History of the Flight
The aircraft, a Piper PA-28-140 (registration G-AVLG), was being flown from Bournemouth Airport to Thruxton Aerodrome for refuelling before continuing to its base at Middle Wallop Airfield. The pilot, a 25-year-old private pilot with 90 hours total flying experience (37 hours on type), had noted '11 US gal' of fuel recorded in the aircraft Technical Log (Tech Log) prior to departure.
During the approach to Thruxton, the pilot joined left base for Runway 25. After completing downwind checks and turning onto final, the engine began to run roughly and lost power. The pilot switched to the right fuel tank, which appeared to have no effect. Realising he would not reach the runway, he selected a field to the right of the extended centre line and performed an uneventful forced landing. The aircraft was undamaged and the pilot uninjured. After landing, the pilot confirmed via the fuel pump and pressure check that the left tank was empty and some fuel remained in the right tank.
Fuel Exhaustion Circumstances
The pilot had collected the aircraft from Bournemouth after its annual inspection. He checked the Tech Log, which recorded '11 US gal' of fuel, and decided to refuel at Thruxton, believing this quantity would be sufficient for the 20-minute flight with reserve. During the pre-flight A-Check, the pilot could not find the fuel tank dipstick and instead looked into each tank through the filler cap. He believed he saw an amount of fuel that matched his expectations based on the Tech Log, and noted the fuel gauges were 'off the stops', assuming fuel was present. However, calculations indicated that only 5 to 7 US gal of usable fuel were actually on board at the start of the flight. The distribution between tanks was unknown.
The Tech Log had not been completed after the previous flight to Bournemouth, and there was no record of fuel used during maintenance engine runs. The fuel entry was therefore unreliable.
Confirmation Bias
According to the AAIB, the pilot experienced confirmation bias when visually checking the fuel tanks, as he was expecting to see fuel based on the Tech Log. This led him to misjudge the actual fuel quantity. The pilot also did not consider refuelling at Bournemouth, as he believed he had enough fuel for the first leg and wanted to maximise fuel for the next day by refuelling at Thruxton.
Conclusion
The serious incident occurred because the pilot was misled by an incorrect fuel quantity entry in the Tech Log and experienced confirmation bias when manually checking the fuel levels. His immediate decision to conduct a forced landing rather than attempt to stretch the glide likely prevented a worse outcome.