Accident Details
On 13 April 1973, at 1522 hours HEC, a Piper PA-18-150 (registration HB-OPF) equipped with skis was aligned on the threshold of grass runway 05 at Geneva-Cointrin airport. The pilot, who intended to conduct a private VFR flight over the Alps with a passenger, received a green signal from the runway vehicle and applied full throttle. After traveling approximately 30 meters, the aircraft deviated to the left, executed a ground loop, and the left wing made contact with the ground. The aircraft came to a stop within the runway limits. Both occupants were uninjured, but the aircraft sustained heavy damage.
Aircraft and Pilot
The aircraft was in airworthy condition and had a valid certificate of airworthiness. The brakes and flight controls functioned normally at the time of the accident. The pilot, born in 1935, held a valid private pilot license. His total flight experience was 501 hours, including 141 hours on the Piper PA-18 type. In the three months preceding the accident, he had flown 5.47 hours, all on a Piper Super Cub. Federal air office records showed no prior incidents, accidents, or violations of air navigation rules. There was no indication that the pilot was not in good health at the time of the accident.
The pilot had placed his navigation briefcase on the right side of the cabin, between the seat and the fuselage wall, as no dedicated stowage space was available.
Analysis
The pilot possessed good experience on the type, which does not present particular difficulties during takeoff. It was surmised that the pilot's briefcase shifted under the influence of vibrations during the takeoff roll and slid under the right rudder pedal, thereby restricting the travel of the rudder control. This would explain the pilot's inability to counter the leftward deviation.
Probable Cause
The accident was attributed to a loss of control of the aircraft during takeoff, probably following the inadvertent movement of an object in the cabin.