Servo tab

A servo tab is a small hinged device placed on an aircraft's control surfaces to help move them more easily. These tabs were first created by a German company called Flettner and were originally named Flettner tabs. Even though they are called "servo" tabs, they are not true servomechanisms because they don't use special signals to keep the control surfaces in exactly the right place. Instead, they simply make it easier for the pilot to control the aircraft by giving a mechanical advantage. This means the pilot can move the controls with less effort, helping the plane respond better to their commands. Servo tabs are an important part of making flying safer and more efficient.

Servo tabs

A servo tab, also called a balance tab, helps pilots control an airplane more easily. It moves in the opposite direction of where the pilot wants the airplane to go. By changing the airflow, the servo tab creates a force that moves the airplane’s control surfaces in the right direction. Because it is placed farther back than the hinge of the control surface, it has an advantage and can move the surface with less effort from the pilot.

In some big airplanes, like the Bristol Britannia and its Canadian versions, the servo tab is the only part connected to the pilot’s control stick or wheel. When the pilot moves the wheel, it moves the servo tab, which then moves the elevator or aileron. This setup allows pilots to control very heavy airplanes flying at high speeds.

Anti-servo tabs

An anti-servo tab, also called an anti-balance tab, works differently from a servo tab. It moves in the same way as the control surface, making it harder for the pilot to move the controls. This might seem strange, but it helps when the controls feel too light. The anti-servo tab makes the controls feel heavier and helps the aircraft stay more stable.

These tabs are often used on stabilators, which need a way to reduce how sensitive they are.

Incorporation of trim tab functionality

A servo or anti-servo tab can also work like a trim tab, helping to keep the control surface in the right place and making it easier for the pilot to control. This means there is no need for an extra device just for trimming, which can make the airplane more efficient.

Anti-servo trim tabs are often used on stabilators, but they can also be found on other parts of the airplane. For example, the Beechcraft RC-12 Guardrail uses a rudder trim tab with anti-servo action, and the Beechcraft U-21 uses elevator and aileron trim tabs with anti-servo action.