History of the Flight
On 25 May 2006, at approximately 1440 hours UTC, a Cessna F150L (registration G-AZXC) departed from Netherthorpe Airfield in Nottinghamshire on a private flight. The pilot and a passenger, both holding private pilot licenses, were on board. The weather was good, with visibility exceeding 10 km and no cloud below 2,500 ft, while the wind was from 250° at 5 to 10 kt.
During pre-flight checks, the passenger removed the lockable fuel caps and replaced them with standard caps. The pilot reported draining a fuel sample from each wing tank and from the gascolator beneath the engine, confirming no water was present. The aircraft carried approximately 96 litres of fuel (total capacity 144 litres), sufficient for the planned flight to Sherburn-in-Elmet, so no refuelling occurred.
The pilot started the engine and performed engine checks at a holding point. The magneto check showed a 100 rpm drop when selecting both left and right magnetos, which the pilot considered more than usual but still within limits. The engine backfired when the throttle was reduced to idle but then ran normally at 600 rpm.
After waiting for another aircraft to land, the pilot taxied onto Runway 24 (grass) and initiated takeoff. The aircraft accelerated normally, reaching 40 KIAS before the runway intersection. The pilot rotated at 50 KIAS, held the aircraft in ground effect until 60 KIAS, then initiated a climb. Shortly thereafter, the engine noise suddenly faded and stopped. The pilot reported the failure was as sudden as pulling the mixture lever to idle-cutoff. He pumped the throttle but had no effect, so he lowered the nose to maintain airspeed and aimed for a field directly ahead. A hedge-lined road lay short of the field; the pilot raised the nose to clear the hedge. The aircraft cleared the hedge but touched down heavily. The nose gear collapsed, and the aircraft flipped upside down, coming to rest. Both occupants exited unassisted via the right door.
Aircraft Examination
The maintenance engineer recovered the aircraft to a hangar and drained fuel from the wing tanks into a container that already contained some fuel. The aircraft was left for inspection by an insurance assessor, who removed the fuel gascolator bowl and emptied its contents into a jar. Approximately two-thirds of the bowl's contents was water, and one-third was fuel. A few days later, the engineer removed the wings; when the right wing was placed on the ground, a small water/fuel mixture drained from the right wing tank's fuel line. No fuel or water drained from the left tank. The pilot reported the aircraft had been parked slightly right wing down.
The aircraft's previous flight was on 18 May 2006, after which it was parked outside for seven days with significant rainfall. A weather station 20 nm south of Netherthorpe reported 43.6 mm of rain, and another 31 nm to the west reported 46 mm for the same period (18 to 25 May).
The insurance assessor examined the standard and lockable fuel caps and found the rubber seals on all four caps satisfactory; he could not explain how water might have entered the tanks.
Analysis
The sudden engine failure after takeoff was caused by excessive water in the fuel. Water is heavier than aviation fuel and settles at the bottom of a tank. The pilot drained both wing tanks and the gascolator without finding water, but because the aircraft was parked right wing low, it is possible the right tank drain was not at the lowest point when the sample was taken. It was not possible to determine how the water entered the fuel system, but it is probable that the heavy rainfall during the week before the flight, while the aircraft was parked outside, was a contributory factor.