What aerial screw did Leonardo da Vinci design as a possible vertical-flight machine?

Leonardo da Vinci designed a helical air screw as a possible machine for lifting itself vertically through the air.

Leonardo drew the aerial screw around 1489. The design featured a large spiral surface wrapped around a central pole, with a platform and framework supporting it. He reasoned that turning the spiral could compress or grip the air and drive the machine upward, an idea often compared with the principle of a modern helicopter rotor.

The machine was never built or flown in Leonardo's lifetime. Its proposed scale, materials, and human-powered mechanism would not have generated enough lift for practical flight. The drawing is therefore a conceptual study rather than a working helicopter.

The aerial screw is distinct from Leonardo's flapping-wing ornithopter. The ornithopter imitates bird flight through wingbeats, while the aerial screw uses a rotating helical surface. Modern helicopters use powered rotors with aerodynamic blades, not Leonardo's continuous linen-covered spiral.