Definition
A positive-displacement pump that uses two meshing spur gears rotating inside a close-fitting housing to move fluid. Fluid is drawn into the spaces between the gear teeth and the housing on the inlet side, carried around the outside of each gear, and forced out at the discharge side as the teeth re-mesh. Commonly used in aircraft engine oil systems and as a fuel pump element.
Plain English
A pump that uses two meshing toothed gears to move oil or fuel. As the gears turn, the spaces between their teeth scoop fluid from the inlet, carry it around the inside of the pump body, and squeeze it out the other side.
Context Anchor
Seen in aircraft engine oil and fuel system descriptions, especially when identifying the type of pressure pump installed on an engine.
Derivation
A spur gear is a flat, straight-toothed gear (the teeth stick straight out like the rowels on a cowboy's spur). The pump is named for the type of gear it uses inside.
Why Pilots Care
Delivers consistent pressure and volume of oil or fuel, directly supporting engine lubrication, cooling, and operation.
Analogy
Works like two paddle wheels locked together that scoop liquid in the pockets between their teeth and carry it from one side of the housing to the other.
Intuition Check
“Spur” does not mean a side path or a boot spike here. In this term, it describes the straight-tooth gear shape used inside the pump.
Example Sentence 1
The engine's oil pressure pump is a spur-gear pump driven off the accessory section.
Example Sentence 2
Mechanics inspect the spur-gear pump housing for scoring to confirm it will maintain proper fuel pressure on the next flight.