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Aircraft Fuel Pumps, Made Simple


Hand-Operated Fuel Pumps, or wobble pumps, are double-acting pumps that transfer fuel manually with each pump of the handle.  There are wide passages within the pump that allow for a back-and-forth movement of fuel. Hand-operated pumps require fuel lines to be run into the cockpit, which could potentially be hazardous.

Centrifugal Boost Pumps are the most common type of auxiliary fuel pump used on an aircraft.  These are electric motor driven, and usually located within the fuel tank or on the outside with the opening of the pump extending inside of the tank.  In this case, pump removal valves are typically installed so the pump can be detached without having to drain the entire tank.

Ejector Pumps are used to help ensure liquid fuel is always at the pump’s inlet, maintaining a constant flow of fuel from the pump to the tank.  These make sure vapor pockets do not form, which could cause structural damage to the aircraft.

Pulsating Electric Pumps, or plunger-type fuel pumps, are commonly used for smaller aircraft because they are less expensive and work the same as centrifugal fuel pumps on larger aircraft. These pumps use a plunger mechanism to pull fuel in and out; during starting they provide fuel before the engine-driven pump kicks in and can be used at higher altitudes to prevent vapor lock.

Vane-Type Fuel Pumps are the most common fuel pumps used for reciprocating-engine aircraft. These pumps can be used as engine-driven primary fuel pumps and as auxiliary/boost pumps.  Vane-type pumps ensure a consistent amount of fuel is kept moving; this can sometimes cause fuel levels to be too high, so most vane pumps have a pressure relief feature that helps with regulation.  The relief valve setting adjusts automatically to provide the correct amount of fuel as air pressure changes due to altitude or turbocharger outlet pressure.