Leonardo da Vinci sketched an ornithopter as a bird-inspired flying machine.
An ornithopter is an aircraft designed to fly by flapping wings, rather than by using fixed wings or a powered rotor. Leonardo studied birds extensively and drew mechanisms intended to convert human muscle power into wing movement. His sketches are among the best-known early attempts to apply anatomical observation to flight engineering.
Leonardo’s proposed machine was not a practical aircraft. A human pilot could not generate enough sustained power to flap wings of the necessary size, and the drawings do not show a completed propulsion system capable of overcoming that limitation. This is why the design is better described as a study or concept than as a successful airplane.
The term is sometimes confused with “helicopter,” because both appear in histories of Leonardo’s flight ideas. His aerial screw was a separate rotor-based concept, while the ornithopter depended on flapping wings. Modern ornithopters exist mainly as small experimental or unmanned aircraft.