What happened
On May 28, 2022, at 15:14, a DG-800 B motor glider, registration HB-2320, crashed into a steep terrain near Crêta Besse, in the municipality of Savièse. The aircraft had departed from Sion Airport (LSGS) earlier that afternoon as part of a regional gliding competition. While flying near the mountainside, the pilot initiated a right-hand turn. Witnesses from other participating gliders observed the aircraft enter a spin during the maneuver. The aircraft subsequently struck the ground, resulting in one fatality and the total destruction of the aircraft.
The investigation
The investigation conducted by the Swiss Transportation Safety Investigation Board (SUST) focused on the flight sequence, the aircraft's technical condition, and the pilot's health. Investigators analyzed flight tracking data from the Open Glider Network and interviewed eyewitnesses.
Technically, the investigation examined the control linkages of the aircraft. While investigators found several loosened locknuts on the push-pull rods at the rod ends, they determined these were not the cause of the accident. The use of split washers (DIN 6798 I) was noted as an ineffective method for preventing loosening due to vibrations from the retractable engine. The investigation also reviewed the pilot's medical status, noting the presence of an anti-fungal medication in the pilot's system, which is known to potentially impair the ability to operate machinery.
Findings
- The primary cause of the accident was that the glider executed a turn at an insufficient airspeed, leading to a stall and subsequent loss of control.
- The aircraft was flying at a low altitude, which prevented the pilot from recovering before impacting the terrain.
- The aircraft's center of gravity was within limits but positioned in the aft zone.
- Although loose locknuts were found on the control rods, these only caused slight play in the controls and did not compromise maneuverability.
- The pilot was under the influence of medication that can negatively affect operational performance, though its direct impact on this specific accident remains unconfirmed.