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There are three axes around which the airplane moves. These axes all pass through the airplane's center of gravity, which is that point which is the center of the airplane's total weight.
The longitudinal axis extends lengthwise through the fuselage from the nose to the tail. Movement of the airplane around the longitudinal axis is known as roll and is controlled by movement of the ailerons. To move the ailerons, the pilot turns the control wheel either clockwise or counter clockwise (or moves the control stick either right or left). This action lowers the aileron on one wing and raises the aileron on the other wing. The downgoing aileron increases the camber of its wing, producing more lift and the wing rises. The upgoing aileron spoils the airflow on its wing, decreases the lift and the wing descends. The airplane rolls into a turn.
The lateral axis extends crosswise from wingtip to wing tip. Movement of the airplane around the lateral axis is known as pitch and is controlled by movement of the elevators. To effect a nose down attitude, the pilot pushes forward on the control wheel or stick. The elevator deflects downward, increasing the camber of the horizontal tail surface and thereby increasing the lift on the tail. To effect a nose up attitude of the airplane, the pilot pulls the wheel toward him. The elevators are deflected upwards decreasing the lift on the tail, with a resultant downward movement of the tail.
The vertical or normal axis passes vertically through the center of gravity. Movement of the airplane around the vertical axis is yaw and is controlled by movement of the rudder. Pressure applied to the left rudder pedal, for example deflects the rudder to the left into the airflow. The pressure of the airflow against the rudder pushes the tail to the right. The nose of the airplane yaws to the left.
There is a distinct relationship between movement around the vertical and longitudinal axes of an airplane (i.e. yaw and roll). When rudder is applied to effect a yaw, for example, to the right, the left wing (on the outside of the turn) moves faster than the inside wing, meets the relative airflow at a greater angle of attack and at greater speed and produces more lift.. The use of rudder, therefore, along with aileron can help to raise the wing and produce a better coordinated turn.
In a roll, the airplane has a tendency to yaw away from the intended direction of the turn. This tendency is the result of aileron drag and is called adverse yaw. The upgoing wing, as well as gaining more lift from the increased camber of the downgoing aileron, also experiences more induced drag. The airplane, as a result, skids outward on the turn. Use of rudder in the turn corrects this tendency.
Rudder rotates the airplane around vertical axis.
Ailerons rotate the airplane around longitudinal axis.
Elevators rotate airplane around lateral axis.
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Updated: March 12, 2004