What happened
On the afternoon of December 7, 1963, a pilot and one passenger departed from Beromünster airfield in a Piper Cub J3C, registration HB-OGC, for a short private flight. At the time of departure, the aircraft was operating under significant weather constraints, with a thick layer of fog situated only 80 to 100 meters above the ground.
Shortly after takeoff, the aircraft entered patches of cloud at an altitude of approximately 60 meters. The pilot, who did not hold an instrument rating, elected to climb through the fog layer to regain visual contact with the ground. While the pilot successfully reached the sun above the clouds, the low fuel level—estimated at only 15 liters—became a critical concern. As the flight progressed, the pilot attempted to reach Kägiswil, but found the fog layer extended too far south. Seeking an alternative, the pilot aimed for Engelberg, but the fuel gauge indicated the supply was nearly exhausted. Consequently, the pilot identified a suitable clearing on the Alp Gibel near Niederrickenbach for an emergency landing. During the final approach, the engine began to sputter, and the aircraft impacted the terrain at 16:05. The landing gear was torn away by uneven ground, causing the aircraft to slide 70 meters on its belly.
The investigation
Investigators examined the aircraft's fuel system and the pilot's flight conditions. While the fuel gauge initially indicated a near-empty tank, subsequent inspections of the wreckage and the fuel tank revealed a discrepancy; a later examination of the tank during repairs showed approximately 15 liters of fuel remained, though the float mechanism was found to be worn and loosely attached to the indicator rod. The investigation also reviewed the pilot's flight experience and the prevailing meteorological conditions at the time of the accident.
Findings
- The primary cause of the emergency landing was the pilot's decision to conduct a visual flight under weather conditions that offered insufficient safety margins.
- The pilot operated with an inadequate fuel reserve, leaving no margin for error should the flight duration increase due to weather diversions.
- The pilot's decision to climb through the clouds was a high-risk maneuver, as he lacked instrument flight training.
- The pilot's subsequent decision to execute an emergency landing on the alpine pasture was considered appropriate given the fuel exhaustion risk.