What helical flying-machine design did Leonardo da Vinci sketch around 1489?

Leonardo da Vinci’s helical flying-machine design sketched around 1489 was the aerial screw.

The aerial screw was a drawing of a large spiral or helical surface mounted around a central shaft. Leonardo proposed that rotating the screw could press against the air and lift the structure, an idea often compared with the principle of a modern helicopter rotor. The famous sketch appears in the Codex Atlanticus.

Leonardo did not build a working full-scale aerial screw, and the design lacked a practical power source and sufficiently light materials. Its historical importance lies in the way it identified vertical lift as a separate engineering problem from ordinary forward flight.

The aerial screw is frequently called a helicopter precursor, but it was not a helicopter in the modern technical sense. It also differs from the ornithopter, whose wings flap, and from the parachute, which is intended to slow a fall rather than provide powered lift.