Leonardo da Vinci’s 1489 design for a flying machine with a large rotating screw is commonly called the aerial screw.
The drawing shows a helical sail wrapped around a frame. Leonardo proposed that a mechanism could rotate the screw and force air downward, creating lift in a way that resembles the principle of a modern helicopter rotor.
There is no evidence that Leonardo built or flew a working aerial screw. The design was a theoretical machine, and its linen-covered helical surface would not have supplied enough lift with the materials and power sources available in Renaissance Italy.
The aerial screw is therefore best understood as an early conceptual ancestor of the helicopter, not as a functioning helicopter. Leonardo’s studies of air, birds and mechanical transmission helped him explore several different approaches to flight.