Accident Summary
On 31 January 1965, a student pilot obtained permission from his flight instructor to conduct the required 300-kilometer triangular navigation flight from Olten in the Piper J3C Cub HB-OVA. The first leg to Prangins/La-Côte was completed, but due to weather, the pilot overnighted in Prangins. The following day, 1 February, he departed at 0900 (MEZ) and landed at Bern at 0956. After consulting his instructor by telephone, who authorized the continuation to Olten based on local weather, he took off from Bern at 1018. While en route, he encountered a cold front moving southward, with fog reducing visibility to 20 meters above ground near Wynau. At 1051, while flying at low altitude, the aircraft suddenly rolled left and descended steeply, crashing. The pilot was fatally injured and the aircraft was destroyed.
Aircraft and Pilot Information
The aircraft was a Piper J3C Cub with a Continental A-65 engine, serial number 12051, built in 1944, and owned by the Motorfluggruppe of the Olten section of the Aero-Club of Switzerland. Its empty weight was approximately 490 kg (below maximum 550 kg), and its center of gravity was within limits. The cruising speed was 110 km/h, and the stall speed in level flight was 60 km/h. No technical defects were found.
The student pilot, born 1926, held a learner's permit for motor flight since May 1963, with an extension for cross-country flights since September 1964. He had about 46 total flight hours and 350 landings, all on the accident type. He had received alpine instruction on 15 December 1964. No health issues were indicated.
The flight instructor, born 1926, held a private pilot license since 1949 and a flight instructor endorsement since 1958. He had over 1800 motor flight hours and 450 glider hours, and had trained 19 pilots without previous incidents.
Weather Conditions
The official weather forecast for the morning of 1 February predicted overcast skies with cloud bases at 1700-2000 m above mean sea level, later lowering to 1000 m, with occasional rain and possible snow showers in the northeast. Visibility was forecast as 2-8 km. For the route from Prangins to Solothurn, conditions were reconstructed as 2/8 to 7/8 stratus at 1200 m, with occasional light rain and visibility of 4-7 km below 800 m. Ground fog was present near Grenchen and Murtensee. For the Solothurn to Wynau leg, conditions deteriorated: 2/8 to 5/8 clouds at 500 m, and 8/8 stratus at 700 m, with light rain and visibility dropping from 4 to 1 km in the front. At Bern, around 0900, visibility was about 10 km with 8/8 cloud cover at about 1000 m above ground. The cold front passed Olten around 1000. At the accident site, dense fog with a ceiling as low as 20 m above ground existed.
Probable Cause
The final cause of the accident was a loss of airspeed at an altitude that did not allow recovery. The accident was primarily due to the flight instructor allowing the student pilot to initiate and conduct a navigation flight in unsuitable weather, and the student pilot flying into weather conditions that no longer permitted a safe continuation of the flight.