Lift & Drag forces 1799 The first analysis of aerodynamic forces was made by Sir George Cayley. His engraving on a silver disk shows the separate lift and drag forces acting on a fixed wing surface. Cayley's second important contribution was his recognition that a curved aerofoil shape produces more lift than a flat plate. Double surfaced aerofoils 1884 Horatio F. Phillips patented a double surfaced aerofoil whose upper surface was expressely designed, in such a way as to cause a partial vacuum to be created over a portion of the upper surface of the blade, thus aiding the air below to support the weight. Thick aerofoils 1917 Gottingen 398 Theoretical developments by Lanchester, Kutta, Joukowski and Prandtl allowed the aerofoil to be described mathematically in the Circulation Theory of Lift (to be completed ...) http://www.desktopaero.com/appliedaero/appliedaero.html