 recirculating fans under the adjacent cabin floor, ducting for the cabin and flight deck conditioned air supply and return, temperature sensors and controls, and cabin and flight deck air outlets. 

The left and right ACPs supply conditioned air to the cabin, and a portion of the right ACP conditioned air is supplied to the flight deck. The left recirculating fan returns the air to the left ACP from the aircraft cabin, while the right fan extracted air from the flight deck. The avionics fan draws air for cooling the avionics from the cabin conditioned air supply. The air is then expelled under floor. 

As part of the modification from passenger to cargo configuration, the left recirculating fan and ducting were removed. This resulted in limited extraction and recirculation of any contaminated air from the cabin interior, while the right recirculating fan would extract and recirculate air solely from the flight deck. 

Cross-valve handle

In the cargo configuration, a cross-valve and handle were added to the air conditioning system ducting between the left and right ACP (Figure 4), with the manual operating handle being located at floor level, next to the FO seat. Closing of the left bleed valve and cross-valve in accordance with the emergency checklist would isolate the supply of air to the cabin in the event of cargo smoke or fire, and the right ACP would supply only to the flight deck. As part of the emergency checklist for ‘cargo compartment smoke’, the left ACP would also be isolated from supplying the cabin. 

Figure 4: Schematic of modified air conditioning system

Source: Saab, annotated by the ATSB

Recirculating fan

The right recirculating fan was a centrifugal impeller type fan and was driven by an AC motor. The fan had an in‑built inverter, supplied by 28-volt DC. The majority of the electronics for the fan unit were contained in the box sub-assembly. This included the inverter, an electromagnetic interference (EMI) filter unit and the electronic card sub-assembly. The box sub-assembly controlled the fan operation, including the thermal control. Each electric motor was equipped with:

• a thermal switch[11] located in the cooler which guarded against an abnormal temperature increase. This switch would cut off the power if the motor temperature exceeded 110°C +/− 5° (230°F +/− 41°). The fan would start again when the temperature decreased to 65°C +/− 5° (149°F +/− 41°)
• a speed sensor which guarded against an abnormal decrease of nominal speed. If the speed fell below 80% of nominal speed for more than 17 seconds, the fan would be stopped.

In 1987, Saab released a service bulletin which gave operators the option to install an upgraded recirculating fan. The original fan was a brush type motor which required regular maintenance, including brush replacement when they had worn from use. Saab had received reports of smoke and burning smells which were attributed to brushes that were incorrectly installed. The brushless fans were introduced to help eliminate this issue and also required less maintenance. 

The fan installed in VH-KDK was the new brushless fan, manufactured in 1990 and fitted in April 1996. The fan history prior to installation was unknown by the operator. The fan accrued 27,585 hours while fitted to VH-KDK. 

Recirculating fan examination

Fire damage was found in the area around the right recirculating fan and on the fan itself (Figure 5). There were no other components in the vicinity of the fan with significant fire damage. As such, it is likely the right recirculating fan was the source of the fire.

Figure 5: Damaged recirculating fan

Source: ATSB 

An examination of the recirculating fan was conducted at the ATSB’s technical facilities in Canberra. The examination found that the fire damage was most significant at the external box sub‑assembly which housed the EMI filter, the resistor support plates and electronic card sub‑assembly. The aluminium cover of the box sub-assembly had melted, the electrical wiring was damaged, and some terminals had disconnected as a result of the fire damage. There was heavy soot and melting of solder in the cooler assembly.

The electronic card sub-assembly was made up 3 circuit boards, mounted to the resistor support plate. The function of the circuit boards was for motor speed detection, timer control, and a logic card. The damage exhibited on the circuit boards showed significant burning, consistent with the other components within the aluminium cover.  

The electromagnetic interference (EMI) filter sub-assembly had considerable damage to the filter itself and to the mounting plate with signs of melting and heat tinting of the steel plate structure, indicating a significant heat source. The heat tint was indicative of temperatures of approximately 310° to 330°C. 

Of note, the fire did not appear to be associated with the motor and there was no indication of damage to the internal components of the fan and was able to rotate freely. There was carbon and soot observed on the external surface on the motor. The crew stated that there had been no circuit breakers tripped that would be associated with the failure of the electronic card sub‑assembly.

The ATSB examination of the recirculating fan could not determine the cause of the failure of the electronic components attached to the assembly. 

Pressurisation system

The Saab 340 cabin is pressurised by the 2 air conditioning packs. The pressurisation system uses bleed air drawn from each engine and was either automatically controlled by a pressurisation controller, or manually controlled by a control valve operated by the flight crew from the flight deck. 

Pressure is able to be regulated by the opening and closing of 2 outflow valves, located in the empennage. The primary outflow valve is electro-pneumatically operated by the pressurisation controller, while the secondary outflow valve is pneumatically controlled from the cockpit and used as a manual standby system.

When emergency pressure relief is required, the primary outflow valve is able to be opened with the emergency pressure dump switch. When the crew of VH-KDK experienced the smoke in the cabin and flight deck, dumping cabin pressure as stated in the ‘smoke removal’ emergency checklist was the method used to assist in rapid removal of the smoke.

Aircraft depressurisation

The severity of the fire resulted in significant damage to the surrounding underfloor furnishings, ducting and airframe structure. The damage was then sufficient to rupture the skin (Figure 6) and caused a subsequent depressurisation of the aircraft. 

Figure 6: Underfloor fire damage showing fuselage hole

Source: Operator, annotated by the ATSB 

Checklists

The pre-flight procedures for the Saab 340A aircraft, including cargo configuration aircraft, were covered by the Aircraft Operations Manual (AOM) normal procedures, produced by the aircraft manufacturer. The AOM pre-flight normal checklist contained a check of the cross-valve handle position prior to flight but did not include a specific check for correct fitment of the smoke barrier curtain. 

A flight crew operating manual (FCOM) was carried on board VH-KDK which was developed by Pel-Air, based on the aircraft manufacturer’s AOM. Unlike the aircraft manufacturer's AOM, the pre-flight checks in the operator's FCOM did not contain any reference to the cross-valve handle. Consistent with the aircraft manufacturer’s AOM, the operator’s FCOM also did not include a specific pre-flight check for correct fitment of the smoke barrier curtain. The weight and balance chapter of the FCOM did show a diagram of the smoke curtain fitted but did not include a requirement to ensure the smoke curtain was in place.

The manufacturer had an airplane flight manual supplement in place, implemented as part of the cargo configuration SB, which included fitting the smoke barrier as a limitation (Figure 7 left). There were no identified interior checks in this supplement, which included the checking of the cross-valve handle prior to flight.

The aircraft manufacturer did have emergency checklists specific to cargo‑configured aircraft. These were compiled into the quick reference handbook (QRH) which was available to flight crew in the aircraft (Figure 7 right). 

Figure 7: Flight manual supplement (left) highlighting smoke curtain use and QRH checklist (right) highlighting cargo cross-valve handle and cockpit door 

Source: Saab, annotated by the ATSB

Flight deck door

The Pel-Air FCOM stated in the Operating Limitations section that during flight, the flight deck door must be kept closed and locked at all times. It is further listed in the engine start checklist that all doors are closed before engine start. 

Evidence from the accident flight, however, shows that before the fire, the crew were operating with the cockpit door open. During interview, the flight crew indicated they closed the door, whilst performing the cargo compartment smoke checklist. This was further supported by the CVR review, where the crew were heard to state the door was to be closed as per the checklist steps, which was followed by the sound of the door shutting. 

Flight crew training

Rex conducted a ground school, including simulator training, for their new Saab 340 flight crew. Under a commercial agreement, Pel-Air flight crews were also trained by Rex. The ground school covered the 340 variants of A, B and B WT. The aim of the ground school was to provide pilots from both operators with the necessary knowledge to gain a Saab 340 type rating. The type rating covered all Saab 340 aircraft and did not distinguish between any variant or configuration of the aircraft.

Following the Rex ground school, Pel-Air then conducted further training through its line training program for its flight crews allocated to freight operations. Delivery of this training was in a practical environment, with pilots learning the systems and differences of the cargo‑configured Saab 340. This included the use of the smoke barrier and the operation of the cross-valve handle. 

The ATSB asked what the process was for Rex pilots to receive this training and knowledge. Pel‑Air advised that a pilot employed by Rex would only receive this if they were to transition to freight operations with Pel-Air in a permanent role. 

Crew familiarity of cargo aircraft

The flight crew operating VH-KDK were both Rex pilots, who were normally rostered for passenger operations. The night before the flight to Wagga Wagga, they were rostered to fly the cargo‑configured 340A. The captain recalled asking the scheduler if they needed a briefing for flying the cargo 340A, and was told that they did not, but it could be arranged if needed. 

The captain decided to speak to a Rex colleague who had flown the cargo‑configured 340A several times previously. They were told there were no differences other than the removal of the seats and a freight interior being fitted and that there were no special procedures to be aware of. 

Both Rex and Pel-Air advised that their respective operations could roster a crew to fly either operator’s aircraft if it was available. Crewing arrangements were such that there was never any mixing of crew, that is that the flight crew would consist of either 2 Rex or 2 Pel-Air flight crew on any flight.

Oxygen mask

The flight crew fitted their oxygen masks and smoke goggles shortly after receiving the cargo smoke warning and smelling the smoke. The FO conducted the functional tests after fitment and found their microphone was barely readable by the captain. The cockpit voice recorder (CVR) indicated that, although muffled, the speech from the FO was recorded and they were also able to be heard by air traffic control (ATC) throughout the emergency.  

The pre-flight checks relating to the crew oxygen system were conducted as part of the interior checklist. The FCOM detailed the checks as: 

RIGHT OXYGEN MASK .................................................................................CHECKED

Check flight crew oxygen mask and microphone in accordance with the following: 

•  …, 

•  set audio panel BOOM - MASK switch to MASK, 

•  increase INT/SPKR volume and knock on mask, 

•  speaker noise indicates proper microphone function, 

•  set BOOM - MASK switch back to the BOOM position, ….

The check on the left oxygen mask was to be performed in the same manner. Although not detected on the CVR, the captain advised the masks were both tested prior to departure. 

Aircraft damage

The damage caused by the underfloor fire was substantial. The fire had damaged underfloor air conditioning ducting and electrical wiring (Figure 8).

Figure 8: Underfloor fire damage

Source: Operator, annotated by the ATSB

Structural components in the surrounding area had been distorted by the extreme heat, including the floor panels, which had collapsed when fire crews entered the aircraft and inadvertently walked over the affected area. The seat track support structure had distorted, and the fuselage was weakened by the fire which breached the outer skin, preventing the aircraft from remaining pressurised (Figure 9).

Figure 9: Fuselage skin breach

Source: Operator, annotated by the ATSB

The fuselage in the immediate area above and below the cabin floor was buckled and delaminated. The heat from the fire most likely travelled between the interior panels and freight lining, leading to the damage observed (Figure 10). Following an engineering inspection of the fire damage, the aircraft was withdrawn from service and not repaired.

Figure 10: Right side delamination on fuselage

Source: Operator, annotated by the ATSB

Recorded data

The ATSB was supplied raw data by the operator from the flight data recorder (FDR). This data was analysed and was found to include the previous 4 flights. 

The recorded data from the occurrence flight showed that at about 59 minutes after becoming airborne at Wagga Wagga, the FDR stopped recording. The recording stopped at about the same time as the initial smoke indication. This was most likely due to fire damage to the electrical wiring which controlled the FDR. 

Flight track information was also obtained from FlightRadar24, which showed the entire flight, including the diversion and landing at Cobar (Figure 11).

Figure 11: VH-KDK flight track and diversion

 Source: Google Earth and Flightradar24, annotated by the ATSB based on CVR recordings

The CVR was removed and sent to the ATSB technical facilities in Canberra. The CVR data was downloaded, with the recovery of 4 channels of audio data of about 120 minutes duration which included the in-flight fire event. Reviewing the recorded CVR data also revealed that coincidentally, just prior to the indication of the cargo smoke caution, the flight crew had been discussing alternate airports in the area, and which one they would select if they had a need to divert. 

The recording contained information from the end of the previous flight, and from the day of incident. It included the:

• flight crew’s initial reaction to the caution warning for the smoke in the cabin
• conduct of the emergency checklists
• additional warnings as they occurred
• crew intercom and communications with Melbourne Centre
• landing at Cobar and subsequent exiting of the aircraft.

The recording also revealed that while conducting the emergency checklist for ‘cargo compartment smoke’ the crew closed the cockpit door as a loud bang was heard, indicating it was open during the flight.  

Safety analysis

Introduction

On 23 April 2023, the Regional Express (Rex) Airlines flight crew operating a Pel-Air Aviation Saab 340A, registered VH-KDK were conducting an internal revenue cargo flight from Wagga Wagga, New South Wales, to Charleville, Queensland. About 1 hour into the flight, the crew experienced an in-flight fire and diverted to Cobar, New South Wales. After experiencing thick smoke on the flight deck and then a cabin depressurisation, the crew performed a safe landing at Cobar. The aircraft was substantially damaged, and the flight crew were not injured. 

