What happened
On 5 August 2021, a Robin DR400-500, registered F-HMYY, crashed in the Savoie region of France while conducting a cross-country sightseeing flight. The aircraft, operated by Aéroclub de Loire Atlantique, was flying with the pilot and three passengers toward Sarlat. After departing Annecy, the aircraft proceeded south through the valley toward the Col du Glandon pass.
As the aircraft entered the valley, it maintained a flight path following the center of the valley floor. While the aircraft's absolute altitude was increasing, the rising terrain caused its height above the ground to progressively decrease. The aircraft eventually struck trees at an altitude of approximately 5,070 feet, caught fire, and was destroyed. The accident resulted in three fatalities and one serious injury.
The investigation
The BEA examined the aircraft's flight path using GNSS data from a navigation application used by the pilot. The investigation found that the aircraft's climb gradient of approximately 5.1% was lower than the 8.4% mean gradient of the valley. The investigation also reviewed the aircraft's technical condition, finding that the engine was delivering power and flight controls were functional at the time of impact, with no mechanical failures identified.
Investigators also assessed the pilot's experience and the aircraft's weight. The aircraft was likely operating near its maximum weight and aft center of gravity limit. The pilot, who had approximately 230 total flight hours, likely lacked specific experience in mountain flying. Furthermore, the investigation looked into the use of the SDVFR navigation application, noting that its display format can make it difficult to visualize complex topography.
Findings
Several factors contributed to the accident:
- Insufficient mountain flying experience, specifically an underestimation of the risks and the lack of specific techniques required for mountainous terrain.
- A flight path that precluded safety margins, as the direct track through the valley did not allow enough time or altitude to clear the pass.
- Reduced maneuvering capability, as the narrowing valley and rising terrain limited the pilot's ability to perform a U-turn.
- Navigation challenges, including the potential difficulty of visualizing terrain gradients when using certain digital navigation applications.