Narrative:A Transall C-160R transport plane, operated by the French Air Force, suffered a fuel tank fire on the ground at Fort de France-Lamentin Air Base (BA 365), Martinique. The three pilots and five mechanics escaped unhurt.
The airplane was attached to the Escadron de Transport Outre-Mer 58 (ETOM 00.058) and was being prepared for a test flight. Shortly after start-up, just as the airplane has commenced taxiing towards the runway, a fire erupted. The airplane was stopped immediately. Three minutes later the fire services arrived and extinguished the fire.
The airplane sustained serious damage to the left wing, left hand fuselage and tail section.
The accident was caused by electrical arcing at the power cable to a submersible fuel pump. This arcing occured above the kerosene liquid inside the tank full of fuel vapors. The cable type used was chosen at the time of the design of the aircraft.
Atmospheric conditions on the apron of Fort de France have raised the temperature of the reservoir beyond the flash point kerosene. The vapors contained in this tank were explosive, and the arc was enough to initiate the blast.
As such, atmospheric conditions are a certain cause of environmental origin of the accident.
The appearance of the arc is, in turn, has only technical causes:
- The quality of cable used and age are in fact responsible for the creation of the electric arc.
- The formation of the insulating sheath of this type of cable is not likely to ensure an absolute seal. This quality is also not claimed by its manufacturer.
Indeed, the analyzes carried out show a porosity of electrical cable, even nine, therefore that it is soaked in kerosene. The presence of kerosene increases the phenomenon of porosity of old cables.
Degradation characteristics of dielectric strength of the cable insulation explains the appearance of the arc.
The accident occurred while the cable was over 19 years old.
The fuel pumps wiring has never been a problem.
But there has not been a cable that had reached the age of 19 years.
The aging of the cable could still degrade the seal.
Finally, maintaining this type of cable on the first C160 series until this accident was part of a complex process in which traceability has not been formally established.
Doubts indeed appeared in 1969 on the quality of these cables, doubts that can be considered today as precursors. Measures had been adopted precisely to overcome these deficiencies. In this regard, the replacement of the fuel pump wiring of the second series C 160 of these cables with a newer type and considered more efficient is particularly significant. Its extension to the first series aircraft might have seemed relevant, and would probably have prevented the accident.
The reasons which led to the maintenance of such cables on the C 160 series first held in both the human factor (underestimation of risk, lack of global view on the issue) and organizational factors, which can be seen as a lack of traceability of technical and logistic actions, a lack of consistency of the measures adopted, and probable deficiencies in the information flow.
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Official accident investigation report
|investigating agency: ||Bureaux Enquêtes Accidents Défense (BEAD) - France |
|report status: ||Final|
|report number: ||BEAD-A-2004-012-A|
|report released:||1 July 2005|
|duration of investigation: ||1 year and 2 months|
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