Leonardo da Vinci sketched an aerial screw, a rotating device often described as an early helicopter concept.
The drawing appears in a manuscript dated to around 1489. It shows a helical surface wrapped around a central mast, with a large frame intended to rotate the screw. Leonardo reasoned that the screw could push against the air and lift the machine, much as a screw advances through water.
The proposal was an important mechanical analogy, but it was not a practical helicopter. The machine would have needed more power and a more efficient rotor than the technology of Leonardo’s time could provide. It also lacked several features needed for controlled modern flight, including a suitable method of stabilization.
The aerial screw should not be confused with Leonardo’s flapping-wing ornithopter. The ornithopter imitates birds, while the aerial screw uses rotary motion. Modern helicopters use powered rotors with carefully shaped blades, an idea related in principle but far more advanced in engineering.