What direction does a servo tab move in relation to the primary control surface?

The servo tab moves in the opposite direction of the primary control surface. This movement is a fundamental aspect of how servo tabs function in an aircraft's control system. When the primary control surface, such as an elevator or aileron, is deflected by the pilot, the pressure differential created by this deflection causes the servo tab to move in the opposite direction.

The purpose of this is to generate a force that assists the pilot in moving the primary control surface. By designing the servo tab to move in the opposite direction, it helps to reduce the control forces needed for maneuvering, making it easier for the pilot to control the aircraft. This principle is particularly useful in larger aircraft where control forces can be significant.

Understanding this relationship between the movement of the servo tab and the primary control surface is crucial for maintaining proper control responsiveness and ensuring effective aircraft handling.