Leonardo da Vinci designed the aerial screw as a helical rotor intended to lift a craft vertically.
Leonardo recorded the concept around 1489 in a manuscript drawing. The design resembles a large screw, with a linen-covered helical surface stretched over a reed framework. He reasoned that rotating the helix rapidly could make it “screw” upward through the air.
The aerial screw is often called a helicopter prototype, but it was not a working helicopter. Leonardo had no lightweight engine capable of turning the rotor, and the drawing does not provide a complete practical power system. Modern helicopters use powered rotors and aerodynamic lift rather than Leonardo’s proposed continuous helical surface.
The design is also distinct from Leonardo’s flapping-wing studies, which are generally called ornithopters. The aerial screw is notable because it imagines vertical flight through rotary motion centuries before powered helicopters became practical.