What happened
On June 2, 2005, a prototype autogire with registration W81-CN was conducting a test flight from the Lombers Castelvert airfield in France. Shortly after takeoff, while maintaining an altitude of approximately 50 meters, the aircraft experienced a significant reduction in engine power. Unable to maintain level flight, the pilot attempted an emergency landing in a nearby field.
During the landing sequence, the pilot attempted to increase power to clear a hedge, fence, and ditch at the edge of the field. The left wheel struck a ditch, causing the landing gear to collapse. As the aircraft continued to slide across the ground, the pilot shut down the engine to avoid hitting a second fence. The aircraft subsequently overturned on its left side while the rotor was still spinning at high speed. The aircraft was destroyed in the accident, and no injuries were reported.
The investigation
The investigation focused on the cause of the engine power loss and the mechanical failure of the engine's electronic injection system. Investigators determined that oil from the engine crankcase had migrated to the electronic injection temperature sensor, contaminating the component. This contamination caused the sensor to detect a false overheat condition.
As a result of this false reading, the engine's electronic control system limited the engine speed to 4,650 rpm, a level insufficient to maintain level flight. The investigation also examined the engine's installation, noting that the engine—a PSA XU7JP unit—was originally designed for automotive use and did not account for the specific mounting requirements of an aircraft.
Findings
- The primary cause of the power loss was oil contamination of the electronic injection temperature sensor.
- The engine's installation angle on the airframe allowed oil to flow from the crankcase toward the sensor.
- The engine, a PSA XU7JP, was an automotive engine whose design did not adequately account for the operational constraints of an aircraft installation.
- Maneuvers performed during the test flight, specifically roll movements, contributed to the oil migration to the sensor.