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 Kid's Page.
for a description of flight control, or
for a discussion of airplane parts.
At the rear of the
most aircraft one finds a horizontal stabilizer
and an elevator. The stabilizer is a fixed wing section
whose job is to provide
stability for the aircraft, to keep it flying straight. The
horizontal stabilizer prevents up-and-down, or
motion of the aircraft nose.
The elevator is the small moving section at the rear of the
stabilizer that is attached to the fixed sections by hinges.
Because the elevator moves, it varies the amount of force
generated by the tail surface and is used to generate and control the
pitching motion of the aircraft.
There is an elevator attached to each side of the
fuselage. The elevators work in pairs; when the right elevator goes
up, the left elevator also goes up.
This slide shows what happens when the pilot deflects the elevator.
The elevator is used to control the position of the nose of the aircraft
and the angle of attack of the wing. Changing the
of the wing to the local flight path changes the amount of lift which the
wing generates. This, in turn, causes the aircraft to
or dive. During take off the elevators are used to bring the nose of
the aircraft up to begin the climb out. During a banked turn, elevator
inputs can increase the lift and cause a tighter turn. That is why
elevator performance is so important for fighter aircraft.
The elevators work by changing the effective shape of the airfoil
of the horizontal stabilizer.
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. With greater downward
deflection of the trailing edge, lift increases. With greater
upward deflection of the trailing edge, lift decreases and can
even become negative as shown on this slide.
The lift force (F) is applied at
center of pressure
of the horizontal stabilzer which is
some distance (L) from the aircraft
center of gravity. This creates a
T = F * L
on the aircraft and the aircraft
about its center of gravity.
The pilot can use this ability to make the airplane
loop. Or, since many aircraft loop naturally, the deflection can be
used to trim or balance the aircraft, thus
preventing a loop. If the pilot reverses the elevator deflection to
down, the aircraft pitches in the opposite direction.
[You can also test the pitch effect yourself using a paper airplane.
Just cut some control tabs in the rear of both wings. Bend both tabs
up to make the tail go down and the nose go up, and the airplane
loops when it is flown. Make small adjustments to trim the airplane
and suppress the loops. The same thing will work on a simple wooden
glider--the tabs can be yellow stick-ums or tape attached to the
On many fighter planes,
in order to meet their high maneuvering requirements, the stabilizer
and elevator are combined into one large moving surface called a
The change in force is then created by changing the
inclination of the entire surface, not by
changing its effective shape as is done with an elevator.
On some aircraft, the pitch stability and control is provided by a
horizontal surface placed forward of the center of gravity
(a tail in the front).
This surface is called a canard. The name is the French word for
duck and it is used because the shape when viewed from above resembles
a duck with bulges near the neck. The
Wright brother's first
used a forward
You can view a short
of "Orville and Wilbur Wright" explaining how the elevator
was used to control the pitch of their aircraft. The movie file can
be saved to your computer and viewed as a Podcast on your podcast player.
Parts of an Airplane:
Aircraft Pitch Motion:
- Beginner's Guide Home Page