Leonardo da Vinci designed an aerial screw as an early helicopter concept.
The drawing, usually dated to about 1489, shows a helical sail wrapped around a central mast. Leonardo proposed that the rotating screw could rise by pushing against the air, much as a screw moves through a solid material. The machine would have needed people to turn a platform or mechanism at its base.
The aerial screw was never built or flown by Leonardo. Its structure was too heavy for the human power available in the fifteenth century, and the design did not include a modern rotor, engine or practical means of controlling flight. For that reason, historians generally describe it as an important idea rather than a working helicopter.
Later helicopter development depended on lightweight engines, aerodynamic research and powered rotors. Leonardo’s sketch is still significant because it identified vertical lift as a separate engineering problem from fixed-wing flight.