Leonardo da Vinci sketched an aerial screw as a conical machine that might rise by rotating a helical sail.
The drawing appears in a manuscript usually dated to about 1489. Leonardo proposed a large spiral structure covered with linen and reinforced with reeds. His idea was that the rotating helix could “screw” itself upward through the air, in a way loosely analogous to a screw moving through a solid material.
The aerial screw was not a working helicopter. Leonardo did not provide a practical engine or a sufficiently light structure, and the concept would require far more power than people of his time could supply. Nevertheless, the sketch is often discussed as an important ancestor of vertical-flight concepts. It should not be confused with the ornithopter, whose wings flap, or with a modern helicopter, whose rotor blades generate lift continuously.