What was Leonardo da Vinci’s human-powered flying-machine concept called?

Leonardo da Vinci’s human-powered flying-machine concept was an ornithopter.

An ornithopter is an aircraft designed to fly by flapping wings, imitating the motion of birds or bats. Leonardo studied bird anatomy, wing structure and the movement of air while developing several flying-machine sketches. His designs generally placed a pilot inside a frame who would operate wing mechanisms with the arms or legs.

Leonardo recognized that human muscles alone could not easily power a machine large enough to carry a person through sustained flight. He therefore explored mechanical arrangements intended to multiply the pilot’s effort. None of his ornithopter designs became a proven aircraft, but the studies show that he was analyzing flight as a problem of anatomy, leverage, balance and air resistance.

The term is broader than Leonardo’s work: ornithopters have been proposed and built by many later designers, including small experimental aircraft. An ornithopter is not the same as a glider, which remains airborne through aerodynamic lift without flapping wings, or a helicopter, which uses powered rotary blades. Leonardo’s flying sketches are best understood as experimental concepts rather than completed inventions.