What happened
On February 12, 2004, a Socata MS 894 A Rallye Minerva, registration F-GIYV, was conducting a check flight following a major maintenance overhaul. The flight, operated for private purposes, departed from Toulouse Lasbordes toward Graulhet with a pilot and a mechanic on board. After completing the initial leg of the flight without noted anomalies, the pilot attempted to return to Toulouse Lasbordes.
While approaching runway 34, the pilot decided to abort the approach at an altitude of approximately 50 feet to test the aircraft's performance through a steep climb. To maintain visual contact with another aircraft taxiing on the runway, the pilot executed a sustained sideslip, banking the aircraft approximately 25 degrees to the right. The pilot maintained this asymmetric attitude at 75 knots for about ten seconds while remaining parallel to the runway centerline.
Upon transitioning back to symmetric flight and initiating a maximum rate climb at full power, the pilot observed a significant drop in engine RPM, with the tachometer falling below 1,000 RPM. The pilot subsequently transitioned into a descent at the best glide speed of 75 knots and selected an emergency landing site between a highway and a stream. During the landing roll, the left wing struck a shrub, causing the wing to break off. The aircraft subsequently entered a ground loop and came to a halt, with the landing gear collapsing and the propeller bending.
The investigation
The investigation focused on the cause of the engine power loss during the climb. Investigators found that the fuel selector was set to the right tank, which was approximately half full. Ground tests conducted on a similar tank demonstrated that fuel delivery is interrupted if a sideslip exceeding three seconds is maintained at a bank angle of 20 degrees when the tank is half empty. Fuel flow is only restored approximately six seconds after the aircraft returns to level flight.
It was determined that the volume of fuel available in the fuel lines and carburetor bowl was sufficient to support takeoff power for approximately 14 seconds. This duration aligns with the interval between the end of the sideslip and the observed loss of power.
Findings
- The engine failure was caused by the insufficient consideration of the effects of a sustained sideslip on the fuel supply.
- The fuel starvation occurred because the fuel pickup was unable to maintain suction during the prolonged asymmetric flight.
- The flight manual contained no specific warnings regarding the risk of fuel starvation during asymmetric flight maneuvers.