Leonardo da Vinci studied an ornithopter, a wing-flapping aircraft inspired by birds and bats.
The word ornithopter means “bird-wing,” and Leonardo’s notebooks contain many observations of wings, feathers, air currents, and animal flight. His proposed machines used a human operator’s arms and legs to drive large wings through mechanical linkages. Some designs were bird-like, while others drew on the membrane wings of bats.
Leonardo correctly recognized that flight depended on lift, balance, and the movement of air. However, he overestimated the strength a human could produce and did not have a lightweight engine. For that reason, none of his human-powered ornithopter designs could realistically carry a person.
An ornithopter is not the same as the aerial screw. The ornithopter rises through flapping wings, whereas the aerial screw attempts vertical lift through a rotating helical surface. Leonardo investigated both approaches as part of a broader study of flight.