Incident Overview
On Sunday, June 14, 1970, a Piper J3C with registration HB-OXV crashed into a grassy field approximately 200 meters south of runway threshold 33 at Triengen airfield. The accident occurred during a training flight involving a flight instructor and a student pilot. Both occupants were killed, and the aircraft was destroyed.
Aircraft and Personnel
The aircraft was a 1943 Piper J3C (serial number 29'258) equipped with a Continental A-65-8 engine. At the time of the accident, it had approximately 568 flight hours since its last major overhaul. The flight instructor, born in 1940, held a commercial pilot license and had roughly 1,004 total flight hours, including about 550 hours on the Piper J3 type. The student pilot, born in 1922, was in the early stages of training with only 5 hours and 32 minutes of dual instruction experience.
Sequence of Events
The aircraft took off from runway 15 at approximately 10:40 local time. Witnesses observed the plane completing a spin maneuver between Triengen and Knutwil, gaining altitude to an estimated 500–800 meters above ground level. The aircraft then pitched up, lost speed, and entered a steep left spin. After approximately four rotations, the spin was arrested, but the aircraft transitioned into a steep climb of about 75 degrees. At this point, the altitude above the ground was only about 50 meters, which was insufficient to recover from the subsequent stall. The aircraft impacted the ground with a longitudinal tilt of 30 to 40 degrees.
Investigation Findings
The Swiss Federal Accident Investigation Commission concluded that the accident was caused by exiting the spin at an altitude too low to allow for recovery from the ensuing stall. The Piper J3C type was not certified for aerobatic maneuvers due to a history of incidents involving spins, although this specific maneuver was part of a hazard awareness training exercise.