<P> A servo tab is a small hinged device installed on an aircraft control surface to assist the movement of the control surfaces . Introduced by the German firm Flettner, servo tabs were formerly known as Flettner tabs . Servo tabs are not true servomechanisms, as they do not employ negative feedback to keep the control surfaces in a desired position; they only provide a mechanical advantage to the pilot . </P> <P> Servo tabs move in the opposite direction of the control surface . The tab has a leverage advantage, being located well aft of the surface hinge line, and thus can use the relative airflow to deflect the control surface in the opposite direction . This has the effect of reducing the control force required by the pilot to move the controls . </P>

Difference between servo tab and anti servo tab