Post-Crash Fires

Post-Crash Fires

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Definition

Post-crash fires are fires which occur after an aircraft has crash landed or has impacted obstacles or other aircraft during ground movement, runway incursion, or runway excursion.

Description

In the event of an impact with the ground or an obstacle that results in structural damage to an aircraft, a fuel-fed fire can start if fuel comes into contact with ignition sources. Equally, if flammable material, carried as dangerous goods on a civil aircraft or as cargo by a military aircraft, is damaged or the containment compromised, it may ignite as a consequence of impact, contact with hot surfaces or, in the case of spillage of unstable chemicals, the atmosphere.

Fire can spread quickly to the fuselage and through the cabin generating heat, smoke, and toxic decomposition products. If the temperature of trapped smoke and gasses reaches the auto-ignition temperature, flashover will occur and an aircraft fuselage can be rapidly engulfed by flames.

Effects

Depending upon the severity of the crash and any resulting fire, the effect on the aircraft can vary from minor damage to total hull loss. Similarly, the potential casualty consequence of a crash/fire event ranges from no injuries to the loss of life of all on board. Collateral damage and casualties are possible dependent upon the location of the crash.

For aircraft with a maximum certified takeoff weight of 5700 kilograms or less, post-impact fire contributes significantly to injuries and fatalities in accidents that are otherwise potentially survivable.

Defences

  • Aircraft Design. Aircraft structures and fuel systems can be designed to minimise the quantity of fuel spillage
  • Fuel - Virtually all large passenger aircraft burn jet fuel and not AVGAS. The much higher flashpoint of jet fuel reduces the potential for a post-crash fire.

Solutions

  • Preparation of the aircraft - where the crash landing is anticipated, for example if an off-field landing is necessary or the aircraft has a landing gear malfunction, then there are several things that can be done to reduce the probability and severity of a fire:
    • Dump Fuel - if time and aircraft design allow, dump to reduce the amount of fuel and improve the handling of the aircraft. For aircraft not fitted with fuel dump capability, the aircraft can loiter in the vicinity of the landing airfield to burn gas. Note that, in the case of an onboard fire, smoke, or fumes, any delay to landing the aircraft, inclusive of dumping fuel, should not be considered.
    • Isolate fuel systems - close crossfeed valves.
    • Cabin - Prepare the cabin for emergency landing.
    • Cargo - Jettison flammable cargo if possible and practical.
  • Aircraft Evacuation - Expeditious emergency evacuation of the aircraft will minimise the loss of life in the event of a post crash fire. Consequently, robust training of the cabin crew in evacuation procedures is essential.
  • Engine Shutdown & Aircraft Systems - To minimize the potential for injury during the evacuation, the flight deck crew will take all necessary actions to shut down and, using fire handles, condition levers, or fire push button (depending on aircraft type) isolate the aircraft engines. Depending upon the degree of damage to the aircraft, this may not always be possible.
  • Rescue and Fire Fighting Services - Rescue and Fire Fighting Services (RFFS) are instrumental in saving lives and minimizing the damage from a post-crash fire. If the crash occurs within the airfield boundaries, the initial RFFS response units will be on site within a very short period of time; often less than a minute. Response to an off-airfield crash may take considerably longer due to the time it may take to locate the crash and to the accessibility of crash site.

Contributing Factors

Large amounts of fuel can be carried by modern aircraft, and an aircraft crash has the potential to rupture the fuel tanks. Should the spilling fuel be exposed to a spark or open flame a fire may occur. This is particularly true of fuels with low flashpoints such as AVGAS. While jet fuels have a higher flashpoint and are less susceptible to sparks, exposing them to operating engines or to hot engine components may raise the temperature of the fuel to its auto-ignition point and a fire will result.

Accidents and Incidents

A selection of incidents from the SKYbrary database related to Post Crash Fire:

E50P, Paris Le Bourget France, 2021

On 8 February 2021, an Embraer 500 Phenom 100 (9H-FAM) crew lost control of their aircraft shortly before the intended touchdown when it stalled due to airframe ice contamination. The resulting runway impact collapsed the nose and main gear, the latter causing fuel leak and resultant fire as the aircraft slid along the runway before veering off it. The Investigation found that flight in icing conditions during the approach had not been accompanied by the prescribed use of the airframe de-icing system and that such non compliance appeared to be routine and its dangers unappreciated.

AT75, vicinity Pokhara Nepal, 2023

On 15 January 2023, an ATR 72-500 positioning visually for an approach to Pokhara suddenly departed controlled flight and impacted terrain. The aircraft was destroyed by the impact and all 71 occupants were killed. A type-experienced Training Captain was overseeing new airport familiarisation for a Line Captain acting as Pilot Flying. The Training Captain unintentionally feathered both propellers in response to a call for Flaps 30 but did not recognise their error or respond to calls that no power was coming from the engines. The airline’s operational safety-related processes and Regulatory oversight of them were both assessed as comprehensively inadequate.

AS50, manoeuvring, Kauai Hawaii USA, 2019

On 26 December 2019, an Airbus Helicopters AS350 on a commercial sightseeing flight over the Hawaiian island of Kauai impacted terrain and was destroyed killing all seven occupants. The Investigation concluded that the experienced pilot had decided to continue the flight into unexpectedly encountered cloud contrary to Company Policy. Contributory factors were identified as the delayed implementation of a Hawaiian aviation weather camera programme, an absence of regulatory leadership in the development of a weather training program for Hawaiian air tour pilots and an overall lack of effective regulatory monitoring and oversight of Hawaiian air tour operators’ weather-related operating practices.

DHC6, en-route, south southwest of Jomsom Nepal, 2016

On 24 February 2016 a DHC6 (9N-AHH) on a VFR flight to Jomsom which had continued towards destination after encountering adverse weather impacted remote rocky terrain at an altitude of almost 11,000 feet approximately 15 minutes after takeoff after intentionally and repeatedly entering cloud in order to reach the destination. The aircraft was destroyed and all on board were killed. The Investigation attributed this to the crew’s repeated decision to fly in cloud and their deviation from the intended route after losing situational awareness. Spatial disorientation followed and they then failed to respond to repeated EGPWS cautions and warnings.

AS50, manoeuvring, southwest of Alta Norway, 2019

On 31 August 2019, all six occupants of an Airbus AS350 B3 being used for a sightseeing flight in northern Norway were killed after control was suddenly lost and the helicopter impacted the terrain below where the wreckage was immediately consumed by an intense fire. The Investigation found no airworthiness issues which could have led to the accident and concluded that the loss of control had probably been due to servo transparency, a known limitation of the helicopter type. However, it was concluded that it was the absence of a crash-resistant fuel system which had led to the fatalities.

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Categories
Fire Smoke and Fumes, Post Crash Fires, Cabin Safety

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