What is the intended function of a fuel flapper valve during flight?

The function of a fuel flapper valve during flight is primarily to prevent fuel from leaving the fuel supply system when the aircraft is in different maneuvers, such as turbulence, climbs, or turns. This valve acts as a one-way mechanism, allowing fuel to flow in a specific direction while effectively blocking the backflow or spillage of fuel under certain conditions. By ensuring that the fuel remains contained within the supply lines and tanks, the flapper valve helps maintain consistent fuel availability and system reliability, which is crucial for engine performance and overall flight safety.

In contrast, measuring fuel consumption involves separate systems designed to track the amount of fuel used, while maintaining pressure is typically the role of pressure relief valves and other components. Filtering impurities is an essential function of fuel strainers or filters, which serve to clean the fuel before it reaches the engine, rather than being the responsibility of the flapper valve.