What happened
On May 23, 2008, a Jodel D140 Mousquetaire, registration F-BNIR, was conducting a mountain flight training mission. The flight, consisting of an instructor and a student, began in Chambéry and included a stop at Alpe d'Huez before proceeding to the Valloire mountain airstrip.
After landing at Valloire, the crew attempted a takeoff from the paved runway. During the takeoff roll, the aircraft drifted to the left of the runway centerline. The aircraft struck trees located approximately 185 meters from the start of the runway, causing it to crash down an embankment. The aircraft overturned and caught fire upon impact. Both occupants, the instructor and the student, sustained fatal injuries.
The investigation
The BEA examined the wreckage, the site of the impact, and the aircraft's mechanical condition. Investigators found that the flight control cables were intact and the engine was producing full power. The aircraft was within its weight and balance limits, and the flaps were set to the "mountain" position.
Reconstruction flights were conducted using an identical aircraft type and engine to evaluate the takeoff performance on the specific terrain. This testing revealed that while the aircraft could reach significant speeds, the wheels could lift off the ground in the area where tracks disappeared, yet the speed remained insufficient to clear the trees if the aircraft drifted off course. Investigators also noted that the runway features a 10% downward slope in its latter section, which is not visible from the takeoff threshold.
Findings
- The aircraft deviated from the runway centerline to the left.
- This deviation may have been caused by imprecise control of engine effects combined with an inadequate corrective action by the instructor.
- Alternatively, the crew may have attempted an evasive maneuver to avoid an obstacle, such as an animal, which could have suddenly appeared as the aircraft entered the downward-sloping section of the runway.
- The investigation noted recent reports of increased animal activity (deer and chamois) crossing the runway area due to local environmental changes.
- The speed acquired during the takeoff roll was insufficient to allow for a successful aborted takeoff on the uneven terrain or to provide enough lift to fly over the trees following the deviation.