Empennage
From Wikipedia, the free encyclopedia
Empennage is an aviation term used to describe the tail portion of an aircraft. "Empennage" and "tail" and "tail assembly" may be interchangeably used. Its main purpose is to give stability to the aircraft and control the flight dynamics: pitch, roll and yaw.
Structurally, the empennage consists of the entire tail-assembly including the fin, tailplane and the part of the fuselage to which these are attached. On an airliner this would be everything behind the rear pressure bulkhead.
The front, fixed section of the tailplane is called the horizontal stabilizer and is used to prevent the airplane from pitching up or down. The rear section is called the elevator and is usually hinged to the horizontal stabilizer. The elevator is a movable airfoil that controls the up-and-down motion of the aircraft's nose.
On some airplanes, the horizontal stabilizer and elevator are combined into one movable unit called the stabilator.
The vertical tail structure, or fin, is also has a fixed front section called the vertical stabilizer, used to prevent the aircraft from yawing back and forth. The principle behind its operation is much like the principle of a deep keel on a sailboat. In light, single-engine aircraft, it also serves to offset the tendency of the aircraft to roll in the opposite direction in which the propeller is rotating. The rear section of the vertical fin is the rudder, a movable airfoil that is used to turn the aircraft.
Most aircraft now include small, moveable surfaces in both the rudder and elevator called "trim tabs". The purpose of these tabs is to adjust air flow over the relevant surfaces to correct up/down and left/right movement of the aircraft without the pilot having to exert constant pressure on his control yoke.
