What happened
On July 31, 2010, a private Fly Synthesis Texan (registration EC-XAQ) was conducting a local flight near the Benagéber reservoir in Fuenterrobles, Valencia. The flight originated from Requena, following a previous arrival from Ibiza.
While cruising, the pilot noticed a significant loss of airspeed and felt that the propeller was no longer providing sufficient thrust. Crucially, the pilot reported that engine parameters, including manifold pressure and engine RPM, remained stable and unchanged during this period. Unable to maintain level flight, the pilot attempted an emergency landing at a nearby airfield in Fuenterrobles.
The approach was performed at a low altitude and at an oblique angle to the runway. During the landing attempt, the pilot lost control of the aircraft's alignment, causing it to veer off the side of the runway, cross a small ravine, and ultimately impact into an olive grove. Both occupants of the aircraft survived the crash without injuries, though the aircraft sustained major damage.
The investigation
The investigation focused on identifying the cause of the loss of thrust, specifically examining whether the issue originated from the engine or the propeller-governor system.
Technical inspections of the Rotax 912 ULS engine revealed no mechanical deficiencies. The gearbox showed no signs of metal shavings or damage, and the clutch was intact. Bench testing of the engine, including various power and magneto tests, confirmed correct operation. Furthermore, the oil filter was found to be clean, indicating no internal engine wear.
The investigation also examined the variable-pitch propeller and its electromechanical governor. While the propeller blades were broken, the damage occurred during the final impact with the ground. The governor was found in a state indicating that the blades were at maximum pitch when electrical power was lost. The pitch-change mechanism was verified to be functioning correctly.
Findings
- The engine was functioning normally, as evidenced by the lack of fluctuations in manifold pressure and RPM reported by the pilot and confirmed by post-crash testing.
- The propeller and governor mechanisms were mechanically sound and capable of adjusting pitch correctly.
- An identifiable cause for the sudden loss of thrust could not be determined from the available evidence, as neither the engine nor the propeller system showed any signs of failure prior to the impact.