Definition
Small, hinged surfaces mounted on the trailing edge of a primary flight control surface (such as an elevator, aileron, or rudder) that the pilot moves directly via the cockpit controls. When deflected, the servo tab uses aerodynamic force from the airflow to move the larger primary control surface, reducing the physical effort the pilot must apply. Servo tabs are most commonly found on larger aircraft where the control surfaces are too large to be moved easily by direct mechanical input.
Plain English
A small flap on the back edge of a control surface that the pilot moves first. The wind pushing on that little flap then swings the bigger control surface for them, so flying takes less muscle.
Context Anchor
Seen in aircraft control system discussions, especially when learning how some aircraft reduce the force needed to move elevators, ailerons, or rudders.
Derivation
From Latin servus, meaning 'servant' or 'slave' — the same root as 'service.' The tab acts as a servant to the pilot, doing the heavy work of moving the larger control surface. 'Tab' is simply a small flap or projection.
Why Pilots Care
Reduces the physical force needed to deflect control surfaces at higher speeds or on larger aircraft, improving controllability without requiring powered assistance.
Analogy
A servo tab is like using a small helper panel to push on a larger panel. The small piece moves into the airflow, and the air does much of the work of moving the larger surface.
Intuition Check
Do not think of a tab here as a label or a pull-tab. In this context, a tab is a small movable surface that changes the air pressure on a larger control surface.
Example Sentence 1
On larger aircraft without hydraulic boost, servo tabs allow the pilot to move heavy control surfaces using aerodynamic force rather than raw muscle.
Example Sentence 2
Servo tabs on the ailerons allowed the pilot to roll the aircraft smoothly even at cruise speed.