Propeller anemometer

Greatly interested in being able to find the most suitable atmospheric conditions for gliding flight, Leonardo designed an instrument capable of measuring wind velocity. The model is constituted of a simple structure in the form of a quarter-circle equipped with a hanging vane and a graduated arc.

When thrust by the wind, the vane deviates from its resting vertical position to an angle proportional to the force of the wind itself, measurable on the graduated arc. In the notes accompanying the drawing, Leonardo emphasizes the necessity of pairing this instrument with a timepiece in order to calculate how much distance can be traveled while being driven by air currents in a specific time interval.