Leonardo da Vinci’s four-winged flying-machine design is an ornithopter.
An ornithopter is an aircraft intended to fly by flapping wings, imitating the motion of birds or bats. Leonardo studied birds extensively and designed several flying machines based on this principle. His sketches show wings, frames, pedals, and mechanical linkages intended to transfer a pilot’s muscular effort to the wings.
Leonardo’s ornithopters were never built as successful human-powered aircraft. A human cannot generate enough sustained power with leg or arm muscles to flap wings of the required size and lift a full-sized body. Modern aircraft instead rely on fixed wings and engines, while experimental ornithopters usually use motors.
Leonardo’s work remains important because it connected careful observation of animal flight with mechanical design. The word “ornithopter” comes from Greek roots meaning “bird wing,” and the term applies to both historical proposals and later experimental aircraft.