Calculating thrust distribution and efficiency of air propellers
A 1927 technical report from the NASA Technical Reports Server, a record of aeronautical research on how air propellers produce thrust and how efficiently they do it. Its single figure is a diagram of a blade section with velocity vectors, angles, and a lift line, labelled for engineers working through propeller calculations. A designer could take from it the clean line-and-angle vocabulary of early engineering schematics, with thin black strokes, small italic labels, and a compass-like arrangement of force arrows.
