The rotating aerial-screw design by Leonardo da Vinci, a forerunner of the helicopter, is commonly called the aerial screw.
Leonardo drew the concept around 1489. The sketch shows a large helical surface mounted on a vertical frame, with people turning crank mechanisms to rotate it. His idea was that the spiral surface might press against the air and lift the machine.
The aerial screw was never built or flown in Leonardo’s lifetime. It lacked a practical lightweight engine, and the proposed human-powered mechanism could not generate enough power for sustained flight.
It is often called a helicopter precursor, not a helicopter itself. Modern helicopters rely on powered rotors, aerodynamic blades, and control systems that Leonardo’s design did not possess. Its importance lies in identifying vertical lift as a separate engineering problem.