What happened
On August 5, 2006, a PIPER PA-34-200T, registration EC-FMX, was conducting a flight training verification for a student pilot. The flight originated from Málaga Airport with the intention of proceeding to Seville Airport. After performing various maneuvers, including slow flight and simulated engine failures, the aircraft began an NDB approach to Seville at 2,000 ft MSL.
Approximately ten seconds after initiating the approach, both engines failed almost simultaneously. The instructor took control and attempted in-flight engine restarts, briefly regaining power before the engines failed again. As the aircraft descended rapidly, the crew declared an emergency when they reached 1,000 ft AGL. Unable to reach the runway, the crew performed an emergency landing in a cultivated cotton field near Carmona, Seville.
The impact on the uneven, stony terrain caused the main landing gear to collapse and the nose gear to fold. The aircraft slid on its fuselage until it came to a halt. Both occupants survived the accident without injuries, though the aircraft sustained major damage to the landing gear, both propellers, the fuselage, and the left wing.
The investigation
The investigation focused on the simultaneous failure of both engines and the fuel system configuration. Investigators examined the fuel tanks, finding the right tank completely empty, while the left tank contained fuel that had leaked through the wing drainage devices due to the impact.
Technical analysis of the fuel system revealed that the aircraft's design allows for crossfeed, where either engine can draw from either tank. Investigators evaluated the fuel consumption, noting that the flight duration and estimated consumption rates (approximately 102.5 l/h) would have depleted the right tank if both engines were drawing from it. The investigation also noted that the pilot had observed a left-wing tendency to bank during slow flight maneuvers, which was consistent with an unbalanced fuel load.
Findings
- The simultaneous engine failure was caused by the depletion of fuel in the right wing tank.
- Both engines were drawing fuel exclusively from the right tank during the flight.
- This occurred because the left engine's fuel selector valve was left in the crossfeed position.
- The error likely originated during the pre-takeoff taxi phase, where the crew performed a crossfeed functional test but failed to return the left selector to the 'ON' position.
- The fuel imbalance caused a noticeable lateral tendency during flight maneuvers.