Fire

The pilot reported that, on approaching top of descent, the flight attendants noticed smoke coming from the rear toilet.

Investigation revealed a small fire in the rear toilet waste bin. The fire was extinguished by crew using water and BCF fire extinguishers. A normal approach and landing was carried out at Maroochydore.

Passengers were subsequently interviewed by Queensland Police but neither the cause of the fire nor the person responsible could not be identified.

The burnt material appeared to be a small quantity of rolled up tissue paper.

In cruise at 10,000 ft the pilot noticed the left alternator light had illuminated, and that the right alternator was now taking all electrical loads. The left engine power then reduced from 31hg to 23hg, suggesting to the pilot that the turbo-charger was malfunctioning. As the aircraft was now unable to maintain its cruise altitude the pilot requested a descent to 7,000 ft. He also requested an airways clearance to return to Parafield.

He changed the left fuel tank selection from the main to auxiliary and turned the left fuel boost pump on. This restored engine power for a short period of time before it suffered a complete failure, followed by a complete loss of electrical power and smoke entering the cabin.

The pilot feathered the left propeller and turned the fuel selector and all electrical switches off. He maintained communications with Adelaide FIS using a mobile telephone. A successful single engine landing was made after the pilot manually extended the landing gear.

An investigation indicated that the alternator field wire had chaffed on the engine fuel supply line, wearing through its insulation which allowed the barbed wire to then arc on the line, eventually burning a hole through it. The ensuing loss of fuel supply through the hole, with associated loss in fuel pressure, contributed to the reduction of engine power. Activation of the fuel boost pump assisted in restoring some pressure, and power.

Fuel spraying from the holed line was ignited by the arcing alternator field wire, causing fire damage to the wing leading edge skin, wing structure rear of the firewall, oil pressure, hydraulic and fuel supply lines, and the nacelle fuel tank and vent lines. The electric loom between the engine and cabin had the insulation burnt off, allowing it to short circuit and cause the electrical failure. The magneto earth wires, being part of this loom, and also bared of insulation, grounded both magnetos, shutting down the engine.

The engine failing due to the grounded magnetos, and the pilot's action of turning the fuel off, probably deprived the fire of fuel before it became established, and self-extinguished.

The helicopter was dropping incendiary bombs, from 100 feet above ground level, as part of a controlled bush burn. Prior to take-off the pilot had placed his flying jacket between the rear of the pilot's seat and the incendiary delivery machine.

During an incendiary dispatch run the exit chute became detached from the incendiary machine body allowing ignited bombs to fall inside the aircraft. One of these bombs set fire to the pilot's jacket and this along, with the burning incendiaries, filled the cabin with dense black smoke.

Despite the fact that the passengers opened their doors the dense smoke prevented the pilot from seeing anything either inside or outside the helicopter. He elected to land the aircraft immediately so the crew could extinguish the fire.

During the unsighted landing in dense scrub the helicopter collided with a number of trees.

It was reported that the clamp attaching the exit chute to the machine body had been secured normally prior to departure. The clamp design relied on friction only, to keep the chute in place. It is probable that natural helicopter vibration was sufficient to overcome the friction allowing the chute to separate. Once the chute separated, ignited incendiary balls were free to roll around inside the aircraft and set fire to the jacket.

The design of the incendiary machine did not include any means of restricting the movement of the incendiary balls should they fall out of the machine. It was believed that the balls, which were only armed after they had entered the delivery system, could not escape.

For the same reasons it was not believed that flammable material might be in danger if it was stored near the machine and consequently there were no restrictions and no placards prohibiting such storage.

Safety Action

Immediately following the accident, the Bureau of Air Safety Investigation advised the owner of the incendiary equipment that the following modifications would improve the safety of the system.

1. A clearly visible placard should be fitted to the incendiary machine indicating that objects should not be stored in its vicinity.

2. The chute attachment should be redesigned to make it more positive.

3. A fail-safe system be designed to catch loose incendiaries. It is suggested that a metal tray, with sides, located under the dispensing machine would probably meet all requirements.

The operator withdrew all similar incendiary dispensing devices from operations until the defects had been corrected. Redesign and modification of the devices has been completed, and the machines have been returned to service.

On 26 February 2014 at about 1645 Central Standard Time (CST), a Beech 58 aircraft, registered VH-SBS, departed Darwin for Gove, Northern Territory, on a private ferry flight with a supervising pilot and pilot-in-command-under-supervision (ICUS) on board.

At about 1815, the crew detected fumes and smoke emanating from the left side circuit breaker panel. The pilot ICUS immediately switched off the electrical master switch. The supervising pilot seated in the right seat took control of the aircraft and commenced an immediate descent. The pilot ICUS retrieved the BCF extinguisher from underneath his seat and extinguished the fire.

The crew opened the vents and the fumes dissipated. To determine what electrics were available, the pilot selected the master switch on. The fire then reignited and he immediately selected the master switch off. The crew established that the most likely cause of the fire was an electrical malfunction, and opted to continue the remaining 40 NM to Gove aerodrome, where emergency services were available on the ground if required.

The crew observed that both suction indicators showed zero. They increased their lookout for other aircraft, cognisant that they were no longer able to maintain radio contact.

After joining downwind for runway 31, the crew briefly selected the master switch on and used the electric gear lever to lower the landing gear. They could smell fuel so the pilot conducted a closer circuit than normal and landed the aircraft. After parking the aircraft, the crew observed fuel dripping from beneath the aircraft fuselage.

