It is generally accepted that the airplane was invented by Sir George Cayley in 1799 at Brompton, near Scarborough in Yorkshire in the United Kingdom. In 1909 Wilbur Wright himself paid Cayley the following tribute:
"About 100 years ago, an Englishman … carried the science of flight to a point which it had never reached before and which it scarcely reached again during the last century."
Restricted to gliders for lack of a light-weight engine, Cayley employed his own whirling arm experiments, which explored the improved lifting effect of increasing wing incidence. Because of his choice of low wing aspect ratio on structural grounds, such gliders achieved lift-to-drag ratios as low as three and perhaps as high as seven. Initially, Cayley saw his gliders' cruciform tail units as supplying merely steering and re-trimming (for different flight speeds), but in his later designs-notably the governable parachute of 1852 with its duplicated tail-there began to emerge an appreciation of the stabilizing function of the tail. Cayley introduced many innovations-wing dihedral and the tension wheel undercarriage for example. As early as 1809, he brought forth the suggestion that the shape of the rear of a body is as important as the front in determining resistance, so that a streamlined tail is beneficial. Two men who benefited from Cayley's teaching were William Henson and John Stringfellow, whose designs and steam-powered models of the 1840s extended Cayley's concept by the inclusion of propeller propulsion and externally braced high aspect ratio wings.
The next major advance in the understanding of resistance came in 1845 from George Gabriel Stokes, whose re-working of the Newtonian viscosity concept supplemented the earlier work of Navier and others in France by introducing the idea that internal stresses within a flow are proportional to the fluid's rate of strain. In 1851 Stokes used the resulting Navier-Stokes equations, coupled to the no-slip condition imposed at the surface of a slow moving sphere, to produce the first finite drag prediction to overcome the earlier inviscid flow zero drag paradox of Euler and d'Alembert. Stokes must also be credited with first stating publicly the theorem, obtained from William Thomson (later, Lord Kelvin) that gives the vital connection between vorticity and circulation, and with providing in 1843 the beginnings of the method of singularities later exploited in 1864 and 1871 by William John Macquorn Rankine in the calculation of the inviscid flow about bodies.
In 1866 the Aeronautical Society (now the Royal Aeronautical Society) was founded in London and in 1871 the first wind tunnel was built for the society's use by Francis Herbert Wenham, who had earlier lectured to the society on the advantages of high aspect ratio wings with multiplane layout and propeller propulsion. This tunnel was used solely to explore the lift and drag characteristics of flat surfaces.
However, in 1884 a second wind tunnel, using steam ejection, was used by Horatio Phillips so as to demonstrate the improved lifting qualities of mildly cambered surfaces. The understanding of lift itself took a further step forward with the analysis of Lord Rayleigh. He combined the inviscid flow field about a circular cylinder with that of a vortex centered at the cylinder, thereby producing a side, or lifting, force. This effect had been noted as early as 1672 by Isaac Newton in discussing the swerving flight of spinning tennis balls, had been demonstrated by Robins in 1747 by the imposition of a spinning motion on an oscillating pendulum bob, and had become more widely recognized through the work of Magnus in Berlin in 1852 in which a spinning cylinder was exposed to an air jet.
Lord Rayleigh also introduced the crucial correction to the common rule in a series of analyses between 1892 and 1910, which established an additional dependence on the Reynolds and Mach numbers. The importance of the Reynolds number itself had already begun to emerge from observations published in 1883 dealing with transition in pipe flows carried out by Osborne Reynolds at the University of Manchester. Many of these ideas began to come together in the work of Frederick William Lanchester between 1892 and 1907. In the early 1900s Lanchester not only recognized the crucial role of viscosity in the explanation of drag but independently of Prandtl discovered the presence of the boundary layer. From his crude model of this "inert layer," as he called it, he was nonetheless able to predict correctly the dependence of laminar flow skin friction on Reynolds number. Lanchester is more widely recognized as the first to grasp the role of the trailing vortices behind lifting wings and as the initiator of the circulation theory of lift although, prior to about 1900, he had believed that the upflow/downflow exhibited by a cambered wing was caused by a wing-generated wave upon which the wing rode. His definitive work emerged in 1907, predicting lift, induced, and form drags with reasonable accuracy, from which he was able to deduce that airplanes would experience both minimum drag and minimum power conditions.
All of these scientific advances proved crucial to the future, post-Wright, development of the airplane and some were beneficial to the British pioneers of the pre-Wright era. For example, the efficacy of mildly cambered surfaces also became evident to the expatriate American inventor Sir Hiram Maxim after his own extensive whirling arm and wind tunnel tests. Armed with further test results from a wide variety of propeller configurations, he constructed a man-carrying machine that would lift itself from the ground and succeeded at Baldwyns Park, Kent, in 1894. However, this massive machine, having a wing span close to that of a Vulcan bomber and powered by two ingenious 130 kW steam engines driving enormous pusher propellers of 5.4 meters in diameter, suffered failure of its height-restraining system on its third run and became significantly damaged. Repairs enabled the continuation of tests until 1895, after which Maxim abandoned the project. He had made virtually no provision for control in the air. The hang-glider of Maxim's one-time assistant, Percy Sinclair Pilcher, benefited considerably from the advice and gliding experience afforded by the German hang-gliding pioneer, Otto Lilienthal, near Berlin in 1895 and 1896. Pilcher progressed with varying success through four gliders of his own design and the fourth, the Hawk of 1896, like its predecessors, incorporated the Lilienthal practice of radiating rods for the wing structure (for ease of ground transit) and the dubious choice of an up-hinging tail unit. Although Pilcher enjoyed some success with this glider, the structural failure of its tail assembly in 1899 caused a crash that killed him. Prior to this, he had been working on a powered development of the Hawk design, using a petrol engine driving a pusher propeller, but there is no indication he intended to attempt aerodynamic control.
Official interest in powered flight in Britain came about through the activities of an American, Samuel Franklin Cody, who had developed an ingenious system of man-lifting kites as an artillery observation and reconnaissance system. Appointed chief kiting instructor to the British Army and based at the Balloon School at Farnborough, Cody had successfully built and tested by 1905 a form of biplane kite-glider that appears to have incorporated aerodynamic control. He went on to develop the powered airplane in which, it is generally conceded, he achieved the first sustained airplane flight in Britain in October 1908. The biplane was powered by a 37kW Antoinette engine and was designed around the Wright-type layout of forward elevator and rear rudder, but it used a single surface mounted centrally over the upper wing for roll control and a tricycle undercarriage with outrigger wheels at the wingtips. In the following year Alliott Verdon Roe was successful at Lea Marshes, near Hackney, with the second of his tri-plane machines powered by a 7kW JAP engine. Meanwhile, John William Dunne had placed his faith in achieving aerodynamic stability with a tailless airplane using swept-back biplane wings. A glider of this configuration was tested on behalf of the Army at Blair Atholl in 1907 and Dunne achieved some success later with a powered machine. Far greater success was achieved through Farnborough's recruitment of Geoffrey de Havilland, who had successfully flown a powered machine of his own design in 1910.
Provided to the AIAA for the sole purpose of its Evolution of Flight Campaign.