What happened
On June 28, 2008, a DG-400 glider, registration HB-2123, was performing a winch-assisted takeoff at Samedan Aerodrome (LSZS). During the launch, the aircraft lifted off normally but quickly entered an excessively steep climb. At an altitude of approximately 40 to 50 meters, the aircraft rolled sharply to the left and transitioned into an inverted position. The glider struck the main runway at a 45-degree angle on its back before sliding into the grass adjacent to the runway. The pilot sustained fatal injuries in the impact.
The investigation
Investigators examined the aircraft's configuration and the environmental conditions at the time of the accident. The investigation found that the aircraft's wing camber settings were incorrectly configured; while the flight manual prescribed a setting of +8°, the control lever was found in the -10° position. Meteorological data revealed significant wind shear and a tailwind component at the takeoff position.
Technical analysis of the winch cable showed that the use of synthetic Dyneema rope, rather than traditional steel cable, could increase acceleration by up to 25%, potentially affecting the pilot's ability to manage the climb. Furthermore, the investigation noted that the breaking strength of the cable attachment (750 daN) exceeded the manufacturer's recommendation of 500 daN, which might have otherwise caused the cable to break during the extreme pitch-up maneuver.
Findings
- The primary cause of the accident was an inadequate flight technique at low altitude, which led to an aerodynamic stall.
- The pilot utilized an incorrect wing camber setting (-10° instead of +8°), which significantly increased the stall speed.
- A tailwind component at the takeoff point contributed to the higher ground speed during the initial roll, complicating the transition to a climb.
- The pilot's winch launch proficiency had not been formally reviewed since 1982.
- There was a lack of recent, specific training regarding winch launch operations.