Aerodynamic principles of the direct lifting propeller
This is a 1934 NASA technical report on the aerodynamics of a direct lifting propeller, issued by NASA's Technical Reports Server for aeronautical engineers and researchers. Its pictures are plain engineering line charts and diagrams: lift-drag ratio curves plotted against angle of attack, an induced-inclination graph with labelled curves, a flow velocity chart along the radius, and a blade-force vector diagram. A designer might take their clean black-and-white graph and vector-arrow style for technical diagrams.
