What happened
On May 23, 1964, a Jodel D-112 aircraft, registration HB-SUB, was involved in a fatal accident near Obergrenchenberg, Switzerland. The flight began in Grenchen, where the pilot and a passenger departed without filing a flight plan or notifying air traffic services. During the flight, the pilot performed an unauthorized landing at a site near the Obergrenchenberg mountain house.
During the subsequent departure, the pilot attempted to take off with a tailwind. Rather than utilizing the full length of the available terrain, the pilot positioned the aircraft approximately 100 meters short of the marked runway start. Throughout the takeoff roll, the pilot failed to lift the tail, keeping the aircraft in a taildragger configuration. This resulted in an excessively long takeoff run. The aircraft finally lifted off in a high angle of attack, nearly 25 meters past the end of the marked runway. Shortly after takeoff, the aircraft struck a tree, causing it to crash and catch fire. The impact resulted in two fatalities, and the aircraft was completely destroyed.
The investigation
The investigation examined the pilot's qualifications, the aircraft's mechanical condition, and the regulatory environment. It was established that the pilot did not possess the required special authorization for mountain landings, and the landing site was not an officially designated mountain landing strip. The investigation also reviewed recent changes to aviation regulations regarding off-airport landings that had been implemented just weeks prior to the accident.
Technical examination of the Jodel D-112 revealed no mechanical failures. The aircraft's weight was approximately 510 kg, and the center of gravity was within limits. The investigation also noted that the pilot had a history of performing unauthorized landings without permission.
Findings
Several critical factors contributed to the accident:
- The pilot lacked the necessary training and certification for mountain flying.
- The takeoff was performed with a tailwind, which significantly extended the required takeoff distance.
- The pilot failed to utilize the available runway length, starting the roll significantly short of the marked threshold.
- The pilot maintained a high angle of attack during the takeoff roll by not lifting the tail, which prevented the aircraft from accelerating efficiently.
- The pilot attempted a takeoff from an unauthorized landing site that did not meet the regulatory requirements for mountain operations.