Definition
In an autopilot system, servos are the small electric or electro-pneumatic motors that physically move the aircraft's flight controls — typically the ailerons, elevator, and sometimes the rudder or trim — in response to commands from the autopilot computer. They convert the autopilot's electrical signals into the mechanical force needed to deflect a control surface.
Plain English
Servos are the little motors the autopilot uses to actually move the controls. When the autopilot decides the aircraft needs to turn or pitch up, the servos do the muscle work the pilot would normally do with the yoke and rudder pedals.
Context Anchor
Seen in autopilot discussions when explaining how the autopilot moves the ailerons, elevator, rudder, or trim.
Derivation
From the Latin servus, meaning 'slave' or 'servant.' A servo is literally a small device that obeys commands and does the work for you — fitting, since it acts on the controls in the pilot's place when the autopilot is engaged.
Why Pilots Care
Without working servos the autopilot cannot change the aircraft's attitude or maintain a desired flight path.
Analogy
A servo is like the motor in an automatic door. The control unit decides when the door should move, but the motor is the part that actually pushes it open or closed.
Intuition Check
Do not think of servos as the autopilot’s brain. Think of them as the autopilot’s muscles: they move the controls after the command is made.
Example Sentence 1
During the preflight autopilot check, the pilot engaged each axis and felt the servos drive the yoke through small test movements.
Example Sentence 2
A failed servo caused the autopilot to disconnect and hand control back to the pilot.