Investigation Summary
The aircraft, military serial RR299, had a documented history of fuel system anomalies. In 1994, British Aerospace (BAe) noted a 'low fuel pressure' warning that triggered during maneuvers involving less than 1g. Although the issue was attributed to an incorrectly wired fuel gauge and the carburetor was inspected, the zero-g sensitivity persisted. Just three weeks before the Barton accident, the aircraft suffered an engine failure during a display in Lille, France. Despite these warnings, the aircraft was cleared for the Barton Aerodrome show. During the display routine, which consisted of non-aerobatic climbs, descents, and wingovers, the left engine backfired as the aircraft performed a steep climb into a wingover to the right. The resulting loss of power caused the aircraft to depart controlled flight. While the pilot appeared to regain some measure of control in the final seconds, the altitude lost during the initial spiral was too great to prevent impact.
Final Conclusions
The AAIB Field Investigation concluded that the accident resulted from a loss of control following a temporary loss of power from the left engine. The failure was linked to the unpredictable nature of the engine's response to negative g-force conditions, exacerbated by carburetors that did not meet specific flow and adjustment requirements. The investigation cleared the pilot of fault, noting he had operated the boost levers correctly and was attempting to manage the aircraft's known engine quirks.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Pilot
Kevin Moorhouse; joined British Aerospace in 1963 and previously served as a flight engineer on Nimrods. He had accumulated over 60 hours on type and over 520 hours on other light aircraft.
Systems & Failure Modes
Rolls-Royce Merlin Engines
The aircraft was powered by two Merlin engines. The investigation found that the carburetors on these engines were sensitive to negative g-forces, which could lead to fuel flow interruptions and backfiring.
Carburetor Fuel System
Post-crash analysis suggested that the carburetor settings and fuel flow rig requirements were not met, contributing to the engine's unpredictable behavior during maneuvering.
Interesting Facts
- 01The aircraft was the last airworthy de Havilland Mosquito in the world at the time of the crash.
- 02The airframe was constructed primarily of hardwoods like balsa and birch to conserve metal during WWII.
- 03The left engine had a known history of fuel pressure warnings during low-g maneuvers.
- 04The aircraft had experienced a similar engine failure in Lille, France, only three weeks prior to the fatal accident.
- 05The pilot had over 60 hours of flight time specifically on the Mosquito type.
Safety Actions & Advisories
Rolls-Royce Merlin Maintenance Advisory
Recommendations were made to Rolls-Royce to communicate with all Merlin engine operators regarding the correct adjustment of carburetors and the interpretation of engine manuals.
Flow Rig Calibration
Investigators advised organizations involved in Merlin maintenance to adhere strictly to flow rig requirements to ensure consistent fuel delivery during all flight attitudes.