What is a Rudder? If you've ever looked at the tail end of a plane, you've probably noticed the large tail assembly, which is used to help maintain the position of the plane. One important part of the tail assembly is the rudder, a long, vertical, teardrop-shaped flap which controls the yaw of the plane. Yaw Yaw is the rotation of the plane around a vertical axis; otherwise explained, the rotation to the left or right. The rudder is operated by a set of foot pedals, which cause the rudder to rotate left or right. If a pilot wanted to turn to the right, he would press down on the right rudder pedal, turning the rudder right. A pilot has to be careful while turning, because used alone, the rudder is not useful; a rudder change alone would send the plane into a skid, where it moves forwards, while turned at an angle relative to its motion. Therefore, the set of actions described in the introduction to the control section must be used. Aerodynamics As the rudder position changes, the airflow around the tail assembly comes off at an angle, changing the forces on the tail (think action-reaction). The air has a small tendency to stick to the surface of the wing (viscosity), which causes it to follow the path of the wing as it moves. The air hitting the front of the tail is moving in a straight line, but when the rudder is at an angle, the air curves around the tail. From Newton's Third Law, the force of the rudder disturbing the air's path is reciprocated, with the air pushing back on the rudder, causing the plane to change its course.