Leonardo da Vinci’s aerial screw was a helical-rotor machine intended to rise into the air.
Leonardo drew the design around 1489 in a notebook now associated with his studies of flight. The device has a large spiral surface made from reeds, linen, and wire. He proposed that turning the screw would force air downward and lift the structure upward, an idea that resembles the principle behind a helicopter rotor.
The aerial screw was never built and tested by Leonardo, and its proposed human-powered mechanism would not have produced enough lift. It is therefore not a helicopter in the modern engineering sense. The design is better described as a conceptual precursor.
The word “aerial” refers to flight, while “screw” describes the spiral shape. Leonardo also studied flapping-wing machines and parachutes, but those devices used different aerodynamic ideas. Modern helicopters became practical only after engines and rotor control systems made sustained powered flight possible.