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 "Fire in the Air" 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 borne 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 (i.e., an Uncontained Engine Failure), 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 slides onto the runway rather than an uncertain surface at the side of the runway.
Manoeuvring the aircraft after touchdown
Some of the above advice on aircraft handling is contentious; if you have an opinion regarding this, please contact the Editor: [email protected]
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 Incidents
On 1 September 2018, a Boeing 737-800, making its second night approach to Sochi beneath a large convective storm with low level windshear reported, floated almost halfway along the wet runway before overrunning it by approximately 400 metres and breaching the perimeter fence before stopping. A small fire did not prevent all occupants from safely evacuating. The Investigation attributed the accident to crew disregard of a number of windshear warnings and a subsequent encounter with horizontal windshear resulting in a late touchdown and noted that the first approach had meant that the crew had been poorly prepared for the second.
On 5 January 2018, an out of service Boeing 737-800 was pushed back at night into collision with an in-service Boeing 737-800 waiting on the taxiway for a marshaller to arrive and direct it onto the adjacent terminal gate. The first aircraft s tail collided with the second aircraft s right wing and a fire started. The evacuation of the second aircraft was delayed by non-availability of cabin emergency lighting. The Investigation attributed the collision to failure of the apron controller and pushback crew to follow documented procedures or take reasonable care to ensure that it was safe to begin the pushback.
On 28 October 2017 the left main landing gear of an MD10-10F that had just touched down at Fort Lauderdale collapsed which led to the aircraft departing the side of the runway and catching fire. The Investigation found that the collapse had occurred because of metal fatigue which had developed in the absence of protective plating on part of the leg assembly. The reason for this could not be determined but it was noted that had the aircraft operator’s component overhaul interval not been longer than the corresponding manufacturer recommendation then the collapse would probably not have occurred.
On 27 November 2010, collateral damage to the wing of an IL-76 in the vicinity of an uncontained engine failure, which occurred soon after take-off from Karachi, led to fuel in that wing igniting. Descent from a maximum height of 600 feet occurred accompanied by a steadily increasing right bank. Just under a minute after take-off ground impact occurred and impact forces and fire destroyed the aircraft. The Investigation concluded that the engine failure was attributable to component fatigue in the LP compressor and that it would have been impossible for the crew to retain control.
On 27 June 2016, a Boeing 777-300ER powered by GE90-115B engines returned to Singapore when what was initially identified as a suspected right engine oil quantity indication problem evidenced other abnormal symptoms relating to the same engine. The engine caught fire on landing. The substantial fire was quickly contained and an emergency evacuation was not performed. The cause of the low oil quantity indication and the fire was a failure of the right engine Main Fuel Oil Heat Exchanger which had resulted in lubrication of the whole of the affected engine by a mix of jet fuel and oil.