Summary
On Saturday, 24 June 1961, the pilot of a Bücker 131 Jungmann, registration HB-URG, was returning from a pleasure flight. While performing low-altitude maneuvers over an institute near Rolle where he had stayed several months earlier, the aircraft entered a spin during a chandelle. At approximately 1204 hours (HEC), the aircraft crashed at the edge of a rye field. The pilot sustained serious injuries to his head and legs; the aircraft was 85% destroyed.
Investigation
The final report of the Federal Aircraft Accident Investigation Commission was issued on 15 December 1961.
Pilot Information
The pilot, born in 1942, was a U.S. citizen. He held a special pilot license issued by the Federal Air Office on 17 August 1960 based on a FAA Temporary Airman Certificate, with an extension for aerobatics, valid until 9 December 1960. A renewed Temporary Airman Certificate was issued 27 April 1961, valid until 27 July 1961. His flight training began in summer 1957. At the time of the accident, he had accumulated 450 flight hours, including 15 on the Bu-131. The pilot was described as well-trained, calm, and reserved. No prior accidents, incidents, or violations were noted, and there was no indication that he was not in full possession of his faculties at the time of the accident.
Aircraft Information
The aircraft, type Bücker 131 "Jungmann", serial number 34, was manufactured by Dornier-Werke A.G., Altenrhein SG, in 1938. It was a tandem two-seat sport and touring biplane with mixed construction, powered by a Hirth HM-504-A2 engine of 105 HP driving a two-blade wooden K+W propeller. The owner and operator was the Geneva Section of the Ae.C.S. The airworthiness certificate was issued on 29 May 1961, valid until 29 May 1962, with aerobatics permitted. Maximum weight 670 kg; actual weight at time of accident was about 530 kg. Center of gravity was within limits. Total time since last major overhaul was 75 hours. Flight characteristics were described as excellent, with a stall speed in straight flight of 70-80 km/h. In turns, slight cross-control at stall could induce a sudden lateral stall. Approximately 150 meters of altitude were required to recover from a spin under the conditions of the accident. There was no indication that the aircraft was not airworthy at the time.
Flight History
On 24 June 1961, the pilot flew to Bern on business, having obtained permission to use the Bu-131 HB-URG, recently acquired by the club. The flight instructor gave authorization exceptionally, as this aircraft was normally reserved for aerobatics. Before departure from Geneva, the instructor advised the pilot, explicitly prohibiting any aerobatics or stunts, and noted he was not carrying a parachute since it was a pleasure flight. The pilot departed at 0800 (HEC) for Bern, arriving at 0859.
On return, the pilot left Bern at 1104 in good weather and excellent visibility. He climbed to 3500 m to enjoy the Alpine panorama. Over Lausanne he began descent, and upon reaching Rolle he made a low pass over the Institut "Le Rosey". Surprised to see no one, he checked his watch and realized it was noon; he concluded the residents were in the refectory. As he prepared to continue, he turned back and saw some students attracted by the aircraft noise coming out of the building.
Changing his mind, the pilot made a right turn with a low-altitude pass in a slight descent, without gaining much speed. At the bottom of the trajectory (estimated by him as 50 m, by witnesses between 5 and 20 m), he performed a chandelle by pulling back firmly on the control stick. According to the pilot, while watching his companions on the ground, he looked to the right behind him. At about 250 m above ground, the aircraft suddenly banked left and entered a spin. The pilot immediately reduced power and stopped the rotation after about 2.5 turns. However, during the subsequent recovery, the aircraft struck the ground at 1205 due to insufficient altitude.
A witness captured three photographs of the fall, including the initial contact with the rye field.
Damage
- Pilot: seriously injured to the head and legs.
- Aircraft: 85% destroyed.
- Third parties: trampled rye over an area of about 150 m².
Probable Cause
The investigation determined that the main cause of the accident was the pilot's decision to perform low-altitude maneuvers.