Leonardo da Vinci called his helical vertical-flight machine an aerial screw. He sketched it around 1489, showing a large spiral surface mounted on a frame and imagining that it could screw upward through the air if rotated rapidly.
The design is frequently described as an ancestor of the helicopter because it anticipates the use of a rotating lifting surface. However, Leonardo's aerial screw would not have worked as drawn with the materials and power available in the fifteenth century. Its broad linen-covered spiral would have been heavy, and human operators could not supply enough continuous power.
The aerial screw was a conceptual machine, not a documented aircraft. It also differed from a helicopter, whose rotor blades generate lift through aerodynamic rotation and whose control systems stabilize flight.
The sketch remains historically important because it shows Leonardo reasoning about vertical flight rather than only imitating bird wings. His work on screws, rotors, and air resistance became part of a larger collection of studies into mechanical flight.