What happened
On April 22, 1965, a Piper J3C Cub, registration HB-OGT, was conducting a dual instruction flight at Geneva Airport. The flight, operated by the Geneva section of the Aero-Club de Suisse, began with a successful initial departure from the grass runway 05. Following a brief circuit, the aircraft commenced a second departure at 14:18.
During the initial climb, at an altitude of approximately 20 meters, the aircraft experienced a sudden loss of control. The student pilot reported that the aircraft began to drift and oscillate. Despite attempts by both the student and the instructor to correct the flight path with rudder and aileron inputs, the aircraft suddenly banked to the right at an angle of approximately 45 degrees. The aircraft subsequently struck the ground with the right wingtip, resulting in the destruction of the aircraft. The instructor sustained grievous injuries, including a concussion and facial contusions, while the student pilot remained uninjured.
The investigation
The investigation examined the flight sequence, the aircraft's condition, and the surrounding air traffic. The Piper J3C Cub was found to be in a proper configuration, with the center of gravity within limits and no mechanical defects suspected. The investigation also reviewed the recent heavy aircraft movements on the adjacent main runway, which had seen several large-tonnage aircraft, including Boeing 707s and a Viscount, performing takeoffs and landings just minutes prior to the accident.
Findings
The investigation focused on two primary possibilities for the sudden roll. The first was a potential lack of vigilance by the instructor, which might have allowed the aircraft to enter a critical attitude. The second was the influence of wake turbulence generated by the heavy aircraft operating on the nearby main runway. While the intensity of wingtip vortices is linked to aircraft weight, the exact positions of the preceding heavy aircraft could not be definitively established to confirm this theory.
Ultimately, the commission concluded that the accident was caused by the instructor losing control of the aircraft at an altitude too low to recover the normal flight attitude.