What happened
On August 29, 1968, a pilot was conducting a flight from Lausanne to Prangins to deliver a Stark Turbulent D, registration HB-SVW, following its sale. While flying at an altitude of approximately 200 to 250 meters above the Prangins airfield, the aircraft entered a left-hand spin. Witnesses on the ground observed the aircraft performing roughly five rotations before impacting the ground in a wheat field. The impact resulted in the death of the pilot and the total destruction of the aircraft.
The investigation
Investigators examined the aircraft's condition, the pilot's medical history, and witness accounts. The engine and control cables were found to be in good working order, and the engine examination revealed no evidence of mechanical failure. The aircraft's weight and balance were within prescribed limits at the time of the accident. An autopsy of the pilot revealed no signs of impairment, such as alcohol consumption or physical ailments, that would explain a sudden loss of consciousness.
Witnesses reported hearing a high-pitched whistling sound during the approach, which was attributed to the aircraft's slotted wings rather than a mechanical defect. One witness noted that the aircraft appeared to initiate a sharp left turn immediately before the spin began.
Findings
- The primary cause of the accident was a spin that the pilot was unable to recover from.
- The specific trigger for the spin could not be definitively established, though investigators considered that a sudden increase in the angle of attack or a slip could have induced the maneuver.
- The pilot's failure to recover from the spin remains unexplained, with potential contributing factors including the effect of surprise, disorientation, or limited advanced maneuvering training.
- The pilot's only apparent reaction to the abnormal flight condition was to reduce engine power.