What happened
On April 22, 2011, a DG-800 S glider, registration HB-3253, was performing a winch launch at Mollis airfield (LSMF) in Switzerland. During the takeoff sequence, the aircraft lifted off relatively early as the winch was operated at full power. However, the transition into the climb was abrupt and excessively steep. The glider appeared to lose airspeed, and the climb angle increased until it became nearly vertical. At an altitude of approximately 40 meters, the aircraft pitched over its right wing and plummeted nose-first into the airfield grounds. The pilot sustained fatal injuries, and the aircraft was destroyed.
The investigation
Investigators examined the aircraft's configuration and the pilot's recent flight history. The investigation revealed that the seatback in HB-3253 had been modified in 1997 to accommodate a taller pilot, which shifted the pilot's pelvic position backward by approximately 26 cm compared to the factory design. This modification meant the pilot's legs were positioned differently, potentially affecting pedal contact.
Regarding the pilot's experience, the investigation found that while the pilot held the necessary licenses, they had not flown for approximately 15 months prior to the accident. Furthermore, this was the pilot's first time performing a winch launch in this specific aircraft model. Meteorological data also indicated that a sudden change in wind conditions, specifically the onset of the Föhn wind, occurred around the time of the accident, which may have introduced wind shear into the flight path.
Findings
- The primary cause of the accident was the pilot losing control of the glider because flight control movement was likely restricted due to a shift in the pilot's seating position.
- A modified seatback caused the pilot's hips to be positioned significantly further back than the standard configuration.
- The pilot had limited recent training in winch launch operations.
- The pilot lacked specific experience performing winch launches in the DG-800 S.
- There was insufficient mental preparation regarding the specific risks associated with winch launches.
- The presence of wind shear may have contributed to the severity of the accident.