What Leonardo da Vinci design proposed a spiral device for vertical flight?

Leonardo da Vinci’s spiral vertical-flight design was the aerial screw.

Leonardo sketched the aerial screw in 1489, probably in the period when he was studying the behavior of air and the flight of birds. The design shows a large helical surface wrapped around a central mast. Leonardo proposed that turning the structure could make it rise by pushing against the air.

The drawing is often called a helicopter predecessor, but it was not a helicopter in the modern engineering sense. It lacked an engine, rotor-control system, and demonstrated method of operation. The idea was conceptual, and historians disagree about whether the screw could have generated enough lift with the materials and power available in Leonardo’s time.

Its importance is still substantial. It shows Leonardo thinking about vertical lift rather than only gliding or flapping flight. The aerial screw is separate from his parachute and ornithopter designs, which addressed descent and birdlike flight in different ways.