What happened
On June 25, 2013, a DG-800 B motor glider, registration HB-2346, departed from Gap Tallard aerodrome for a local flight. Approximately eight minutes into the flight, the pilot shut down the engine. While maneuvering over a ridge line oriented east-west, the pilot entered a right-hand spiral. During this maneuver, the aircraft lost control, struck trees, and ultimately collided with the ground near Melve.
The investigation
Investigators analyzed onboard computer data, which revealed that the aircraft's trajectory had been generally descending from about one minute prior to the engine shutdown until the moment of impact. During the final spiral, the airspeed was decreasing while the altitude was increasing. At the final recorded point, located 200 meters from the wreckage, the airspeed was 95 km/h. The bank angle during this final maneuver was estimated at approximately 40 degrees. At the end of the spiral, the aircraft was facing a peak located roughly 50 meters below its position.
An examination of the wreckage revealed no mechanical anomalies that contributed to the accident. The engine was in the retracted position at the time of impact, and the aircraft's weight and balance were within manufacturer limits. Meteorological conditions at the site were reported as CAVOK with moderate turbulence and a 6-knot wind.
Findings
- The aircraft likely entered an autorotation during the spiral maneuver.
- This loss of control was caused by a decrease in airspeed coupled with an increase in altitude.
- The proximity of the terrain likely caused the pilot to focus on monitoring altitude at the expense of maintaining adequate airspeed.
- The low altitude at the time of the maneuver significantly limited the pilot's ability to recover control of the aircraft.