What rotating-wing aircraft concept did Leonardo da Vinci draw?

Leonardo da Vinci drew an aerial screw, a rotating-wing aircraft concept often regarded as an early helicopter idea.

His drawing from around 1489 shows a large helical structure made from reed, linen, and wire. Leonardo reasoned that if the screw rotated rapidly enough, its surface could push against the air and lift the machine. The concept was inspired partly by the action of an Archimedes screw, which moves through water or other material.

The aerial screw was not a practical helicopter. It lacked a suitable lightweight engine and a reliable method of producing enough continuous torque. Unlike modern helicopters, it also did not clearly separate lift, propulsion, and control systems. Nevertheless, the drawing is historically important because it presents a vertical-lift idea centuries before powered rotorcraft became possible.