Flight Controls

effectively maneuver the aircraft. As a result, the increase i y n a w ai l i e s r o es n p d e e c f i l a e l c ly ti o e n v i c d a e u n s t e i s n a a n i r i c n r c a r f e t a w se it h in l a o d n v g e w rs i e n g y a s w pa . n T s h . e Aileron deflected u p Application of the rudder is used to counteract adverse yaw. The amount of rudder control required is greatest at Differential aileron low airspeeds, high angles of attack, and with large aileron deflections. Like all control surfaces at lower airspeeds, the vertical stabilizer/rudder becomes less effective and magnifies the control problems associated with adverse yaw. Aileron deflected down All turns are coordinated by use of ailerons, rudder, and elevator. Applying aileron pressure is necessary to place Figure 6-6. Differential ailerons. the aircraft in the desired angle of bank, while simultaneous the drag created by the lowered aileron on the opposite wing application of rudder pressure is necessary to counteract the and reduces adverse yaw. [Figure 6-7] resultant adverse yaw. Additionally, because more lift is required during a turn than during straight-and-level flight, The frise-type aileron also forms a slot so air flows smoothly the angle of attack (AOA) must be increased by applying over the lowered aileron, making it more effective at high elevator back pressure. The steeper the turn, the more elevator angles of attack. Frise-type ailerons may also be designed back pressure that is needed. to function differentially. Like the differential aileron, the frise-type aileron does not eliminate adverse yaw entirely. As the desired angle of bank is established, aileron and Coordinated rudder application is still needed when ailerons rudder pressures should be relaxed. This stops the angle of are applied. bank from increasing, because the aileron and rudder control surfaces are in a neutral and streamlined position. Elevator Coupled Ailerons and Rudder back pressure should be held constant to maintain altitude. Coupled ailerons and rudder are linked controls. This is The roll-out from a turn is similar to the roll-in, except the accomplished with rudder-aileron interconnect springs, which flight controls are applied in the opposite direction. The help correct for aileron drag by automatically deflecting aileron and rudder are applied in the direction of the roll-out the rudder at the same time the ailerons are deflected. For or toward the high wing. As the angle of bank decreases, the elevator back pressure should be relaxed as necessary Neutral to maintain altitude. In an attempt to reduce the effects of adverse yaw, manufacturers have engineered four systems: differential ailerons, frise-type ailerons, coupled ailerons and rudder, and flaperons. Differential Ailerons Raised With differential ailerons, one aileron is raised a greater distance than the other aileron and is lowered for a given movement of the control wheel or control stick. This produces an increase in drag on the descending wing. The greater drag results from deflecting the up aileron on the descending wing Drag to a greater angle than the down aileron on the rising wing. While adverse yaw is reduced, it is not eliminated completely. Lowered [Figure 6-6] Frise-Type Ailerons With a frise-type aileron, when pressure is applied to the control wheel, or control stick, the aileron that is being raised pivots on an offset hinge. This projects the leading edge of the aileron into the airflow and creates drag. It helps equalize Figure 6-7. FrisFei-gtyupree a5i-l4er. o Fnrsis.e-type ailerons. 6-4