What happened
On July 5, 1969, a pilot participating in a regional gliding competition took off from Granges in a Schempp-Hirth SHK1, registration HB-875. The flight was part of a 100 km triangular course. After successfully reaching the first waypoint near Dittingen, the pilot encountered deteriorating conditions near the Scheltenpass. As the available lift became insufficient to clear the terrain, the pilot decided to terminate the flight and perform a forced landing in a field near Corban in the Val Terbi.
During the approach, the pilot initially selected a landing strip oriented north-south. However, upon realizing the steep 10% slope of the chosen field would force a landing too far down the slope, the pilot attempted to modify the approach. To extend the glide path, the pilot retracted the air brakes but failed to jettison the previously deployed braking parachute. While attempting a low-altitude turn to realign the aircraft against the slope, the sudden drag from the parachute caused a rapid loss of airspeed and a subsequent loss of roll control, leading to a wing strike and ground impact.
The investigation
The investigation examined the aircraft wreckage, the landing site, and the pilot's flight logs. Investigators reviewed the aircraft's weight and balance, noting that while the total weight was approximately 2 kg over the maximum limit, the center of gravity was within prescribed limits. The investigation also reviewed the pilot's qualifications and the operational history of the SHK1.
Findings
- The pilot was properly qualified for the flight and the aircraft was airworthy with a valid certificate of airworthiness.
- The primary cause of the accident was the failure to jettison the braking parachute after retracting the air brakes during a modified approach.
- The drag produced by the deployed parachute caused a rapid decrease in airspeed during a low-altitude turn.
- This loss of speed led to a loss of lateral control and an increase in bank angle, making it impossible to avoid striking the ground with the wing.
Safety action
No specific safety recommendations were recorded in the final report.