Aileron

An aileron (French for 'little wing') is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement around the aircraft's longitudinal axis), which normally results in a change in flight path due to the tilting of the lift vector. Movement around this axis is called 'rolling' or 'banking'.

The aileron was first patented by the British scientist and inventor Matthew Piers Watt Boulton in 1868, based on his 1864 paper On Aërial Locomotion. Even though there was extensive prior art in the 19th century for the aileron and its functional analog, wing warping, in 1906 the United States granted an expansive patent to the Wright Brothers of Dayton, Ohio for the invention of a system of aerodynamic control that manipulated an airplane's control surfaces. Considerable litigation ensued within the United States over the legal issues of lateral roll control, until World War I which compelled the U.S. Government to legislate a legal resolution.

The name 'aileron', from French, meaning 'little wing', also refers to the extremities of a bird's wings used to control their flight. It first appeared in print in the 7th edition of Cassell's French-English Dictionary of 1877, with its lead meaning of "small wing". In the context of powered airplanes it appears in print about 1908. Prior to that, ailerons were often referred to as rudders, their older technical sibling, with no distinction between their orientations and functions, or more descriptively as horizontal rudders (in French, gouvernails horizontaux). Among the earliest printed aeronautical use of 'aileron' was that in the French aviation journal L'Aérophile of 1908.

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