Leonardo da Vinci sketched an aerial screw as a possible flying device.
The design appears in his Codex Atlanticus, compiled from notebooks dating largely to the late fifteenth and early sixteenth centuries. It shows a helical surface mounted around a central mast, with a suggested diameter of about five meters. Leonardo reasoned that the rotating screw might rise by pressing against the air, in a way loosely comparable to a screw advancing through wood.
The aerial screw is often called an early helicopter concept, but it was not a practical helicopter. Leonardo supplied no workable engine, and the materials and human power available in his time could not have produced enough lift. Modern reconstructions therefore treat it as an important conceptual predecessor rather than a successful aircraft.
It is also different from Leonardo’s parachute and ornithopter sketches. The aerial screw depends on rotary lift, while the parachute descends and the ornithopter imitates flapping wings.