Leonardo da Vinci’s aerial screw was a flying-machine concept with a large helical rotor intended to lift the device from the ground.
Leonardo drew the design around 1489. Its frame was meant to support a spiral surface made from reeds and cloth. He reasoned that turning the spiral rapidly could force air downward and push the machine upward.
The aerial screw resembles a modern helicopter rotor in broad concept, but it could not have flown as drawn. Renaissance materials and human muscle power could not provide enough energy to turn such a large rotor quickly enough.
The design is often called a helicopter precursor, although it was not an actual helicopter. Leonardo’s importance lies in analyzing vertical flight and proposing a mechanical solution, rather than in building a successful aircraft.