What happened
On April 13, 1973, a Piper PA-18-150, registration HB-OPF, was preparing for a private VFR flight over the Alps. The aircraft, which was equipped with skis, was lined up on the grass runway 05 at Geneva-Cointrin Airport with one passenger on board.
Upon receiving the green signal from the runway vehicle, the pilot applied full power. Shortly after the takeoff roll began, approximately 30 meters into the run, the aircraft veered sharply to the left. This movement resulted in a ground loop, during which the left wing made contact with the ground. The aircraft came to a stop within the runway boundaries. There were no injuries to the occupants, though the aircraft sustained heavy damage.
The investigation
The investigation examined the pilot's credentials, the mechanical state of the aircraft, and the environmental conditions at the time of the incident. The pilot held a valid private pilot license with 501 total flight hours, including 141 hours on this specific type. The aircraft was found to be airworthy, with all flight controls and brakes functioning normally.
Weather conditions were favorable, characterized by good visibility, a dry runway surface, and a headwind of 15 to 20 knots. Investigators focused on the cabin configuration, noting that during loading, the pilot had placed a navigation towel on the right side of the cabin, wedged between the seat and the fuselage wall, because there was no dedicated storage space for it.
Findings
- The investigation determined that the aircraft's mechanical systems were not at fault.
- An unsecured object in the cockpit obstructed the rudder pedals.
- It is believed that during the takeoff roll, vibrations caused the navigation towel to slide under the right rudder pedal, restricting the travel of the directional control.
- This mechanical interference prevented the pilot from effectively countering the leftward deviation, leading to the loss of directional control.