The airplane is controllable around its lateral, longitudinal, and vertical axes by deflection of flight control surfaces. These control devices are hinged or movable surfaces with which the pilot adjusts the airplane's attitude during takeoff, flight maneuvering, and landing. They are operated by the pilot through connecting linkage by means of rudder pedals and a control stick or wheel (Fig. 2-5).
The rudder is attached to the fixed vertical portion of the empennage - the vertical fin or vertical stabilizer. It is used by the pilot to control the direction (left or right) of yaw about the airplane's vertical axis. It is not used to make the airplane turn, as is often erroneously believed. This fact will be explained in the chapter of The Effect and Use of Controls.
The elevators are attached to the horizontal portion of the empennage - the horizontal stabilizer. The exception to this is found in those installations where the entire horizontal surface is a one piece structure which can be deflected up or down to provide longitudinal control and trimming. The elevators provide the pilot with control of the pitch attitude about the airplane's lateral axis.
The movable portions of each wing are the ailerons. The term "aileron" is the French word for "little wing." They are located on the trailing (rear) edge of each wing near the outer tips. When deflected up or down they in effect change the wing's camber (curvature) and its angle of attack, and therefore change the wing's lift/drag characteristics. Their primary use is to bank (roll) the airplane around its longitudinal axis. The banking of the wings results in the airplane turning in the direction of the bank.
The ailerons are interconnected in the control system to operate simultaneously in opposite directions of each other. As the aileron on one wing is deflected downward, the aileron on the opposite wing is deflected upward. this action causes more lift to be produced by the wing on one side than the wing on the other, resulting in a controlled roll or bank.
The effect and use of the flight controls is explained in more detail in Chapter 4.