An engineering inspection found that exhaust gas temperature (EGT) wiring had penetrated through the heater supply fuel line causing it to arc out and burn a hole in the fuel line.

This incident provides a valuable reminder for all pilots to know the location and operation of the aircraft fire extinguisher.

Aviation Short Investigations Bulletin - Issue 29

On 15 October 2013, the pilot of a Robinson R44 helicopter, registered VH-TZE, was conducting gravity survey work, north of Daly Waters, Northern Territory. On board were the pilot and a geophysical field technician. The survey consisted of landing about every 4 km along a planned grid to collect data. 

At about 1630 Central Standard Time (CST), the pilot conducted a routine landing at a designated grid point. The technician disembarked with his equipment to carry out a reading, about 5 m away from the helicopter. 

A short time later, the pilot saw the technician waving his arms in an attempt to gain his attention. The pilot looked toward the rear of the helicopter and saw a fire underneath, which was spreading into the engine bay. The pilot exited the helicopter and notified the landholders via phone so they could construct fire breaks to contain the ensuing grass fire. The occupants were uninjured; however, the helicopter was destroyed by the fire.                 

The Australian Transport Safety Bureau (ATSB) has been notified of 13 occurrences since 2000 where a helicopter has been destroyed by grass fire, with many reports highlighting the speed with which the grass ignited and the fire spread beyond control.

Robinson R22 and R44 helicopters have exhaust systems that are low to the ground. The Pilot Operating Handbook for both types has a note in Section 10, Safety Tips stating:

‘Do not land in tall dry grass. The exhaust is low to the ground and very hot; a grass fire may be ignited.’

Pre-flight briefings highlighting the dangers of landing on grass, especially in areas of high temperatures and low humidity, can reinforce the importance of carefully choosing a landing site.

Aviation Short Investigations Bulletin - Issue 29

On 19 June 2012 at about 1645 Central Standard Time, a Eurocopter AS-350BA helicopter, registered VH-HEB (HEB), was en-route from Ceduna to Border Village, South Australia when abnormal fumes were detected in the cockpit. The pilot conducted an emergency landing. Once on the ground, the passenger exited the aircraft and noticed smoke and fire emanating from the aft cargo compartment. The pilot and passenger left the vicinity of the helicopter, which was subsequently destroyed as a result of the fire. This accident highlights the importance of having appropriate practices and procedures in place for the transport of dangerous goods and conducting remote area operations.

Aviation Short Investigation Bulletin – Issue 14

On 12 September 2011, a Robinson Helicopter Co. R44 Astro helicopter, registered VH-HBA, departed Heartbreak Hotel, Northern Territory, for a local scenic flight with one pilot and three passengers onboard.

The pilot conducted a thorough safety brief prior to departure. Shortly after take-off, and at about 1,500 ft above ground level, the engine fire warning light illuminated. The pilot commenced a descent to carry out a precautionary landing. Shortly before touchdown the engine oil pressure light illuminated, and the pilot observed a rapid loss of oil pressure. 

After landing, the pilot observed flames originating from under the engine cowling at the rear of the helicopter. All three passengers evacuated the helicopter. The helicopter was subsequently destroyed due to fire.

An engineering inspection could not determine the cause of the fire.

This incident highlights the importance of thorough pre-flight safety briefs. The brief assisted the passengers in being able to exit the helicopter quickly. The pilot also commented that emergency equipment stored under the seat was difficult to access in a fire. Future consideration would be given to placing this equipment in a more accessible location.

The aircraft was on climb towing a glider when the pilot saw smoke and flames around the left rudder pedal area. The glider was released and the pilot landed the aircraft in a paddock. He abandoned the aircraft before it was destroyed by fire. Because of the severity of damage the cause of the fire could not be determined. It was established that the fire melted fuel lines in the cockpit walls and fuel released then fed the fire which completely gutted the aircraft.

The pilot was stock-spotting with both side windows of the aircraft open. He noticed smoke trailing from the aircraft, and saw that some towelling material and a chamois were smouldering under the rear seat. He closed the windows to reduce the flow of air to these articles and proceeded to select a suitable landing area. In the meantime, smoke in the cabin forced him to open a side window again, resulting in the smouldering material bursting into flame. He attempted to douse the flames with water from his water bottle with little success. During the landing on a flat-topped hill, he had to keep his head out the window for visibility. The aircraft bounced several times and overturned. The pilot was knocked unconscious for a period of about five minutes. When he regained consciousness he released his harness and extinguished the remnants of the fire with the aircraft's extinguisher. He believes the loose extinguisher struck him on the head during the overturn sequence. This accident was not the subject of an on-site investigation.

The pilot was carrying out a check of the station windmills prior to commencing mustering operations. About 15 minutes after DEPARTURE he reported that an acrid smelling gas entered the cabin. He turned off the radios, the master switch and closed the cabin air vent and diverted to the nearest suitable strip. Enroute the acrid smell intensified and as the pilot was having trouble breathing he decided to land the aircraft in a nearby clearing. The throttle was closed in an endeavour to reduce the fumes but reapplied when this was not successful. However, the engine did not respond and the aircraft was landed short of the cleared area. During the landing roll the aircraft collided with trees. Following the last engine start the starter relay contacts remained closed due to internal corrosion, this resulted in the motor continuing to operate. The continuous operation of the starter produced enough heat to melt the non-standard engine earth strap at the attachment point to the firewall. Earth was then made through the tachometer cable and magneto switch leads, which overheated and burnt causing the magnetos to earth and the engine to subsequently fail.