Leonardo da Vinci designed an aerial screw with a spiral linen sail intended to lift a machine by rotating through the air. The concept is one of his best-known studies of vertical flight.
Leonardo drew the design around 1489 in a manuscript now associated with the Codex Atlanticus. His notes proposed a helical surface made from linen coated with starch and supported by a reed structure. The machine was meant to be turned by people using a central mechanism.
The aerial screw is often called a helicopter ancestor, but it was not a working helicopter. It lacked a practical powered engine, and its proposed human-powered rotation could not provide enough lift for sustained flight. Its importance lies in recognizing that a rotating screw could act on air in a way related to modern rotorcraft.