Leonardo da Vinci sketched an aerial screw as a proposed flying device with four rotating blades around a central mast.
Leonardo drew the design in the 1480s, probably around 1489. Its helical linen-covered surface was intended to press against the air and lift the machine, much as a screw moves through a solid material. The concept is often described as an ancestor of the modern helicopter, although it could not have flown as drawn.
The aerial screw was a study rather than a tested aircraft. Leonardo did not have a lightweight engine or a practical method for powering the large rotor, and the materials shown would have been too heavy. It is also commonly called a helicopter screw, but that name describes its later historical interpretation rather than a machine Leonardo built. The sketch is significant because it shows Leonardo reasoning about vertical flight centuries before powered helicopters became practical.