This analysis will explore:

• origin of the in-flight fire
• aircraft preparation for the flight
• oxygen mask use and technical problem of the microphone
• cabin depressurisation
• flight crew knowledge of aircraft systems
• flight crew operating with the cockpit door open
• Pel-Air and Rex flight crew operating manual information deficiencies
• training of Rex flight crews
• Saab pre-flight inspection checklists
• Rex crew familiarity of cargo aircraft. 

Origin of the in-flight fire

The source of the in-flight fire was traced to the right recirculating fan assembly. Although the fan was not damaged internally, the fire damage was most significant at the box sub-assembly, which was mounted external to the fan and housed the electrical control circuit boards. It is likely that an electrical component or components within the box sub-assembly failed, resulting in the underfloor fire. The fire damaged underfloor insulation and plastic air conditioning ducting components, which led to thick smoke filling the cabin and cockpit and aircraft structural damage. 

The avionics warning received by the crew during the diversion was most likely associated with the avionics cooling air that was being drawn from the now smoke-filled cabin. This was also stated in the ‘cargo compartment smoke’ checklist. 

The ATSB examination of the recirculating fan could not determine a cause for the failure in the electronic control cards which led to the fire. 

When the crew received the air conditioning system right duct over temperature caution light, it was most likely due to the distribution duct over temperature being affected by the fire and the melting which occurred as a result. When the over temperature was sensed, the right bleed valve closed automatically as a function of system logic for over temperature protection.    

Smoke barrier curtain

Cargo operations can have a greater fire risk than passenger operations due to the carriage of cargo that could be the source of a fire and the lack of cabin crew available to fight a fire. As such, additional protection was available to minimise flight crew exposure to cabin smoke in the form of additional smoke detectors and a smoke curtain. 

However, the smoke curtain was not installed into position by anyone involved in the flight preparation. The flight crew, who normally operated the same aircraft type but in a passenger configuration, did not notice there was a placard at the aircraft entrance stating the smoke curtain was to be fitted for all cargo flights. The flight crew remained unaware of the smoke barrier curtain and its use for cargo operations. Further, the engine being transported was positioned in the cargo area of VH-KDK, on both occasions, by Rex engineers. As the curtain was usually installed by freight handlers during normal cargo operations, it is possible the Rex engineers were also unaware of its requirement to be fitted.  

In this accident, the source of the fire was an aircraft component rather than the cargo being carried. If a similar fire occurs in a passenger‑configured Saab 340 aircraft, then the smoke curtain would not be in place. However, the smoke curtain was available and was required for use for this flight, so its non-use increased risk for this event.

The flight deck door was not closed during flight as prescribed in the operator’s FCOM operating limitations and checklists. Having the door closed would have likely prevented the smoke being able to flow into the flight deck. 

The result of not having the smoke barrier fitted and the flight deck door closed as part of the aircraft pre-flight preparation was that smoke from the fire was not contained to the cabin area and was able to move forwards toward the flight deck. 

Oxygen mask fault

The flight crew fitted their oxygen masks and smoke goggles when alerted of the presence of smoke by the central warning panel. This decision may have prevented the crew from being overcome by smoke and fumes in the cockpit in the next several minutes. However, once fitted, the crew had difficulty communicating with each other, as a result of the mask microphone being very faint and difficult for the captain to hear the first officer (FO). This appeared to be an internal fault only, as the cockpit voice recording (CVR) showed that the FO was able to be adequately heard by ATC. 

This breakdown of communication delayed the crew by 57 seconds, in which emergency checks were not initiated due to the breakdown of communication. It created confusion and distraction between the crew while trying to execute the emergency checklist. 

A review of the CVR captured prior to flight could not positively determine if the pre-flight check action in relation to the oxygen mask was performed. This is an important check of the emergency communication system whilst on oxygen and was designated as a mandatory check item for a daily inspection as required by the Rex and Pel-Air FCOM.

Cross-valve handle

While the flight crew were conducting the emergency checklist items for cargo compartment smoke, they were unable to locate the cross-valve handle. This was due to the combination of the thick smoke obscuring their vision and their lack of knowledge of the differences in the cargo‑configured aircraft. 

Had the location and function of the cross-valve handle been known by the flight crew, the time taken to identify it during completion of the emergency checklist would have been minimised, which would have limited the delay of smoke removal from the flight deck. 

In this case, the subsequent depressurisation resulted in the smoke dissipating even in the absence of the cross-valve.     

Cabin depressurisation

The weakening of the fuselage structure due to the underfloor fire resulted in a breach of the fuselage skin, which led to a subsequent depressurisation of the aircraft during the descent. Although adding to another caution alert indication for the flight crew and subsequent checklist to be conducted, it also benefited in the removal of smoke from the cabin and flight deck. 

At the time of the depressurisation, VH-KDK was at FL 160 and descending. The crew, when alerted to the depressurisation, increased the rate of descent to below 10,000 ft. The cabin depressurisation occurred 4 minutes after the initial smoke warning occurred.

Due to the size of the hole created, the smoke removal most likely occurred at a greater rate than using the aircraft pressurisation outflow valves alone. The resulting fortuitous reduction in the amount of smoke in the flight deck improved visibility and allowed the crew to carry out a safe landing into Cobar.

Crew familiarity of cargo‑configured aircraft

The flight crew had not flown or had any prior training on the cargo‑configured Saab 340 and were not familiar with the differences of the passenger configuration. The captain chose to liaise with a colleague to gain information on the cargo‑configured aircraft instead of accepting the company offer for a briefing. 

This non-formal approach to understanding the differences between the 2 aircraft types ultimately did not pass on the required operational differences and potential safety aspects of the change of aircraft configuration.

Rex and Pel-Air manuals

Both operators (Rex and Pel-Air) manuals, which were designed to provide essential information to flight crews, did not include the required information to enable the pre-flight checks to be conducted adequately. While the weight and balance chapter of the FCOM showed the smoke barrier curtain location, there was no information on its importance to cargo operations, and as the crew had not been informed of any differences, they would not have been expecting that this section contained this information. The smoke barrier curtain installation information that was contained in the Saab service bulletin and flight manual supplement was not included in the pre‑flight checklists. As a result, the flight crew did not have awareness of its use. 

The operators' manuals also did not have a check to verify the position of the cross-valve handle. As discussed above, when the checklist called for the crew to use this handle when the aircraft was already filling with smoke, the crew could not locate it.

Flight crew training

The Rex ground school provided type rating training on the Saab 340 series aircraft to both Rex and Pel-Air pilots. This training was based on the passenger‑configured aircraft. Pel-Air pilots undertook further training which gave them the knowledge and skills for the cargo‑configured aircraft. 

In scheduling their flight crews to operate the cargo‑configured Saab 340, Rex did not have a process to ensure that the additional training or knowledge sharing for their crews in the differences applicable to aircraft operated by Pel-Air was delivered.

Saab pre-flight checklists

As discussed above, both operators’ manuals had no inclusion of a pre-flight interior check for the smoke barrier curtain or the cross-valve handle. Likewise, there was no pre-flight interior check for these items in the manufacturer’s documentation. Saab confirmed that there were no checks in the pre-flight checklist for the crew to specifically verify that the smoke barrier curtain was correctly fitted.

The result of the manufacturer’s pre-flight and interior checklists not detailing information for the smoke curtain was that the operator did not detail these in their own FCOM. This information was not available for the flight crew who, even without prior knowledge of the cargo‑configured variant, would have been alerted to these changes while conducting these pre-flight checks in accordance with the FCOM. 

Findings

From the evidence available, the following findings are made with respect to the in-flight fire and cabin smoke involving a Saab 340A, VH‑KDK, 114 km east-north-east of Cobar, New South Wales, on 23 April 2023. 

Contributing factors

• It was likely that an electrical component of a control circuit board on the recirculating fan failed, resulting in an in‑flight fire under the cabin floor.
• The smoke curtain was not fitted as required for the cargo configuration, and the flight deck door was open, which allowed smoke from the in‑flight fire to enter the flight deck.
• The underfloor fire caused weakening of the fuselage structure, which led to a subsequent depressurisation of the aircraft during the descent. However, the depressurisation aided in the removal of enough smoke from the flight deck on approach to allow an unhindered visual approach at Cobar.
• Crew were not familiar with the cargo configuration and were unaware of the smoke curtain requirements and location of the cross-valve handle.
• The Pel-Air and Rex Saab 340 flight crew operating manuals did not include reference to the location and operation of the cross-valve handle or the operation and use of the smoke curtain. (Safety issue)
• Rex did not ensure its flight crews received training in the differences between passenger and freight‑configured Saab 340 aircraft, prior to being scheduled to fly freight operations. (Safety issue)
• Saab did not include the smoke curtain fitment in pre-flight documentation for the cargo‑configured Saab 340 aircraft to inform flight crew of this difference from the passenger-configured version. (Safety issue)

Other factors that increased risk

• When the flight crew donned their oxygen masks, the first officer's oxygen mask microphone did not function correctly. This led to difficulty in communication between the flight crew and a delay in responding to the emergency.
• Due to the combination of the smoke density and lack of prior knowledge, the flight crew were unable to locate the cross-valve handle during the emergency, therefore delaying the removal of smoke from the flight deck.

Safety issues and actions

Saab documentation for cargo configured aircraft

Safety issue number: AO-2023-020-SI-01

Safety issue description: Saab did not include the smoke curtain fitment in pre-flight documentation for the cargo‑configured Saab 340 aircraft to inform flight crew of this difference from the passenger‑configured version.

Operator documentation and crew familiarity

Safety issue number: AO-2023-020-SI-02

Safety issue description: The Pel-Air and Rex Saab 340 flight crew operating manuals did not include reference to the location and operation of the cross-valve handle or smoke curtain.

No formal company training

Safety issue number: AO-2023-020-SI-03

Safety issue description: Rex did not ensure its flight crews received training in the differences between passenger and freight‑configured Saab 340 aircraft, prior to being scheduled to fly freight operations.

Safety action not associated with an identified safety issue

Additional safety action by Regional Express

Rex advised that it is implementing a fleet‑wide inspection of the flight deck and passenger compartment recirculation fans at the next aircraft heavy maintenance visit. The inspection will be focused on the electronic sub-assembly module of the recirculation fan due to this component being identified to have the most significant fire damage on the fan assembly removed from VH‑KDK.

Glossary

Sources and submissions

Sources of information

The sources of information during the investigation included:

• the crew of VH-KDK
• Regional Express Airlines
• the chief pilot of Pel-Air Aviation
• the manager training and checking and head of operations for Regional Express Airlines
• Civil Aviation Safety Authority
• Bureau of Meteorology
• Fire and Rescue New South Wales
• Saab
• Airservices Australia
• the cockpit voice recorder and flight data recorder
• recorded data from Flightradar24. 

References

Australian Government 2023, Part 91 (General Operating and Flight Rules) Manual of Standards 2020, Civil Aviation Safety Authority, Canberra, ACT, viewed 30 April 2024, <Federal Register of Legislation - Part 91 (General Operating and Flight Rules) Manual of Standards 2020> 

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:

• Civil Aviation Safety Authority
• Airservices Australia
• Crew of VH-KDK
• Regional Express Aviation
• Pel-Air Aviation
• Swedish Accident Investigation Authority (SHK)
• Bureau of Enquiry and Analysis for Civil Aviation Safety (BEA).

Submissions were received from: 

• the captain of the crew
• Regional Express Aviation
• Pel-Air Aviation
• Swedish Accident Investigation Authority (SHK)
• Bureau of Enquiry and Analysis for Civil Aviation Safety (BEA).

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 2024   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 Commonwealth Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this report is licensed under a Creative Commons Attribution 4.0 International licence. The CC BY 4.0 licence enables you to distribute, remix, adapt, and build upon our material in any medium or format, so long as attribution is given to the 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.

The investigation

The occurrence

Approach to Sydney

On 8 November 2022, a QantasLink De Havilland Canada DHC-8-202 aircraft, registered VH‑TQS departed Lord Howe Island on a scheduled passenger flight to Sydney, New South Wales with 3 crew and 23 passengers on board. The first officer (FO) was the pilot flying (PF)[1] and the captain was the pilot monitoring (PM).  

At about 1658 local time, while descending through flight level (FL)[2] 175 on approach to Sydney (Figure 1), the flight crew were alerted to a failure of the traffic alert and collision avoidance system (TCAS)[3] as well as the ground proximity warning system (GPWS).[4] Shortly after, they noticed the radio altimeter (RadAlt) had also failed.

Figure 1: ADS-B[5] derived flight data showing the approximate location of the radio altimeter failure on approach to Sydney

Source: FlightRadar24 and Google Earth, annotated by the ATSB

The FO continued flying the aircraft while the captain consulted the Quick Reference Handbook (QRH) for the GPWS, TCAS and RadAlt failure procedures. The flight crew then informed air traffic control of the TCAS failure, and the FO continued with a visual approach to runway 34R[6] at Sydney.

