Leonardo da Vinci sketched an aerial screw as a spiral-shaped machine intended to rise through the air.
The design appears in Leonardo’s notes from the late fifteenth century and has a large helical surface wrapped around a central mast. His written idea suggested that if the spiral screw were properly made and rapidly rotated, it could push against the air and lift the machine.
The aerial screw is often described as a conceptual ancestor of the modern helicopter, but it was not a working helicopter. Leonardo did not have a practical lightweight engine capable of supplying the needed power, and the design lacks many features required for controlled flight. It is also distinct from his ornithopter studies, which sought lift through flapping wings.