What happened
On May 7, 1972, at approximately 13:50, an ASW-15 glider, registration HB-990, was engaged in a cross-country flight as part of a regional competition. The flight originated in Bern with a planned route returning via Romont. During the return leg, the pilot encountered difficulties locating the Bern airfield, causing the aircraft to deviate south of the intended course.
While near the Schwarzenburg shortwave transmitter, the pilot experienced a failure of the aircraft's electrical variometer. This loss of instrumentation hindered the pilot's ability to utilize the weak thermal lift available at the time. Due to the declining altitude, the pilot decided to perform an emergency landing in a nearby field near Winterchrut, located in the Rüschegg-Graben area. The chosen landing site was a small meadow approximately 160 meters long, which was obstructed by trees and telephone lines on the approach side and an orchard on the far side.
Upon approaching the field, the pilot noted that the terrain dropped slightly behind a telephone line before rising again midway through the meadow. Despite utilizing a glide slope and fully extending the airbrake flaps, the ASW-15 did not come to a halt until roughly 120 meters into the field. Realizing the aircraft would not stop before hitting a heavy fence at the end of the meadow, the pilot intentionally dropped the left wing to the ground to execute a controlled skid. This maneuver resulted in the fuselage buckling behind the wing and damage to the tail unit.
The investigation
The investigation examined the pilot's credentials, the aircraft's mechanical state, and the environmental conditions. The pilot, a radio technician with approximately 470 hours of flight experience, was found to be in good health and holding a valid glider license. The ASW-15 was confirmed to be airworthy and properly registered. Investigators also noted that the aircraft was equipped with a secondary mechanical total-energy variometer to supplement the electrical unit.
Findings
- The primary cause of the accident was an unsuitable landing in terrain not intended for landing.
- The failure of the electrical variometer contributed to the pilot's inability to maintain altitude using available thermals, leading to the decision to land.
- The pilot's decision to execute a wing-drop maneuver was an attempt to avoid a collision with a substantial fence, though it caused significant structural damage to the fuselage and tail.