What happened
On May 18, 2011, at 10:24 local time, a Schleicher ASH25 glider, registration F-CHIT, departed from the Chambéry - Challes les Eaux airfield for a training flight. The flight was being conducted by a student pilot in the front seat and an instructor in the rear seat. Following a tow release at an altitude of 1,700 meters, the crew proceeded toward the Chamechaude mountain range.
Around 10:45, the aircraft began performing ridge soaring maneuvers on the eastern slope of the mountain at approximately 1,900 meters. According to FLARM data, the glider was maintaining an average altitude of between 50 and 70 meters above the terrain, performing turns toward the valley as is standard for such maneuvers. At 10:51, another glider pilot observed F-CHIT in a steep left bank with a high nose-down attitude, estimating the aircraft was at an altitude of less than 100 meters. Shortly thereafter, the glider struck the terrain. The wreckage was recovered at 1,740 meters, approximately 300 meters east and below the mountain summit.
The investigation
The investigation focused on the flight data provided by the aircraft's FLARM proximity warning system and the examination of the wreckage. Physical inspection of the debris revealed no mechanical failures or anomalies that could account for the accident.
Investigators analyzed the meteorological conditions at the time of the impact. While visibility was good (CAVOK), a south/southwest wind of 10 knots was present, which increased in speed near the ridge line. This wind, combined with potential thermal convection, created significant atmospheric turbulence. The pilot of a nearby glider confirmed that the air was very turbulent during the period in question.
Findings
- The aircraft was flying at a very low altitude, averaging only 50 to 70 meters above the terrain.
- The crew was operating in highly turbulent atmospheric conditions caused by ridge-induced wind acceleration and thermal activity.
- For reasons that remain undetermined, the crew entered a steeply banked turn at a low altitude.
- The instructor, despite extensive flight experience, was unable to recover the aircraft from the high-bank, nose-down attitude before impact.
- The accident resulted in two fatalities (the pilot and the instructor) and the total destruction of the glider.