Some experiments on autorotation of an airfoil
A 1929 NASA technical report on autorotation of an airfoil, produced for aeronautical engineers and researchers studying how wings spin in flight. The pictures are engineering graphs of the dimensionless rotation parameter R = pb/V plotted against angle of attack, yaw angle and aspect ratio, with curves labelled by yaw and alpha values; a designer might take from them only the clean grid-and-curve plotting style and the labelled-curve layout.
