What is the primary function of flapper-type check valves in integral fuel tanks?

The primary function of flapper-type check valves in integral fuel tanks is to prevent fuel from flowing away from the boost pumps. These valves allow fuel to flow in one direction, ensuring that once it is pulled into the boost pumps, it does not flow back into other areas of the tank, particularly when the pumps are not operating. This function is crucial for maintaining fuel availability at the pumps, especially during maneuvers that may cause fuel to shift within the tank.

While improving fuel flow efficiency and regulating fuel pressure are important aspects of a fuel system, these functions are typically handled by other components, such as fuel pumps and regulators. Meanwhile, preventing contamination of fuel is vital as well, but flapper check valves are not specifically designed for filtration or contamination prevention; their role is more about controlling the direction of fuel movement.