Landing and taxi

After touching down, the FO retarded the power levers into beta range[7] to use the propellers to help slow the aircraft, as was standard procedure. When this happened, the beta lockout warning horn sounded. The power levers were brought forward to flight idle, which silenced the horn. Shortly after, the captain took over as PF as the aircraft’s nose-wheel steering tiller is located on the left (captain’s) side of the cockpit.

As they vacated the runway, the flight crew noticed that the GPWS and TCAS faults were resolved, but also identified that both the #1 and #2 engine manual caution lights were now illuminated, indicating that the electronic control units (ECU) of both engines were now in manual mode. The ECU normally controls the under-speed governing of the propellers during ground operations. However, when in manual mode, the power levers must be manually advanced by the flight crew to control the propeller speed and avoid the prohibited range[8] below 780 revolutions per minute (RPM). It also meant that reverse thrust would not be available to assist with slowing the aircraft during landing and the taxi.

As the captain advanced the power levers to maintain the propeller speed above 780 RPM, they noted that additional wheel braking was required to maintain a normal taxi speed. While the captain was taxiing the aircraft, the FO consulted the QRH checklist for the engine manual warnings, however, the checklist was prescribed for only a #1 or #2 engine manual caution light, not both simultaneously.

After about 3.3 km of taxiing, the aircraft reached the bravo 8 holding point (Figure 2). The captain brought the aircraft to a stop as air traffic control had instructed them to hold. While stopped, the flight crew contacted engineering support seeking advice on the dual engine manual condition. However, engineering was unable to provide advice within the available timeframe.

Once permitted, the taxi continued towards the domestic terminal. From this point, the taxi had a slight downhill slope and the captain started to notice the response from the brakes reducing. The braking performance continued to deteriorate, and during the final turn into the domestic 1A area (Figure 2), after about 5.5 km of taxiing, there was no braking response and the captain verbalised, ‘We’ve lost brakes’. The captain manoeuvred their aircraft to avoid colliding with another aircraft that was turning into a bay, and then brought the aircraft to a stop. At that time, the cabin crew reported via the interphone that there was fire, including visible flames, from both sides of the aircraft. The captain initiated an evacuation at which point the FO referenced the checklist in the QRH. They then exited the aircraft with the fire extinguisher. As the passengers disembarked, the FO went to both landing gear and attempted to extinguish the fires. A short time later, emergency services arrived and extinguished both fires using foam fire retardant.

No crew or passengers were injured during the evacuation.

Post-flight inspection

Following the occurrence, the aircraft was inspected by maintenance personnel. That inspection identified that all 4 main wheels and brakes were heat affected. Several of the brake and wheel components were replaced as a result of the brake fires. Maintenance testing could not replicate the RadAlt fault and the reason for its failure remains unknown.

Figure 2: ADS-B derived flight data showing the track of the aircraft on the ground at Sydney and the location of the brake failure

Source: FlightRadar24 and Google Earth, annotated by the ATSB

Context

Flight crew information

The captain had been flying for over 10 years and had about 5,000 hours of aeronautical experience with 2,272 hours on DHC-8 aircraft. The FO had been flying for about 9 years and had about 2,400 hours of aeronautical experience, of which 1,734 were on the DHC-8.

Aircraft information

General

VH-TQS was a high-wing, pressurised aircraft manufactured by De Havilland Canada in 1995. It was powered by 2 Pratt & Whitney Canada PWC123D turboprop engines, each driving a Hamilton standard 14-SF-23 4-blade, feathering and reversible, constant speed propeller. QantasLink had been operating the aircraft since 2011.

Radio altimeter

The aircraft was fitted with a radio altimeter (RadAlt). The RadAlt measures the height of the aircraft above terrain immediately below the aircraft, known as the radio altitude, and typically has an operating range of between 0 and 2,500 ft. The RadAlt system on the DHC-8-200 consists of a transmitter/receiver unit mounted under the cabin floor and 2 antennas on the underside of the fuselage. It is integral to the operation of the TCAS and GPWS, as well as the beta lockout system.

Beta lockout system

The power levers on the DHC-8-200 operate in 2 zones, flight mode and beta mode. In flight mode, the levers control engine speed between flight idle and take-off power. While in beta mode, the power levers control propeller pitch directly. The beta range is used for ground operations such as slowing the aircraft after landing and for ground manoeuvring. While in beta range, the ECUs regulate power to provide under-speed governing of the propellers.

As the levers are retarded in the flight mode towards flight idle, a flight idle gate prevents unintentional movement of the levers into the beta region. The gate is overridden by raising gate release triggers, allowing the power levers to be moved further aft to the ‘DISC’ detent. At this point, the propeller blade angle is at +1.5° which is used to slow the aircraft after touchdown. For ground manoeuvring, the levers can be retarded further to maximum reverse, at which point the propeller angle reaches -11.0°.

To ensure the beta condition is not activated in-flight, the system is disabled by the beta lockout while the aircraft is airborne. The beta lockout system is disabled from ground to 50 ft above ground level by the radio altimeter, or from an on-ground indication from the weight on wheels (WoW) system. Both the RadAlt and WoW are interlinked to the beta lockout system to prevent activation of beta lockout in the event that the aircraft bounces slightly during landing.

Weight on wheels system

The WoW system on the DHC-8-200 consists of proximity sensors on each of the landing gear and prevents the gear from retracting while on the ground. The proximity sensors register an on‑ground condition when the suspension compresses due to the weight of the aircraft. The beta lockout system requires the consensus of the main landing gear sensors, whereas the flight data recorder requires the consensus of all 3 gear (both main and nose) to provide a WoW indication in the recorded flight data. Further, it is possible for a sensor to record an in-air condition due to a decompression of the landing gear suspension, even when the wheel remains in contact with the ground.

Engine control unit

On the DHC-8-200, each aircraft engine is fitted with an ECU. The primary function of the ECU is for fuel flow regulation and torque management to optimise performance while protecting the engine from operational hazards such as exceedances of certain engine parameters, including temperature and RPM. In the event of a fault, the ECU will drop offline, and engine management will revert to manual control, as indicated by the illumination of the ECU manual light on the caution panel. In manual mode the flight crew must manually control fuel flow and there will normally be a difference between the 2 engine power lever positions for the same torque.

There are limitations on the use of lower power lever settings, particularly after landing, as the ECU normally controls the engine under-speed governor. With this, in manual mode, the flight crew must manually advance the power levers to maintain the propeller RPM above the ground operating restricted zone. Consequently, reverse thrust is no longer available for the affected engine.

Operational information

Landing procedures – power levers

The QantasLink Flight Crew Operating Manual (FCOM) contains landing procedures. Regarding the setting of the power levers during landing, the FCOM stated that:

Quick Reference Handbook guidance 

The DHC-8-200 QRH did not have guidance in the event of a failure of the radio altimeter. Neither was there any information regarding the implications that the failure would have on the beta lockout system. There was some pertinent guidance available in other manuals. For example, the Operating Data Manual stated:

However, the flight crew would not be expected to access this manual during this phase of flight.

The QRH contained guidance on the GPWS and TCAS failures, but there was no reference to radio altimeter failures. In addition, the QRH contained no information for a dual engine caution condition, however, it did include guidance on an individual #1 or #2 engine manual caution.

Evacuation procedures

Both the Aircrew Emergency Procedures Manual and the QRH contained guidance on actions and flight crew responsibilities in the event of an evacuation. Both documents required the FO to exit the aircraft with a fire extinguisher and torch.

Fire extinguishers

The DHC-8-200 was fitted with a Chubb Bromo Chloro di-Fluoromethane (BCF) fire extinguisher.  The Aircrew Emergency Procedures Manual, available in the flight crew’s electronic flight bag, contained guidance on the use of the BCF, which was for general use on most fires except some burning metals. The manual specifically stated that:

The Chubb material safety data sheet stated that hazardous decomposition products:

In response to a draft of this report, the operator advised that their annual emergency procedures training for flight crew covers BCF extinguisher description, serviceability, operation and precautions. This included a discussion on the warning, as noted above, and that the extinguisher can be used on in-flight fires.

Flight crew comments

During interview, both flight crew stated that they had never used a BCF fire extinguisher before. Both recalled from their training that the BCF extinguisher should not be used on some metal fires. However, they could not recollect that they were not to be used on brake fires on the DHC-8-200 aircraft. After the evacuation, the FO considered whether to use the BCF extinguisher on the brake fires. Aware that passengers were evacuating, and as the response time of the emergency services was unknown at that point, they elected to deploy the extinguisher on both fires.

Recorded flight data

The aircraft was fitted with an L3[9] FA2100 flight data recorder and L3 FA2100 cockpit voice recorder. Both units were transferred to the ATSB technical facilities in Canberra for download. Figure 3 shows a portion of the flight data recorded during the touchdown phase of the flight.

The data showed that the WoW system indicated an on-ground condition on initial touchdown (black track in Figure 3). One second later, the system recorded an in-air condition for one second, before returning to the on-ground condition for the remainder of the landing sequence. In that one second period in which the WoW returned to the in-air state, the data showed (red and green traces in Figure 3) that both propellers were placed into the beta mode. Coincident with this, the data showed the master caution (orange trace) activating.

Figure 3: Recorded flight data showing the timing of weight on wheels indication in relation to when the propellers were placed into beta mode

Source: ATSB

Safety analysis

Radio altimeter failure

Both the TCAS and GPWS relied on data from the RadAlt. Thus, the failure of the RadAlt resulted in the subsequent failures of the TCAS and GPWS. Further, the beta lockout system was interlinked with both the RadAlt and WoW systems to prevent the beta range from activating in‑flight. This meant that once the RadAlt had failed, the beta lockout system was relying solely on the WoW indication.

Weight on wheels

The flight data showed that, in the same second the power levers were retarded to beta range, the WoW sensors recorded a momentary ‘in-air’ condition. With the system registering an ‘in-air’ condition while the power levers were in beta range, the beta lockout system activated. The activation of the beta lockout resulted in engine manual caution warnings for both engines as the ECUs reverted to manual mode. Consequently, as the ECUs were not providing the under-speed governing during ground operations, this meant that reverse thrust was not available to slow the aircraft during the landing and subsequent taxi.

Brake failure

With both engines in manual mode and the requirement to avoid the ground operating restricted range, the flight crew had to manually advance the power levers on both engines to an increased propeller speed above 780 RPM. This subsequently increased the amount of wheel braking required.

The flight crew were able to safely stop the aircraft at the bravo 8 holding point, after about 3.3 km of taxiing. It was only after this point the braking performance deteriorated, eventually failing, igniting and initiating the evacuation. The combination of the additional burden placed on the brakes due to the increased thrust required to avoid the restricted propeller speed, as well as the length of the taxi with a downhill component, likely both contributed to the brakes overheating then failing, and igniting.

Operator guidance – engine manual warning and RadAlt

After the failures of the GPWS, TCAS and RadAlt, the flight crew consulted the DHC-8-200 QRH finding guidance for the TCAS and GPWS failures, but none for the RadAlt failure. Had the QRH contained information regarding the flow on effects of the RadAlt failure on the beta lockout system, it was likely the flight crew would have delayed the movement of the power levers into beta range during the landing until weight on wheels was assured.

Similarly, when the flight crew observed the engine manual caution warnings on both engines, they again consulted the QRH, finding guidance for only a #1 or #2 engine manual warning. Had the QRH provided additional guidance on dual engine manual cautions, the flight crew could have safely terminated the taxi at the bravo 8 holding point, or at any point prior, likely avoiding the brake failure, fire, and subsequent evacuation. 

Fire extinguisher usage

Before evacuating the aircraft, the FO consulted the QRH and in accordance with the checklist exited the aircraft with the BCF fire extinguisher. Cognisant of the proximity of evacuating passengers, and unaware of the response time of the emergency services, the FO elected to deploy the BCF on both brake fires. Although no-one was adversely affected in this occurrence by the use of the BCF fire extinguisher, their use on high temperature metal fires (such as a brake fire on the DHC-8-200 as noted in the Aircrew Emergency Procedures Manual), can result in the production of a number of toxic fumes.

Guidance on the use of the BCF extinguisher was provided in the Aircrew Emergency Procedures Manual, however, it was unlikely that flight crew would review this manual during an emergency evacuation. This information was not covered in the QRH, which was reviewed by the flight crew immediately prior to the evacuation. While the FO exited with the extinguisher, they could not specifically recall that it was not to be used on this type of fire. Therefore, it was likely that, in this occurrence, additional guidance in the QRH could have prevented the use of the BCF on the high temperature brake fire.

Findings

From the evidence available, the following findings are made with respect to the brake failure and fire involving DHC-8-202, VH-TQS, Sydney Airport, New South Wales, on 8 November 2022.

