What happened
On 22 October 2005, a Piper PA-38-112 Tomahawk, registration G-BYLE, was performing a training flight near Biggin Hill Airport, Kent. Shortly after departing from Runway 21, the aircraft experienced an engine malfunction. In an attempt to return to the airfield, the pilot initiated a left-hand turn. During this manoeuvre, the aircraft stalled and entered a steep descent, eventually striking a residential road in a valley south of the airport. The impact was severe, and the aircraft was destroyed. The two fatalities involved were the pilot and the student.
The investigation
The AAIB examination of the wreckage revealed that the aircraft was in a steep, nose-down descent with significant rotational momentum to the left at the time of impact. Investigators found that the engine had likely stopped or nearly stopped before the crash. While the possibility of carburettor icing could not be entirely dismissed, evidence pointed toward fuel contamination.
Technical analysis of the fuel system showed that the left fuel filler cap had a defective seal due to age-related cracking and significant wear in the metal bayonet lugs. This defect allowed rainwater to enter the left wing tank. Furthermore, the aircraft was found to be significantly overweight, with a total weight of 1,811 lb, which was 141 lb above the maximum allowable limit. This excess weight increased the stalling speed, making the aircraft more susceptible to a stall during the engine-failure recovery attempt.
Findings
- The primary cause of the accident was an attempted turnback following an engine malfunction.
- The engine failure was likely caused by water contamination in the fuel supply, which entered the left tank through a defective filler cap seal.
- The aircraft was operating significantly above its maximum permitted weight, which increased the stall speed and compromised control during the turn.
- The pilot's lack of recent experience on this specific aircraft type contributed to the difficulty in managing the aircraft during the critical phase of flight.