Leonardo da Vinci sketched an aerial screw, a rotating helical flying-machine concept, in the Codex Atlanticus.
The drawing dates to about 1489 and shows a large helical surface wrapped around a central mast. Leonardo proposed that rapidly turning the screw would cause the device to rise by “screwing” through the air, an idea often compared with the principle of a modern helicopter rotor.
The machine was not a working helicopter. Its proposed linen-and-reed structure would have been heavy, and Renaissance power sources could not provide the necessary sustained lift and rotation. The aerial screw also lacked the modern helicopter’s separate rotor and control systems.
Historians usually describe it as a precursor or conceptual ancestor rather than an invention that directly became the helicopter. Leonardo’s sketch nevertheless shows a clear attempt to apply the geometry of a screw to vertical flight, more than four centuries before powered helicopters became practical.