Leonardo Da Vinci developed a number of designs that were well before their time. His vision of vertical flight with his spiral helicopter, paddle wheel-powered vessels, and the early armored car may have been laughable in his day, but were the stepping stones for today's MV-22 Osprey, turbine-powered Ticonderoga-class cruisers, and M1 Abrams tank (and their analogs from other nations of course).
With Da Vinci's flying machine, he developed a mechanical model to mimick the movements and structure of a bird. Like the bird, his machine uses movement (flapping) of the wings for propulsion. Of course man achieved powered flight though no designs to date have used flapping for propulsion (though you might think otherwise watching the wings in flight during turbulance!).