Leonardo da Vinci’s proposed flying machine with a helical linen sail is called the aerial screw.
Leonardo drew the design around 1489–1490. It shows a large spiral surface supported by a framework, with the idea that rotating the structure would make it “screw” upward through the air. The concept resembles a modern helicopter rotor in broad outline, although Leonardo’s machine had no engine capable of turning it and no practical control system.
The design is often described as a helicopter precursor, but it was not a helicopter in the modern engineering sense. A helicopter depends on powered rotor blades, aerodynamic lift, and controlled flight. Leonardo’s aerial screw was mainly a theoretical investigation into whether a helical surface could generate upward motion.
It is also frequently confused with Leonardo’s ornithopter. The ornithopter flaps wings like a bird, whereas the aerial screw relies on rotary motion. The distinction matters because Leonardo was exploring several unrelated approaches to human flight.