What happened
On December 6, 2014, a Cessna 172 carrying a pilot and three passengers departed for a local flight near Mortagne-sur-Sèvre. While climbing to approximately 2,000 feet, the aircraft's FADEC system triggered red warning lights, and the engine power began to decrease steadily. The pilot attempted to restart the engine but was unsuccessful. After notifying the Cholet-le-Pontreau airfield information service of his intention to return, the pilot realized he could not reach the aerodrome and opted for an emergency landing in a nearby field at an altitude of roughly 500 feet.
During the final approach, the pilot focused on selecting a landing site and lost monitoring of the aircraft's airspeed. To avoid treetops in the flight path, the pilot pulled back on the control column, triggering the stall warning. The aircraft struck the ground and immediately overturned. All four occupants evacuated the aircraft safely, though the aircraft sustained significant damage.
The investigation
The investigation focused on the cause of the engine power loss and the mechanical state of the aircraft. Investigators examined the engine, specifically the fuel system and the Thielert TAE 125-02-99 diesel engine components. The examination confirmed that the fuel circuit was continuous from the tanks to the engine, no fuel contamination was present, and no mechanical damage was found that could explain the power loss. Subsequent bench testing of the engine showed it functioned normally.
Investigators also looked into the fuel selector switch, which has three positions: Left, OFF, and Right. Notably, the fuel system includes a reserve that can power the engine for approximately seven minutes even when the selector is in the OFF position. The investigation noted that the pilot, who had recently obtained his PPL(A) and had only four hours of experience on this specific model, was unfamiliar with the FADEC system's operation. Furthermore, the pilot had manually moved the fuel selector to the 'Right' position after the accident, and the position of the selector prior to takeoff could not be definitively determined.
Findings
- The engine power loss was likely caused by a lack of fuel supply to the engine.
- This fuel starvation was likely due to the fuel selector being left in the OFF position prior to takeoff, a failure to verify the setting during pre-flight checks.
- The pilot's focus on obstacle avoidance during the emergency approach led to a loss of airspeed monitoring and a subsequent stall warning.