Accident Overview
On 25 July 1995 at approximately 1530 local time, a Piper J-3C aircraft registered as HB-OWS made a forced landing about 5 km southwest of Fleurier, Switzerland. The aircraft sustained substantial damage: the fuselage, engine mount, and propeller were deformed; the engine block was cracked; the right wing was torn off; and the left wing was deformed and perforated. One medium-sized fir tree was broken. The pilot and passenger were uninjured or lightly injured and exited the wreckage unaided.
Flight History
The aircraft was a private Piper J-3C, HB-OWS, approved for day VFR flights. The pilot, born in 1941, held a valid private pilot license with 392:34 total flight hours, including 139:1 hours on type. The passenger held an expired private pilot license.
On 21 July 1995, the club's technical responsible noticed a fuel primer pump leak and placed a notice not to use it. He added 31 liters of fuel and believed he correctly secured both fuel caps. On 25 July, the pilot arrived at the airfield at 1400 hours. He and the passenger performed a preflight inspection, checked oil, and observed that the fuel gauges indicated full. The pilot visually confirmed the fuel caps were in place but did not open the tanks. No fuel smell was noticed. The engine was started by the passenger pulling the propeller, and the aircraft taxied to runway 05. Engine checks revealed no anomalies.
At 1415 hours, the aircraft departed for a local flight. The pilot observed the left fuel gauge 2 cm below maximum and the right at maximum. The fuel levels later equalized. The flight proceeded over Creux-du-Vent, Lake Neuchâtel, Yverdon-les-Bains, Orbe, Le Suchet, and Lake Joux. At Le Suchet, the pilot noted about half fuel in each tank. The aircraft then turned back over Mont d'Or and Chasseron, crossing the Col des Étroits at about 4800 ft before descending toward the approach sector of Môtiers aerodrome. The engine operated normally throughout the flight.
Forced Landing and Aftermath
Approximately 3.5 km north-northeast of Ste-Croix, while descending, the engine emitted one or two brief misfires and then stopped. The pilot verified that the mixture control was full rich, carburetor heat was cold, and magnetos were on, but did not check the fuel gauges. He focused on executing a forced landing, maintaining adequate speed. The terrain was wooded near the Le Buttes stream. The pilot attempted to fly between two fir trees and then bank left toward the streambed. The right wing struck a fir tree, and the right wheel hit the creek bank; the aircraft came to rest in the stream. The pilot and passenger exited without assistance around 1530 hours.
Findings
- The pilot held a valid license and no health issues were suspected.
- Aircraft mass and center of gravity were within limits at the time of the accident; at takeoff, mass was maximum.
- The aircraft had not been flown since the last fuel refill on 21 July. Normal endurance was 2 hours plus reserve; the engine stopped after about 1 hour 15 minutes of flight.
- After the accident, the left fuel tank contained no fuel, and 5 liters were drained from the right tank.
- The left fuel cap was found two days later on the ground in front of the hangar where the aircraft had been started. When placed on the filler neck, it locked normally.
- Examination of the engine and accessories (spark plugs, magnetos, carburetor, fuel filter) found no defects; a 15-minute full-power bench test showed no anomalies.
- The fuel primer pump leak was not related to the fuel supply interruption.
- Weather at nearby stations reported no precipitation, with temperatures around 20-26°C and light winds.