Boost pumps in aircraft fuel systems are typically which type?

• A. Positive displacement
• B. Centrifugal
• C. Diaphragm
• D. Gear

Answer: (B)

Boost pumps are used to ensure a reliable flow of fuel to the engine-driven pump, especially when gravity feed isn’t enough or during startup and high-demand phases. The typical choice is a centrifugal pump because it delivers a healthy volume of fuel at relatively low discharge pressure, which is exactly what a boost pump needs to push fuel through the system and prime the engine pump without creating excessive pressure. Its simple, rugged construction makes it reliable for continuous electric operation in the wing tanks, and it can handle the modest pressures involved without the complexity or weight of positive-displacement options. Diaphragm or gear pumps would pressurize fuel more than is required and add more complexity and potential maintenance, while positive-displacement pumps are often unnecessary for this duty. So, the centrifugal design aligns with the boost pump’s role of providing steady, adequate flow with minimal fuss.