Which of the following is considered a secondary flight control?

A servo tab is considered a secondary flight control because it assists primary flight controls, such as ailerons, elevators, and rudders, by providing additional force and reducing the pilot's workload. It operates by moving in the opposite direction of the primary control surface when the pilot inputs a command, which helps to create a control force that assists the pilot in maneuvering the aircraft more effectively.

In contrast, rudders, inboard ailerons, and elevators are classified as primary flight controls. These controls directly influence the aircraft's pitch, roll, and yaw during flight. The operational function of a servo tab is to enhance the effectiveness of these primary controls, rather than directly controlling the aircraft's movement itself. This distinction is important for understanding the hierarchy of flight control systems and how they work together to create stable and precise aircraft handling.