What happened
On June 30, 2011, a Schleicher ASH 25 E motor glider, registration D-KKYB, departed from Serres La Bâtie for a flight in the Briançon region. The aircraft was part of a group of three gliders being towed by a lead glider. After approximately eight hours of flight, the pilot engaged the engine near Sisteron and separated from the formation. The pilot remained in radio contact with the lead glider and reported no issues.
As the flight progressed toward dusk, the aircraft entered a valley at a low altitude. By approximately 21:22, the aircraft was flying with the engine running through an ascending valley leading toward the Col de Faye. While flying in a straight line, the aircraft struck a tree with its left wing before colliding with the ground in a dry riverbed. The accident resulted in two fatalities (the pilot and the passenger) and the destruction of the aircraft.
The investigation
The investigation examined the meteorological conditions and the flight path. At the time of the accident, the weather featured CAVOK conditions but included moderate to locally strong turbulence, with downdrafts present on the eastern slopes of the terrain. The sun had set at 21:24.
Investigators established that when the aircraft emerged from the valley at a low altitude, the engine's performance was insufficient to gain the altitude required to clear the surrounding terrain, turbulence, and downdrafts. The investigation also noted that several fields near the town of Serres were available for a precautionary landing, which the pilot did not utilize.
Findings
- The flight concluded at a low altitude in a valley floor during the onset of night.
- The aircraft was operating in unfavorable aerological conditions that the engine power could not overcome.
- The pilot's decision to continue the flight through difficult terrain despite the lack of performance capability was the primary cause.
- The pilot failed to execute a precautionary landing in available fields despite the opportunity to do so.