What happened
On June 11, 2022, at approximately 15:44, a DG-80 and B motor glider, registration HB-2347, departed from Montricher airfield (LSTR) using an autonomous takeoff procedure. The aircraft flew toward the nearby Mont Tendre, where witnesses observed it following the ridge at a low altitude. While navigating the ridge toward the northeast, the aircraft entered a steep climb followed by a high-bank turn. The aircraft subsequently entered a spin and struck a wooded slope at approximately 16:00. The pilot sustained fatal injuries, and the aircraft was destroyed.
The investigation
The investigation examined the aircraft, the pilot's medical status, and the flight conditions. The aircraft, a single-seat motor glider manufactured in 2000, had been properly maintained with its annual inspection and airworthiness review up to date. The weight and center of gravity were within prescribed limits. An examination of the wreckage found no pre-existing technical failures capable of causing the accident, though investigators noted several loosened locknuts on the control linkage rod ends; however, these were determined not to have reduced the maneuverability of the aircraft.
Regarding the pilot, the autopsy revealed no health issues or presence of substances that could have influenced the flight. Meteorological conditions at the time were clear with light winds and temperatures of 17 °C, though conditions were not conducive to thermal activity.
Findings
The investigation established that the accident was caused by the aircraft performing a turn at an insufficient speed. This loss of airspeed led to a stall and subsequent loss of control. Because the maneuver was being executed at a low altitude, the pilot was unable to recover before the impact with the terrain.