What flying machine did Leonardo da Vinci design with a rotating spiral screw?

Leonardo da Vinci designed the aerial screw as a flying machine with a rotating spiral screw.

Leonardo sketched the device around 1489–1490 in his notebooks. It had a large, helical linen surface mounted around a central mast. His idea was that rotating the screw would make the spiral surface “screw” upward through the air, somewhat like a modern helicopter rotor.

The aerial screw was a concept, not a demonstrated aircraft. Leonardo did not have an engine light and powerful enough to turn it, and the design would probably have required substantial mechanical changes to become practical. It is often called a helicopter precursor, but it did not use the powered rotor-and-tail arrangement of a modern helicopter.

The aerial screw is also sometimes mistakenly described as Leonardo’s first helicopter. That label is informal: the sketch shows an early flight concept, not a functioning helicopter or a proven machine.