Accident Overview
On 14 November 2002 at 1522 UTC, a Gulfstream AA-5A Cheetah (registration G-BGVW) was involved in an accident near Elstree Aerodrome, Hertfordshire. The single-engine aircraft, powered by a Lycoming O-320-E2G piston engine and manufactured in 1978, was on a private ferry flight to Blackbushe. The pilot, the sole occupant holding a Commercial Pilot's Licence with an Instructor's Rating and 645 hours total flying experience (375 on type), sustained minor injuries. The aircraft sustained damage to its canopy, wings, engine, and propeller.
Pre-Takeoff Actions
While taxiing to the holding point, the pilot experienced what he believed to be mild carburettor icing. During the subsequent 6 to 7 minute delay before takeoff, he increased engine power to 1,500 rpm several times and applied carburettor heat to remove any icing. While stationary on the runway prior to takeoff, he set 2,000 rpm and applied carburettor heat for 5 seconds.
Takeoff and Engine Failure
During the takeoff roll, full power achieved 2,200 rpm, and the aircraft climbed away with a rate of climb just less than 500 feet per minute. At 200 feet above the airfield, with full power still applied, the engine rpm reduced to 1,800. The pilot was unable to maintain level flight and conducted a forced landing in a ploughed field half a mile northwest of the airfield. On landing, the nose landing gear collapsed, and the aircraft pitched inverted. The pilot evacuated through the canopy with only minor injuries.
Engineering Investigation
A subsequent engineering investigation revealed a significant amount of water in the electric fuel pump and the carburettor float chamber. The wing fuel caps were found to be in satisfactory condition. The aircraft has four fuel drain points: one in each sump tank at each wing root and one set directly in each of the two wing fuel tanks. The contents of the wing fuel tank enter the fuel drain via two drain holes within the tank. One of the drain holes in each of the wing fuel drains was found to be blocked. The tank contents, however, could still be drained via the remaining unblocked hole. The pilot reported that he carried out a fuel drain check prior to engine start and found water at each drain point, continuing to drain until no trace of water remained.
Weather and Carburettor Icing Considerations
At the time of the accident, weather conditions gave a temperature of +10°C and a dew point of +7°C. The CAA General Aviation Safety Sense Leaflet No 3B, titled Winter Flying, contains a graph depicting conditions conducive to carburettor icing; the reported conditions fall within the area of serious carburettor icing. However, the sudden reduction in engine rpm, the water found in the fuel pump and float chamber, and the fact that the aircraft had been left outside for six weeks prior to the flight with the fuel tanks two-thirds full make water contamination of the fuel a more likely cause of the engine problem.