What happened
On 17 September 2004, a Folland Gnat T Mk 1, registration G-BVPP, was conducting a private flight from North Weald Airfield. The flight was originally intended to proceed to RNAS Yeovilton, but due to deteriorating weather, the pilot decided to return to North Weald.
As the aircraft approached the airfield, the amber fuel warning light illuminated. Shortly thereafter, the engine lost power and failed to accelerate despite the pilot's attempts to use the throttle and relight procedures. Realising that the aircraft lacked the energy to complete the necessary turn to reach the runway, the pilot opted for a forced landing rather than ejecting.
The aircraft performed a belly landing in a partially ploughed field approximately one nautical mile northwest of North Weald at a speed of roughly 160 kt. The aircraft bounced and slid across the ground, causing damage to the underside of the fuselage. Both the pilot and the passenger escaped the aircraft uninjured and were able to move to a safe distance.
The investigation
Following the accident, the aircraft was recovered to North Weald for examination. Investigators focused on the fuel system and the engine's performance. While the engine was found to be capable of producing full power when the air-fuel ratio controller (AFRC) was disconnected, the unit had been contaminated with soil during the ground slide.
Technical examinations of the fuel system revealed that a float switch in the No 1 centre tank had failed because it was stuck to sealant. Additionally, investigators found a small strip of white sealant in a coarse mesh strainer within the fuel transfer pipe. While the investigation could not pinpoint a single definitive cause for the power loss, the evidence suggested a restriction or lack of fuel supply to the engine.
Findings
- The engine lost power during the approach to North Welb Airfield.
- The pilot elected to perform a forced landing instead of ejecting, a decision that avoided the risk of the aircraft potentially striking an inhabited area had it been destroyed by ejection.
- A restriction in the fuel supply to the engine was the most probable cause of the power loss.
- The fuel low-level float switch was inoperative due to being adhered to sealant.
- There was no definitive technical cause established for the initial loss of engine power.