Contributing factors

• The radio altimeter failure led to the beta lockout system relying solely on the weight on wheels to prevent the activation of the beta lockout system.
• During the touchdown, in accordance with standard operating procedures, the power levers were moved into the beta range. As this occurred when the weight on wheels sensors momentarily recorded an in-air condition, the beta lockout system and engine manual condition activated. This meant that reverse thrust would not be available to assist in decelerating the aircraft during the landing and taxi.
• The increased power setting required to avoid the restricted zone while in engine manual mode combined with the long taxi, increased the amount of wheel braking required, resulting in the brakes overheating, failing and igniting.
• The operator did not provide adequate guidance on how to respond to a dual engine control unit or radio altimeter failure on the de Havilland Canada DHC-8-200 aircraft, leaving flight crew without sufficient resources to appropriately deal with such failures.

Other factors that increased risk

• During the evacuation of the aircraft, the Bromo Chloro di-Fluoromethane (BCF) fire extinguisher was used on a high temperature brake fire, increasing the risk of exposure to hazardous by-products.

 Safety actions

Safety action by QantasLink

In response to this occurrence, on 4 October 2023, the ATSB was advised by QantasLink that the following actions had been undertaken:

• They published a technical advisory bulletin to DHC-8-200/300 flight crew outlining the event and learnings from the event, including relevant technical explanations, such as the radio altimeter failure and the flow-on implications with the beta lockout system.
• Further information about the beta lockout system will be added to the DHC‑8‑200/300 Flight Crew Operating Manual Section 4 in an upcoming amendment.
• A new QRH checklist is also being produced for a radio altimeter failure. This new QRH checklist will assist to identify a radio altimeter failure and will provide appropriate actions and considerations. In particular, it will include the following note from the De Havilland Operating Data Manual:

• They are developing a new QRH checklist for a ‘#1 ENG MANUAL and #2 ENG MANUAL (Caution Lights)’ scenario. This new checklist will provide guidance in the event both engines operate in manual mode, including considerations such as maintaining propeller RPM outside the prohibitive range and limiting taxi duration, with consideration given to being towed to the bay (where possible). Specifically:

• Additional guidance regarding the use of brakes has been added to the Flight Crew Operating Manual.

Sources and submissions

Sources of information

The sources of information during the investigation included:

• the flight crew
• QantasLink
• De Havilland Aircraft of Canada Limited
• recorded data from the flight data recorder
• audio recordings from the cockpit voice recorder
• ADS-B data from FlightRadar24.

References

Gunston, B. (2004). The Cambridge aerospace dictionary. Cambridge University Press.

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 flight crew
• QantasLink
• De Havilland Aircraft of Canada Limited
• Civil Aviation Safety Authority
• The Transportation Safety Board of Canada
• Transport Canada.

Submissions were received from QantasLink. 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 2024 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 26 December 2018, a Kavanagh B-350 hot air balloon, registration VH-ZYO, operated as a scenic charter flight by Go Wild Ballooning, departed from Wandin, Victoria with the pilot and 15 passengers on board.

After 20 minutes in flight, and while operating at an altitude of about 800 ft, the pilot recalled hearing a small explosion from the front left burner and observed that a small fire had started on the outside of the burner. The pilot switched off the vapour valve at the fuel tanks to the front two burners and disconnected the hoses.

About a minute later, the pilot attempted to put out the fire using one of two on-board extinguishers, but the fire re-ignited almost immediately. After a further minute, the pilot discharged the second fire extinguisher, but again the fire re-ignited.

Moments later, the pilot’s compartment caught fire. The pilot was wearing a cotton shirt, synthetic vest, rolled-up pants, and rubber slip-on shoes and began to feel uncomfortable with his proximity to the fire. He then moved from the pilot’s compartment to the back left compartment of the basket.

About 8 minutes after the fire started, the pilot identified a suitable landing position and began the approach. During the descent, the basket struck some treetops and the ropes became tangled in the branches. Passengers reported that the branches whipped around and into the basket, with one passenger sustaining cuts to his hand. The pilot freed the ropes from the tree and brought the balloon to rest in the paddock below. As the basket touched the ground, the passengers jumped out and ran to safety.

The fire continued to burn as the pilot secured the balloon. When emergency services arrived on site, flames had engulfed the balloon. By the time firefighters extinguished the flames, the fire had destroyed the balloon.

What the ATSB found

• The ATSB found that the in-flight fire was the result of a fuel leak at the front left burner. Due to severe fire damage, the source of the leak could not be determined conclusively, but it was considered most likely to be the main ball valve, liquid fire valve or liquid fire valve connection to the main valve block.
• The hand-wheel valve on the liquid outlet of the fuel tank and the pilot burners were not shut-off, which resulted in the pilot being unable to control the fire. Installation of a 90-degree valve on the liquid fuel outlet may have assisted the pilot to recognise that the liquid fuel valve was not shut-off.
• In addition, the pilot's clothing did not meet the recommended industry standards for personal protective equipment, which increased the risk to his personal safety.

What's been done as a result

As a result of this occurrence, the Civil Aviation Safety Authority released an Airworthiness Bulletin (AWB 02-063) to address some of the pertinent issues surrounding this occurrence. The AWB included:

• a recommendation to inspect critical componentry
• the use of 90-degree shut-off valves for the fuel tank liquid outlets
• a reminder to close off liquid and vapour valves in the event of a fire
• a reminder to wear appropriate personal protective equipment.

In addition, Go Wild Ballooning has advised the ATSB that they have replaced all hand-wheel valves with 90-degree valves on all fuel tanks and reviewed the company policy on protective clothing.

Safety message

In the event of an in-flight balloon fire, the first priority is isolation of the fuel supply at the fuel tank. It is good practice to rehearse emergency procedures by standing in the basket to run through the checklist steps.

Further ways to reduce risk to individuals and improve survivability outcomes include:

• wearing appropriate protective clothing that includes cotton long‑sleeved shirts and long trousers, leather gloves, and enclosed footwear
• utilising componentry that provides a visual indication of the system status, for example, 90‑degree valves on liquid outlets.

On-board view of in-flight fire involving VH-ZYO

Source: Passenger photo

The occurrence

What happened

On 26 December 2018, at about 0500 Eastern Daylight-saving Time,^[1] a Kavanagh B-350 hot-air balloon, registration VH-ZYO, operated as a scenic charter flight by Go Wild Ballooning, was being prepared for departure from Wandin, Victoria.

Prior to take-off, the pilot, together with another ground crew member, conducted the pre-flight check on the balloon, while a ground crew member conducted a safety briefing with the passengers. Neither person inspecting the balloon observed any defects during the pre-flight check.

At 0537, the balloon lifted off with the pilot and 15 passengers on board. After about 15 minutes in flight, the balloon reached an altitude of 4000 ft. The pilot maintained level flight for a few minutes and then began to descend. At about 800 ft, the pilot recalled hearing a small ‘explosion’ from the front left burner (Figure 1) and observed that a small fire had started on the outside of the burner. The passengers observed that the fire was concentrated around the base of the burner, shooting outwards to the front of the basket.

The pilot switched off the vapour valve (see the section titled Aircraft information) at the fuel tanks to the front two burners and disconnected the hoses. Shortly after, the vapour hose connected to the front left burner burnt through and fell away from the burner.

About a minute later, the pilot attempted to put out the fire using one of two on-board extinguishers, but the fire re-ignited almost immediately. After a further minute, the pilot discharged the second fire extinguisher, but again the fire re-ignited. The first flames appeared in the vicinity of the burner can base, towards the front side of the basket, with the flames directed outwards.

Moments later, the pilot’s compartment caught on fire. The pilot was wearing a cotton shirt, synthetic vest, rolled-up pants and rubber slip-on shoes and began to feel uncomfortable with the proximity of the fire. As a result, the pilot moved from the pilot’s compartment to the back left compartment of the basket. The pilot made a call over the radio, repeating MAYDAY^[2] three times followed by the balloon registration. Air traffic control acknowledged the call and initiated the appropriate emergency procedures in response.

About 8 minutes after the fire started, the pilot identified a suitable landing position and began the approach. During the descent, the basket struck treetops in the landing area undershoot and the ropes became tangled in the branches. Passengers reported that the branches whipped around and into the basket, with one passenger sustaining cuts to his hand. The pilot freed the ropes from the tree and brought the balloon to rest in the paddock below. As the basket touched the ground, the passengers on the right hand side of the basket jumped out causing the right side of the basket to lift off the ground again. In response, the pilot quickly pulled the red line^[3] to evacuate the hot air from the envelope and brought the basket back down to the ground. The remaining passengers then jumped out and ran to safety.

The fire continued to burn as the pilot secured the balloon. When emergency services arrived on site, flames had engulfed the balloon. By the time firefighters extinguished the flames, the fire had destroyed the balloon.

Pilot's comments

The pilot later commented that:

• he was carrying a long woollen coat in the basket as additional protective clothing, however, it was not accessible
• he had not been wearing protective gloves, as they had been burnt earlier in the flight, when he had put them aside to adjust the radio
• during the incident, he followed the priority of, ‘aviate, navigate, communicate’.

Aircraft information

VH-ZYO was a Kavanagh B-350 balloon. The balloon consisted of an envelope, a 16-person basket, a quad burner system and four propane fuel tanks.

Kavanagh Balloons series 3 burner and fuel system

A Kavanagh series 3, quad burner system was installed on the aircraft. The burner unit consisted of four high-pressure propane burners. Each of the burner units had two connections to the fuel tank: a vapour hose (connected to the pilot burner) and a liquid hose, which connected into the burner coil (Figure 1). A standard feature of the system included a secondary burner, known as ‘liquid fire’. This system bypassed the heat exchanger coil and fed liquid propane directly into the burner. The vapour hose drew gaseous propane from the top of the fuel tank and the liquid hose drew liquid propane from the bottom of the fuel tank. The fuel tanks on VH-ZYO had hand-wheel shut-off valves installed at the connections for both the liquid and vapour hoses. The alternative certified configuration was a 90-degree valve. Both valve configurations are shown in Figure 3.

Figure 1: Basket and burner arrangement similar to VH-ZYO

Source: Kavanagh Balloons, annotated by ATSB

An illustrated diagram of a burner unit is shown in Figure 2 below.

Figure 2: Illustrated diagram of the burner system on VH-ZYO

Source: Kavanagh Balloons, annotated by ATSB

Figure 3: Valve types on propane tank

Source: Kavanagh Balloons, annotated by the ATSB

The European Aviation Safety Authority (EASA) has previously published a safety information bulletin (SIB 2018-14) highlighting the advantages of using 90-degree valves over the hand‑wheel valves. EASA recommends operators of hot air balloons use the 90‑degree valves for propane fuel cylinders as they had been found to improve the survivability outcome in the event of fire due to their easy and quick actuation.

Liquid and vapour hoses

The Kavanagh Balloon’s maintenance manual mandates that the liquid fuel hoses have a 10-year life from the date of manufacture. The liquid hoses on VH-ZYO were last replaced in October 2018. Leak checks were conducted as part of the standard replacement procedure and the aircraft had been used multiple times since the replacement.

The liquid hoses were constructed from three layers of material: an inner rubber tubing, an encasing metal braid, and a rubber outer casing. Vapour hoses have a similar construction but do not have a time-limited life.

Main valve block

The main valve block (Figure 2) was an assembly of two solid pieces of aluminium, fastened either side of the main ball valve with four bolt and nut combinations. The liquid fire valve, liquid fuel hose, pressure gauge and cross flow plug each screw into a threaded hole in the main valve block.

Pressure gauge

The manufacturer rated the pressure gauge to a maximum operating pressure of 230 psi,^[4] with design testing conducted to around 345 psi. The normal operating range for the series 3 burner (the same burner installed on VH-ZYO) is 50 – 218 psi. The pilot indicated that the system was generally operated at around 180 psi.

Liquid fire valve and main ball valve

The liquid fire valve was a small ball valve, housed in a steel casing, with no replaceable parts. The maintenance manual specified that the valve was to be replaced as a full unit (based on the valve’s condition). Conditions indicating replacement was necessary included seizing of the valve, the valve not shutting off, or signs of leaking.

The main ball valve was a 90-degree, quick shut-off valve, designed to stop the flow of fuel into the burner can.

Kavanagh Balloons flight manual

Mandatory equipment

The flight manual specified that at least one dry powder (1 kg capacity) fire extinguisher must be carried during each flight.

In-flight fire

The manufacturer’s required actions for managing an in-flight fire were:

• turn off fuel at main tank valves and turn off pilot burners
• put out fire with the fire extinguisher
• if it is safe, re-light pilot burner, proceed as normal and make a landing as soon as possible
• if it is unsafe to re-light the burner, prepare to make an emergency hard landing.

Clothing recommendations

The regulatory bodies in Europe and America have developed guidelines for balloon operators, including the following recommended protective clothing:

• long sleeves and trousers, preferably made of natural fibres
• protective footwear
• leather gloves.

