Text 1. The Tail Unit

The tail unit is one of the principal structural units of the aircraft and the element of airplane frame. Tail assembly or empennage is located at the rear of the airplane. The tail unit consists of two surfaces. One is vertical and the other is horizontal. They are of symmetrical airfoil section. Each section is divided into two parts, the front part is fixed. The front part is fixed. The rear part is in the form of a flap. The vertical surface is called the fin. It provides directional control of the aircraft in flight. The horizontal surface is known as the " stabilizer".

Both the fin and the stabilizer are very similar to the wings in construction They are usually of all-metal construction. The vertical stabilizer or fin provides directional stability of the airplane in flight. It also serves as the base to which the rudder is attached The rudder is a movable surface hinged to the trailing edge of the fin. It provides directional control of the airplane in flight, being deflected to the right or left. The horizontal stabilizer provides longitudinal stability of the airplane in flight. It serves as a support for the elevators.

Elevators are movable airfoils, hinged to the trailing edge of the tail's horizontal stabilizer. They can deflect downwards and upwards. The elevators control the climb and descent of the airplane that is the motion of the aircraft about the lateral axis. To cause the airplane to climb it is necessary to deflect them upward. When the elevators are lowered the aircraft begins to descend.