Leonardo da Vinci sketched an aerial screw in the Codex Atlanticus around 1489.
The device has a large helical surface wrapped around a central mast. Leonardo reasoned that turning the screw could compress air and make the machine rise, much as a screw advances through a solid material. The drawing is one of the best-known early concepts related to vertical flight.
It was not a helicopter in the modern engineering sense. Leonardo provided no practical engine capable of turning the structure, and the design's materials and weight would have prevented successful flight. The concept is therefore a theoretical precursor rather than a functioning aircraft.
The aerial screw is frequently compared with a modern helicopter rotor, but the mechanisms are different. A helicopter rotor generates lift from airfoils rotating through the air; Leonardo's helical canvas structure depended on a screw-like action that was never experimentally demonstrated.