Experimental Research on Air Propellers III
A 1920 technical report from the National Advisory Committee for Aeronautics, issued by NASA's Technical Reports Server, presenting experimental research on air propellers for aeronautical engineers. Its pictures are plain graph plates on gridded paper, with hand-plotted curves for efficiency, thrust and power against advance ratio, each labelled with a propeller model. A designer could take from them the clean, sparse line-chart vocabulary of early engineering data: thin dashed and solid curves, fine grid, and small handwritten labels.
