What kind of flying machine did Leonardo da Vinci model on a bird’s wings?

Leonardo da Vinci modeled one of his flying machines on bird wings as an ornithopter.

An ornithopter is an aircraft designed to fly by flapping wings, rather than by using fixed wings or a propeller. Leonardo studied birds and bats extensively and made numerous sketches of wing structures, harnesses, and mechanical systems intended to imitate their motion.

His proposed human-powered machines were based on the idea that a person could generate enough force through pedals, levers, or other mechanisms to flap large wings. Modern engineering shows that human muscle power is generally insufficient for a practical bird-sized flapping aircraft of this kind, especially when the machine must also carry its structure and pilot.

Leonardo’s work nevertheless contributed to the history of aviation by emphasizing observation, aerodynamic surfaces, and mechanical control. The term ornithopter applies to the machine type, not to one single finished aircraft. No Leonardo ornithopter flew under his own construction or supervision.