Component examination

The ATSB conducted an examination of a number of balloon components. The examination was severely hindered by the extensive fire damage but the following observations were possible:

• the burner from which the fire was emanating still had the liquid fire valve, the mini ball valve (vapour pilot burner) and the burner coil attached (Figure 4)
• the main ball valve was not attached to the coil (Figure 4)
• in-flight photographs showed that the main ball valve was shut during the fire
• all of the main valve block assembly bolts (with nuts attached) and cross-flow plugs were found intact in the wreckage
• examination of the components did not identify any possible sources of a leak or failure that may have contributed to the in-flight fire
• determination of the integrity of the main ball valve and liquid fire valve could not be established as the internal structures were completely disrupted by the fire.

Figure 4: Underside of burner and main ball valve – fire location

Source: ATSB

Previous occurrences

A review of the ATSB occurrence database for similar occurrences identified that in the last 10 years there had been 10 instances of a hot air balloon catching fire. Of these, two incidents were the result of a fuel leak. In the first instance, the leak occurred at the main ball valve and in the other at the liquid fire valve. The pilots of the balloons controlled the fires by shutting off the fuel at the tank and then extinguishing the flames.

Safety analysis

The pilot first observed the fire coming from the front left burner. Physical examination of the components did not identify any possible sources of a leak or failure that may have contributed to the in-flight fire. However, the location of the fire (front left burner) eliminated any of the connections at the fuel tanks as a source of the leak. With the main valve switched off and the liquid fuel remaining on at the tank, only the pressurised components in between could have been the source of the initial leak. The most likely were considered to be the:

• threaded connection between the liquid fire valve and main valve block
• liquid fire valve
• main ball valve.

The direction of the flame (towards the front of the balloon) was in line with the connection of the liquid fire valve into the main valve block. On installation, over-torquing or cross-threading the connection could result in damage to the aluminium valve block. Stresses from pressurisation and thermal cycling over time can cause the damage to develop into a crack, resulting in a fuel leak. However, as this joint did not require frequent adjustment, the likelihood of damage due to installation error or handling was reduced.

The flames emanated from a location near the main ball valve and the liquid fire valve. The valves (moving components) were prone to wear and therefore at higher risk of leaking than static components. The valves were oriented vertically with a handle on the base. It can be expected that any leaking fluid would spray downwards, into the handle, making it unlikely to see the directional flame pointing outwards from the basket. However, given the fire continued for an extended length of time, it is likely that the initial fire heated the surrounding structure causing failure of seals and joint sealant in other components, leading to further leaks and a larger fire. In that context, images and accounts of the flames directed outwards from the basket may be the result of subsequent failures.

As the pilot did not shut the liquid fire valve on the fuel tanks or the pilot burners, the situation escalated rapidly and increased the pilot’s workload in managing the situation. The leaking fuel near to the pilot flames on the adjacent burners caused the fire to re‑ignite immediately after the removal of the fire extinguishers. Use of a 90-degree valve on the liquid fuel outlet may have better assisted the pilot to recognise that he had not shut off the liquid fuel valve, enabling him to control the fire.

The pilot’s clothing did not provide adequate protection from burns, increasing the risk of personal injury. The pilot was carrying additional protective clothing, however, it was not kept in a readily accessible location, and therefore could not be used.

Finally, the MAYDAY broadcast did not provide air traffic control with a current or last known location of the aircraft. In this instance, the lack of information did not result in a delayed response from emergency services. It is important, however, for pilots to follow standard broadcast procedures when declaring an emergency.

Findings

These findings should not be read as apportioning blame or liability to any particular organisation or individual.

• A fuel leak at the front left burner resulted in an in-flight fire. Due to severe fire damage, the source of the leak could not be determined conclusively, but it was considered most likely to be the main ball valve, liquid fire valve or liquid fire valve connection to the main valve block.
• The hand-wheel valve on the liquid outlet of the fuel tank and the pilot burners were not shut off, which resulted in the pilot being unable to control the fire.
• The pilot's clothing did not meet the recommended industry standards for personal protective equipment, which increased the risk to his personal safety.
• Installation of a 90-degree valve on the liquid fuel outlet increases survivability in the event of fire and, may have assisted the pilot to recognise that the liquid fuel valve was not shut off.

Safety action

Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following proactive safety action in response to this occurrence.

Civil Aviation Safety Authority

As a result of this occurrence, the Civil Aviation Safety Authority released an Airworthiness Bulletin (AWB 02-063) to address some of the pertinent issues surrounding this occurrence. The AWB included the following recommendations:

• Inspect the condition and operation of the fuel pressure gauge, stem seal and liquid fire valve.
• Review the fuel system pressurisation limitations. Pressurisation of the fuel gauge beyond the maximum reading may cause catastrophic failure of the pressure gauge.
• Use 90-degree (quick shut-off) valves for the fuel tank liquid outlets.
• Review and rehearse all emergency procedures including in-flight fire and burner malfunctions.
• Both the liquid and vapour valves must be closed on any tanks connected to the burner with a leak or malfunction before any effective firefighting methods can be performed.
• Minimum industry standard protective clothing should be worn, which includes fire-resistant gloves, long-sleeved cotton shirt and sturdy, enclosed footwear
• Carry fire blankets of a size of at least 1.5 m x 2 m.

In addition, CASA conducted a surveillance audit on Go Wild Ballooning. The audit returned a number of findings that the company will be required to rectify.

Go Wild Ballooning

As a result of this occurrence, Go Wild Ballooning has advised the ATSB it has taken the following actions:

• upgraded one basket to the new Kavanagh Quad Burner system and is considering phasing out the older Kavanagh series 3 systems
• replaced hand-wheel valves with 90-degree valves on all fuel tanks
• reviewed the company policy on protective clothing, and are researching new fire-proof gloves.

Safety message

Pilots experience a high workload during in-flight emergencies. However, in the event of an in‑flight balloon fire, the first priority must be isolation of the fuel supply at the fuel tank.

The complex nature of emergencies highlights the importance of rehearsing response procedures. It is also good practice to do this standing in the basket. Further ways to reduce risk to individuals and improve survivability outcomes include:

• wearing appropriate protective clothing, which includes cotton long-sleeved shirts and long trousers, leather gloves and enclosed footwear.
• utilising componentry which provides a visual indication of the system status and is easy to use, for example, 90‑degree valves on liquid outlets.

Civil Aviation Order 201.11, Appendix IV and Civil Aviation Regulation 5.143 provide requirements for pilots to maintain currency of skills. It is important to remember, however, that it is up to individuals to ensure that they maintain a good working knowledge of how to deal with the full range of abnormal indications. Civil Aviation Advisory Publication 5.81-1(1) provides a clear interpretation of the requirements.

 

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 2019 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.

__________

1. Eastern Daylight-saving Time (EDT): Coordinated Universal Time (UTC) + 11 hours.
2. MAYDAY: an internationally recognised radio call announcing a distress condition where an aircraft or its occupants are being threatened by serious and/or imminent danger and the flight crew require immediate assistance.
3. A rope or nylon strap connected to the top of the envelope, which the pilot uses to vent some or all of the hot air inside the envelope in order to descend or land.
4. The imperial unit for pressure, pounds per square inch (psi) is equal to 6.895 kPa.

Safety summary

What happened

At about 1250 Eastern Daylight Time on 21 January 2018, a Schleicher ASH-25E (AMT Jet) experimental powered glider, registered VH-GOA (GOA), was launched from the Bathurst Soaring Club facilities (Piper’s Field) New South Wales. The experienced pilot intended to conduct a cross-country flight, and was the sole occupant.

Eight minutes into the flight, the glider had climbed to about 2,200 ft in a thermal. Shortly after, it abruptly started to descend and track back towards the airfield. Witnesses saw smoke or liquid trailing from the glider and flames in the area behind the cockpit.

At about 1300, when at about 1,100 ft AGL, the pilot jettisoned the front-seat canopy but did not exit the glider. Fire engulfed more of the rapidly descending aircraft’s fuselage before it collided with the ground in a nose-down attitude. The pilot was fatally injured, and the aircraft was destroyed.

What the ATSB found

The glider caught fire in-flight, with flames seen near the engine housing. However, due to the severe post‑impact fire damage, the ignition source of the fire could not be determined. The pilot was probably attempting to return the burning glider to the airfield when it departed controlled flight and collided with terrain. The loss of control was probably due to the effects of fire incapacitating the pilot and/or affecting the aircraft’s flight controls.

The ATSB found that the pilot had the necessary equipment to make an emergency egress from the glider to escape the effects of the fire. He jettisoned the glider's canopy but possibly due to incapacitation, did not exit.

Finally, the glider’s cockpit and engine housing were not separated by a firewall. That resulted in limited containment of smoke and fire, and reduced the available time to make an emergency exit.

What’s been done as a result

Following the occurrence, the Gliding Federation of Australia published an Airworthiness Directive and Airworthiness Advice Notice, both entitled Engine Compartment Fire Containment and Retardation, which provide guidance regarding fire safety. The Airworthiness Directive requires all powered glider operators to inspect and repair fire retardant paint, fit ‘in case of engine fire’ cockpit placards, and ensure there is no flammable material on the cockpit side of any firewalls.

Safety message

Although not an airworthiness requirement, pilots of powered experimental gliders are strongly encouraged to install fire protection between themselves and the engine housing. The ability to exit a glider relies on avoiding incapacitation that can happen quickly in the event of in-flight fires.

Safety analysis

In-flight fire

From the available information, in-flight flames were first seen near the engine housing, at the rear of the cockpit. Therefore, the ATSB considered potential ignition sources associated with the engines and the lithium polymer (LiPo) batteries.

Engine‑related ignition source

Normal operation of the engines only provided an ignition source during the start sequence or when operating. The design of the engine systems prevented the engines from starting while lowered and stowed. Specifically, the START CLEARANCE on the ECU was not displayed until the pylon was fully raised, and an interlock prevented engine start in the lowered position. While a malfunction that bypassed these mechanisms could not be ruled out, it was considered unlikely that the start sequence initiated while the engines were housed inside the fuselage.

The pilot had experienced an in-flight engine fire on VH‑GOA (GOA) in the past, and had reportedly lowered the engine into the housing to extinguish it. While it was therefore likely that he would have performed the same action if faced with another in‑flight fire, the ATSB could not find any supporting evidence that the pilot attempted to start the engines in flight. Specifically:

• The pilot did not run the engines on the ground before the occurrence flight. Given his reported past practice, this indicated that he was not intending to use them.
• Witnesses reported that they did not hear the distinctive sound of the engines either before or after the departure of GOA. It was also not possible to discern from the witness photos whether the engines were raised.
• The rate of climb that GOA achieved in the thermal was possible without the engines.
• The engines were likely lowered at the time of the impact (although it was not possible to determine what their position was at all times during the flight).

The ATSB was therefore unable to determine if the source of the fire was related to an attempt (successful or not) to raise and start the engines. However, given the recorded engine operation the previous day - fuel leakage and excessive flaming, similar in-flight behaviour during the accident flight could have resulted in an airborne fire. Additionally, as propane ignites at lower temperature than the diesel fuel, a propane leak could also have plausibly ignited.

Prior to the installation of the jet engines in 2010, the ASH-25E had a forward shroud and fire protection paint within the engine housing, but it appears the shroud was removed with the original engine. Based on several sources of evidence, there was no effective fire protection between the engine housing and the cockpit on GOA.

Thermal runaway

The pilot had charged the batteries on the evening before the occurrence. If a battery experienced thermal runaway, the resulting heat would be sufficient to ignite any diesel or propane nearby, as well as causing the fuselage to combust. However, due to the intense post‑impact fire, the battery was not identifiable within the wreckage, so it was not possible to assess the likelihood that it was the source of ignition.

Summary

The investigation found that the in-flight fire probably started near the aircraft’s engine housing. However, the extent of fire damage precluded identification of the specific ignition source.

Despite that, the circumstances of this accident (and previous occurrences) clearly illustrate the importance of having a sealed firewall to prevent, or at least delay, the effects of fire reaching the cockpit area. In that context, the ATSB recommends that any modifications to powered gliders are conducted with reference to the European Aviation Safety Agency Certification Specification CS‑22 Sailplanes and Powered Sailplanes.

Loss of control and collision with terrain

After disengaging from the aero tow aircraft, the glider started to climb in a thermal. The other glider that departed a few minutes before GOA climbed to about 10,000 ft in the same thermal, indicating that it would likely have supported the continuation of a positive climb for GOA. Therefore, when the pilot of GOA broke off from the thermal, this was probably a result of identifying the fire behind the cockpit. The glider then tracked back towards the direction of the airfield.

The subsequent high rate of descent indicated that the pilot probably deployed the glider’s air brakes to expedite the descent. The glider passed by the threshold of runway 21 when in the continuous nose-down, left-bank attitude, a configuration that could indicate the pilot was no longer in control. It collided with terrain in this same configuration at a relatively high speed.

The ATSB assessed that the control loss was probably due to the effects of fire incapacitating the pilot and/or affecting control of the glider.

