second device for trimming, which would increase drag. Anti-servo trim tabs are particularly found on stabilators, but are also found on other control surfaces. The Beechcraft RC-12 Guardrail uses a rudder trim tab which incorporates anti-servo action, and the Beechcraft U-21 uses elevator and aileron trim tabs which incorporate anti-servo action. See also Trim tab Nolder Balanced rudder § Aircraft References External links The Quest for Reduced Control Forces (NASA) — Monographs in Aerospace History: William Hewitt Phillips. A thorough dissertation on the reduction of control forces in high speed and large aircraft in the 1940s, with excellent links to NACA reports of the time, holding present day validity Aircraft controls