What happened
On 15 August 1998, a Fairchild M-62A Cornell, registration G-BVCV, was participating in a vintage aircraft rally at Woburn Abbey. After an earlier flight, the aircraft was prepared for a return journey to a farm strip near Winchester. During the takeoff roll at Woburn Abbey, witnesses observed a light haze emanating from the engine exhaust.
As the aircraft climbed to approximately 150 feet, the engine began to misfire and power significantly reduced. Observers noted puffs of dark smoke emerging from the exhaust. The pilot attempted to execute a left turn to return to the airfield, but the engine eventually stopped entirely. The aircraft entered a slow descent and, at an altitude of less and than 100 feet, the left wing dropped, leading the aircraft into an incipient spin. The aircraft struck the ground approximately 800 metres from the runway, causing the destruction of the airframe. The pilot sustained fatal injuries, while the passenger suffered serious injury.
The investigation
The investigation focused on the engine and fuel systems following reports of power loss. While the engine had previously shown high oil consumption and a tendency to run rich, investigators found no evidence of structural failure or flight control issues.
Analysis of the fuel remaining in the wing tanks revealed that the aircraft was using motor gasoline rather than Avgas. This fuel type has a much higher volatility, making it susceptible to vapour lock. Testing of the engine components, including the carburettor and the unapproved Chandler Evans fuel pump, showed that the pump delivered appropriate pressures and did not cause flooding. However, the investigation noted that the fuel lines passed close to the hot engine bay, which could facilitate the formation of fuel vapour bubbles.
Findings
- The use of motor gasoline instead of Avgas increased the risk of vapour lock due to the fuel's high volatility.
- The engine experienced a sudden loss of power likely caused by fuel starvation from vapour bubbles entering the carburettor.
- A similar power loss event had occurred in the same aircraft one year prior under similar warm weather conditions.
- The engine's high oil consumption and the presence of carbon soot on spark plugs were noted, though not the primary cause of the power loss.