Leonardo da Vinci’s aerial screw used a rotating screw-shaped airfoil to rise vertically. Leonardo sketched the design around 1489, imagining a helical surface that would press against the air as it rotated.
The drawing shows a large linen-covered spiral mounted around a central mast. Leonardo compared the device to a screw moving through a solid material, reasoning that a sufficiently strong and rapidly turning mechanism could produce lift. The concept resembles the principle behind a helicopter rotor, although it lacks the practical rotor blades, engine and control systems required for powered flight.
The aerial screw was never built and flown by Leonardo. It is also important not to confuse it with the ornithopter, another Leonardo design based on flapping wings. Modern historians generally view the aerial screw as a bold theoretical study rather than a directly workable helicopter.