Definition
A mechanical or electromechanical device that converts rotary motion or fluid pressure into straight-line (linear) motion to extend or retract a shaft, rod, or jackscrew. Linear actuators are commonly driven by electric motors, hydraulic pressure, or pneumatic pressure, and are used to position aircraft components such as flaps, landing gear, trim surfaces, and cargo doors.
Plain English
A device that pushes or pulls something in a straight line. It takes power -- usually from an electric motor or hydraulic fluid -- and uses it to move a rod in or out, which then moves whatever is attached to it.
Context Anchor
Seen in aircraft systems that move or position parts such as flaps, trim tabs, landing gear doors, cowl flaps, seats, or cargo doors.
Derivation
From Latin linearis (meaning 'of a line') and actuare ('to put into action'). Together it literally means 'something that produces motion along a line' -- which is exactly what it does.
Why Pilots Care
These devices provide precise, reliable movement of flight controls and landing gear; failure can limit aircraft performance or create emergency situations.
Analogy
A powered car seat uses a similar idea: a motor moves the seat forward or backward in a straight path, rather than just spinning freely.
Intuition Check
Linear does not mean “simple” here. It means the motion is straight-line motion, usually a push or pull.
Example Sentence 1
An electric linear actuator drives the flaps up and down when the pilot moves the flap selector.
Example Sentence 2
During the preflight inspection the mechanic verified that the landing gear linear actuator moved freely without binding.