TM 1-410. Technical Manual, Airplane Structures 1941: Section 5 - Stabilizers

SECTION V: STABILIZERS

14. General.-Stabilizing units of an airplane consist of vertical and horizontal airfoils located at the rear portion of the fuselage as a part of the empennage or tail assembly. The vertical surface is generally called the "fin" and the horizontal surface is generally referred to as the "stabilizer."

15. Structure.-a. Construction features of stabilizers are in many respects identical with that of wings. They are usually of allmetal construction of the cantilever type having two main members or spars, and ribs to which the metal skin is attached. Fabric-covered structures may be braced internally with tie rods against drag. Fairing is used to round out the angle formed between stabilizers and fuselage.

b. The vertical stabilizer or fin maintains directional stability of the airplane in flight, that is, about its turning or vertical axis. In.the case of single-engine airplanes the fin is almost invariably offset. A fin is offset when its leading edge is located away from the center line and toward one side of the fuselage. This is done to obtain more accurate directional stability by balancing out the forces acting on the airplane as a result of engine torque and unsymmetrical airflow of slipstream from the propeller. The vertical fin also serves as the base or anchorage to which the rudder is attached.

a. The horizontal stabilizer provides longitudinal stability of the airplane in flight, that is, about its lateral axis. The stabilizer is generally constructed in a. continuous section mounted on or through the fuselage although it is sometimes built in left- and right-hand sections. The stabilizer is similar to the vertical fin in internal construction and serves as a support for the elevators.

16. Maintenance.-Maintenance of stabilizers corresponds to that of fuselages and wings (see par. 13).