What rotating aircraft concept did Leonardo da Vinci call an aerial screw?

Leonardo da Vinci’s rotating aircraft concept was the aerial screw.

The aerial screw is a Renaissance design for a machine that would rise through the air using a large helical rotor. Leonardo sketched it in the 1480s, describing a linen-covered framework that would act like a screw when rotated. The concept is often cited as a distant ancestor of the modern helicopter.

Leonardo did not build a powered, working helicopter. The design lacked a practical engine and would also have faced major problems involving weight, torque, and efficient lift. Its importance lies in identifying the possibility of vertical flight through a rotating surface.

The aerial screw is easy to mix up with Leonardo’s ornithopters. Ornithopters imitate birds by flapping wings; the aerial screw uses rotary motion. Neither concept became a functioning aircraft in Leonardo’s lifetime, but both demonstrate his systematic attempts to study flight mechanically.