Leonardo da Vinci sketched an aerial screw as a conical rotor intended to lift a machine into the air.
Leonardo drew the design around 1489, making it one of the earliest known concepts resembling a helicopter. His manuscript describes a large helical structure covered with reeds, linen, and a sealing material. The idea was that the rotating screw would push against the air and rise, much as a screw moves through a solid material.
The drawing is imaginative but not a practical helicopter blueprint. The proposed machine would have required more power and stronger, lighter materials than Renaissance technology could provide. Leonardo also did not establish the aerodynamic principles needed to make the design work reliably. Modern replicas have produced limited experimental results, but they do not show that the original design could have flown.
The aerial screw is commonly mixed up with Leonardo’s ornithopter. An ornithopter uses flapping wings, while the aerial screw uses a rotating helical rotor. The later helicopter developed through different engineering solutions, including powered rotor systems and improved materials.