||In one of the most interesting sections of the Codex, Leonardo compares air to water, and flying to swimming.
Air, he reasons, is like a fluid that keeps the flying machine suspended, and it is thus necessary to know how to ‘navigate’ with the correct instruments. In the drawings he analyses the action of the air flows that strike the wings from various directions.
In the notes he affirms that artificial wings must copy natural ones, adding that which in birds is a kind of ‘thumb’: the alula or bastard wing, a feathered protuberance that allows the wing to cut the wind, improving the aerodynamic profile.
«Con le ali e con la coda l'uccello fa nell'aria la stessa cosa che fa nell'acqua il nuotatore con le braccia e con le gambe»
(With the wings and the tail the bird does the same thing in the air that the swimmer does in water with the arms and the legs.)
NOTE. For each page of Leonardo’s Codex we provide a brief summary, with the quotation of one that page’s most significant passages edited in modern Italian, with an English translation.
translation by Kim Williams