What type of aircraft did Leonardo da Vinci design with rotating spiral blades?

Leonardo da Vinci designed an aerial screw with rotating spiral blades as a proposed flying machine.

In a manuscript drawing dated to about 1489, Leonardo showed a large helical device resembling a screw turned vertically in the air. He proposed that a linen-covered frame could rise if the spiral surface were rotated quickly enough. The drawing is often described as an ancestor of the helicopter, although it was not a helicopter in the modern engineering sense.

The idea depended on human-powered rotation and lacked a workable engine, lightweight materials, and a proven method of controlling lift. Leonardo therefore produced a bold aerodynamic concept rather than an operational aircraft.

The design is sometimes incorrectly called Leonardo's helicopter. Modern helicopters use powered rotors that generate lift through airfoils; Leonardo's aerial screw relied on a rotating helical surface. Its historical importance lies in imagining vertical flight more than in providing a buildable machine.