What lifting device did Leonardo da Vinci design with a large helical air screw?

Leonardo da Vinci designed an aerial screw, a helical lifting device often called an early helicopter concept.

The drawing appears in the Codex Atlanticus and is generally dated to about 1489. It shows a large spiral surface mounted around a central mast. Leonardo reasoned that rotating the spiral could push against the air and lift the structure, an idea analogous to the action of a screw moving through water.

The machine was not a working helicopter. Leonardo did not have a sufficiently light engine or a practical rotor system, and the proposed structure would have been difficult to rotate. The aerial screw is therefore important as a conceptual study of vertical flight rather than as the first successful helicopter.

Modern helicopters use powered rotors that generate lift through carefully shaped blades and controlled rotation. Leonardo’s spiral sail was mechanically and aerodynamically different, although its goal—rising vertically without a runway—resembles that of a helicopter.