What flying device did Leonardo da Vinci sketch with a large helical rotor?

Leonardo da Vinci sketched an aerial screw with a large helical rotor.

Drawn around 1489, the aerial screw is one of Leonardo’s best-known studies of vertical flight. Its framework resembles a giant screw or modern helicopter rotor, with a helical surface intended to press against the air and lift the machine.

The design was not a working helicopter. Leonardo proposed that a rotating mechanism could turn the screw, but the power sources available in the Renaissance were far too weak for a full-scale machine. The sketch is therefore best understood as a theoretical flight concept rather than a completed invention.

People sometimes call the aerial screw the first helicopter, but that description is only approximate. Modern helicopters use powered rotors that generate lift through airfoils, while Leonardo’s proposed screw relied on a different idea. The drawing is historically important because it shows Leonardo thinking about vertical takeoff centuries before practical rotorcraft existed.