What type of aircraft did Leonardo da Vinci sketch with a large rotating screw?

Leonardo da Vinci sketched an aerial screw as a proposed aircraft with a large rotating helical rotor.

The design appears in a manuscript dated to around 1489. Leonardo imagined a linen-covered helical surface rotating around a central mast. His notes suggested that the screw could push against the air and lift the machine, an idea that resembles the principle behind a modern helicopter rotor.

The aerial screw was a concept rather than a working aircraft. Its proposed materials and human-powered mechanism could not provide enough lift with Renaissance technology. It is therefore not accurate to call Leonardo the inventor of the modern helicopter, but his drawing is an important early example of thinking about vertical flight through rotating airfoils.