Leonardo da Vinci studied an ornithopter as a flying-machine type based on bird-wing motion.
An ornithopter is an aircraft designed to fly by flapping wings, rather than by using fixed wings or a rotating rotor. Leonardo examined birds closely and filled notebooks with observations about their wings, feathers, balance, and movement. His machine designs included large wings intended to be operated by a person.
Leonardo’s ornithopters were never demonstrated as practical aircraft. Human muscles cannot supply enough sustained power for a machine of the proposed size, and the designs lacked a lightweight engine. This is why Leonardo is best described as a pioneer of aeronautical study, not the inventor of a successful airplane.
The term is sometimes confused with “helicopter,” but a helicopter gains lift from powered rotating blades. Leonardo also drew a separate aerial-screw design, which was a different concept from the flapping-wing ornithopter.