What Leonardo da Vinci flying-machine concept used a rotating helical blade?

Leonardo da Vinci’s rotating-blade flying-machine concept is called the aerial screw.

Leonardo sketched the aerial screw around 1489. The machine featured a large helical surface made from reeds and linen, mounted on a central framework. His notes suggested that turning the structure could make the screw press against the air and lift the machine, an idea that resembles the basic action of a helicopter rotor.

The design was not a functioning helicopter. Leonardo did not have an engine light and powerful enough to rotate the large screw, and the proposed materials would not have produced sufficient lift in practice. The machine also lacked the detailed rotor control and stability systems required for vertical flight.

The aerial screw is historically important because it shows Leonardo thinking about rotary lift rather than only imitating birds. Modern helicopters use powered rotors with airfoil-shaped blades, not a continuous spiral surface. The resemblance is conceptual, not a direct mechanical blueprint for a modern helicopter.