What happened
On 10 September 2000, a DH8lyA Tiger Moth, registration G-ANMV, was conducting a pleasure flight near Aston, near Henley-on-Thames. Approximately 20 minutes into the 30-minute flight, the passenger requested aerobatic manoeuvres. The pilot performed several basic movements, including loops and barrel rolls.
During the final manoeuvre, initiated at 2,000 feet, the pilot pitched the nose up to 80 degrees at 100 kt before applying full right rudder to yaw the aircraft. As the aircraft yawed, the throttle was reduced. During this phase, the engine experienced a cough and ceased running. While the propeller initially continued to windmill, it stopped rotating after approximately three seconds.
With the engine failed, the pilot leveled the aircraft at 1,000 feet and descended at a glide speed of 55 kt. After declaring a MAYDAY, the pilot executed steep 'S' turns to align with a chosen field. Upon touchdown at approximately 70 feet, the main landing gear collapsed. The aircraft slid across the ground and subsequently pitched over, coming to rest in an inverted position. The passenger sustained minor injuries, including a cut above the eye and back pain, while the crew remained uninjured.
The investigation
The investigation examined the engine's performance and the aircraft's mechanical state following the crash. The pilot noted that the engine had coughed during this specific manoeuvre on at least ten occasions since its overhaul, though the propeller had previously continued to windmill during those instances. The engine had been installed in February 2000 and had flown for 67 hours without recorded defects.
Post-accident inspections confirmed that the fuel tanks contained fuel, the fuel filters and carburettor jets were unobstructed, and the magnetos and spark plugs were in serviceable condition. No mechanical defects were found that would have caused the engine to stop.
Findings
- The engine failure was caused by fuel starvation resulting from the aircraft's lack of an inverted fuel system during aerobatic manoeuvres.
- The combination of low airspeed and the engine stopping prevented the propeller from maintaining a windmill state.
- High compression in the recently overhauled engine likely made it impossible to restart the engine using only airflow.