1967 Piper J3C HB-OUD Accident at Bienne Aerodrome

Overview and Investigation Status On 30 July 1967, a Piper J3C registered HB-OUD was involved in an accident at Bienne aerodrome. The Federal Commission for Aircraft Accident Investigations approved the investigation report on 3 November 1967, with three amendments, and circulated the decision in January 1960 according to the source document. The accident was reported immediately to the Federal Air Office duty service. An initial decision not to conduct a full investigation was reversed on 3 August 1967, and the wreckage was visited on 5 August 1967. Cantonal authorities did not participate in the investigation. ## Aircraft and Personnel The aircraft was a Piper-Cub L 4 H, a high-wing, single-engine, two-seat mixed-construction airplane used for training and touring, owned and operated by Aé.C.S., Motorfluggruppe Biel. It was equipped with a Continental C 90-12 F engine manufactured in 1958. The airworthiness certificate had been issued by the Federal Air Office on 30 March 1963 and was valid until 16 December 1967. At the time of the accident, the aircraft’s weight and centre of gravity were within limits. It had accumulated about 2,700 hours since introduction into Switzerland, including 796 hours 40 minutes since the last general overhaul. The last 50-hour inspection was performed on 18 July 1967 by Maison Airbase at 770 hours 39 minutes. The pilot, born in 1941, held a private pilot licence issued on 2 September 1964, valid until 13 December 1967, with an extension on the Jodel D 140 C dated 29 April 1967. His total experience was 109 hours 54 minutes and 460 landings, including 90 hours 01 minutes and 286 landings solo. His last flight before the accident was on 29 July 1967. He was in good health at the time. The passenger had no aeronautical experience. ## Flight and Accident Sequence At 1930 hours local time, the pilot departed Bienne with one passenger for a short flight. The route included overflights of Bienne, Île St-Pierre, and Aarberg before returning to Bienne. During the approach, the aircraft passed over the aerodrome at 300 metres above ground, reduced speed, and prepared for a power-on landing. The pilot used carburettor heat briefly during the approach. About 700 metres before the runway, when the pilot attempted to increase power, the engine did not respond. The pilot then landed the aircraft in a wheat field 190 metres before the threshold of runway 07. The accident occurred at 1945 hours local time. ## Site, Weather, and Damage The accident site was immediately adjacent to Bienne aerodrome, a few metres before the aerodrome boundary on the runway 07 threshold side. A 7-metre-wide road bordered the aerodrome, with a 13-metre-wide cereal field on the other side; the aircraft came to rest in that field. The runway threshold was located 160 metres after the beginning of the aerodrome area. The site was in the municipality of Bienne at an elevation of 440 metres, with coordinates 588 300/223 000. Weather was fair and warm, with visibility of 30 km, wind from the north to north-east at 2–4 knots, and 1/8 stratocumulus with a base at 1,800 metres. Temperature at 400 metres was +25 °C with 50% relative humidity. Pressure was 1017 mb, 4 mb above standard. The sun was at an elevation of 3° and azimuth 295°. The pilot sustained minor contusions; the passenger was uninjured. The aircraft was seriously damaged: the landing gear was sheared off, the propeller was broken, the engine was damaged, and the fuselage was twisted. Approximately 30 square metres of wheat were trampled. ## Technical Findings and Cause A technical examination of the engine by Maison Transair SA did not identify any defect that could have caused an engine failure. Inspection of the fuel sump by the person responsible for the Biel motor flight group’s equipment found no water in the fuel and only a very small deposit. The temperature conditions excluded carburettor icing below 1,600 metres; any icing that might have occurred above that altitude would have cleared well before the power application in the approach. The Transair report noted a slightly rich carburettor setting, which could cause a brief engine stall during rapid throttle movement, but such an event is generally short-lived. The pilot confirmed that the event was not a misjudgment but an engine failure. The investigation therefore could not determine the cause of the possible engine failure.