Aircraft Fuel Pumps, Made Simple

For any aircraft, a continuous and reliable supply of fuel to the engine is an essential requirement for flight. While some small aircraft may depend solely on gravity to move fuel from tanks to the engine, most modern aircraft require one or more fuel pumps to deliver fuel under pressure, regulate flow, and uphold operational safety in all conditions. This blog will explore the different variations of fuel pumps, as well as dive into general details about how they are designed to suit various aircraft types.

Types of Aircraft Fuel Pumps

1. Engine-Driven Fuel Pumps

Engine-driven fuel pumps are as they sound, being mechanically powered by the rotation of the aircraft engine. Serving as the primary source of fuel pressure during flight in both reciprocating and turbine engine aircraft, this offers a reliable supply of fuel that scales proportionally with engine speed. They are particularly vital for sustained high-performance operation where gravity feed would be insufficient, variations including:

• Vane-Type Pumps: Widely used in reciprocating-engine aircraft, these pumps maintain fuel flow by rotating vanes within a cavity. Their design allows for self-priming and consistent delivery even under variable engine speeds, often employing pressure relief valves or altitude compensating features to regulate flow as ambient or manifold pressures change.
• Gear-Type Pumps: Common in turbine-powered aircraft, gear pumps utilize two intermeshing gears that create a vacuum to draw in fuel and push it through the system under high pressure. Known for their simplicity and robust performance, gear pumps can manage the higher pressure demands of jet engines and high-altitude, high-speed operations.

2. Electric Auxiliary Fuel Pumps

Electric auxiliary fuel pumps support an engine-driven pump, particularly during startup, takeoff, or emergency scenarios. In some smaller or lighter general aviation aircraft, they may even serve as the sole pumping mechanism. Notable subtypes are:

• Centrifugal Boost Pumps: These pumps use a high-speed rotating impeller to impart kinetic energy to the fuel, increasing pressure and ensuring proper flow when attitude might affect gravity-fed movement. Typically mounted within or just outside the fuel tank, centrifugal pumps are crucial during phases like engine start and takeoff, or anytime vapor lock prevention is necessary.
• Plunger-Type (Pulsating) Pumps: These pumps use a solenoid-actuated plunger to pull and push fuel in a pulsed cycle, making them suitable for light aircraft with lower fuel volume demands. They are often used to prime the system before engine start or to prevent vapor lock at higher altitudes in carbureted engine aircraft. Though they are generally less durable than centrifugal pumps, their straightforward construction is economical and easy to maintain.

3. Ejector Pumps

Ejector pumps, also known as jet pumps, are passive fuel delivery devices that direct pressurized fuel from a primary pump through a nozzle, creating suction that draws fuel from secondary tanks or low points within the main tank. This process helps prevent vapor pockets and maintains feed line priming, which is essential to avoid cavitation especially during steep climbs or rapid altitude changes.

Because ejector pumps contain no moving parts, they offer exceptional reliability and require minimal maintenance. Their design also makes them particularly valuable in large aircraft fuel systems with multiple tanks, where they keep the main fuel pump inlet continuously supplied.

4. Hand-Operated Fuel Pumps

Hand-operated, or “wobble,” pumps are manual fuel transfer devices most commonly found in older aircraft or retained as backup systems. These double-acting pumps are manually actuated via a cockpit-mounted lever, with each pump stroke drawing fuel in one direction and pushing it in the other.

Despite being effective for priming or emergency use, hand pumps have largely been phased out in favor of electric auxiliary pumps in newer aircraft. Nonetheless, they remain functional and reliable in vintage models and for operations conducted in remote or austere environments where electrical support may be limited or unavailable.

Procure Fuel Pump Parts from Aviation Sourcing Solutions

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