An operational fire is considered to be a fire which occurs during the operation of an aircraft either in flight or on the ground.
The effect of an operational fire on an aircraft, its passengers and crew can vary from inconsequential to catastrophic depending upon the type and location of the fire, the success of the crew's attempts to identify the source of the fire, the success of the fire suppression equipment and procedures, and the ultimate outcome of any post landing event such as an Aircraft Evacuation.
Modern aircraft are designed and equipped with the possibility of a fire in mind. Aircraft engines, including the APU have fire detection and fire extinguishing systems installed. Overheat detectors are installed in the vicinity of bleed air ducts and the bleed system is designed so it can be partially or totally isolated if required. Brake temperature indicators may be installed and will give indication of a brake or tyre fire. Lavatories are equipped with smoke detectors and lavatory waste bins have automatic fire suppression equipment. Fire-fighting equipment is carried in the flight deck and the cabin. Above all else, both flight deck and cabin crew are well trained in dealing with all fire, smoke and fume emergencies. They are well supported in this endeavour by the Crash Fire Rescue personnel manning the aerodrome fire stations.
Activation of the fire detection system on one of the engines generates a fire warning in the flight deck. The crew shuts down the engine in accordance with the fire checklist and activates the fire extinguishing system. After a few seconds, the fire warning indication goes out. The aircraft is diverted to a nearby airport and lands without further incident.
Passenger meals are inadvertently put into a galley oven without having the plastic over-wrapping removed. During the heating process, the plastic melts and catches fire when it drips onto the oven heat element. The Flight Attendants electrically isolate the oven by pulling the circuit breaker and put out the fire with a BCF (halon 1211) extinguisher. The smoke dissipates quickly and the flight continues to destination.