1964 Piper Super Cub accident at Crans-sur-Sierre (HB-OPE)

Incident overview and flight details On Wednesday, 29 January 1964, at 1139 HEC, a pilot departed from Crans for Sion in Piper Super Cub Pa-18A HB-OPE. After rising only a few meters, the aircraft experienced an unexpected loss of power. It then struck a bank and came to rest approximately 500 meters from the departure point, heavily damaged. The pilot sustained minor injuries. ## Aircraft and operator information The aircraft was a Piper Super Cub Pa-18A, equipped with a 150 hp Lycoming O-320 engine. It was a tandem-seat, high-wing, strut-braced monoplane with mixed construction. On the day of the accident, it was fitted with metal skis. The owner and operator was the Valais Section of the Swiss Aero Club, Sion. The aircraft had a maximum weight of 794 kg and weighed about 700 kg at the time of the accident, with the center of gravity within prescribed limits. ## Pilot and operational context The pilot was born in 1930 and held a French private pilot license issued on 28 August 1959, valid until 15 January 1965. He had about 800 hours and 1,300 flights of total training, including about 50 hours on the Piper Cub J3C and 9 hours 42 minutes and 134 landings on the Piper Super Cub Pa-18 during the week before the accident. The flight was part of a glacial landing course organized by the Valais Section of the Swiss Aero Club, which operated under an authorization granted on 27 January 1955. ## Accident sequence and damage The takeoff was made westward. The engine responded well and the aircraft lifted off normally after about 130 meters. A few meters above the ground, the pilot noticed a loss of power, immediately reduced the throttle, and touched down after passing a depression at the end of the runway. The aircraft bounced for about 100 meters and struck the toe of the skis against the bank of an embankment road crossing the depression. The landing gear was sheared, with wheels and skis folded to the right. The aircraft crossed the road, where the propeller was torn off, and stopped on a mound about 30 meters later after making a half-turn to the right. The pilot was lightly injured, the aircraft was 60 percent destroyed, and ground damage was negligible. ## Investigation findings and probable cause Examination of the engine, carburetor, and fuel lines revealed nothing abnormal. The discussion noted that the 200 to 300 rpm drop observed during the carburetor heat test was significant but not extraordinary, and that the pilot’s decision to depart was justified. Weather conditions on the day—cloud cover 7/8 at 900 m, visibility 4 km, west wind 3 to 5 knots, pressure 857 mb, temperature -2°C, and relative humidity 85 percent—could have caused carburetor icing. In the absence of another apparent cause, carburetor icing was considered fairly probable. The commission concluded unanimously that the accident was probably due to a loss of power during takeoff, resulting from carburetor icing.