What happened
On the evening of July 26, 1999, a Robin DR 400-180, registration F-GSBO, was involved in an engine fire at the Etampes refueling station. The aircraft, operated by a flying club, was preparing for departure following a flight of over two hours. While the three passengers remained on board, the pilot attempted to start the engine.
During the startup sequence, the electric fuel pump was set to the ON position. The pilot made three separate start attempts, during which several fuel injections were performed. On the final attempt, white smoke and flames became visible near the engine. The pilot immediately ordered the evacuation of the aircraft and exited the cockpit, having only managed to switch off the magnetos. In the ensuing urgency, the pilot was unable to locate nearby fire extinguishers. The fire spread rapidly, resulting in the total destruction of the aircraft within minutes.
The investigation
Investigators examined the engine start procedures and the mechanical state of the aircraft. While the exact positions of the throttle and mixture controls during each start attempt could not be definitively confirmed, the investigation focused on the accumulation of excess fuel. The investigation also reviewed the Lycoming O-360 engine manual, which warns that excessive fuel injection can flood the carburetor and air box, potentially leading to fire in the fuel system or externally.
Findings
- The primary cause of the fire was an inappropriate engine start procedure.
- Excessive fuel injections during the startup attempts likely caused fuel to overflow from the carburetor into the air box and down into the lower engine cowling.
- The ignition of this accumulated fuel was likely caused by a backfire toward the carburetor during the engine's compression stroke as the starter motor was disengaged.
- The investigation noted that similar engine fires have occurred during hot starts involving fuel injections in other aircraft.