What happened
On the evening of May 24, 2010, a private Tecnam P 92-JS, registration HB-KFZ, was conducting a VFR flight from Bad Ragaz to Wangen-Lachen and back. During the return leg, while descending from 5,000 ft to 4,000 ft near Mels, the engine began to sputter. The pilot attempted several standard procedures, including checking fuel valves, activating the electric fuel pump, and applying carburetor heat. Although the engine RPM briefly stabilized, the power continued to fluctuate before the engine failed completely at approximately 3,000 ft QNH.
Recognizing that reaching the airfield was no longer possible, the pilot identified a suitable mown field near "Ragnatsch" for an emergency landing. During the final approach, the pilot deployed full flaps. However, the aircraft maintained excessive speed and altitude for the chosen landing site. As the pilot attempted to maneuver to avoid trees and compensate for the rising terrain, the left main landing gear struck the ground heavily. The impact caused the gear to break off, leading the aircraft to tilt onto its left wing and skid, resulting in significant damage to the airframe.
The investigation
Investigators examined the wreckage and the engine components to identify the source of the power loss. The engine, a Bombardier-Rotax 912 S2, was subjected to a test run and showed no abnormalities, though the idle setting was found to be incorrect. The fuel system was inspected, and while a slight leak was noted at the electric fuel pump and some stiffness was found in a tank vent check valve, these were ruled out as causes for the engine failure. The propeller remained undamaged, confirming that the engine was not producing power at the moment of impact.
Findings
- The engine failure occurred during the transition from level flight to a descent.
- The pilot's decision to perform an off-field landing was appropriate given the engine state and the proximity of populated areas.
- Meteorological conditions, specifically the temperature and dew point, presented a risk of carburetor icing.
- The heavy landing was influenced by the pilot's attempt to avoid obstacles during the final approach in twilight conditions.
- There were no mechanical defects found in the fuel system or engine that could have caused the total engine shutdown.