What happened
On the afternoon of October 4, 1962, a Piper L-4 (registration HB-OGZ) departed from the Lommis airfield for a private flight. Shortly after the aircraft lifted off from the grass runway, the pilot experienced a sudden and significant drop in engine power. Despite attempts to increase thrust via the throttle, the engine failed to respond, forcing the pilot to perform an immediate landing.
The aircraft''s landing roll extended beyond the airfield boundaries. During the excursion, the plane crossed a stream located approximately 150 meters west of the runway end. The impact with the terrain caused the landing gear to shear off, and the aircraft eventually came to rest on its fuselage. Both occupants of the aircraft remained uninjured.
The investigation
The investigation examined the aircraft, the engine, and the environmental conditions at the time of the accident. The aircraft, a Piper L-4 powered by a Continental A-65 engine, was owned by a Thurgau aero club. Investigators noted that the weather was clear with a ground temperature of 20°C and 60% humidity.
Following the incident, the engine was subjected to a ground run and approximately 20 subsequent flight hours without any further issues. The investigation also noted that the scene had been partially altered by private parties who moved debris and conducted engine tests prior to the official investigator's arrival.
Findings
- The primary cause of the accident was a severe loss of engine power during the takeoff phase.
- While carburetor icing was considered, the ambient temperature and humidity levels made this unlikely.
- Potential contributors to the power loss included an insufficient fuel supply, possibly caused by a partially closed fuel valve or a momentary blockage in the carburetor nozzle due to impurities or water.