. Pitch, Roll, and Yaw

itch, roll, and yaw are the three ways in which aircraft and space­craft can change their direction of flight. Pitch, roll, and yaw are rotations. When something rotates, it turns around an imaginary line called an axis.

Defining Pitch, Roll, and Yaw

Imagine an airplane with a stick pushed through it from nose to tail, so the plane can spin on the stick. This type of rota­tion is called roll, and the stick is the roll axis. A stick pushed through a plane from wingtip to wingtip is the pitch axis. A stick pushed through a plane from top to bottom is the yaw axis. The position, or angle, of an aircraft-the amount of pitch, roll, and yaw it has-is called its attitude. In a standard airplane, the pilot generally can change the plane’s atti­tude by operating controls that move the elevators, ailerons, and rudder.

Changing an airplane’s pitch makes its nose tip up or down. The pilot changes the pitch by using the control stick to tilt the elevators, which are at the back of the tail. Pulling the stick back tilts the elevators up. Air flowing over them pushes the plane’s tail down and raises its nose. Pushing the stick for­ward has the opposite effect.

Rolling, or banking an aircraft to one side, enables it to turn. When it rolls, the lift produced by the wings tilts to one side instead of acting straight upward. The sideways part of the lift pulls the plane into a turn. A pilot makes a plane roll by pushing the control stick to one side or (on a larger airplane) turning the yoke on top of the control column. This control moves the ailerons, which are at the back of the wings. When the

О The B-2 Spirit Bomber (along with other flying wing aircraft) has elevons (circled) at the back of its wings that function as combined ailerons and elevators.

aileron on one wing tilts down, the wing rises. The aileron on the other wing tilts up, and the wing sinks.

Yaw is the name for the motion when a plane’s nose turns to the left or right.

Yaw is controlled by a rud­der, which is mounted on an airplane’s tailfin. The rudder is operated by a pair of foot pedals. Turning the rudder to one side pushes the plane’s tail to the opposite side and swings the nose around. When a plane rolls into a turn, the pilot also adjusts its pitch and yaw to keep the plane’s nose pointing in the right direction.