Leonardo da Vinci sketched the aerial screw as a possible device for achieving vertical flight.
In a notebook drawing usually dated to about 1489, Leonardo showed a large helical rotor wrapped around a central mast. He reasoned that if the screw-shaped surface were turned rapidly, it might screw upward through the air. The concept is often compared with the basic idea of a helicopter rotor, although Leonardo’s proposed mechanism was not a functioning modern helicopter.
The design required materials and power sources unavailable in the Renaissance. Its large sail-like surface would also have faced major problems involving weight, rigidity, control, and aerodynamic efficiency. Leonardo did not build a working full-scale version.
The aerial screw is sometimes called a helicopter in popular summaries, but that label can be misleading. A modern helicopter uses powered rotor blades and a carefully controlled system of lift and stability; Leonardo’s sketch was an imaginative early proposal for rotary vertical flight.