Servo tab

A servo tab is a small hinged part on an airplane's control surfaces. It helps move the controls more easily.

These tabs were first made by a German company called Flettner and were called Flettner tabs. Even though they are called "servo" tabs, they are not true servomechanisms. They don't use special signals to keep the controls in the right place.

Instead, they help the pilot control the airplane with less effort by giving a mechanical advantage. This helps the plane respond better to the pilot's commands. Servo tabs make 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.

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 helps pilots 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 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 work like a trim tab. It helps keep the control surface in the right place and makes 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.