Leonardo da Vinci designed an aerial screw using a large screw-shaped rotor.
The machine appears in a drawing dated to about 1489. Its helical surface was intended to press against the air and lift the structure upward, much as a screw advances through a solid material. Leonardo’s notes suggest a frame about 5 metres across, covered with reed or linen material stiffened with a substance such as starch.
The aerial screw is often described as an ancestor of the helicopter, but it was not a helicopter in the engineering sense. The drawing does not provide a practical engine, a workable control system, or a clear method for producing enough continuous power. Four people were apparently expected to turn a central mechanism, which would not provide sufficient lift for the proposed size.
The design is historically important because it shows Leonardo reasoning about vertical flight. It should not be confused with a modern propeller: the machine’s lifting surface was a continuous helical form rather than separate rotating blades.