The Wing in Flapping Flight: Elbow, Air-Wedge and Oval Path
Notes and diagrams on wing motion, the wedge of air, and a 3-pound bird's balance
This densely written sheet analyses how a wing moves in flapping flight. Leonardo describes how, as the hand (the wing's outer part) rises the elbow drops and presses the air, and how, thrown forward edgewise into the wind on its acquired impetus, the wing lets the air form a wedge beneath the elbow so the bird climbs without beating; he reckons a bird of 3 pounds, its breast a third of the wing's width, loads its wings with only two-thirds of its weight. A left-hand column keyed to the letters a, b, c, d traces the wingtip through a long, narrow oval, since it rises along a higher line than it descends. A detail of the mechanical wing is drawn in the right column, with small figures of a bird and a bird's wing in the margin.
On this page
Elbow, air-wedge and climbing without beating the wings
As the hand (the wing's outer part) rises the elbow drops and presses the air; lowered, the elbow rises and stays edgewise so as not to hinder the motion. Sent forward edgewise a little into the wind on the impetus already gained, the wing lets the wind strike beneath the elbow and form a wedge, on which the bird climbs without beating its wings. A bird of 3 pounds whose breast is a third of the wing's width loads its wings with only two-thirds of its weight.
The wingtip traces a long narrow oval (a, b, c, d)
The palm of the hand goes from a to b at nearly equal angles, pressing the air, then turns edgewise at b and returns upward along line c d; reaching d it turns face-on and descends along line a b, always turning about the centre of its width. Because the tip rises along a higher line than it descends, its going and returning paths enclose a long, narrow oval.
Detail of the mechanical wing
The right-hand column carries a figure isolating a detail of the mechanical wing. It is the built counterpart to the bird's wing whose flapping is analysed in the surrounding notes.