Definition
A mechanical or electromechanical device that converts an input signal or power source — typically hydraulic, pneumatic, or electrical — into physical motion to operate an aircraft component such as a flight control surface, landing gear, flap, or valve.
Plain English
The part that actually moves something when you flip a switch or move a lever. It takes power coming in and turns it into push, pull, or rotation that moves a piece of the aircraft.
Context Anchor
Seen in aircraft systems such as landing gear, flaps, flight controls, doors, valves, and other parts that must be moved or positioned.
Derivation
From the Latin actus, meaning 'a doing' or 'an act.' An actuator is literally the thing that does the action — it carries out the command coming from the pilot or system.
Why Pilots Care
Actuators directly control movement of flight surfaces and gear; a failed actuator can limit handling or prevent safe takeoff and landing.
Intuition Check
Do not think of an actuator as just the switch or control the pilot touches. The actuator is the device that physically moves the aircraft part after the command is made.
Example Sentence 1
When the pilot selected gear down, hydraulic pressure drove the actuator that extended the main landing gear.
Example Sentence 2
Mechanics replaced the faulty actuator after the landing gear failed to retract.