Incident Overview
On July 21, 1964, at approximately 19:26 local time, a Piper J3C aircraft with registration HB-OUC crashed near the aerodrome of Gruyères in the canton of Fribourg, Switzerland. The accident occurred less than one minute after takeoff during a solo training flight. The pilot was injured, and the aircraft was destroyed.
Aircraft and Pilot Details
The aircraft was a Piper J3C manufactured in 1943 by Piper Aircraft Corp. It was powered by a Continental C85-12F engine and equipped with a McCauley two-blade fixed-pitch propeller. The plane had been purchased by the Société d'aviation de la Gruyères S.A. on June 26, 1964. At the time of the accident, the airframe had approximately 98 hours since its last airworthiness certificate issuance, and the engine had about 1,883 total hours.
The pilot was a student born in 1935, holding a student pilot license issued on April 14, 1964. At the time of the crash, he had accumulated 33 hours of flight time, including 9 hours and 71 landings solo. He had logged 1 hour and 50 minutes specifically in the accident aircraft.
Sequence of Events
The student pilot took off from the Gruyères aerodrome to repeat a series of right-hand spirals previously performed with an instructor. Shortly after takeoff, while at an altitude of approximately 40 to 50 meters above ground level, the engine began to sputter. The pilot identified this as a fuel supply issue. After attempting to restart the engine by manipulating the throttle, it failed completely.
The pilot feathered the propeller to maintain speed and initiated a left turn to return toward the airfield. However, due to obstacles ahead, he continued the turn and aimed for an adjacent field separated from the runway by a ditch. Witnesses observed the aircraft in a normal glide path with sufficient speed. Despite this, the aircraft did not round out for landing. Instead, it impacted the ground with its nose, landing gear, and wingtip. The plane rebounded and rotated 180 degrees before coming to rest.
Investigation Findings
The investigation determined that the engine failure was caused by fuel exhaustion (running dry). The aircraft featured two communicating wing tanks with a total capacity of 68 liters, equipped with glass sight tubes and float indicators. These indicators were only valid for reading during flight. A red mark indicated the minimum level for starting and climbing. On the day of the accident, the pilot had not explicitly verified the fuel levels before takeoff, relying on club members who typically refueled the aircraft in the evening. The investigation found no evidence that the aircraft was mechanically unfit or that the pilot was physically or psychologically unsuitable for flight. Meteorological conditions were clear with light winds and a temperature of 25°C, playing no role in the accident.