natural feel. At low airspeeds, the controls usually feel soft  and sluggish, and the aircraft responds slowly to control  applications. At higher airspeeds, the controls become  increasingly firm and aircraft response is more rapid.  Movement of any of the three primary flight control surfaces  (ailerons, elevator or stabilator, or rudder), changes the  airflow and pressure distribution over and around the airfoil.  These changes affect the lift and drag produced by the airfoil/  control surface combination, and allow a pilot to control the  aircraft about its three axes of rotation.  Design features limit the amount of deflection of flight  control surfaces. For example, control-stop mechanisms may  be incorporated into the flight control linkages, or movement  of the control column and/or rudder pedals may be limited.  The purpose of these design limits is to prevent the pilot from  inadvertently overcontrolling and overstressing the aircraft  during normal maneuvers.  A properly designed aircraft is stable and easily controlled  during normal maneuvering. Control surface inputs cause  movement about the three axes of rotation. The types of  stability an aircraft exhibits also relate to the three axes of  rotation.  [Figure 6-4]  Ailerons control roll about the longitudinal axis. The ailerons  are attached to the outboard trailing edge of each wing and  move in the opposite direction from each other. Ailerons are  connected by cables, bellcranks, pulleys, and/or push-pull  tubes to a control wheel or control stick.  Moving the control wheel, or control stick, to the right  causes the right aileron to deflect upward and the left aileron  to deflect downward. The upward deflection of the right  aileron decreases the camber resulting in decreased lift on  the right wing. The corresponding downward deflection of  the left aileron increases the camber resulting in increased  lift on the left wing. Thus, the increased lift on the left wing  and the decreased lift on the right wing causes the aircraft  to roll to the right.  Since the downward deflected aileron produces more lift as  evidenced by the wing raising, it also produces more drag.  This added drag causes the wing to slow down slightly.  This results in the aircraft yawing toward the wing which  had experienced an increase in lift (and drag). From the  pilot’s perspective, the yaw is opposite the direction of the  bank. The adverse yaw is a result of differential drag and the  slight difference in the velocity of the left and right wings.  [Figure 6-5]  Adverse yaw becomes more pronounced at low airspeeds.  At these slower airspeeds, aerodynamic pressure on control  surfaces are low, and larger control inputs are required to  Figure 6-4.  Airplane controls, movement, axes of rotation, and  type of stability.  Figure 6-5.  Adverse yaw is caused by higher drag on the outside  wing that is producing more lift.  6-3  Ailerons  Adverse Yaw  Lateral axis (longitudinal stability)  Aileron—Roll  Rudder—Yaw Elevator—Pitch  Longitudinal axis (lateral stability)  Vertical axis  (directional stability) Aileron  Roll  Longitudinal  Lateral  Rudder  Yaw  Vertical  Directional  Elevator/  Stabilator  Pitch  Lateral  Longitudinal  Primary Control  Surface  Airplane Movement  Axes of  Rotation  Type of Stability  Lift  Drag  Lift Drag $^{A}$d  v  $^{e }$r  s  e  y a w 