Leonardo da Vinci designed an ornithopter, a flying-machine concept with wings intended to flap like a bird's.
The word ornithopter comes from Greek roots meaning “bird” and “wing.” Leonardo studied bird anatomy and flight, then produced several sketches of machines whose wings would move through muscular or mechanical action. Some designs placed a pilot inside a frame and used pedals, levers, and wing structures to imitate the downstroke and upstroke of a bird.
Leonardo's ornithopters were theoretical projects rather than successful aircraft. Human muscles cannot provide enough power for a large flapping machine, and the proposed mechanisms would have been too heavy and inefficient. Leonardo nevertheless recognized important aerodynamic questions, including lift, balance, and the role of air currents.
An ornithopter is different from a glider, which has fixed wings, and from an aerial screw, which uses rotary motion. Modern experimental ornithopters exist, but Leonardo's Renaissance machines were never demonstrated as practical human-carrying aircraft.