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|Category:||Fire Smoke and Fumes|
A fire which occurs on an aircraft outside of the cabin, for example on the wings.
Fire in the air is one of the most hazardous situations that a flight crew can be faced with. A fire can lead to the catastrophic loss of that aircraft within a very short space of time. Once a wing fire has become established, it is unlikely that the crew will be able to extinguish it.
The article "In-Flight Fire" deals with the subject of fire on board an aircraft, particularly hidden fires. This article considers the quite different subject of external fires, specifically wing fires, which are thankfully less common but equally as dangerous and about which there is very little guidance for crews.
Most modern aircraft carry the majority of their fuel in wing tanks. If those fuel tanks or the associated pipes leak, or they are damaged, and fuel comes into contact with an ignition source, then fire can break out within, on, or under, the wing. While this article is titled "Wing Fire", the discussion is equally applicable to fires associated with tail mounted engines, undercarriage bays, and bomb bays - external to the cabin and usually inaccessible to the crew.
It should also be born in mind that whilst the liquid fuel that is often the primary cause of continuing wing fires, the risk of fuel-related ignition is generally considered to be much greater in respect of the fuel vapour which is given off by liquid fuel in the presence of adjacent free space, particularly if this is a confined space such as the ullage of partly filled fuel tanks.
Heat. Heat from wing fires will affect aircraft systems, cause deformation of wing surfaces and ultimately affect the structural integrity of the aircraft leading to Loss of Control.
Airworthiness. This, and related articles, do not consider the aspects of aircraft design which reduce the risk of in-flight fires, just the general principles and issues related to the safety of a flight once fire has broken out.
A fire is detected on an outboard engine. The crew carry out the appropriate emergency drills, shutting down the engine, cutting off fuel and electrical supply to the engine, and firing extinguishant into the engine, but the fire warning remains. The cabin crew confirm that there are flames visible behind the number 1 engine. The Captain declares a MAYDAY and initiates an immediate maximum rate descent and diversion to the nearest airfield. On landing, the pilot brings the aircraft to a halt, having turned the aircraft such that the burning wing is downwind, and orders an immediate evacuation.
Engine Fire. An engine fire is normally detected and extinguished satisfactorily by the fire detection and extinguishing systems. However, if an associated engine failure or malfunction is explosive to the extent that it is not contained within the engine casing, then a fire may spread to the wing and/or fuselage.
- Detection & Confirmation. First indications of a wing fire may come from onboard systems, physical shock (from an explosion or impact), or observation. Clear communication between flight deck crew and cabin crew is essential. The cabin crew should check for signs of fire and continue to keep the captain informed of the development of any fire until the aircraft is safely on the ground. In some situations it may not be possible to see the fire, particularly if it is under the wing or in the undercarriage bay. In such circumstances, and depending on the stage of flight and location of the aircraft, it may be possible to ask other aircraft or an air traffic control tower to confirm the existence of the fire. Monitor aircraft systems, skin temperature in the vicinity of the suspected fire (if crew can gain access) and, if a fire is confirmed or suspected:
LAND AS SOON AS POSSIBLE
- Descent & Emergency Landing.
- See the section titled "Plan for Immediate Descent and Landing" in the separate article In-Flight Fire: Guidance for Flight Crews for guidance on emergency descent and landing. It is vital to get the aircraft on the ground before loss of control occurs.
- Aircraft Handling. Few manufacturers and operators offer guidance to pilots on the handling of an aircraft with a wing fire. There are several things which a pilot could consider, depending on the nature of the fire and the aircraft type, that are aimed at limiting the spread of the fire:
- Don't slow down - keep the speed up to prevent the fire propagating forward. Some pilots even suggest that a steep dive might blow the fire out but this approach is not without risk.
- Side slip can hinder propagation of the fire towards the fuselage but should only be considered if the emergency response procedures of the aircraft operator provide for this.
- Manoeuvring the aircraft after touchdown (or a rejected take off) so as to stop the aircraft into wind or beyond may be important since it can materially delay propagation of a wing fire towards the fuselage. This strategy is equally applicable to a fire that is still confined to the engine/nacelle since it could quickly spread to the wing. Consideration should be given to the ability of fire and rescue services to access the aircraft. It may also be preferable to deploy evacuation chutes onto the runway rather than an uncertain surface at the side of the runway.
Some of the above advice on aircraft handling is contentious; if you have an opinion regarding this, please contact the Editor: firstname.lastname@example.org
The strategy adopted to survive a wing fire is very much a matter of judgment for the pilot in command at the time considering aircraft type-specific issues and procedures as well as the flight crew's best information or guess as to what is actually happening.
Accidents and Serious Incidents
- SW4, Mirabel Montreal Canada, 1998 (On 18 June 1998, the crew of a Swearingen SA226 did not associate directional control difficulty and an extended take off ground run at Montreal with a malfunctioning brake unit. Subsequent evidence of hydraulic problems prompted a decision to return but when evidence of control difficulties and fire in the left engine followed, a single engine diversion to Mirabel was flown where, just before touchdown, the left wing failed upwards. All occupants were killed when the aircraft crashed inverted. The Investigation found that overheated brakes had caused an engine nacelle fire which spread and eventually caused the wing failure.)
- NIM, manoeuvring, northern North Sea UK, 1995 (On 16 May 1995, an RAF BAe Nimrod on an airworthiness function flight caught fire after an electrical short circuit led indirectly to the No 4 engine starter turbine disc being liberated and breaching the No 2 fuel tank. It was concluded by the Investigation that the leaking fuel had then been ignited by either the electrical arcing or the heat of the adjacent engine. After the fire spread rapidly, the risk of structural break up led the commander to ditch the aircraft whilst it was still controllable. This was successful and all seven occupants were rescued.)
- CONC, vicinity Paris Charles de Gaulle France, 2000 (On 25th July 2000, an Air France Concorde crashed shortly after take-off from Paris CDG following loss of control after debris from an explosive tyre failure between V1 and VR attributed to runway FOD ruptured a fuel tank and led to a fuel-fed fire which quickly resulted in loss of engine thrust and structural damage which made the aircraft impossible to fly. It was found that nothing the crew failed to do, including rejecting the take off after V1 could have prevented the loss of the aircraft and that they had been faced with entirely unforeseen circumstances.)
- B763, Chicago O'Hare IL USA, 2016 (On 28 October 2016, an American Airlines Boeing 767-300 made a high speed rejected take off after a catastrophic and uncontained failure of the right engine, a GE CF6-80C2B6. A successful emergency evacuation of the 170 occupants was completed as a major fuel-fed fire destroyed the failed engine and caused substantial damage to the aircraft structure. An NTSB investigation is taking place.)
- Boeing article: Flight Crew Response to In-Flight Smoke, Fire, or Fumes
- FAA Advisory Circular 120-80 “In Flight Fires”
- Reflections on the Decision to Ditch a Large Transport Aircraft - an account by the aircraft captain and pilot of a RAF Nimrod which ditched into the North Sea following an engine fire which spread to the wing; edited version of RAF leadership: Able to handle ambiguity by Gp Capt John Jupp, RAF Magazine ‘Spirit of the Air’ Volume 2 No 3, 2007