Leonardo da Vinci sketched an aerial screw as a possible rotating-wing flying machine.
His drawing, usually dated to about 1489, shows a helical sail wrapped around a frame. Leonardo reasoned that the rotating structure might screw itself upward through the air, using an idea analogous to a screw moving through a solid material.
The aerial screw could not have lifted itself with the human power available in Renaissance technology. It is often described as a precursor to the helicopter because both use rotating lifting surfaces, but Leonardo’s design was not a helicopter and had no modern rotor, engine, or control system. The sketch is significant as an early attempt to reason about vertical flight rather than simply copying the flapping motion of birds.