A study of autogiro rotor-blade oscillations in the plane of the rotor disk
This 1936 NACA Technical Note, issued by the National Advisory Committee for Aeronautics in the United States, reports flight measurements of autogiro rotor-blade motion for engineers studying rotor dynamics. Its pictures are plain graphs on squared grids, with data points marked by circles, crosses, squares and triangles against tip-speed ratio, and a designer might borrow the clean grid-and-marker layout for technical data graphics.
