Leonardo da Vinci’s helical flying-machine concept was the aerial screw.
Leonardo drew the aerial screw in a manuscript usually dated to about 1489. The design shows a large spiral surface mounted around a central mast. Leonardo reasoned that if the screw-like surface rotated rapidly, it might “screw” itself upward through the air, much as a screw moves through wood.
The drawing is often called a helicopter precursor, but it was not a helicopter in the modern engineering sense. Leonardo did not have a lightweight engine capable of providing the necessary continuous power, and his design lacked the modern helicopter’s rotor, transmission system, and control mechanisms.
The aerial screw is nevertheless historically significant. Its rotating-lift idea resembles the principle behind later rotorcraft, although the practical development of helicopters required nineteenth- and twentieth-century work in aerodynamics, engines, materials, and control. The design should therefore be described as a conceptual precursor, not a functioning Renaissance helicopter.