What happened
On 26 June 2023, a Piper PA-28-140, registration G-AVLG, was performing a private flight from Bournemouth Airport to Thruxton Aerodrome. The pilot intended to refuel the aircraft at Thruxton before proceeding to Middle Wallop Airfield. During the final approach to Runway 25 at Thruxton, the engine began to run roughly before losing power. The pilot attempted to switch to the right fuel tank, but the engine failed to recover. Realising the runway could not be reached, the pilot executed a successful forced landing in a field adjacent to the runway centerline. There were no injuries and the aircraft sustained no damage.
The investigation
The AAIB investigation established that the aircraft' and the pilot's initial assessment of fuel levels were inaccurate. Prior to the flight, the pilot had reviewed the aircraft Technical Log, which recorded 11 US gallons of fuel. Based on this figure, the pilot determined that the amount was sufficient for the short flight to Thruxton. However, the investigation found that the Technical Log had not been updated following the previous flight to Bournemouth, and there was no record of fuel consumed during maintenance engine runs.
During pre-flight checks, the pilot was unable to locate the fuel tank dipstick and instead visually inspected the tanks through the filler caps. The pilot noted that the fuel gauges were at their maximum limits. Calculations later indicated that the actual usable fuel was only between 5 and 7 US gallons, significantly less than the recorded amount.
Findings
- The primary cause of the engine failure was fuel exhaustion caused by an inaccurate fuel quantity entry in the Technical Log.
- The pilot experienced confirmation bias, as the visual inspection of the fuel tanks matched his expectation based on the incorrect log entry.
- The Technical Log lacked an updated record of fuel remaining after the previous flight and did not account for fuel used during maintenance procedures.
- The pilot's decision to perform an immediate forced landing rather than attempting to reach the runway prevented a more serious outcome.