Leonardo da Vinci designed ornithopters, flying machines intended to gain lift through the flapping motion of wings.
An ornithopter imitates the action of a bird or bat rather than using a fixed wing or a rotating rotor. Leonardo studied bird anatomy and flight mechanics extensively, then produced several sketches of human-powered flying machines. Some designs place the pilot inside a frame and use pedals, levers, or other mechanisms to move the wings.
Leonardo's ornithopters were concepts, not successful aircraft. Human muscle power is insufficient for the wing area and sustained flapping required by such a machine, and the designs did not include a practical power source. They also differ from his aerial screw, which uses a rotating helical surface instead of flapping wings.
The studies nevertheless helped connect observation of living creatures with mechanical engineering. Leonardo analyzed weight, balance, wing movement, and air resistance, making his flight notebooks important historical records even though his aircraft never achieved powered flight.