Perfect horizon stabilizer5/10/2023 On the Gloster Meteor T.7 a stall could be triggered by turbulence when the airbrakes were deployed. On some types, the demand in this flight mode has been so extreme that it has caused the tailplane to stall. This is particularly so when flying slowly and at a high angle of attack (AoA). Some aircraft and flight modes can require the tailplane to generate substantial downforce. An example is provided by the Bachem Ba 349 Natter VTOL rocket-powered interceptor, which had a lifting tail and was both stable and controllable in flight. But with care a lifting tailplane can be made stable. Louis, the Gee Bee Model R Racer - all aircraft with a reputation for being difficult to fly, and the easier-to-fly Fleet Finch two-seat Canadian trainer biplane, itself possessing a flat-bottom airfoiled tailplane unit not unlike the earlier Bristol Scout. Later examples of aircraft from World War I and onwards into the interwar years that had positive lift tailplanes include, chronologically, the Sopwith Camel, Charles Lindbergh's Spirit of St. The requirements for stability were not understood until shortly before World War I - the era within which the British Bristol Scout light biplane was designed for civilian use, with an airfoiled lifting tail throughout its production run into the early World War I years and British military service from 1914-1916 - when it was realised that moving the centre of gravity further forwards allowed the use of a non-lifting tailplane in which the lift is nominally neither positive nor negative but zero, which leads to more stable behaviour. However this arrangement can be unstable and these designs often had severe handling issues. On some pioneer designs, such as the Bleriot XI, the centre of gravity was between the neutral point and the tailplane, which also provided positive lift. It is sometimes assumed that on a stable aircraft this will always be a net down force, but this is untrue. 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 oscillation.ĭepending on the aircraft design and flight regime, its tailplane may create positive lift or negative lift (downforce). This is caused by the relative wind seen by the tail as the aircraft rotates around the centre of gravity. In addition to giving a restoring force (which on its own would cause oscillatory motion) a tailplane gives damping. when the flight controls are subject to aerodynamic forces but not pilot input forces. The longitudinal stability of an aircraft may change when it is flown "hands-off" i.e. 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). 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. Tailplane (in shadow) of an easyJet Airbus A319Ī wing with a conventional aerofoil profile makes a negative contribution to longitudinal stability.
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