Fuel Systems in General Aviation Aircraft

What is a fuel system?

    The fuel system is a combination of systems that stores, cleans and distributes fuel to an aircrafts engine. This can includes fuel tanks, lines, pumps, primers, strainers, sumps, drains, and the carburetor or injectors. (PHAK, 2016) The fuel tanks, usually in the aircraft wings, store the fuel. The lines are the piping or hose that the fuel travels. The pumps provide pressure to the fuel system. The primer is used during cold weather to draw fuel to the engine cylinders for engine start. The strainer removes sediment and moisture from the fuel and stores it in the sump. The drains are connected to the fuel tanks to allow samples to be pulled as well as the sump to remove the accumulated sediment and moisture. And the carburetor or fuel injectors vaporize the fuel to be combusted in the engine. (PHAK, 2016)

Potential issues in the fuel system

    Fuel systems are prone to issues from contaminated fuel, icing, and component failure. Fuel contamination is caused by the presence of water or sediment in the fuel. (PHAK, 2016) Water in the fuel can cause decreased engine performance, engine failure, and icing in the fuel system. Icing occurs when water in the fuel freezes in the carbonator blocking the path of the fuel to the engine or freezes in the fuel tanks that will give an inaccurate fuel quantity and potentially thaw and reintroduce water in the fuel that can refreeze in the carburetor. Lastly, component failure can because by worn or damage components failing mid-flight. 

Maintenance and Prevention

    Fuel system issues can be prevented by inspecting the components for signs of wear or damage and  the quality of your fuel should be checked by taking samples from the drain valve and checking for signs of contamination. Contamination can be identified by looking at your sample and checking the color, smell, and sediment. The color should match the dye used to identify the desired fuel type; Red for AVGAS 80, Green for AVGAS 100, Blue for AVGAS 100LL, and colorless/straw for JET A. (PHAK, 2016) Smell can also help identify fuel type because JET A will smell like kerosene and AVGAS will smell like regular petrol. When you are draining your sample if the flow is restricted it could be a sign of sediment or ice blocking the drain port. If this happens, the aircraft should be stored in a warm hanger and a sample should be taken at a later time.

References

Federal Aviation Administration (FAA). (2016). Pilot’s Handbook of Aeronautical Knowledge (PHAK). Retrieved July 13, 2022, from https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak

(PHAK, 2016)