At the rear of the
most aircraft one finds a horizontal stabilizer and an
elevator to provide stability and control
of the up-and-down, or
motion of the aircraft nose.
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
Because the stabilator 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 usually a stabilator on each side of the
fuselage and they work in pairs; when the right stabilator goes
up, the left stabilator also goes up.
This slide shows what happens when the pilot deflects the
The stabilator 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 stabilators are used to bring the nose of
the aircraft up to begin the climb out. During a banked turn, stabilator
inputs can increase the lift and cause a tighter turn. That is why
stabilator performance is so important for fighter aircraft.
The stabilators work by changing the angle of attack
of the horizontal stabilizer.
As described on the inclination effects slide,
changing the angle of attack of an airfoil changes
the amount of lift generated by the foil. With greater downward
deflection of the leading edge, lift increases in the downward direction.
upward deflection, lift increases in the upward direction.
The lift force (F) is applied at the
center of pressure
of the the stabilator 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 dive.
Let's investigate how a stabilator works by using a Java
Due to IT
security concerns, many users are currently experiencing problems running NASA Glenn
educational applets. The applets are slowly being updated, but it is a lengthy process.
If you are familiar with Java Runtime Environments (JRE), you may want to try downloading
the applet and running it on an Integrated Development Environment (IDE) such as Netbeans or Eclipse.
The following are tutorials for running Java applets on either IDE:
You can change the stabilator setting by using the slider at the right.
You can download your own copy of this simulator for use off line. The program
is provided as Stablat.zip. You must save this file on your hard drive
and "Extract" the necessary files from Stablat.zip. Click on "Stabview.html"
to launch your browser and load the program.
On most aircraft, the horizontal
stabilizer and elevator are separate pieces with the elevator being connected
to the stabilizer by a hinge. These aircraft rely on changing the
shape of the tail airfoil to produce a change
in the down force for control.
On some aircraft, the pitch stability and control is provided by a
canard which is a horizontal surface
placed forward of the center of gravity (a tail in the front). The
Wright brother's 1903
used a forward
for pitch control.