Flight Controls

Antiservo tab Down spring Stabilator Pivot points Elevator Balance weight Pivot point Bell crank Figure 6-13. The stabilator is a one-piece horizontal tail surface that pivots up and down about a central hinge point. Figure 6-12. When the aerodynamic efficiency of the horizontal tail surface is inadequate due to an aft CG condition, an elevator down of the main wings. In effect, the canard is an airfoil similar to spring may be used to supply a mechanical load to lower the nose. the horizontal surface on a conventional aft-tail design. The difference is that the canard actually creates lift and holds airflow over the empennage. This, coupled with the reduced the nose up, as opposed to the aft-tail design which exerts landing speed, makes the elevator less effective. downward force on the tail to prevent the nose from rotating downward. [Figure 6-14] As this discussion demonstrates, pilots must understand and follow proper loading procedures, particularly with regard The canard design dates back to the pioneer days of aviation. to the CG position. More information on aircraft loading, Most notably, it was used on the Wright Flyer. Recently, the as well as weight and balance, is included in Chapter 10, canard configuration has regained popularity and is appearing Weight and Balance. on newer aircraft. Canard designs include two types–one with a horizontal surface of about the same size as a normal aft-tail Stabilator design, and the other with a surface of the same approximate As mentioned in Chapter 3, Aircraft Structure, a stabilator is size and airfoil of the aft-mounted wing known as a tandem essentially a one-piece horizontal stabilizer that pivots from wing configuration. Theoretically, the canard is considered a central hinge point. When the control column is pulled more efficient because using the horizontal surface to help back, it raises the stabilator’s trailing edge, pulling the nose lift the weight of the aircraft should result in less drag for a of the aircraft. Pushing the control column forward lowers given amount of lift. the trailing edge of the stabilator and pitches the nose of the aircraft down. Because stabilators pivot around a central hinge point, they are extremely sensitive to control inputs and aerodynamic loads. Antiservo tabs are incorporated on the trailing edge to decrease sensitivity. They deflect in the same direction as the stabilator. This results in an increase in the force required to move the stabilator, thus making it less prone to pilot-induced overcontrolling. In addition, a balance weight is usually incorporated in front of the main spar. The balance weight may project into the empennage or may be incorporated on the forward portion of the stabilator tips. [Figure 6-13] Canard Figure 6-14. The Piaggio P180 includes a variable-sweep canard The canard design utilizes the concept of two lifting surfaces. design that provides longitudinal stability about the lateral axis. The canard functions as a horizontal stabilizer located in front 6-7