What happened
On 23 December 2024, a Rockwell Commander 112 TCA, registration N469SB, departed from controlled flight shortly after taking off from Fife Airport for a local flight. CCTV footage from the airport captured the aircraft climbing before it appeared to enter an incipient spin. Simultaneously, recordings from the nearby village of Kinglassie captured the sound of an engine misfiring, followed by the aircraft striking rising ground. The pilot, who was the sole occupant, was 1 fatality.
The investigation
The AAIB examination of the aircraft's fuel system revealed significant water contamination throughout the system, downstream of the fuel selector valve. Testing confirmed that water had reached the carburettor float bowl, which caused the engine to run roughly and eventually lose power.
Investigators found that the rubber grommets on the wing fuel tank filler caps were in poor condition, with visible through-thickness cracking and age-related hardening. Because the aircraft had been parked outside and had been exposed to recent rainfall, it was determined that water had leaked through these degraded seals into the fuel tanks. The investigation also noted that while the aircraft's engine monitor recorded the loss of power, the exact sequence of the loss of control could not be definitively determined, though wind turbine wake vortices were considered and largely discounted due to the distance from the site.
Findings
- The engine failure and subsequent loss of power were caused by water entering the carburettor via the fuel system.
- The fuel tank filler cap grommets were heavily deteriorated, allowing rainwater to enter the tanks while the aircraft was parked.
- The aircraft's maintenance manual lacked specific inspection criteria or life limits for these rubber grommet seals.
- Pre-flight fuel sampling was not effective in removing the water present in the system prior to takeoff.