Leonardo da Vinci’s aerial screw was an early helicopter concept.
Leonardo sketched the design around 1489 in his notebooks. It shows a large helical structure made from reeds and linen, with a frame beneath it. Leonardo reasoned that turning the screw could make it rise by pushing against the air, much as a screw advances through wood.
The aerial screw was never built or tested by Leonardo, and it could not have flown successfully in its original form because the proposed materials and human power were insufficient. It is therefore best described as a conceptual flying machine, not the first working helicopter.
The idea is frequently linked with modern rotorcraft because its rotating, spiral surface resembles a rotor. However, the modern helicopter uses powered rotor blades that generate lift in a very different aerodynamic arrangement. Leonardo also designed other flying-machine concepts, including an ornithopter and a parachute.