What is Aircraft Yaw Motion?
Yaw is the motion of the aircraft through its yaw (also vertical) axis. The yaw axis is perpendicular to the wings and lies in the plane of the aircraft centerline (when you are standing under a parked airplane, your position is vertical). A yaw motion is a side to side movement of the nose of the aircraft.
The yawing motion is being caused by the deflection of the rudder of the aircraft. The rudder is a hinged section at the rear of the vertical stabilizer.[1]
Changing the angle of deflection at the rear of an airfoil changes the amount of lift generated by the foil. For the vertical stabilizer and rudder, the orientation of the foil causes a side force to be generated. With greater deflection of the rudder to the left, the side force increases to the left. The lift generated by the rudder acts through the center of pressure of the rudder and vertical stabilizer and is located some distance from the center of gravity of the aircraft. The change in the side force caused by deflecting the rudder generates a torque about the center of gravity which causes the airplane to rotate. The pilot uses this ability to keep the nose of the aircraft pointed in the direction of travel.[1]
Foot pedals are connected by means of wires or hydraulics to the rudder of the tail section. Foot pressure on the left rudder pedal will deflect the rudder to the left, and will rotate the airplane to the left. Foot pressure on the right rudder pedal will deflect the rudder to the right and will rotate the airplane to the right.
On all aircraft, the vertical stabilizer and rudder create a symmetrical airfoil. This produces no side force when the rudder is aligned with the stabilizer and allows the combination to produce either positive or negative side force, depending on the deflection of the rudder. Some fighter planes have two vertical stabilizers and rudders because of the need to control the plane with multiple, very powerful engines.[1]
*gif