It is possible that the pilot became incapacitated, for the following reasons:

• exposure to smoke, fumes or fire (there was evidence that smoke entered the cockpit)
• a medical event, possibly linked to the stress of the in‑flight fire and/or his coronary heart disease
• the canopy or associated airflow may have impacted the pilot as it was jettisoned.

Based on the available evidence, the ATSB was not able to determine whether the pilot became incapacitated prior to the impact with terrain. However, as discussed further below, the apparent partial completion of the egress sequence could support that conclusion.

Images of GOA just prior to impact indicated that the glider was structurally intact prior to impact however, it is possible that the flight control cables and/or pushrods were damaged by the in‑flight fire. Due to the severity of the post-impact fire, it was not possible to ascertain if the flight controls were fire‑damaged before the ground impact.

Glider egress

The ATSB established that the pilot was wearing a parachute, which probably had a minimum deployment height of 500 ft, and that he was probably sitting on his egress assist cushion. He therefore had the necessary equipment to be able to exit the glider.

The time between the pilot breaking off from the thermal and then jettisoning the canopy was about 54 seconds, and it appeared as though the glider was under control. However, witnesses reported the fire visibly became more intense over that time. There was smoke residue on the inside of the canopy, which indicated that the pilot was exposed to at least one incapacitating factor before jettisoning the canopy. Fire smoke contains a mixture of narcotic and irritant gases, and incapacitation results from exposure to this combination, where ‘incapacitation’ encompasses a range of possible conditions, including unconsciousness, severe physical distress, or inability to determine how to escape (Gann, 2004).

Jettisoning the canopy required the pilot to pull a handle in the cockpit. This indicated that he was not incapacitated up to that moment. However, it is possible that after jettisoning the canopy, the pilot was not able to exit due to incapacitation. Alternatively, he may have assessed that he was now too low to exit the aircraft, or made a conscious decision to land the glider.

The occurrence

At about 1250 Eastern Daylight‑saving Time^[1] on 21 January 2018, a Schleicher ASH-25E (AMT Jet) experimental powered glider, registered VH-GOA (GOA), launched from the Bathurst Soaring Club’s facility at Piper’s Field, New South Wales (Figure 1). The glider was launched by an aero‑tow aircraft from runway 21 with the pilot as the sole occupant. The purpose of the flight was for GOA and another glider to conduct a cross-country flight. The other glider launched about 5 minutes before GOA.

Figure 1: Bathurst Soaring Club facilities at Piper’s Field

Source: Bathurst Soaring Club, with permission, modified by ATSB

Witnesses at the airfield reported that, after departing, (Figure 2, item 1), GOA tracked out for about 1.5 NM. The pilot released from the aero-tow aircraft at 800 ft above ground level (AGL)^[2] (Figure 2, item 2), made a radio call on the Soaring Club frequency that he had disengaged from the aero-tow. On-board GPS position and altitude information showed that by 1258:58 GOA had climbed to 2,205 ft AGL in a thermal situated to the south of the airfield. The glider then abruptly departed the thermal and started to descend and track back towards the northern end of the airfield (Figure 2, item 3).

Witnesses reported seeing something trailing from GOA, which they thought was smoke or a liquid, while the glider was in a steep nose-down attitude. They then saw flames emanating from the top and bottom of the airframe, behind the cockpit (Figure 3). The pilot jettisoned the front seat canopy at 1259:52, at a height of about 1,100 ft AGL (Figure 2, item 4), but despite wearing a parachute, he did not exit the glider.

Figure 2: Aircraft track as recorded by the on-board GPS and as recalled by witnesses

Source: GPS data overlaid on Google earth, annotated by ATSB

Figure 3: Photograph of GOA after the front canopy was jettisoned

Source: Witness photograph, modified by ATSB.

At this stage, GOA was seen maintaining a steep nose-down attitude and high speed with a bank angle of about 15°. Witnesses also recalled that there did not appear to be any discernible control inputs after the canopy was jettisoned and by the time the glider descended to about 500 ft AGL, more of the fuselage was engulfed in fire. At about this time, at least one of them called emergency services.

The soaring club’s closed-circuit television camera recorded that the glider banked left just prior to impact (Figure 4). A witness similarly reported that the glider’s left wing tip impacted the ground first, before it came to rest in an inverted position. The wreckage continued to burn after impact, and a fire spread to the surrounding grass.

Some witnesses moved to the accident site with handheld fire extinguishers to control the fire. About 10 minutes later, fire services arrived on the scene and extinguished the fire before it spread to neighbouring properties.

The pilot received fatal injuries and the aircraft was destroyed.

Figure 4: The glider immediately before impact

Source: CCTV camera still image, modified by ATSB

__________

1. Eastern Daylightsaving Time (EDT): Universal Coordinated Time (UTC) + 11 hours.
2. Above Ground Level (AGL): the height measured with respect to the underlying ground surface.

Context

Pilot information

The pilot held a valid Glider Pilot Certificate issued by the Gliding Federation of Australia (GFA) in October 2017. He also held a Private Pilot (Aeroplane) License that was issued in July 1977. In addition to holding all necessary qualifications for gliding operations, his endorsements included:

• carriage of private passengers
• cross-country/touring (self-launching sailplane)
• low level finish
• self-launching sailplane.

At the time of the occurrence, the pilot had accrued between 8,000 and 11,000 hours of gliding experience over more than 2,000 flights. The pilot also held a maintenance authority to conduct specific powered glider and airframe maintenance.

The pilot held a valid medical Certificate of Fitness issued by a Medical Practitioner as required by GFA. The criteria for issuing a Certificate of Fitness were based on the medical standards that Austroads set for issuing a driver’s license medical certificate for a private motor vehicle. He had previously held a class 2 aviation medical certificate, which expired in 2012.

Evidence to assess the likelihood of the pilot experiencing fatigue was gathered, including available information on sleep obtained, any factors potentially affecting his ability to maintain adequate alertness during the flight, and other aspects that affects sleep opportunity. However, there was insufficient evidence to ascertain whether the pilot was likely to have been experiencing a level of fatigue known to affect performance.

Aircraft information

The Alexander Schleicher ASH-25E is a two-seat, mid-wing, powered sailplane with camber changing flaps, t-tail unit, retractable landing gear, and provision for water ballast. The aircraft also has a retractable engine pylon that accommodates a Rotax 275 engine, designed for self‑sustaining flight. The engine pylon extension/retraction mechanism was powered by a 12 V lead-acid battery. The glider had front and rear canopies, each of which could be separately jettisoned in-flight by the pilot.

The major construction materials for the ASH-25E airframe included carbon fibre-reinforced polymer rebar in the wings and winglets, carbon and aramid fibres in the fuselage, hard foam sandwich in the fin, wings and control surfaces, and fibreglass in the winglets. The flight control cables were steel ropes, the long push rods were aluminium alloy, and the shorter push rods were steel.

VH-GOA was manufactured in Germany in 1988. In 2010, the pilot removed the Rotax engine and propeller and replaced them with two diesel‑fuelled Titan AMT gas turbine engines. Two 25 L collapsible fuel cells were installed into the wing root to supply the replacement engines. Information about the design standards, the cockpit and canopy, the engines, fire protection and maintenance is summarised below.

Design and airworthiness

Following the engine modification, the glider was re-classified as experimental, and listed as an ASH-25E (AMT Jet). This re‑classification meant there was no regulatory requirement for GOA to comply with existing design standards.

A special Certificate of Airworthiness (CoA) was issued in 2014 under the Civil Aviation Safety Regulations (CASR) Part 21.191 (i) Private Operation of a Prototype Aircraft for the purposes of research and development, showing compliance with regulations, exhibition and air racing. Under the CoA, the glider was expressly limited to using the jet engines for ‘sustainer flight’^[3] only. Once the glider was listed as an experimental aircraft, the aircraft could be modified, but operated under the GFA under Civil Aviation Orders (CAO) 95.4 Power-assisted sailplanes, powered sailplanes and sailplanes.

The Gliding Federation of Australia published the Manual of Standard Procedures (MOSP) Volume 3 Airworthiness Procedures and, under Section 2.6 Experimental Certificate, it outlined that:

Flying in an aircraft under an [Experimental Certificate] is entirely on the basis of voluntary acceptance of risk by the persons who elect to do so [and that person] should ensure they have sufficient knowledge to understand the nature of the risk...GFA promotes innovation and some member’s desire to build, modify and service their own aircraft.

EC’s may only be issued in accordance with CASR Part 21.191 to 21.195B. All ECs will clearly list the terms and limitations applicable to the allowed flight(s)…

Cockpit and canopy

The cockpit of GOA contained two seats, one behind the other. The pilot operated the glider from the front seat on solo flights. In addition to the standard instruments, installed equipment included two engine control unit (ECU) displays, a rear-facing camera (to see the engines when operating) and an ‘LxNav’ flight recorder.

A placarded canopy jettison release handle was positioned on the top right side of the instrument panel (Figure 5).

Figure 5: View from front seat in GOA’s cockpit

Source: Flight Manual, amended by the ATSB

Engine start system

The two vertically-aligned Titan AMT Netherlands gas turbine engines were installed on the existing dual-sided pylon. The Titan was constructed from a single radial compressor and an axial flow turbine stage (Figure 6). Fuel attachments on the front cowl of the engine, with Teflon tubing and push-in Polytetrafluoroethylene (PFTE) fittings were used. The engines were housed in the engine bay when not in use, and were raised as part of the one-switch start sequence.

The Titan engines’ fuelling and operating speed were controlled by the two electronic control units (ECUs), which also regulated performance, and were each powered by a lithium polymer battery. The ECU displays were fitted inside the cockpit (Figure 5). The engines’ ignition system was designed in a manner to prevent start-up when the pylon was lowered. In the event of an emergency, the flight manual recommended lowering the pylon, which would cause the fuel flow to stop immediately.

The ignition system for the engines comprised a disposable propane gas bottle installed in the engine bay. The specially developed ASH-25J Flight Manual for GOA contained further information on the propane system:

A disposable canister of propane connects to two solenoid operated valves which are controlled by the ECU. These valves are open only during the start up phase. PFAN tubing is used to carry the propane gas...Since the valves are open only during the start phase of the engine, the risk of gas release through ruptured hoses is minimised.

The engines were started sequentially. An electric starter would spin up the turbine, a glow plug activated, and propane was then fed into the engine. If the propane ignited successfully, the EGT would start to increase and the fuel pump would switch on. The solenoid valve to the propane was then closed.

Figure 6: Images of the engines fitted to GOA

Source: ASH-215J Flight Manual

The ATSB conducted a bench test on the fuel system plumbing, constructed from plastic tubing to confirm the product was fire-resistant. The test results showed that the tubing had high temperature resistance and did not support combustion.

ECU batteries

A dedicated rechargeable lithium polymer (LiPo) battery powered each engine’s running circuit. The batteries were situated at the rear of the cockpit along with the other ECU components, the lead‑acid battery, fuel lines, and other electrical leads and components (Item B in Figure 7). The fuel lines from the wing fuel cells were situated next to the batteries.

Thermal runaway describes an accelerating process whereby increased temperature releases energy that in turn further increases temperature. If defective, or handled improperly, some rechargeable batteries with sealed cells can explode during thermal runaway. The ASH-25J Flight Manual noted that ‘LiPo batteries are potentially dangerous’, and that it was important to ensure that they were protected from mechanical forces and the effects of heat due to their ‘high energy density’. The GFA investigation report for this occurrence stated that:

[LiPo batteries] can undergo thermal runaway…due to overcharge, over-discharge, over-temp, short circuit, mechanical damage…

Witnesses reported seeing the pilot removing the LiPo batteries after a flight the day before, and recharging them.

Fire protection

Sealed firewalls reduce the spread of fire and prevent the leakage of flammable substances, like propane gas or diesel, reaching the cockpit.

When lowered, the engines were accommodated within the fuselage tail boom (Figure 7, item A). Regarding the aircraft design, Schleicher confirmed that the ‘ASH-25E was not [originally] equipped with a forward firewall’ and it appeared that during the subsequent modification, one was not added. Schleicher also confirmed that ‘the factory-made engine compartment was primed with a fire protection paint’.

Between the engine housing and the shelf in the cockpit, there was an unobstructed opening through to the timber particle shelf (Figure 7, item B and C). In their investigation report, GFA stated that ‘it is likely that when the two stroke engine removal [was done], the electronic shroud cover and carbon fibre electronics bay were removed from the aircraft and not refitted.’ An inspection of the images of the particle shelf, and remnants of fuel lines, indicated that there did not appear to be any heat protective sleeves used.

Figure 7: Engine housing and cockpit (A. Engines – rear view, B. Cockpit area – rear view, C. Area between engine housing and particle shelf)

Source: Gliding Federation of Australia, with permission

The European Aviation Safety Agency (EASA) Certification Specification CS-22 Sailplanes and Powered Sailplanes (introduced in 2003) set design specifications applicable to the manufacturing of Schleicher gliders. Under Power-Plant Fire Protection, it outlined that:

The engine must be isolated from the rest of the sailplane by a firewall, shroud or equivalent means.

