What name is commonly given to Leonardo da Vinci’s spiral aircraft design?

Leonardo da Vinci’s spiral aircraft design is commonly called the aerial screw.

Leonardo drew the design around 1489–1490 in the Codex Atlanticus. It consisted of a large helical or screw-shaped surface mounted on a frame. Leonardo reasoned that if the screw rotated quickly enough, its surface could press against the air and lift the structure upward. The concept resembles a modern helicopter rotor in its use of rotating lift, although its mechanism and scale were very different.

The aerial screw was a theoretical design, not a demonstrated aircraft. Leonardo did not possess a lightweight engine capable of powering it, and the materials available in Renaissance Italy would have made a working version difficult. Modern reconstructions have been built as demonstrations, but they do not prove that the original design could have flown.

The aerial screw is often incorrectly called a helicopter. “Helicopter” is the name of the later aircraft type; “aerial screw” is the traditional name for Leonardo’s specific concept.