A Servo tab (sometimes called a Flettner tab after its inventor Anton Flettner) is a small hinged device installed on an aircraft control surface to assist the movement of the control surface.
In the case of some aircraft the servo tab is the only control that is connected to the pilot's stick or wheel. The pilot moves the wheel which moves the servo tab and then the servo tab, using its mechanical advantage, moves the elevator or aileron, which is otherwise free-floating.
On some aircraft with all-flying stabilators an anti-servo tab acts as a trimming device. In this use some manufacturers term it a "balance tab" or "anti-balance tab".
On Your Tail: The Tail Is There to Balance Forces Created by the Wing's Lift and to Minimize Yaw. How Your Tail Is Designed Influences How It Works and the Airplane's Stability
Jul 01, 2013; Of all the major components of a conventional airplane, the tail--empennage, if you prefer--may be the least understood. Yes, we...
Trimming: effectively using the secondary flight controls means we first have to learn using the primary ones.(AIRMANSHIP)
Mar 01, 2008; Like most student pilots, I tended to fly with the type of casual elan my primary instructor described, none too deferentially,...