The firewall or shroud must be constructed so that no hazardous quantity of liquid, gas or flame can pass from the engine compartment to other parts of the sailplane…The firewall and shroud must be fireproof...

The materials accepted as fireproof included stainless steel (0.38 mm thick), mild steel sheet (0.5 mm thick), and/or steel or copper-based alloy firewall fittings.

The CASR 1988 Part 22 Airworthiness standards for sailplanes and powered sailplanes stated that the standards set out in EASA CS-22 were in force. The engineering report to support the experimental CoA stated that there was little risk of fire in the engine bay, as the engines were only able to operate in a raised configuration. That report did not document any specific consideration of compliance with the firewall requirements outlined in CS-22, although due to its experimental classification there was no regulatory requirement to comply.

Aircraft maintenance

General information

The special CoA stipulated that glider maintenance was to be conducted in accordance with the manufacturer’s recommendations, the requirements of the GFA Manual of Standard Procedures (MOSP) 3 and the Maintenance Manual ASH 25-J Turbo Engine Project. A review of the aircraft’s maintenance documentation indicated that there was no history of issues associated with the fuel system, batteries or engines.

Pre-flight maintenance issues

On the day before the occurrence, the pilot was observed performing ground testing on the glider’s engines. A video was also taken of the tests. Significant observations included:

• fuel pouring out of the lower engine on lowering (Figure 8, item A)
• significant engine flaming (Figure 8, item B)
• white smoke billowing from the lower engine (Figure 8, item C)

After shutting down the engines, the pilot was heard on the video commenting that the exhaust gas temperature (EGT) read 906C. The maintenance manual for the engines listed an EGT of 700 C as normal. Following the engine testing, the pilot took a passenger for a flight. The passenger reported that the pilot did not start the engines during the flight. After landing, the passenger helped the pilot with further engine testing.

The ATSB considered how the recorded fuel leak from the lower engine may have occurred, and consulted with gliding experts and the manufacturer. They advised that there may have been a leak within the fuel lines, or at the connection point between the PFTE tubing and the engine cowling. It was the manufacturers’ opinion that this can occur when the lines are roughly cut (for example using pliers).

It was evident from the video taken that the radial compressor on the lower engine was not rotating. Therefore, another possible source of the leak may have been the way the fuel flow was initiated. The system was designed to engage the fuel pump only when the engine speed reached a certain level. Therefore, it should not have been possible for fuel to flow while the compressor was not rotating.

Figure 8: Photographs from engine testing

Source: witness, with permission

Operational information

The ASH-25E flight manual listed operating limitations, including a ‘never exceed speed’ (VNE) of 151 kt. The normal operating speed range for the glider was between 52‑97 kt.

Pre-flight checks

According to the ASH-25J flight manual, a pre-flight inspection of the engines was required, including raising the engine pylon, inspecting all hoses for leaks, all electrical cables and connections for integrity, and checking the security of restraining wires and the engine bay floor for leaks. The GFA Inspector’s handbook for powered sailplanes stated that a daily walk-around was required, which included an inspection of the battery installation, instruments and radio, oxygen bottle and systems and powerplant, and a ‘check [that] there are no fuel or oil leaks’.

Witnesses, and others who knew the pilot, reported that he would often perform an engine run prior to departure, but they did not see him do so on the day of the occurrence.

In-flight engine use

In order to deploy and operate one or both of the engines in-flight, the pilot needed to:

• turn on the key switch
• activate the master circuit breaker
• move the engine pylon switch forward and wait till it had raised (which the pilot could see via a rear-facing camera) then, after seeing START CLEARANCE on the ECU,
• move one or both of the engine control switches forward to START/RUN and then open up the throttle once the ECU displayed STARTED UP.

The ASH-25J Maintenance Manual outlined that the engine’s pylon circuit was powered from the glider’s 12V battery, and triggered the START CLEARANCE on the ECU, without which the engines could not be started.

• Stopping the engines in flight was achieved by selection of a POWER DOWN switch. In an emergency, selection of the STOP/OFF position or movement of the pylon switch rearwards would instantly stop the fuel.

Recorded data

The ATSB recovered data from a flight recorder unit that the pilot had fitted to the canopy of GOA. The device was a LxNav Nano flight recorder, which is a 66-channel GPS receiver, altimeter and effective noise level sensor. The standard recording rate is once per second, and the unit was configured to automatically start recording once movement above 1 m/s was detected.

Medical and pathology

Post-mortem/toxicology reports and consultation with aviation medical experts identified that:

With regard to possible smoke inhalation, examination results ‘suggest that the deceased may not have had the chance to inhale the smoke related to the fire’.

The pilot suffered from advanced stage coronary artery disease at the time of the occurrence but there was insufficient evidence to determine if that may have influenced the development of the accident.

Survivability

Egress assist cushion

The pilot had designed his own egress assistance cushion to allow an easier in‑flight exit from the glider, particularly if the occupants needed to egress in the case of a mid-air collision. It consisted of two hermetically-sealed carbon dioxide cartridges from commercially-available life jackets that fed the gas through to an inflatable bag via a manifold and flexible hose (Figure 9). Using it required both hands – one to steady the pouch, and the other to manipulate a lanyard.

In the case of an emergency that required abandoning the aircraft, the pilot would jettison the canopy first, undo the seat harness, open the flap of the pouch to reveal a lanyard attached to the actuators, and then pull the lanyard to activate the flow of gas.

Due to the extent of fire damage, it could not be determined whether the pilot deployed the egress assistance cushion.

Figure 9: The components of the egress assist cushion

Source: ATSB

Pilot parachute

Glider pilots typically wear a parachute to exit a glider in an emergency. The passenger that the pilot had taken flying the day before recalled that they both wore a parachute, and the egress assistance cushions (described above) were in both the front and rear seats on the glider. Images from the wreckage indicated the pilot was wearing a parachute.

The most common minimum deployment height of parachutes typically worn by glider pilots was 500 ft AGL.

Site and wreckage

Wreckage location

The aircraft wreckage was located in a large burnt patch of grass on the property of Bathurst Soaring Club, about 445 m away from the threshold of airstrip runway 03. The wreckage trail was spread across about 125 m. Ground scars and evidence from the wreckage indicated that GOA impacted the ground in a nose-down, left wing configuration in a northerly direction, then rolled or tumbled after the initial impact and came to rest inverted. It was determined that the impact sequence was likely not survivable. The in-flight fire continued and spread to the surrounding area (Figure 10).

The shattered components of the canopy, as well as the GPS unit and flight recorder, were found on private property adjacent to Piper’s Field, about 440 m away from the fuselage.

Figure 10: Location of the wreckage on the Bathurst Soaring Club property

Source: ATSB

On-site examination

On-site examination of the severely fire‑ and impact-damaged fuselage, wings (Figure 11) and engines did not identify any obvious pre-existing faults that could have contributed to the accident. The wings, although destroyed in the post-impact fire, had all carbon fibre structures accounted for. The flap position at time of impact could not be determined. The engine pylon appeared to have been lowered at the time. A propane canister was found, but damage from the fire meant that it was not possible to determine whether it had contained any gas. The landing gear mechanism was found in the extended position, suggesting it had been lowered prior to the impact. The pilot was located within the wreckage around the area of the cockpit, although it could not be determined if he was secured in his seat.

A small number of components were retained for further examination and testing. The shattered components of the canopy’s Perspex were also examined. There was evidence of smoke residue on some of the shards (Figure 12) on the internal side of the canopy. There was also some residue on the forward third on the external side of the canopy’s ‘clearview’ hatch. These indicated that there was some smoke inside the cockpit, and it had passed through that hatch.

Figure 11: Wreckage of VH-GOA

Figure 12: Canopy in-situ (in a field adjacent to the Bathurst Soaring Club)

Source: ATSB

Related occurrences

The pilot and the same glider were involved in a previous occurrence reported to GFA. On that occasion, during the launch of the glider, the pilot ‘noticed abnormal engine readings and saw flames coming from the jet engine via the monitor.’ In response, the pilot shut down and then lowered the engine and continued the flight.

Other related occurrences

In 2007, GFA completed its investigation into an occurrence involving a Stemme model powered glider S-10, registration VH-ZVT involved in in-flight fire, which resulted in two fatalities. The investigation identified that at some stage before impact, the pilot jettisoned the canopy. The GFA also determined that the complex nature of the fuel systems on board, and the use of fuel lines that were not fireproof, would have allowed any leaking fuel to come into contact with engine‑related heat sources.

The United States National Transport Safety Board investigated an accident involving a Stemme S10-VT in Wisconsin on 14 July 2001. The pilot took off using the engine in its self‑launching capacity. Shortly after, the engine began running rough and smoke entered the cockpit. The pilot shut down the engine, initiated an emergency landing and exited the glider. Within five minutes of the engine failure, the aircraft was engulfed in flames. The fire originated in or around the engine compartment. Following that occurrence, it was recommended that certification standards require the evaluation of the engine compartment such that liquids, smoke and gases cannot pass freely between it and the cockpit, and for extinguishing systems be installed.

In 2017, the Air Accident Investigation Branch in the United Kingdom issued a special bulletin relating to a battery fire on board an HPH Glasflugel 304 eS powered sailplane. It was determined that there was insufficient warning to the pilot of a fire in the front electric sustainer (FES) battery compartment, and that fires behind the pilot are difficult to see. This reduced the time available for a pilot to make a decision about abandoning the aircraft by parachute. One of the recommendations was for the European Aviation Safety Agency to require manufacturers to install a FES warning system in all powered sailplanes to alert the pilot to fire or smoke.

__________

3. Sustainer flight: to sustain or extend the glider in flight including maintaining level flight or initiating a climb.

Sources and submissions

Sources of information

The sources of information during the investigation included:

• Alexander Schleicher
• the AMT Netherlands
• Bathurst Soaring Club and its members
• the Civil Aviation Safety Authority
• the Gliding Federation of Australia and members of the gliding community
• New South Wales Police
• Witnesses and neighbours of the Soaring Club.

References

AAIB, Special Bulletin S3/2017 on HPH Glasflugel 304 eS, G-GSGS, 25 September 2017, Air Accidents Investigation Branch United Kingdom

CASA, CASR Part 22 – Airworthiness standards for sailplanes and powered sailplanes, Civil Aviation Safety Authority

EASA 2003, Certification Specification CS-22 – Sailplanes and Powered Sailplanes, European Union Aviation Safety Agency

NTSB, Docket CHI01LA216, accident involving a Stemme S10-VT in Wisconsin on 14 July 2001, National Transport Safety Board

Submissions

Under Part 4, Division 2 (Investigation Reports), Section 26 of the Transport Safety Investigation Act 2003 (the Act), the Australian Transport Safety Bureau (ATSB) may provide a draft report, on a confidential basis, to any person whom the ATSB considers appropriate. Section 26 (1) (a) of the Act 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 Gliding Federation of Australia and the Civil Aviation Safety Authority.

Submissions were received from the Gliding Federation of Australia and the Civil Aviation Safety Authority. The submissions were reviewed and, where considered appropriate, the report was amended accordingly.

Safety action

Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following proactive safety action in response to this occurrence.

The Gliding Federation of Australia

As a result of this occurrence, and others throughout the gliding and recreational aviation sectors, GFA advised the ATSB that on 11 March 2019, GFA published an Airworthiness Advice Notice (AAN), and on 15 March 2019 published an Airworthiness Directive (AD), both entitled Engine Fire Containment and Retardation. The affected aircraft types included all self-launching and power‑assisted sailplanes, including those fitted with jet engines.

The AAN stated that:

…many instances have been found of potential fire hazards in the form of fuel leaks, oil leaks and deficient exhaust systems. Instances found of fires starting, then self-exhausting. Adding to the mix are some powered sailplane types that may not fully meet the fire protection standards…’

The AAN outlined the fire protection standards from EASA publication CS-22 (summarised in the Context section of this report), the engine installations of key concern (including the ‘fully buried’ engine such as GOAs), and the risks of defects in any fire retarding paint. Intumescent paint was suggested for use, which is ‘a paint cover which, when heated, expands [to shelter] the material it is covering, from heat and combustion...’ Glider pilots were also encouraged to consider the effects of airflow on fire propagation, and used a diagram of the ASH 25E (Figure 13). Lastly, the AAN covered pilot actions in the case of an engine fire, with the key advice being to shut off the fuel supply and contain the fire.

Figure 13: ASH 25E diagram displaying pressure, airflow in and out of the airframe

Source: Gliding Federation of Australia  

The AD provided pilots with inspection guidelines and procedures to meet a minimum standard for fire containment and retardant. Before 30 June 2019, all glider operators and inspectors needed to complete a Form 2 inspection, inspect the condition of fire retardant paint, determine the configuration of the firewall(s), and provide the Inspection Schedule to GFA. By 30 November 2019, all paint deficiencies were required to be rectified. All subsequent inspections then needed to include a paint inspection, and also an assurance that no flammable material is attached to the cockpit side of the firewall. If the glider cannot be fitted with a firewall, a ‘strong case for non compliance’ must be made to GFA.

