What happened
On April 28, 1968, a Mucha Standard glider, registration HB-658, was conducting a training flight near the Hausen am Albis airfield. After performing several turns to dissipate altitude, the pilot initiated the landing sequence for runway 27. During the base leg, the pilot suddenly observed another glider, a Ka-8, approximately 80 meters ahead on its final approach.
Distracted by the unexpected appearance of the other aircraft, the pilot attempted to increase separation by deploying the airbrake while turning into the final approach. During this maneuver, the aircraft encountered a slight gust and subsequently stalled, causing the aircraft to drop over the right wing. Due to the extremely low altitude, the pilot was unable to recover the flight attitude. The fuselage struck a ground undulation, and the left wing clipped an electric fence, causing the aircraft to come to a halt across the airfield. The pilot sustained no injuries.
The investigation
The investigation examined the flight sequence, the weather conditions, and the pilot's recent flight history. At the time of the accident, the weather consisted of light easterly winds and weak turbulence. The investigation also reviewed the flight path of the second aircraft, a Ka-8 with registration HB-765, which had been performing a distance flight. While the pilot of the second aircraft had used a different approach pattern than the local custom, the investigation determined this was not a direct cause of the accident.
Findings
- The pilot was flying at a speed near the minimum threshold during the base leg.
- The deployment of airbrakes during the turn into final approach, combined with a potential gust, caused the airspeed to drop below the minimum required speed.
- The Mucha Standard model is noted for its tendency to enter a stall without significant warning.
- The low altitude of approximately 10 to 20 meters prevented an effective recovery attempt.