What is the purpose of flapper type check valves in integral fuel tanks?

Flapper type check valves serve a crucial role in integral fuel tank systems by ensuring that fuel is directed toward the boost pumps and preventing it from flowing away. These check valves operate on a simple mechanical principle, where a flapper opens to allow fuel to pass in one direction (toward the pump) but closes to block flow in the opposite direction. This function is vital for maintaining the required flow of fuel to the engine during operation.

By preventing backflow, flapper check valves help to maintain pressure in the fuel lines, ensuring that the boost pumps can effectively supply fuel to the engine. This reduces the risk of unintentional fuel starvation, which could occur if the fuel were to flow back into the tank, particularly during maneuvers that might otherwise cause the fuel to shift.

The correct understanding of these valves is important because it directly impacts fuel system reliability and efficiency. In scenarios where the boost pump is the primary fuel delivery mechanism, having check valves in place secures an uninterrupted supply of fuel, enhancing the overall safety and performance of the aircraft fuel system.