What is the primary purpose of a fuel drain valve?

The primary purpose of a fuel drain valve is to remove contaminants from the fuel tanks. In aviation fuel systems, the presence of water, sediment, or other impurities in the fuel can significantly affect engine performance and safety. Fuel drain valves provide a means to regularly inspect and purify the fuel by allowing unwanted substances to be drained from the bottom of the tanks, where they typically settle.

By effectively managing fuel cleanliness, the fuel drain valve helps ensure that only pure, uncontaminated fuel is delivered to the engine. Regular maintenance and checks of these valves are vital for the reliability and efficiency of the fuel system, as contamination can lead to malfunctions or damage in the aircraft's fuel components and engines.