What happened
On June 14, 1970, a flight instructor and a student pilot departed from Triengen Airfield in a Piper J3C, registration HB-OXV, to conduct a training flight focused on hazard introduction. During the flight, the aircraft completed an initial spin and regained some altitude. However, a subsequent spin was terminated at an insufficient altitude. This maneuver transitioned the aircraft into a steep dive, which could not be recovered before the aircraft struck a grassy meadow approximately 200 meters south of the runway threshold. The impact, occurring at a longitudinal pitch of 30 to 40 degrees, resulted in two fatalities and the total destruction of the aircraft.
The investigation
Investigators examined the aircraft's condition, the flight profiles, and the pilot qualifications. The investigation confirmed that the Piper J3C was airworthy and that no mechanical failures contributed to the accident. The engine was found to have been running at idle during the impact. The investigation also reviewed the cockpit instruments, noting that the aircraft was equipped with a coarse altimeter that could have made precise altitude monitoring difficult. The flight instructor was a highly experienced pilot with approximately 1,000 flight hours, and the student was undergoing basic training. There was no evidence of alcohol consumption or health issues affecting the crew.
Findings
- The primary cause of the accident was that the aircraft was pulled out of a spin at an altitude that did not provide enough margin to recover from the resulting steep dive.
- The aircraft entered a steep left-hand spin, which eventually stabilized into a flatter, faster rotation before the recovery attempt.
- It remains unclear whether the second spin was an intentional maneuver or if the instructor was surprised by the aircraft's behavior.
- The use of a coarse-scale altimeter may have hindered the crew's ability to accurately monitor their height above the ground during the maneuvers.