Definition 1 of 2
Definition
A small powered device that moves a flight control surface or system component in response to an electrical, hydraulic, or pneumatic signal. In autoflight and stability augmentation systems, servos translate computer commands into physical motion of the ailerons, elevator, rudder, or trim.
Plain English
A small motor or actuator that moves something — like a control surface — when it gets a signal telling it what to do.
Context Anchor
Seen in discussions of automatic flight-control systems, especially the yaw damper and how it moves the rudder-control system.
Derivation
From Latin servus, meaning 'slave' or 'servant.' The name fits: a servo is a device that quietly does what it's told, moving a control on command from a larger system.
Why Pilots Care
It reduces pilot workload and prevents Dutch-roll oscillations that would otherwise require constant rudder input, especially in swept-wing jets.
Intuition Check
A servo is not the same as the whole yaw damper system. The servo is the part that does the moving after the system gives it a command.
Example Sentence 1
When the yaw damper is engaged, a rudder servo makes small, automatic rudder inputs to dampen unwanted yaw.
Example Sentence 2
The autopilot servos adjusted the rudder during cruise to maintain coordinated flight without pilot input.