Leonardo da Vinci’s bat-like human-powered flying-machine design is an ornithopter.
An ornithopter is an aircraft intended to fly by flapping wings, rather than by using fixed wings and a propeller. Leonardo studied birds and bats and filled several notebooks with sketches of wings, frames, pedals, and mechanical linkages intended to transfer human movement to the wings.
His designs were inventive but probably could not have lifted a person. Human muscles do not provide enough sustained power for a full-size flapping aircraft, and the proposed structures would have been heavy. Leonardo also lacked modern aerodynamic theory and lightweight materials.
The term does not mean that Leonardo built a successful airplane. It describes the type of machine he investigated. His work remains historically important because it treated flight as an engineering problem involving lift, weight, thrust, and control.