Leonardo da Vinci designed an ornithopter, a human-powered flying machine intended to imitate the flapping wings of birds.
The word ornithopter means a machine that flies by moving its wings like a bird. Leonardo studied bird anatomy, wing structure, balance, and air movement in numerous notes and sketches. His proposed machines commonly placed a pilot in a central frame, using pedals, levers, or other mechanisms to move broad wings.
Leonardo understood that flight depended on more than simply copying a bird's appearance. He investigated how wings generate lift and how a pilot might control the machine. However, human muscles could not provide enough sustained power to make his large designs fly, and none of his ornithopters became an operational aircraft.
The term covers many later experimental machines, so it should not be confused with the aerial screw, which used a rotating spiral surface. Leonardo's ornithopter belongs to the flapping-wing tradition. His work remains important because it connected close biological observation with mechanical design, even though the proposed power source was inadequate.