Incident Overview
On Saturday, October 23, 1976, at approximately 15:08 local time, a pilot departed from Flugfeld Buttwil in a Chipmunk T 22 A, registration HB-TUL. The aircraft was towing a Ka8 glider, registration HB-704. After releasing the glider at an altitude of roughly 700 meters above ground level, the pilot returned to the airfield and discarded the tow rope at approximately 30 meters above ground.
Sequence of Events
The pilot initiated a standard circuit for landing on Runway 34. During this time, a motor glider (Falke, HB-2021) prepared for takeoff but delayed its start to avoid contact with the discarded tow rope. As the motor glider reached full throttle, the Chipmunk was already in the short final approach. A ground observer signaled the motor glider pilot to abort the takeoff, which was done immediately.
The Chipmunk pilot, observing the signals and the rolling motor glider, decided to go around. He entered a tight turn at approximately 20 meters above ground level. The pilot later stated that he believed the signals were directed at him, possibly due to a perceived issue with the tow rope release mechanism, despite the control light indicating the rope was released. During this low-altitude maneuver and the subsequent landing curve, the pilot repeatedly looked backward to check for the rope.
Crash and Damage
While looking back in the landing curve, the aircraft dropped below its minimum safe speed of 37 knots. The plane stalled and could not be recovered in time. It crashed into a forest and came to rest on its nose in a narrow ravine at approximately 15:15 local time. The crash site was located 550 meters before the threshold of Runway 34, at an elevation of 720 meters above sea level.
The pilot, born in 1938, was not injured. The aircraft was destroyed, and minor damage occurred to the surrounding forest. Investigations revealed no prior technical defects; the tow hook and control light functioned normally. The probable cause was identified as inappropriate flight tactics, distraction from flying tasks during the landing curve, and dropping below minimum speed near the ground.