What rotating device did Leonardo da Vinci design to suggest vertical flight?

Leonardo da Vinci designed an aerial screw as a rotating device intended to suggest vertical flight.

His drawing from about 1489 shows a large helical structure with a linen-covered frame. Leonardo reasoned that if the screw could rotate rapidly, its spiral surface might push against the air and lift the machine. The concept is frequently described as an early helicopter idea, although it was not a working helicopter.

The aerial screw was probably inspired partly by the structure of a screw and by observations of the autorotating seeds of some plants. It also reflects Leonardo’s effort to understand whether air could provide support in the same way that water supports boats.

Modern helicopters use powered rotors, control systems, and lightweight materials that Leonardo did not have. The aerial screw therefore represents a theoretical ancestor of vertical-flight machines rather than a successful aircraft. It should also be distinguished from his wing-flapping designs, which were based on bird flight.