What happened
On June 22, 2016, at approximately 18:15 local time, a Schempp Hirth Nimbus 4D glider, registration F-CPHR, was conducting a flight originating from the Château-Arnoux Saint-Auban aerodrome. The aircraft was carrying a pilot and one passenger, who was also a licensed glider pilot.
After departing at 12:30, the flight proceeded toward the Tarentaise Valley. Around 16:30, the pilot decided to return to the home aerodrome. While crossing the Lautaret Pass at an altitude of 2,900 meters and heading toward Briançon, the pilot encountered rain and a lowering cloud ceiling. Initially, the pilot attempted to reach the Mont-Dauphin Saint-Crépin aerodrome; however, as weather conditions continued to degrade, a change of plan was made to land in a known field at Le Casset.
Due to the rain, the glider's glide ratio had decreased by approximately 30%, making the intended field at Le Casset unreachable. The pilot subsequently chose to land in an alternative field previously flown over. Upon touchdown, the glider encountered a bump hidden by tall grass, causing the aircraft to bounce. This motion resulted in the right wing striking the ground, causing the aircraft to perform a ground loop.
The investigation
The investigation focused on the pilot's decision-making process and the environmental factors present during the descent. Investigators reviewed the pilot's experience, noting they held an ATPL(A) airline transport pilot license and had been flying gliders since 1980, with 800 total glider flight hours. Meteorological data at the time indicated an east-northeast wind of 3 knots, a temperature of 24°C, and a QNH of 1024 hPa, with localized showers and a cloud ceiling of approximately 3,000 meters.
Findings
- The primary cause of the accident was the pilot's late decision to terminate the flight.
- Heavy rain significantly degraded the aircraft's aerodynamic performance, reducing the glide ratio by roughly 30%.
- The presence of tall grass obscured a bump in the landing field, which triggered the bounce and subsequent wing strike.