Animated Elevator - Pitch

Glenn Research Center

 

This slide shows what happens when the pilot deflects the elevator, a hinged section at the rear of the horizontal stabilizer. There is usually an elevator on each side of the stabilizer. The elevators work in pairs; when the right elevator goes up, the left elevator goes up also.

As described on the shape effects slide, changing the angle of deflection at the rear of an airfoil will change the amount of lift generated by the foil. With greater downward deflection, lift increases in the upward direction. With greater upward deflection, lift increases in the downward direction (as shown in this slide). The change in lift created by deflecting the elevator will cause the airplane to rotate about its center of gravity as shown in the slide. The pilot can use this ability to make the airplane loop or, since many aircraft will 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 will pitch in the opposite direction.

[You can test this 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 will loop 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 horizontal stabilizer.]

On many aircraft, the horizontal stabilizer and elevator create a symmetric airfoil like the one shown on the left of the shape effects slide. This produces no lift when the elevator is aligned with the stabilizer and allows the combination to produce either positive or negative lift, depending on the deflection of the elevator. 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 stabilator. The change in force is created by changing the inclination of the entire surface, not by changing its effective shape.

Back to top

Go to...

Beginner's Guide Home Page

byTom Benson
Please send suggestions/corrections to: benson@grc.nasa.gov