What happened
On June 22, 2012, a Schempp-Hirth Discus 2T motor glider, registration D-KDGY, was engaged in a long-distance flight from Esslingen, Germany, to Puimoisson, France. After approximately 7.5 hours of flight, the pilot was navigating the Allevard region, seeking thermal lift by heading east toward higher terrain.
Data from the aircraft's FLARM system indicated that the pilot was flying at low altitude within a mountainous cirque, following the terrain. While attempting to utilize ridge soaring, the pilot's ground speed decreased from 110 km/h to 80 km/h in the minute preceding the impact. The aircraft subsequently collided with trees near Le Collet d’Allevard. The aircraft was destroyed in the accident, and no fatalities were reported.
The investigation
The investigation examined the pilot's flight profile, the aircraft's configuration, and the environmental conditions. Investigators noted that the pilot had recently emptied the water ballasts near Albertville, which resulted in an aft center of gravity. This configuration made low-speed flight handling more difficult.
Analysis of the flight trajectory revealed that the pilot had alternative flight paths available that would have provided greater altitude margins. The investigation also reviewed the pilot's recent flight history, noting a high frequency of long-duration flights, including several exceeding eight hours, within the preceding three months. Meteorological data at the time showed CAVOK conditions with a light, variable wind shifting toward the northwest, which could favor ridge soaring but also introduced local instability and convective currents below 2,000 meters.
Findings
- The primary cause of the accident was the pilot's persistence in seeking lift, which led to a loss of sufficient altitude and airspeed margins to maintain safety.
- The drive to achieve high-performance results during long-duration flights likely prompted the pilot to accept reduced safety margins.
- The pilot's concentration may have been impaired by fatigue resulting from the extended duration of the flight.
- The aircraft's aft center of gravity, following the discharge of water ballast, complicated low-speed maneuvering.