Accident
On 22 April 1965, a Piper J3C Cub registered HB-OGT operated by the Geneva Section of the Aero-Club of Switzerland crashed during takeoff from Geneva-Cointrin Airport. The aircraft was destroyed, the instructor sustained serious injuries, and the student pilot escaped unharmed.
Sequence of Events
The instructor, born in 1923, held a private pilot license with instructor rating and had approximately 1,800 flight hours. The student, born in 1934, had a student pilot card issued in November 1964 and had completed one 15-minute introductory flight in December 1964 and one 39-minute training session one week before the accident.
At about 14:00 local time, the student arrived for a training session. The first takeoff from grass runway 05 occurred at 14:12 and was uneventful, lasting five minutes. After landing, the aircraft returned to the threshold and began its second takeoff at 14:18. Weather conditions were fine with a north-east wind at 12 knots from 050° and temperature +10°C.
In the minutes prior, five heavy aircraft (Boeing 707s, DC-3, Viscount, SE-210) had taken off or landed on the adjacent main runway 05, 175 meters south of the grass runway.
The instructor reported a sudden right bank and control inputs without effect. The student stated that after a normal takeoff at 60 mph, the aircraft felt like it was crabbing left with a slight left bank. The instructor said "to right," and the student corrected, but then a slight oscillation occurred. Believing the instructor was busy with his kneeboard, the student corrected again, after which the aircraft banked sharply right to about 45°. The instructor retook control but could not recover, and the aircraft struck the ground with the right wingtip. The last indicated airspeed was 60–65 mph.
Investigation
The aircraft was a Piper J3C Cub with a Continental A-65 engine, maximum weight 550 kg, actual weight 515 kg, center of gravity within limits. No pre-existing defects were found. The student's account was corroborated by witnesses regarding the aircraft's attitude during takeoff.
Two hypotheses were considered: (1) the instructor was caught off guard by a student maneuver, and (2) the aircraft encountered wingtip vortices from a preceding heavy aircraft. The investigation could not determine the exact takeoff and landing points of the heavy aircraft, leaving the vortices hypothesis unconfirmed. The commission stated that neither hypothesis appeared more probable than the other, and a combination could not be excluded.
Cause
The official conclusion stated that the accident resulted from the instructor losing control of the aircraft at a height insufficient to regain normal attitude.