Plain English Meaning

A system that raises and lowers the landing gear by using a pump to push fluid through small cylinders, which then move the gear up or down on command from the cockpit.

Full Definition

A landing gear retraction system that uses pressurized fluid, driven by an engine-driven or electrically-driven hydraulic pump, to extend and retract the landing gear. The pump pressurizes hydraulic fluid in a reservoir; selector valves direct that pressurized fluid to actuators (cylinders) at each gear leg, which mechanically push the gear up into its wells or down into the locked-down position. Check valves, sequencing valves, and gear-down locks ensure the gear travels in the correct order and stays locked when fully extended.

Context Anchor

Encountered when studying operation, gear-up/gear-down checks, and abnormal landing gear .