Definition
A positive-displacement pump that moves fluid by means of one or more pistons reciprocating inside cylinders. Each piston draws fluid into the cylinder on its intake stroke through an inlet check valve, and forces it out under pressure on its discharge stroke through an outlet check valve. Piston-type pumps are used in aircraft hydraulic systems where high pressures are required, and they may be of fixed-displacement or variable-displacement design.
Plain English
A pump that uses pistons sliding back and forth inside cylinders to suck fluid in and then push it out under high pressure.
Context Anchor
Seen in aircraft system discussions involving hydraulic pressure, fuel movement, or other systems that need a steady supply of fluid under pressure.
Derivation
From the Latin pistare, meaning 'to pound' or 'to crush.' A piston is a part that moves up and down inside a cylinder, and a pump using this action to move fluid is therefore a piston-type pump.
Why Pilots Care
Delivers steady fluid flow even when system pressure changes, supporting reliable operation of landing gear, flaps, and brakes.
Analogy
A hand bicycle pump is a simple piston-type pump: the handle moves a piston back and forth, drawing air in and pushing it out under pressure.
Intuition Check
Do not assume piston-type means the pump is part of the engine piston system. Here it means the pump itself uses piston movement to move fluid.
Example Sentence 1
The aircraft's hydraulic system uses an engine-driven piston-type pump to maintain pressure for the landing gear and flaps.
Example Sentence 2
Piston-type pumps are often used in small aircraft because they maintain consistent output across a wide range of engine speeds.