Crash shortly after takeoff
The accident occurred on 23 December 2024 at Fife Airfield in Scotland. The Rockwell Commander had previously spent several weeks parked outdoors. Following the pre-flight check and an extended engine run, the 50-year-old pilot took off from runway 24.
About one minute later, a security camera recorded a roughly running engine. Shortly afterwards, the pilot lost control of the aircraft during the initial climb. The aircraft impacted rising terrain, and the pilot was killed.
Around 0.24 litres of water in the fuel system
During the technical investigation, the investigators found no classic mechanical defect in the engine. However, the fuel system showed significant water contamination.
The situation in the carburettor was particularly critical: there was so much water in the float chamber that it could cover the inlet of the main jet. A total of around 0.24 litres of water was recovered from the fuel system.
Water is heavier than avgas and collects at the lowest points of tanks and lines. If it reaches the carburettor or fuel injection system, it can lead to rough engine running, loss of power or complete engine failure.
Damaged fuel cap seals as the cause
The investigators found significant cracks in the rubber seals of the fuel filler caps. Tests showed that rainwater could enter the tanks through them. Between the last flight at the beginning of November and the day of the accident, the aircraft had been parked outdoors for around seven weeks and repeatedly exposed to precipitation.
It is noteworthy that water had been found in the tanks months earlier. However, maintenance work in the area of the tank caps apparently did not eliminate the actual cause. The AAIB therefore recommended that the manufacturer include specific inspection criteria for these seals in the maintenance documentation.
Why the engine still ran normally on the ground
Smooth engine running before takeoff does not rule out water in the tank. The water can initially collect at the bottom of the tank while the engine continues to receive clean fuel. It is only during taxiing, acceleration and climbing that the liquid can move and reach the fuel pickup.
That is precisely why a prolonged, uneventful engine run must not be regarded as a substitute for a thorough fuel check.
All drain points must be checked
The Commander's flight manual requires fuel samples to be taken from all designated drain points before the first flight of the day. If water is found, draining must continue until the system is free of contamination.
Whether the pilot had actually checked all the drain points on the day of the accident could not be conclusively determined. For pilots, this provides an important lesson: with multiple drain points, it is not sufficient to check only the gascolator or a single tank. Water can collect locally in another area of the system.
Even a clear sample can deceive
Another danger is less well known: if there is only water in the sample container, the typical separation layer between water and fuel is missing. Such a sample can therefore be mistakenly assumed to be clean fuel.
Smell is also not a reliable criterion, because water can smell of fuel after contact with avgas. Avgas 100LL is normally dyed blue; an unusually clear or colourless sample should therefore be viewed with particular caution.
After take-off: aviate first
The accident also shows why engine problems immediately after take-off are particularly dangerous. At low altitude, there is hardly any time for troubleshooting or complicated procedures.
The first task is always to maintain control of the aircraft and a safe speed. Only after that can measures to restore engine power be carried out, provided altitude and time permit.
The well-known principle Aviate – Navigate – Communicate is crucial right now in this situation.
Particular care after rain and extended periods of inactivity
For aircraft that have been left outside for some time, checks for water should be carried out with particular care after heavy precipitation. The condition of fuel filler caps and seals is also part of the pre-flight check.
Recurring water ingress should never be dealt with simply by draining it again. The key is to find and eliminate the point of entry.
Conclusion
The Rockwell Commander accident shows how what seems to be a simple contamination can turn into a fatal chain of events. Rainwater apparently got into the fuel system via damaged fuel cap seals, leading to engine trouble shortly after takeoff.
For pilots the consequences are clear: check all prescribed drain points, assess the colour and condition of the sample and have recurring findings of water investigated technically. And if the engine has problems after takeoff, flight control always takes priority over troubleshooting.
Source references:
Aviation magazine
