What happened
On July 10, 2008, a Robin DR 400-140 B Major, registered F-GYKY, was conducting a local VFR flight near La-Côte-d’Arbroz, France. The aircraft was carrying the pilot and three teenage passengers, who were participants in an aeronautical training program organized by the local aero club.
After flying over the Col de l'Encrenaz at a very low altitude, the aircraft entered a mountain cirque dominated by the Roc d'Enfer. While attempting to navigate the terrain, the aircraft entered a steep left turn and subsequently entered a spiral descent. The aircraft struck the terrain below the Col de la Bolire, resulting in four fatalities and the total destruction of the aircraft. Witnesses observed the aircraft flying at high power settings and performing high-bank maneuvers near the rocky walls.
The investigation
The investigation focused on the flight path, the aircraft's technical condition, and the pilot's maneuvers. Investigators examined the wreckage and found no evidence of mechanical failure; the engine was delivering power at the time of impact, with the tachometer indicating 2,200 RPM.
Analysis of video footage from a similar flight conducted two days prior revealed that the pilot had been performing high-inclination maneuvers and flying at very low altitudes through mountain passes. The investigation also noted that the aircraft was heavily loaded, operating near its maximum authorized mass. Furthermore, the investigation established that the pilot was operating outside the club's supervision during a lunch break, having offered these unauthorized 'thrill flights' to the trainees for a fee.
Findings
- The pilot failed to adhere to fundamental mountain flying safety rules, specifically regarding the safe crossing of mountain passes.
- The aircraft was operating at a weight near its maximum limit.
- Atmospheric conditions were highly favorable for the development of downdrafts (rabattants) on the shaded side of the terrain.
- The pilot's decision to attempt a pass at low altitude and in a climbing configuration during unfavorable aerological conditions led to the loss of control.