What aerial machine did Leonardo da Vinci sketch as a rotating helical screw?

Leonardo da Vinci’s rotating helical flying-machine design is known as the aerial screw.

Leonardo drew the machine around 1489 in a manuscript now associated with the Institut de France. The design has a large helical structure intended to push against the air and lift the craft, making it an important early ancestor of helicopter concepts.

The aerial screw was not a powered aircraft. Leonardo lacked a sufficiently light engine and did not provide a complete practical method for controlling or driving the machine. Modern reconstructions therefore interpret it as a visionary concept rather than a demonstrated aircraft.

Its appearance can resemble a giant screw or an early rotor. That distinction matters: the aerial screw is not the same design as Leonardo’s flapping-wing ornithopter, which attempted to imitate bird flight.