A tailplane, also known as horizontal stabilizer (or horizontal stabiliser), is a small lifting surface located on the tail (empennage) behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed wing aircraft such as helicopters and gyroplanes. However, not all fixed-wing aircraft have tailplanes, such as those configured with canards (where the "tail-plane" is located in front), flying-wing aircraft, where there is no tail, and v-tail aircraft where the fin/rudder and tail-plane are combined to form two diagonal surfaces in a V layout. The tailplane serves three purposes: equilibrium, stability and control.
The tailplane comprises the tail-mounted fixed horizontal stabiliser and movable elevator. Besides its planform, it is characterised by:
Some locations have been given special names:
An aeroplane must be in balance longitudinally in order to fly. This means that the net effect of all the forces acting on the aeroplane produces no overall pitching moment about the centre of gravity. Without a tailplane there would be only one combination of speed and center of gravity position for which this requirement was met. The tailplane provides a balancing force to maintain equilibrium for different speeds and center of gravity positions. Because the tailplane is located some distance from the center of gravity, even the small amount of lift it produces can generate a large pitching moment at the centre of gravity.
An aeroplane with a wing only is normally unstable in pitch (longitudinal instability). This means that any disturbance (such as a gust) which raises the nose produces a nose-up pitching moment which tends to raise the nose further. With the same disturbance, the presence of a tailplane produces a restoring nose-down pitching moment which counteracts the natural instability of the wing and makes the aircraft longitudinally stable. A stable aeroplane can be flown "hands-off" and will not depart significantly from its airspeed and pitch attitude.
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