What type of propeller did Leonardo da Vinci design for a possible aerial machine?

Leonardo da Vinci designed an aerial screw, an early screw-propeller concept intended to lift a machine by rotating through the air.

His drawing, usually dated to around 1489, shows a helical surface wrapped around a central shaft. Leonardo reasoned that the rotating screw might “screw” itself upward through the air, somewhat as a ship’s propeller moves through water.

The design was not a working helicopter and there is no evidence that Leonardo built a full-size model. It also lacked the lightweight engine and precise control systems needed for practical powered flight.

The aerial screw is often linked to later helicopter history, but it should not be confused with Leonardo’s separate ornithopter studies. Its importance lies in recognizing rotary lift as a possible solution to flight.