Definition
A landing gear actuation system that uses an electric motor to drive a hydraulic pump, which then provides the fluid pressure needed to extend and retract the landing gear. The system normally remains depressurized until the pilot selects gear up or down, at which point the pump runs only long enough to move the gear and pressurize the lines.
Plain English
A landing gear system that combines two power sources: electricity to run a small pump, and hydraulic fluid pressure to actually push the gear up or down. The pump only runs when the gear is being moved.
Context Anchor
Seen in landing gear system descriptions, especially for airplanes where the gear is moved by hydraulic pressure produced or controlled electrically.
Derivation
Electro- comes from electricity; hydraulic comes from the Greek hydraulikos, meaning 'water-driven,' but in aviation it refers to any system driven by pressurized fluid. Together the word describes a system where electrical power drives the hydraulic pressure that does the work.
Why Pilots Care
Understanding this system helps pilots recognize normal gear operation, diagnose failures, and follow correct emergency extension procedures.
Intuition Check
Do not read “electrohydraulic” as purely electric. The electric part starts or controls the pressure; the hydraulic part provides the force that moves the component.
Example Sentence 1
When the pilot moved the gear handle to the down position, the electrohydraulic system's pump ran for a few seconds until the gear was locked down.
Example Sentence 2
With a hydraulic pump failure the electrohydraulic system could still extend the gear using its backup electric motor.