This page is intended for college, high school, or middle school students.
For younger students, a simpler explanation of the information on this page is
available on the
Aircraft Yaw Motion
In flight, any aircraft will rotate about its
center of gravity,
a point which is the average location of the mass of the aircraft.
We can define a three dimensional coordinate system through the
center of gravity with each axis of this coordinate system perpendicular
to the other two axes.
We can then define the
of the aircraft by the amount of
rotation of the parts of the aircraft along these principal axes.
The yaw axis is perpendicular to the wings
and lies in the plane of the aircraft centerline. A
is a side to side movement of the nose of the aircraft as shown in the
The yawing motion is being caused by the deflection of the
rudder of this aircraft. The rudder is
a hinged section at the rear of the vertical
As described on the shape effects slide,
changing the angle of deflection at the rear of an airfoil changes
the amount of lift generated by the foil. For the vertical stabilizer and
rudder, the orientation of the airfoil causes a side force to be generated.
deflection of the rudder to the left, the side force
increases to the right. With greater
deflection to the right, the side force increases to the left.
The lift generated by the rudder
acts through the
center of pressure
of the rudder and vertical stabilizer and is located at
some distance from the center of gravity of the aircraft.
The change in side force created by deflecting the rudder
about the center of gravity which
causes the airplane to rotate.
The pilot uses this ability to keep the nose of the
aircraft pointed in the direction of travel.
On all aircraft, the vertical
stabilizer and rudder create a
This produces no side force when the rudder is aligned with the stabilizer and
allows the combination to produce either positive or negative side force,
depending on the deflection of the rudder.
Some fighter planes have two vertical
stabilizers and rudders because of the need to control the plane with
multiple, very powerful engines
You can view a short
of "Orville and Wilbur Wright" explaining how the rudder
was used to control the yaw of their aircraft. The movie file can
be saved to your computer and viewed as a Podcast on your podcast player.
Here is a still slide version of this animation:
Aircraft Yaw Motion:
- Beginner's Guide Home Page