What did Leonardo da Vinci call his rotating aerial machine with a helical sail?

Leonardo da Vinci called his rotating aerial machine an aerial screw.

He sketched the concept in the 1480s, showing a large helical surface wrapped around a central mast. Leonardo reasoned that if the screw rotated rapidly, its surface might push against the air and lift the machine. The idea is therefore often compared with a helicopter rotor, although the mechanism would not work efficiently as drawn.

The aerial screw was not a helicopter and was never demonstrated as a flying vehicle by Leonardo. Renaissance materials and human muscle power could not provide the sustained energy needed for controlled vertical flight. Modern reconstructions are useful for illustrating the geometry, not for proving that the original machine was practical.

The design is important because it separates vertical-lift thinking from the flapping-wing machines Leonardo also studied. It is one of his clearest early attempts to treat air as a medium that could be engaged by a rotating surface.