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The following tables give the values of Ky, Kx, L/D, and center of pressure movement for flat plates of various aspect ratios. The center of pressure (C. P.) for each angle is given as a decimal fraction of its distance from the leading edge, in terms of the width or "Chord."

Fig. 16. Plan View of Plate with Long Edge to Wind. Fig. 17. Plate with Narrow Edge to Wind, Showing Loss in Lift. 17a Shows Effect of Raked Tips.

Fig. 16 shows the top view or plan of a lifting surface, with the direction of the wind stream indicated by the arrows w-w-w = w. The longer side or "span" is indicated by S, while the width or chord is C. Main lifting surfaces, or wings, have the long side at right angles to the wind as shown. When in this position, the surface is said to be in "Pterygoid Aspect," and when the narrow edge is presented to the wind, the wing is in "Apteroid Aspect." The word "Pterygoid" means "Bird like," and was chosen for the condition in Fig. 16, as this is the method in which a bird's wing meets the air. Contrary to the case with true curved aeroplane wings, flat planes usually give better lift in apteroid than in pterygoid aspect at high angles. The aspect ratio will be the span (S) divided by the chord (C), or Aspect ratio = S/C.