What happened
On July 3, 2010, a Robin DR 40 and00-160, registration F-GAVH, departed from runway 03 at the Bordeaux-Léognan-Saucats aerodrome for a local flight. The aircraft was carrying the pilot and three passengers at a takeoff mass near the manufacturer's maximum limit.
During the initial climb, the aircraft failed to maintain a sufficient climb gradient. GPS data recovered from the aircraft indicated that the takeoff roll was twice the distance specified in the flight manual, with the ground speed reaching 120 km/h at rotation before steadily decreasing. The aircraft's climb gradient was approximately 10% before the flight path curved approximately 60 degrees to the right, leading to a stall and subsequent impact in a clearing to the right of the runway. The accident resulted in the pilot and passengers being injured and the destruction of the aircraft.
The investigation
The investigation focused on the aircraft's performance and maintenance history. Examination of the wreckage revealed that the flaps were set in the landing configuration and that the air filter had been installed incorrectly. This filter had been removed the previous day during a 50-hour periodic inspection and reinstalled without proper verification.
Testing on a similar aircraft demonstrated that this specific incorrect installation obstructed the engine's airflow. This obstruction created a vacuum effect that caused the carburetor heat valve to open, resulting in a loss of approximately 150 RPM at full throttle, which equated to a power loss of roughly seven horsepower.
Additionally, the investigation looked into previous flight logs. Two instructors had previously flown the aircraft for training and noted insufficient performance; one had recorded the issue in the club's technical observation log, while the second noted a weak variometer. However, these notes were not recorded in the aircraft's logbook, and the pilot involved in the accident had not consulted the technical observation log.