Foot-powered flying machine, to be tested over a lake
A wing apparatus driven by both feet, with a spring up-stroke and a safety wineskin
A single large drawing shows a foot-powered flying machine whose lettered controls twist, turn, lower and raise the wing, the operator working the wings with his feet at f and d. The long note explains that the pole M must lean out of the vertical so the descending wings also move toward the operator's feet to drive the bird forward, and it advises testing the machine over a lake while wearing a long wineskin so as not to drown. Both feet should power the down-stroke, allowing the flier to balance himself like a kite, while a spring or the drawing-in of the feet handles the up-stroke.
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Lettered controls and the leaning pole M
The controls are lettered so that a twists the wing, b turns it with the lever, c lowers it and d raises it, while the operator's feet at f and d lower and raise the wings. The pole M must lean out of its perpendicular so the wings, as they descend, also move toward the man's feet, which is what drives the bird forward.
Test over a lake with a wineskin
Leonardo advises trying the instrument over a lake while wearing a long wineskin girded on, so that if the flier falls he will not drown. Powering the down-stroke with both feet at once lets him balance himself by lowering one wing faster than the other, as the kite and other birds do.
Spring-driven up-stroke
The two-footed down-stroke is twice as strong as with one foot, though twice as slow. The raising of the wings is to be done by the force of a spring, or by hand, or by drawing the feet in, which is better because it leaves the hands free.