RE: Boost tab on rudder - ?
Rotaryphile is right on the money......DC-9/MD-80...known as the Maintenace Delay-80....or 100 ft long "Sewer Pipe"....has servo tabs( and "geared" tabs)...... for ailerons/elevators...with hydro boost for elevator down only for stall recovery......rudder is hydro powered.........after working on these for a number of years....still amazed on how well the servo tabs worked.......yes...servo tabs move the opposite direction of the primary surface that it is attached to......Bill......