An airplane has three (3) axes about / around which it can move in flight.
In the image above, you are seeing all three of these axes:
Longitudinal axis: from the nose to the tail of the airplane
Lateral axis: from wingtip to wingtip
Vertical axis: from the bottom of the airplane to the top of the airplane
Each of these three axes meet at the center of gravity (CG) of the plane. The CG is the point at which the airplane would balance if you could lift it up by an imaginary string that attached at that exact point. You can think of the CG also as a kind of fulcrum (like on a teeter-totter) that the plane rolls and pitches around.
Anyway, back to the axes of the plane. Here’s what you need to know about them and why they are important.
The Longitudinal axis (the one that runs the length of the plane from nose to tail) is the axis that stays fixed when the airplane “rolls” or “banks” – such as in a turn. In this case, the plane is rotating “about” or “around” the longitudinal axis. This is caused by the airplane’s ailerons, which change the camber of the wing and increase its lift on one side,making the wing climb, and spoil the lift on the other side, making the wing drop.
The Lateral axis (the one that runs from wingtip to wingtip) stays fixed when the plane “pitches” – raising or lowering the nose (such as for a climb or a descent). The plane pitches about the lateral axis. This is done using the airplane’s elevators. The elevators change the shape of the horizontal stabilizer, causing it to decrease lift (tail goes down, nose goes up) or increase lift (tail goes up, nose goes down). Some aircraft have “stabilators,” where the entire horizontal surface moves instead of just the elevator, but the concept (and result) is still the same.
The last one is the Vertical axis, which runs vertically (up and down) through the fuselage. This one stays fixed when the airplane “yaws” – meaning the nose moves left or right. When the plane yaws, it is turning about the vertical axis. This is like turning a car (the car doesn’t roll or pitch, it just turns, or “yaws”). This can be done by moving the rudder, which is the movable control surface on the vertical stabilizer (the upright portion of the tail). Moving the rudder right puts it into the airflow and pushes the tail to the left (and the nose to the right). Generally, the rudder is used in tandem with the ailerons to coordinate an airplane’s turns, because when an airplane banks, there is a change in drag, making the nose want to move away from the turn initially. the rudder is used to “yaw” the nose the right way and keep the whole plane moving in the direction the pilot (you) want it to go.
It is possible to move an airplane about all three axes at one time, and rarely does an airplane move about just one at a time. You, as the pilot in command, will use all the control surfaces to move the plane about all of its axes and make it do what you want it to do.
Do you have any questions about the three axes of an airplane, or do you have any hints or tricks or stories to share that relate to them? Leave a comment and tell us all about it!
Andrew Hartley is a Certificated Flight Instructor in Columbus, Ohio.