What was Leonardo da Vinci’s spiral rotor design intended to make possible?

Leonardo da Vinci’s spiral rotor design was intended to make vertical flight possible.

Known as the aerial screw, the design appears in a manuscript drawing dated to around 1489. It has a large helical structure made from reeds and linen, supported by a wooden framework. Leonardo reasoned that if the screw rotated rapidly enough, its surface could push against the air and lift the machine.

The aerial screw is frequently described as an early helicopter concept, although it was never built and tested by Leonardo. The proposed mechanism also lacked a practical power source: human muscles could not provide enough energy to rotate such a large rotor.

Modern helicopters use powered rotors that generate lift through aerodynamic blades. Leonardo’s aerial screw did not function like a modern helicopter in detail, but its central idea—using a rotating structure for vertical ascent—makes it an important early flight concept.