What happened
On 29 May 2009, a pilot was ferrying a Europa XS, registration G-BYFG, from Fishburn Airfield to Tatenhill. During the cruise phase of the flight, the engine experienced a sudden and significant loss of power. The pilot attempted standard emergency procedures, including the application of carburettor heat and switching to an alternative fuel source, but none of these actions restored engine performance.
With the engine failing, the pilot declared a MAYDAY and attempted to locate a suitable landing site. Due to the presence of power cables in the primary intended field, the pilot opted for an alternative location. During the forced landing in a down-sloging field, the aircraft collided with a tall hedge. The impact resulted in substantial damage to the aircraft, including the detachment of the engine. The pilot sustained minor injuries and was able to exit the cockpit without assistance.
The investigation
The AAIB investigation focused on the cause of the engine power loss and the state of the aircraft's fuel system. The aircraft had recently undergone repairs following a previous landing accident and had been cleared for flight after successful test flights in March 2009.
Investigators examined the fuel system and discovered that a modification had been made to the fuel lines. Specifically, an additional return line had been installed to facilitate the use of Mogas. However, this modification had not been approved by the LAA. Testing performed on a test stand revealed that when this bleed return line was opened to the atmosphere, air was drawn into the engine-driven fuel pump, which caused a significant drop in engine power.
Findings
- The engine suffered a sudden loss of power that could not be definitively attributed to a single cause.
- An unapproved modification to the fuel system may have been a contributory factor, as the modified return line allowed air to be drawn into the fuel pump.
- Carburettor icing was considered a possibility due to the ambient temperature and dewpoint, though the pilot's actions did not confirm this.
- Vapour locking was also considered a potential factor, though no prior history of such issues existed for this aircraft.
- The aircraft's fuel tank was sufficiently filled for the planned mission prior to departure.