What happened
On August 6, 1999, a Schleicher K 10A glider, registration HB-785, was engaged in a private soaring flight near Saanen, Switzerland. The flight began at 14:10 local time via a tow takeoff. During the flight, the pilot encountered broken thermals caused by prevailing Föhn wind conditions.
While flying at a relatively low altitude near Alp Wildeneggli, the pilot attempted to gain altitude to continue the flight. During this maneuver, the aircraft encountered lee-side turbulence. This turbulence caused the aircraft to drop below its minimum flying speed, leading to an aerodynamic stall. The glider entered a steep dive and struck the terrain at high speed. The impact was so severe that the right wing was completely severed from the fuselage, and the aircraft was destroyed. The pilot sustained fatal injuries.
The investigation
Investigators from the Swiss Transportation Safety Investigation Board (SUST) examined the wreckage and the flight conditions. The investigation established that the aircraft's weight and center of gravity were within permissible limits. Technical examination of the wreckage revealed no evidence of mechanical failure; all control surfaces were free and functional, and no pre-existing defects were found.
Medical examinations of the pilot showed no presence of alcohol and no acute health issues that could have influenced the flight, although underlying coronary artery disease was noted but ruled out as a contributing factor to the accident. Meteorological data confirmed that Föhn-related turbulence was expected in the Bernese Oberland region at the time of the occurrence.