Leonardo da Vinci studied an ornithopter, a human-powered aircraft designed to fly by flapping wings like a bird.
Leonardo made numerous observations of birds and used them to investigate lift, balance, wing shape, and the movement of air. His ornithopter designs generally placed a person inside or beneath a frame with large articulated wings. The pilot would operate the wings through pedals, levers, or other mechanical linkages.
No Leonardo ornithopter is known to have flown. Human muscles cannot provide the sustained power required to flap wings large enough to lift a person, and the proposed structures would also have faced serious problems of weight, control, and stability. Leonardo’s studies nevertheless helped connect biological observation with mechanical design.
An ornithopter differs from a glider, which relies on fixed wings, and from an aerial screw, which uses a rotating helical surface. The term remains in use for experimental aircraft and small models whose wings flap rather than rotate like propellers.