What happened
On 15 October 2004, a Gulfstream AA-5B Tiger, registration G-BFZR, was being used for a private flight to demonstrate the aircraft to potential buyers. The flight departed from Oxford Kidlington Airport with the pilot and two passengers on board. During the climb, at an altitude of approximately 800 feet, the engine suffered a sudden loss of power, with RPM dropping to roughly 1,500.
The pilot attempted to rectify the issue by switching to the left fuel tank and applying carburettor heat, but the engine failed to regain power. The aircraft subsequently performed a forced landing in a large field of recently sown crops. During the landing, the nose landing gear collapsed. All three occupants, who were wearing appropriate safety harnesses, exited the aircraft through the rear canopy without injury.
The investigation
An inspection of the aircraft following the accident revealed damage to the propeller, cowlings, and the nose wheel leg. Investigators examined the fuel system, which consists of two wing tanks and two sump tanks. While pre-flight fuel samples taken by the pilot had shown no signs of contamination, post-accident analysis found significant amounts of rusty water within the carburettor bowl, the electric fuel pump filter, and the fuel lines located behind the firewall.
Crucially, the four primary drains—located in each fuel tank and each sump tank—did not show any evidence of water. However, large puddles of water were observed within the main fuel tanks. The aircraft had been parked outdoors for approximately two months with the tanks less than three-quarters full prior to the flight.
Findings
- The sudden engine power loss was caused by significant water contamination within the fuel system.
- Although pre-flight sampling of the tanks and sumps showed no water, substantial amounts of water had accumulated in the carburettor and fuel pump filter.
- The aircraft's storage conditions, being parked outside with partially filled tanks, likely allowed for water ingress through fuel cap seals or condensation.
- The fuel system design lacks a strainer at the lowest point or a dedicated drain for the fuel filter, meaning water can bypass standard sampling points.