What happened
On 9 May 2003, an Aeroplam A22 Foxbat, registration G-FXBT, was conducting a private flight near Wimborne, Dorset. After an uneventful takeoff, the aircraft was cruising at approximately 600 feet when the engine suddenly faltered and lost RPM, followed by a complete stoppage within seconds. The pilot, unable to attempt a restart due to the low altitude, selected a nearby farm strip for a forced landing.
The landing site consisted of rough grass pasture with an upward slope. The aircraft touched down on the nose and left main wheel, bouncing briefly before settling on all three wheels. During the landing roll, the nosewheel struck a pothole, causing the nose leg to collapse and the underside of the aircraft to contact the ground. There were no injuries to the pilot or the passenger, though the aircraft sustained damage to the nose wheel, engine firewall, engine bearer, and cabin floor.
The investigation
Investigators focused on the engine and fuel system to determine why the engine had stopped. While the engine showed no mechanical defects, a ground run revealed fuel overflowing from the right-hand carburettor, though this was not deemed the primary cause of the failure. The fuel system was found to be clean, with no contamination identified in the gascolator filter.
During a subsequent flight to a private landing field, the pilot observed that fuel levels were shifting between the tanks. Specifically, the right tank level increased while the left tank level decreased. Further testing on the ground revealed that the fuel lines required suction to initiate flow, a phenomenon the pilot had noted previously. Additionally, testing showed that the propeller wash created differential dynamic pressure between the two fuel tank vent lines, as the left side experienced higher pressure than the right.
Findings
- The engine failure was consistent with fuel starvation.
- Differential pressure caused by the propeller wash led to fuel being transferred from the left tank to the right tank.
- Small amounts of unidentified debris, consisting of alumino-silicate and aliphatic ester, were found inside the fuel tanks.
- The aircraft's fuel tank construction prevented a thorough inspection of the fuel outlets.