Aerial screw

Aerial screw

Aerial screw

Inv. 9392
Interpretation by Alberto Mario Soldatini e Vittorio Somenzi, 1998

"I find that if this instrument in the form of a screw is well made – that is, made of linen cloth, with its pores being plugged using starch – and if it is turned rapidly, this screw will penetrate the air, and it will mount aloft. Take the example of a wide, thin ruler that you turn through the air with fury: you will see your arm being guided along the line of the edge of that board. Let the framing for the above-mentioned cloth be of long, thick canes. A small model of it can be made of paper, so that its post is a thin strip of iron, which is twisted by force, and when it returns to liberty, it will cause the screw to turn again."

The model is constructed on a fixed circular base inscribed in a mobile corona, which in turn is connected to a vertical transmission shaft. A helicoid structure tapering upward is mounted on the shaft, connected by braces to the rotating corona of the base. Leonardo conceived a structure inspired by the helicoid forms found in nature, as in the case of maple seeds, which can fly to great distances rotating about themselves. Here for the first time the spiral-form structure, previously used since antiquity in the field of hydraulics, is applied to flight and air. In the notes accompanying the drawing, he specifies the measures for the base (8 Florentine braccia, about 5 m) and the materials: wood, cord, and starched linen canvas. The machine could not have functioned, considering its theoretical weight and the insufficient energy that would have been produced by the four men moving it, at least according to the interpretation provided by the model’s project designers, Soldatini and Somenzi, who perhaps went a bit beyond the elements effectively drawn by Leonardo. In a study of a small-scale prototype, Leonardo probably was thinking of a mechanism actuated by a spring or a cord. He even suggested limiting the experiment to making a small paper model, conscious that an actual-size realization would never have been able to function, primarily because of the obvious lack of suitable motor.

The model is based on the drawing:

  • Manuscript B f. 83 v. (1486-1487)
    Paris, Institut de France