Incident Overview
On August 11, 1966, at approximately 05:12 MEZ, a Piper L4-J3 with registration HB-OGZ departed from Lommis airfield for a training flight. The aircraft was operated by the Motorfluggruppe Thurgau of the AeCS as part of the FVS course M54. The pilot-in-command was a flight instructor, and the rear seat occupant was a student pilot.
Flight Progression
Shortly after takeoff, the instructor initiated an emergency landing exercise by reducing engine power. However, the engine stopped completely shortly thereafter. The instructor attempted to restart the engine by pushing the propeller but had to abort this maneuver due to low altitude. The aircraft then descended toward a nearby field.
Accident Sequence
During the final approach, the aircraft flew slowly and entered a stall condition while pulling up. It struck a grass-covered embankment that crossed the landing area. The impact caused the landing gear to be torn off, and the aircraft slid on its fuselage for approximately 20 meters before coming to rest. Both occupants escaped without injury.
Investigation Findings
The investigation determined that the engine failure was likely due to carburetor icing or a lean mixture condition exacerbated by high humidity and rapid power reduction. The accident occurred because the instructor failed to see the ground ridge, possibly due to low light conditions, mist, and the rapid sequence of events. The aircraft sustained significant damage to the fuselage, landing gear, and wing struts.