What happened
On August 6, 1970, a Piper J3C, registration HB-OUS, was involved in an accident during a landing training session at Grenchen airfield. While performing a dead-stick approach—a maneuver conducted without engine power within a 150-meter distance from the runway—the student pilot executed a landing that resulted in a hard impact. The aircraft sustained substantial damage as a result of the incident.
The investigation
The investigation focused on the flight parameters during the final approach of the training maneuver. Investigators examined the descent profile and the pilot's management of the aircraft's energy during the engine-off approach. The inquiry established that the aircraft's flight path was not stabilized for the intended touchdown.
Findings
Technical analysis of the flight sequence revealed that the pilot allowed the aircraft to fly too high during the approach. This resulted in a loss of lift or a sudden drop in altitude (sinking) from a height of approximately 2 meters just before touchdown. This unstable glide path led directly to the hard landing and the subsequent structural damage to the aircraft.