A military Transall C-160R (Transall) was being prepared for a test flight on the Fort de France-Lamentin Air Base on the island of Martinique on this day in aviation history. The test flight was necessary after the replacement of the #2 (right hand) engine, a Rolls-Royce RTy.20 Tyne Mk 22 turboprop proving 6100 hp.
The aircraft on fire (Source: BEAD © Unknown)
After completion of the necessary checklists to prepare the aircraft for flight and after the engines were started, ATC cleared the aircraft to taxi to the runway at 13.58 local time. When the aircraft starts to roll the brakes are tested satisfactorily. 6 seconds later the crew here a loud noise and feel a shock through the airframe, The commander immediately stopped the aircraft.
The maintenance crew, on-site to assist with the departure of the aircraft, witness an explosion of the lefthand fuel tank and immediately indicated by a hand signal that a fire had broken out. A signal that was not understood by the crew.
On the left, the ICAO hand signal for a fire and on the right. the IFALPA hand signal for a fire (Source: www.skybrary.aero)
13 seconds after the explosion the commander notices the commotion that had ensued outside the aircraft and orders the engines to be shut down. 5 seconds later (18 seconds after the explosion) the commander sees the fire from the cockpit. Several seconds later he orders the evacuation of the aircraft. The crew evacuates the aircraft via de crew door, just aft of the cockpit, as the aircraft was with its nose in the wind the flames and smoke were blown towards the tail. Three minutes after the explosion firefighters are at the scene and quickly extinguish the fire.
Firefighters are on the scene, and the fire is nearly extinguished (Source; BEAD © Unknown)
The incident was investigated by the BEAD (Bureau Enquêtes Accidents Défense, French military air accident investigators) and in July 2005 they published their investigation report. (available by clicking here, note the report is in French). They identified the following possible cause;
Deteriorated insulation on the power cables to a fuel pump in the wing allowed a short circuit to cause a spark above the fuel level in the tank, which was a fuel vapour rich environment. The atmospheric conditions, specifically the high temperature (30ºC) raised the temperature of the fuel causing more vapours to build up. which was ignited by the spark causing the explosion.
The fuel pump with traces of arcing (Source: DEAB © Unknown)