Which ancient engineering principle did Leonardo da Vinci apply to his aerial screw design?

Leonardo da Vinci applied the principle of Archimedes’ screw to his aerial screw design.

Leonardo sketched the aerial screw around 1489. The machine featured a helical surface intended to push against the air as it rotated, much as Archimedes’ screw moves water through a spiral mechanism. Leonardo wrote that if the screw were made from linen and reinforced with reeds, it might rise into the air.

The idea was visionary, but it was not a practical helicopter. The proposed craft had no suitable lightweight engine, and human power could not provide enough energy for sustained vertical flight. The drawing is best understood as an early exploration of rotary lift rather than a working aircraft.

The aerial screw is sometimes called a helicopter because its shape resembles a rotorcraft. That modern comparison is useful but incomplete: a helicopter uses powered rotating blades and aerodynamic lift, whereas Leonardo’s design relied on a large helical surface.