A tailplane, also known as a 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. Not all fixed-wing aircraft have tailplanes. Canards, tailless and flying wing aircraft have no separate tailplane, while in V-tail aircraft the vertical stabiliser, rudder, and the tail-plane and elevator are combined to form two diagonal surfaces in a V layout. The function of the tailplane is to provide stability and control. In particular, the tailplane helps adjust for changes in position of the centre of pressure or centre of gravity caused by changes in speed and attitude, fuel consumption, or dropping cargo or payload. Tailplane types The tailplane comprises the tail-mounted fixed horizontal stabiliser and movable elevator. Besides its planform, it is characterised by: Number of tailplanes - from 0 (tailless or canard) to 3 (Roe triplane) Location of tailplane - mounted high, mid or low on the fuselage, fin or tail booms. Fixed stabiliser and movable elevator surfaces; movable stabiliser and movable elevator (e.g. Boeing 737); or a single combined stabilator (e.g. General Dynamics F-111 Aardvark) Some locations have been given special names: Cruciform: mid-mounted on the fin (Hawker Sea Hawk, Sud Aviation Caravelle) T-tail: high-mounted on the fin (Gloster Javelin, Boeing 727) Stability A wing with a conventional aerofoil profile makes a negative contribution to longitudinal stability. 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 may counteract the natural instability of the wing and make the aircraft longitudinally stable (in much the same way a weather vane always points into the wind). The longitudinal stability of an aircraft may change when it is flown "hands-off"; i.e. when the flight controls are subject to aerodynamic forces but not pilot input forces. Damping In addition to giving a restoring force (which on its own would cause oscillatory motion) a tailplane gives damping. This is caused by the relative wind seen by the tail as the aircraft rotates around the centre of gravity. For example, when the aircraft is oscillating, but is momentarily aligned with the overall vehicle's motion, the tailplane still sees a relative wind that is opposing the