What did Leonardo da Vinci call his rotating-blade aircraft concept?

Leonardo da Vinci called his rotating-blade aircraft concept the aerial screw.

The design appears in a manuscript associated with Leonardo and is usually dated to about 1489. It shows a helical sail or screw intended to rotate around a central mast. Leonardo reasoned that the screw could press against the air and lift the machine, using an idea analogous to a screw moving through a solid material.

The aerial screw is often described as an early helicopter ancestor, but it was not a helicopter in the modern engineering sense. It lacked a practical engine, a reliable rotor system, and a demonstrated method for controlling torque. The proposed structure was also extremely large and heavy for the materials and power sources available in Renaissance Italy.

Modern helicopters use powered rotors that generate lift by rotating airfoils. Leonardo’s sketch is historically important because it recognized rotary lift as a possible route to vertical flight, even though the mechanism could not be built successfully in his lifetime.