What happened
On May 16, 1970, a Piper PA-18-150 Super Cub, registration HB-ORZ, was completing a flight involving glider towing operations at Sion Aerodrome. After successfully releasing the tow rope, the pilot attempted to land on grass runway 26. During the landing roll, the aircraft's right wing made contact with the ground. This contact triggered a sudden 90-degree right-hand ground loop. The aircraft then pivoted forward, lifting into a nose-up attitude, before coming to a halt resting on the propeller hub and the two main landing gear wheels.
The investigation
The investigation focused on the sequence of the landing roll and the environmental conditions present at the time of the incident. Investigators examined the aircraft's behavior following the release of the tow rope and the physical impact of the wing strike. The assessment included an analysis of the pilot's control inputs and the aerodynamic state of the aircraft during the final approach and touchdown.
Findings
The investigation established that the accident was caused by the combined effects of an excessively low approach speed, ground-level turbulence, and the improper application of the wheel brakes. These factors together destabilized the aircraft during the landing phase, leading to the loss of directional control and the subsequent wing strike.