Aircraft principal axes

When an airplane flies, it can move in different directions: up and down, side to side, and front to back. To help describe these movements, we use something called "principal axes."

Think of an airplane like a toy plane you might play with. If you hold the toy plane by its nose and give it a little shake, it will wiggle side to side. The imaginary line that runs from the nose to the tail of the plane is called the "longitudinal axis." This axis is used to describe side-to-side movements of the plane, like when it banks or rolls.

Next, think about what happens when you hold the toy plane by its wings and give it a little shake. It will wiggle up and down, right? The imaginary line that runs from wingtip to wingtip is called the "lateral axis." This axis is used to describe up-and-down movements of the plane, like when it climbs or descends.

Finally, think about what happens when you hold the toy plane by its bottom and give it a little shake. It will wiggle back and forth, right? The imaginary line that runs from the top of the plane to the bottom is called the "vertical axis." This axis is used to describe front-to-back movements of the plane, like when it pitches up or down.

So, to sum up: airplanes have three imaginary lines running through them that help us describe their movements. The longitudinal axis describes side-to-side movement, the lateral axis describes up-and-down movement, and the vertical axis describes front-to-back movement. These are the "principal axes" of an airplane.