What happened
On July 4, 1973, a Piper PA-18-150 Super-Cub, registration HB-OYD, departed from Bonn-Hangelar in West Germany, bound for Bern, Switzerland. The flight was conducted under Visual Flight Rules (VFR). After initially climbing to 3,500 feet and later ascending to 5,500 feet, the pilot began a descent near the Feldberg mountain due to heavy haze and poor visibility.
While flying at an altitude of approximately 200 to 250 meters near Wehr, the engine suffered a sudden loss of power over the village of Magden. The pilot immediately attempted several emergency procedures, including adjusting the mixture to full rich, checking the carburetor heat, verifying the fuel selector valve, and checking the fuel gauge and ignition switches.
In search of an emergency landing site, the pilot identified two small fields. Upon attempting an approach to the first field, the pilot discovered a ditch crossing the terrain. He diverted to a second nearby field, but during the maneuver, the aircraft clipped a grain field approximately 15 meters from the landing area. The aircraft subsequently overturned and came to rest on its back. The pilot sustained no injuries, though the aircraft was heavily damaged.
The investigation
The investigation focused on the cause of the sudden engine failure. The aircraft was found to be within weight and balance limits, and the fuel tanks were fully loaded at departure. While the engine and fuel system were inspected, the fuel strainer was too severely damaged during the accident to determine its level of contamination.
Investigators found debris, including dirt particles and scraps of newspaper, inside the left fuel tank. However, the volume of this debris was insufficient to account for the total loss of engine power. The technical analysis concluded that the engine failure was caused by an interruption in the fuel supply.
Findings
- The engine failure was caused by a disruption in the fuel supply.
- It could not be definitively determined if the interruption was caused by a blockage in the fuel strainer or a pilot error, such as leaving the fuel selector valve in the 'off' position or failing to switch tanks properly.
- The presence of debris in the left tank was not large enough to be the primary cause of the failure.