What happened
On June 8, 2005, a Robin DR 400-140B, registration F-GJQO, operated by an aero club, departed from the Bordeaux Léognan Saucats airfield for a private flight. During the takeoff roll on runway 03, witnesses observed significant black smoke and an abnormally long ground roll.
As the aircraft climbed to approximately 60 meters, the pilot experienced a sudden and significant loss of engine power. To avoid obstacles, including a nearby industrial park, the pilot initiated a right-hand turn to return to the airfield. During this maneuver, the aircraft maintained a low airspeed, triggering the stall warning. The aircraft subsequently struck the treetops, collided with several pine trees, and came to rest upside down at the edge of a forest. The accident resulted in one serious injury to the pilot and one minor injury to the passenger. The aircraft was destroyed.
The investigation
The investigation focused on the engine's performance and the cause of the power loss. Laboratory analysis of the Lycoming O-320-D2A engine revealed that the internal surface of the spark plugs and the exhaust pipe were covered in soot, indicating an excessively rich fuel mixture.
Investigators discovered that a piece of felt, which covers the inner face of the carburetor heat valve, had become detached and partially obstructed the carburetor's air intake. While a previous airworthiness directive (AD) required visual and tactile inspections of this felt during 100-hour maintenance checks, the inspection performed on the aircraft 81 hours prior to the accident had failed to detect the deterioration.
Findings
- The primary cause of the accident was a loss of engine power resulting from the ingestion of felt into the carburetor air intake.
- The detachment of the felt from the carburetor heat valve caused an obstruction in the fuel-air mixture.
- Existing maintenance procedures and the application of the relevant airworthiness directive were insufficient to detect the degradation of the felt before it caused a failure.
- The pilot's attempt to return to the airfield was hampered by the low airspeed and the presence of trees in the flight path.