What happened
On June 12, 2021, at 17:10 local time, an Arcus T sailplane, registration HB-2486, collided with a steep embankment approximately 100 meters before the threshold of runway 29 at Dittingen airfield. The aircraft was operating under Visual Flight Rules (VFR) for a private passenger flight.
Prior to the accident, the pilot had successfully completed two passenger flights earlier that day. During the final approach, the aircraft performed a wide left turn over the town of Ditting and entered the left downwind leg. Flight data indicates that while the true airspeed remained relatively constant at approximately 125 km/h, the net sink rate increased significantly at the start of the downwind leg. The aircraft eventually struck the terrain short of the runway. The pilot and the passenger sustained one light injury, and both were able to exit the wreckage independently.
The investigation
Investigators from the SUST examined the wreckage and analyzed flight data recorded by the LX9000 flight computer. The technical examination of the HB-2486 revealed no mechanical failures; all control surfaces, including the airbrakes and spoilers, were fully functional at the time of the crash. The damage to the aircraft was attributed entirely to the impact and subsequent recovery efforts.
Meteorological data analysis showed that wind speeds had increased compared to earlier flights, with a western wind of approximately 25 km/h recorded during the accident approach. The investigation also noted that the pilot's approach pattern for this flight was significantly wider than the two successful landings performed earlier in the day.
Findings
- The pilot initiated a high sink rate of 7.6 m/s at the start of the downwind leg, which was caused by the deployment of airbrakes.
- The approach was executed much further from the runway threshold than in previous successful flights.
- The pilot failed to recognize that the wide and deep approach, combined with the prevailing wind conditions, would result in an undershoot.
- The accident was caused by the pilot's failure to plan the approach according to fundamental gliding principles and a lack of safety-conscious decision-making.