Piper J3C G-BSYO fuel exhaustion incident at Cranfield

Overview and flight details On 23 June 2000 at 1355 UTC, a Piper J3C, registration G-BSYO, made an off-airport landing in a wheat field approximately one nautical mile north-west of Cranfield Airport, Bedfordshire. The aircraft was on a private visual flight rules (VFR) flight from Pent Farm, near Folkestone in Kent, to attend the Popular Flying Association (PFA) rally at Cranfield. The pilot and one passenger were on board, and neither was injured. The aircraft sustained substantial damage. ## Aircraft and pilot The aircraft was a 1946 Piper J3C equipped with one Continental O-200-A piston engine. The pilot held a Private Pilot's Licence and was 20 years old. His total flying experience was 91 hours, of which 15 were on type. In the 90 days before the incident, he had 8 hours of experience, and in the 28 days before the incident, he also had 8 hours. ## Fuel system and pre-flight checks During pre-flight checks, the pilot visually checked the main and auxiliary fuel tanks. The main tank, located in the forward fuselage and with a capacity of ten imperial gallons, was confirmed to be full. The auxiliary tank in the right wing was estimated to contain between ten and twelve gallons. The main tank could be topped up by gravity feed from the auxiliary tank, with the transfer controlled by a selector in the cockpit. The pilot's fuel calculations, based on an assumed consumption of four imperial gallons per hour, indicated more than adequate fuel for the estimated two-hour flight. ## Flight and loss of power The aircraft departed Pent Farm at 1200 UTC after about five minutes on the ground with the engine running. The pilot selected the fuel transfer selector off for takeoff and then on again during the climb to begin topping up the main tank. He was satisfied that fuel had begun transferring because he could see fuel in the transparent transfer pipe passing through the cockpit. About 45 minutes into the flight, the pilot noticed that fuel was no longer visible in the transfer pipe and concluded that fuel had stopped transferring from the auxiliary to the main tank for an unknown reason. Because there was no fuel quantity indication system for the auxiliary tank, he could not determine how much fuel had already transferred. However, he was not unduly concerned because the float valve on the main tank was still indicating full, which he believed confirmed that fuel transfer had been occurring. The pilot continued the flight. On reaching Royston, he realised that the float gauge on the main tank had become stuck, as it had not dropped as far as it should have done in the given time. He decided to continue to Cranfield because it was one of the nearest suitable airfields. The remainder of the flight was uneventful until the pilot turned onto the downwind leg to land at Cranfield, having slowly descended to 1,200 feet QNH (approximately 850 feet QFE). About one minute after the turn downwind, the engine began to lose power. All engine settings were checked and found to be correct. The pilot repeatedly pumped the throttle, which caused the engine to pick up again for about ten seconds, allowing the aircraft to climb back to 1,100 feet QNH, at which point the engine failed completely. ## Off-airport landing The pilot was able to turn the aircraft into the wind and land in a wheat field that he had seen earlier. During the landing, the aircraft nosed over and came to rest inverted, causing damage to the engine, fin, rudder, and port axle. The pilot and passenger, who were wearing four-point harnesses, were uninjured and evacuated the aircraft without difficulty. ## Assessment The pilot believed that less fuel than anticipated may have transferred to the main tank, which, combined with a stuck float gauge, caused him to believe that he had more usable fuel than was in fact available. The aircraft had not yet been repaired at the time of the bulletin, and any significant findings were to be reported in an addendum.