Leonardo da Vinci’s bird-inspired aircraft was an ornithopter, a machine designed to fly by flapping wings.
Leonardo studied birds and bats extensively because he believed their wing movements could reveal the principles of human flight. His notebooks contain drawings of wings, joints, control surfaces, and mechanisms intended to transmit a pilot’s motion to large artificial wings.
An ornithopter differs from a glider, which remains airborne with fixed wings, and from a helicopter, which uses rotating blades. Leonardo’s proposed machines generally depended on a human pilot’s muscular effort, making them impractical because a person cannot generate enough power to flap wings of the required size.
Modern ornithopters have been built as small mechanical or radio-controlled aircraft. Leonardo’s studies nevertheless helped establish a systematic approach to aeronautical design: observe nature, analyze forces, and translate biological movement into engineering mechanisms.