What type of machine did Leonardo da Vinci sketch as a possible vertical-flight device?

Leonardo da Vinci sketched an aerial screw as a possible vertical-flight device.

The drawing appears in a manuscript traditionally dated to about 1489. It shows a large helical structure covered with reeds and linen, with a rotating platform and supporting framework. Leonardo reasoned that the screw could rise if its surface “screwed” through the air, an idea analogous to a screw moving through wood or a ship’s propeller moving through water.

The aerial screw is often described as an early helicopter concept, but it was not a helicopter in the modern engineering sense. Leonardo did not provide a practical engine or a sufficiently light power source, and the proposed machine would probably have been too heavy for human-powered flight. The sketch is therefore best understood as a theoretical flight experiment rather than a working aircraft.

Its significance lies in the idea of vertical lift. Centuries later, powered helicopters used rotating blades to generate lift, making Leonardo’s drawing an important early example of rotary-wing thinking.