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Primary Motions | |
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An airplane can basically move in six different ways; these are called the six degrees of freedom of motion. An easy way to demonstrate the motions is to use the right hand rule. This is a technique or method engineers use to help them define (identify) the orientation (position) of an object (like an airplane) and the ways it can move. Using the right hand, (palm down) extend the thumb and point it forward. Point the index finger to the right, but even with the thumb, so that they are on the same level. Then point the middle finger downward (see sketch below). These are the three axes (centers) of motion for the airplane. Think of the airplane with its nose pointing out along the thumb and the wing out along the index finger. The plane can move forward or backwards along the thumb (the x axis). It can move left or right along the index finger (the y axis), and it can go up or down along the axis of the middle finger (the z axis). These three motions are known as translations or movements along the axes. Use the handshape above to demonstrate roll, pitch and yaw. Roll: hold the thumb steady and rotate the hand back and forth. The index finger represents the wings. As it moves up and down it shows how the wings move during a roll. Pitch: tip the thumb up and down. The thumb represents the nose of the plane. The pitch of the airplane is directly connected to the lift calculation. Yaw: Move the hand from side to side at the wrist. The nose and wings are shown in a sideways motion.
These three rotations: roll, pitch, and yaw, combined with the three
translations, define the six degrees of freedom of motion.
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