No Dumb Questions: Stabilators v. Elevators

Q. I?ve noticed that on the Piper Cherokee, the entire horizontal stabilizer acts as the elevator, while most other aircraft have a conventional fixed horizontal stabilizer with a movable elevator attached. Does the moving stabilizer handle any differently, and what are its advantages and disadvantages?

A. The Piper Cherokee that you saw has what is called a stabilator. Walk the airport ramp and you?ll see that almost all Piper singles and piston twins have a stabilator. The exceptions are the largest piston-powered Piper single and twin, the Malibu/Mirage and Navajo. The first Piper to have a stabilator was the Comanche, which debuted in 1958.

Engineers at The New Piper Aircraft Co. consider the stabilator to be cleaner in design and more effective in control response than a conventional stabilizer-elevator arrangement, in part because the stabilator is a much larger overall pitch-control surface than a traditional elevator. The engineers also say the stabilator design is lighter and produces less drag than a more conventional elevator.

The strong control response of the stabilator is the reason for the unusual pitch trim design, called anti-servo. The trim tab moves in the same direction as the stabilator, but with increased travel. The effect on the pilot is that pitch control force?the effort required to move the yoke forward or back?increases with airspeed and control deflection. In other words, the faster the airplane is flying, or the farther back or forward the pilot moves the yoke, the more difficult it becomes to move the yoke. It?s a safety measure to enhance longitudinal stability and also to prevent the pilot from overcontrolling, possibly causing structural damage.

Despite the differences in design and structure between a stabilator and a conventional horizontal tail, for all practical purposes a pilot won?t notice much of a difference in handling qualities.