Definition
A small auxiliary control surface hinged to the trailing edge of a primary flight control (such as an elevator, rudder, or aileron) that moves in the opposite direction to the primary surface. When the pilot moves the cockpit control, the servo tab deflects first, and the aerodynamic force on the tab then drives the larger primary surface into position. This reduces the physical effort required from the pilot to move the control.
Plain English
A small flap on the back edge of a flight control that does the heavy lifting for the pilot. When you move the controls, the little flap moves first, and the airflow pushing on it swings the bigger control surface into place — so you don't have to muscle it yourself.
Context Anchor
Seen in flight control system descriptions, aircraft walkarounds, and discussions of how control forces are reduced on some airplanes.
Derivation
From Latin servus, meaning 'servant' or 'slave' — the same root as 'servant.' The tab serves the pilot by doing the work of moving the larger control surface. 'Tab' simply refers to its small, flap-like shape.
Why Pilots Care
Reduces control forces on larger or faster aircraft, improving handling and reducing pilot fatigue.
Intuition Check
A servo tab is not simply a trim tab. A trim tab holds a control surface in a selected position to reduce steady pressure, while a servo tab helps move the main control surface when the pilot makes a control input.
Example Sentence 1
The pilot noticed lighter-than-usual elevator forces because the servo tab was doing most of the work of deflecting the elevator.
Example Sentence 2
Servo tabs on the ailerons helped the aircraft roll smoothly even at high speeds.