What happened
On May 17, 1969, during the West Swiss gliding championships, a Foka Standard SZD-24 C glider, registration HB-727, was performing a competition triangle flight. The pilot was attempting to climb above a local inversion layer by utilizing ridge lift along the Crête Sex Riond. After reaching an altitude of approximately 1,700 meters, the pilot attempted to transition toward the Crête Besse.
While executing a left-hand turn away from the ridge, the aircraft entered a left-hand spin. Although the pilot managed to stop the rotation after one full revolution, the aircraft's flight path led toward a steep, wooded slope. The pilot attempted to maneuver the nose of the glider between two fir trees to avoid the terrain, but the aircraft ultimately struck the trees, resulting in the total destruction of the glider. The pilot sustained minor injuries.
The investigation
Because the accident occurred in May and the investigation was conducted later in the year, the commission relied on the pilot's report, as no independent investigation was conducted by local authorities. The investigation reviewed the pilot's extensive flight experience, which included over 2,800 hours of flight time, and confirmed the aircraft's airworthiness and valid registration. The investigation also examined the meteorological conditions, noting a high-pressure system and a local inversion that limited upward development below 1,800 meters.
Findings
- The primary cause of the accident was a loss of airspeed during the turn.
- The terrain, characterized by rocky slopes and forests, created significant turbulence near the ridges.
- The aircraft was operating within its weight and balance limits at the time of the incident.
- While the meteorological conditions and terrain presented a challenging environment, the investigation concluded that the pilot's training should have been sufficient to manage the circumstances.