Findings

From the evidence available, the following findings are made with respect to the collision with terrain on the experimental ASH-25E glider, registered VH-GOA that occurred 13 km west‑north‑west of Bathurst Airport (Piper’s Field) on 21 January 2018. These findings should not be read as apportioning blame or liability to any particular organisation or individual.

Contributing factors

• Shortly after launch, an in-flight fire commenced near the engine housing. The ignition source of the fire could not be determined due to severe post-impact fire damage.
• The pilot was probably attempting to return the burning glider to the airfield when it departed controlled flight and collided with terrain.
• The pilot had the necessary equipment to make an emergency exit from the glider and escape the effects of the fire. He jettisoned the glider's canopy but possibly due to incapacitation, did not exit.

Other factors that increased risk

• The glider's cockpit and engine housing were not separated by a firewall. This limited containment of the in-flight fire, resulting in greater exposure of the pilot to fire/smoke and reduced egress time.

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 2019 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.

What happened

On 23 March 2017, a Gippsland Aeronautics GA-8 aircraft, registered VH-AJZ, was being used to conduct incendiary bombing aerial work operations^[1] in the Prince Regent River area of northern Western Australia (WA). On board were a pilot, a navigator seated in the co-pilot seat and a bombardier in the rear of the aircraft cabin.

While conducting the incendiary bombing operations, the bombardier advised the pilot that he was suffering from motion sickness. The pilot elected to land at Gibb River aircraft landing area (ALA), WA, to take a lunch break and provide the bombardier with time to recover from the motion sickness.

At about 1255 Western Standard Time (WST), the aircraft landed on runway 07 at Gibb River. During the landing roll, the engine failed. The aircraft had sufficient momentum to enable the pilot to turn the aircraft around on the runway and begin to taxi to the parking area at the western end of runway 07. Shortly after turning around, the aircraft came to rest on the runway. The pilot attempted to restart the engine, but the engine did not start. The pilot waited about 10–20 seconds before again attempting to restart the engine.

While attempting the second restart of the engine, the pilot heard a loud noise similar to that of a backfire. The navigator then observed flames and smoke coming from around the front of the engine and immediately notified the pilot. After being notified of the fire, the pilot immediately shut down the engine and switched off the aircraft electrical system.

As the pilot switched off the aircraft electrical system, the navigator located the aircraft fire extinguisher and evacuated from the aircraft through the co-pilot door. After evacuating from the aircraft, the navigator observed fire on the aircraft nose wheel. The navigator had difficulty preparing the fire extinguisher for use and was unable to discharge the fire extinguisher onto the fire.

While the navigator was attempting to extinguish the fire, the pilot exited the aircraft through the pilot door and assisted the bombardier to exit the aircraft. After assisting the bombardier, the pilot moved to the front of the aircraft to assist the navigator with the firefighting. The pilot was able to activate the fire extinguisher and extinguished the fire on the nose wheel. The pilot observed fire continuing to burn within the engine compartment. Due to the heat of the fire, the pilot was unable to access the engine compartment to extinguish this fire. The pilot determined that no more could be done to contain the fire, and therefore, the pilot, navigator and bombardier moved clear of the aircraft to a safe location as the fire continued.

The crew members were not injured. As a result of the fire, the aircraft was destroyed (Figure 1).

Figure 1: VH-AJZ wreckage

Source: Operator

Pilot comments

The pilot of the aircraft provided the following comments:

• The temperature at Gibb River at the time of the landing was about 33–34 °C.
• There were no abnormal engine indications prior to the engine failing.
• The engine failed in a manner similar to a normal engine shutdown. The pilot had not experienced an engine failure in that manner before.
• The electric fuel pump remained on after landing and throughout the attempted starts. During the attempted starts, the pilot ‘cracked’ the throttle and advanced the mixture lever while cranking the engine. Between the first and second start attempts, the mixture control was selected to idle cut-off.
• When assisting the bombardier to evacuate, one box of incendiary capsules was removed, however, three or four boxes remained in the aircraft.

Chief pilot comments

The operator’s chief pilot provided the following comments:

• Due to the significant fire and heat damage, the cause of the fire could not be determined (Figure 2).
• When taxiing in high ambient temperatures and at low power settings, fuel may vaporise within the mechanical engine fuel pump, and this can lead to the engine failing. When operated in these conditions, the aircraft should be taxied with the electric fuel pump on to prevent fuel vaporisation.

Figure 2: Fire damage to engine

Source: Operator

Engine fire during start emergency procedure

The GA-8 emergency procedures included the ‘engine fire during start emergency procedure.’ In case of an engine fire during start, the procedural steps to be followed are shown in Figure 3.

Figure 3: GA-8 fire during start on ground emergency procedure extract

Source: Mahindra Aerospace

After the fire was detected, the pilot shut down, rather than continued cranking the engine. After the engine was shut down, the fuel shutoff valve was not selected off.

Safety analysis

The extent of damage to the engine and aircraft prevented the reasons for the engine failure being determined.

The presence of fire on the nose wheel below the engine indicates that the fire was probably fed by a fluid. However, the extent of damage to the engine prevented the reason of the fire being determined.

After identifying the engine fire, the engine was shut down, and cranking was not continued in accordance with the emergency procedure. Cranking the engine may have extinguished the fire before it became unmanageable. After the engine was shut down, the fuel shutoff valve was not closed to provide a barrier between the fuel tanks and the engine. Not completing this step of the engine fire during start emergency procedure increased the likelihood of fire and allowed the fire to intensify.

Findings

These findings should not be read as apportioning blame or liability to any particular organisation or individual.

• The cause of the engine failure and fire could not be determined.
• After the fire was identified, two steps in the emergency procedure were omitted. This included not closing the fuel shutoff valve, which likely resulted in the fire not being extinguished and subsequently intensifying.

Safety Action

Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following proactive safety action in response to this occurrence.

Aircraft operator

As a result of this occurrence, the aircraft operator has advised the ATSB that they are taking the following safety actions:

Retraining

• The pilot has completed retraining with an emphasis on fire procedures.

Safety message

This investigation highlights the importance of knowing and understanding flight manual normal and emergency procedures. In this accident, steps in the engine fire during start procedures were omitted. When facing a situation as serious as a fire, the published emergency procedures provide the foundation for emergency response management.

Aviation Short Investigations Bulletin - Issue 62

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 2017 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.

 __________

1. Incendiary bombing operations is a method of fire hazard reduction using devices dropped from the aircraft that start fires to conduct controlled burns.

What happened

On 21 June 2016, a Qantas Airways Boeing 747-438 aircraft, registered VH-OJS, operated flight QF11 from Los Angeles, California, United States to New York, New York, United States.

At about 0700 Coordinated Universal Time (UTC), a cabin crewmember responded to a request for assistance from a passenger seated in business class seat 3A. The passenger advised the crewmember of a missing personal electronic device (PED). The PED was identified as containing a lithium type battery. The crewmember, along with the passenger, searched around the seat for the missing PED. While searching, the seat position was moved. As the seat moved, the passenger in the next seat observed the PED within the seat mechanism. The seat was then inadvertently moved, resulting in the PED being crushed (Figure 1). The crushed PED immediately began hissing and emitting smoke. Moments later, the PED ignited. A second crewmember then initiated the basic fire drill.

The second crewmember obtained a fire extinguisher, and as they proceeded toward seat 3A, they advised a third crewmember of the incident and requested assistance. This crewmember also obtained a fire extinguisher and proceeded toward seat 3A. The customer service manager (CSM) and another crewmember observed the activity and also followed, providing additional support.

When the cabin crewmembers carrying fire extinguishers arrived at seat 3A, they observed an orange glow emanating from the seat. A crewmember discharged a fire extinguisher into the seat, extinguishing the glow. At this time, the CSM acted as a communicator with the flight crew to inform them and keep them updated on the incident.

After confirming the PED fire had been extinguished, the cabin crew attempted to remove the PED in order to place the device in water, in accordance with lithium type battery fire procedures. The PED could not be removed without further damage and risk of fire. Therefore, the cabin crew elected to leave the device in place and position a crewmember with a fire extinguisher near seat 3A for the remainder of the flight. About 10–15 minutes after the incident, this crewmember identified further heat coming from the crushed PED. They again discharged the fire extinguisher onto the PED, eliminating the heat.

After confirming the incident was contained, the CSM advised the captain that the situation was under control. The captain discussed the incident with the first officer and considered the event had been dealt with appropriately. The flight proceeded to New York and landed about 40 minutes later without further incident.

Two passengers reported feeling unwell after the event, but it was unclear if this was as a result of the incident. The aircraft seat sustained minor damage.

Figure 1: Crushed PED after removal from seat

Source: Qantas

Cabin crew comment

The responding cabin crewmember commented that the provision of designated storage close to the charging port could assist in preventing PEDs entering seat structure.

Passenger comment

The passenger in seat 3A commented that the amenities pack provided to passengers in this seat type could be changed to include PED storage. This could assist preventing PEDs entering the seat structure.

Operator investigation report

The aircraft operator investigated the incident and provided a copy of their investigation report to the ATSB. The report included the following:

A review of reported events revealed 22 similar occurrences of trapped or crushed PEDs. Seven of these occurrences resulted in smoke and/or heat being produced. This incident was the first event to result in fire.

• The investigation determined that the likely area for the PED to intrude into the seat mechanism was adjacent to the seat belt anchor point. This area becomes more exposed as the seat reclines towards the flat position.
• Mesh netting within the seat structure is designed to capture objects that fall behind the seat. Damage to seat 3A consisted of an approximate 5 cm melt area to this mesh netting. There was no other damage noted to the seat structure.

Lithium battery thermal runaway

The United States Federal Aviation Administration (FAA) document Safety alert for operators SAFO 09013: Fighting fires caused by lithium type batteries in portable electronic devices, and the associated document SAFO 09013 Supplement, detail the risk of thermal runaway in lithium type batteries:

• Lithium batteries are capable of ignition and subsequent explosion due to overheating. Overheating may be caused by shorting, rapid discharge or overcharging. Overheating results in thermal runaway, which is a chemical reaction within the battery causing the internal temperature and pressure to rise. The result is the release of flammable electrolyte from the battery and, in the case of disposable lithium batteries, the release of molten burning lithium. Once one battery cell goes into thermal runaway, it produces enough heat to cause adjacent battery cells to also go into thermal runaway. This produces a fire that repeatedly flares up as each battery cell in turn ruptures and releases its contents.

SAFO 09013 Supplement also details the following information on fighting fires caused by lithium type batteries:

• Relocate passengers away from the device.
• Utilise a halon, halon replacement, or water fire extinguisher to prevent the spread of the fire to adjacent battery cells and materials.
• Pour water, or other non-alcoholic liquid, from any available source over the cells immediately after knockdown or extinguishment of the fire.
• Only water or other non-alcoholic liquid can provide sufficient cooling to prevent re-ignition and/or propagation of the fire to adjacent batteries. Water, though it may react with the tiny amount of lithium metal found in a disposable battery, is most effective at cooling remaining cells, stopping thermal runaway and preventing additional flare-ups. Significant cooling is needed to prevent the spread of fire to additional cells in a battery pack.

Safety action

Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following proactive safety action in response to this occurrence.

Seat manufacturer

As a result of this occurrence, the aircraft operator has advised the ATSB that the seat manufacturer is developing design solutions to prevent ingress of PEDs into the seat structure.

Aircraft operator

The aircraft operator has advised the ATSB that they are taking the following safety actions:

Changes to passenger briefings

An enhanced passenger briefing has been released to include:

If you lose your electronic devices at any time, it’s important you don’t move your seat as this could severely damage your device and may be a fire hazard. Please contact a crew member who will be able to recover your device.

A cabin crew service brief has been released which includes:

Passenger announcement to remind passengers not to move seats when devices have been lost.

Individual interactions between cabin crew and passengers when preparing the bed to include a discussion to raise passenger awareness of the possibility that the PED could be crushed if it is lost during the flight.

Establishment of working group

A working group has been established to develop further solutions for this issue.

Safety message

This incident serves as an excellent example of an effective response to an emergency situation. The cabin crew quickly implemented the basic fire drill procedure. This defined the roles and responsibilities of the responding crew, enabling a rapid and coordinated response to the incident using all available resources. As a result, the incident was quickly and effectively contained. The effective implementation of this procedure also ensured the flight crew were kept informed as the situation developed.

This incident also highlights the hazards of transporting lithium-ion battery powered PEDs aboard aircraft. The Civil Aviation Safety Authority has released information on the safe carriage of lithium type battery powered devices aboard aircraft in the web page: Travelling safely with batteries and pamphlet: Is your luggage safe?

Aviation Short Investigations Bulletin- Issue 52

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 2016 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.