The drag characteristics of several airships determined by deceleration tests
A 1932 NASA technical report on airship drag, compiled from deceleration tests and issued for aeronautical engineers and researchers. Its two pictures are plain graph plots with a grid, a straight solid line and a dashed extension, showing true air speed in miles per hour against propeller speed in revolutions per minute and against another measured quantity. A designer could take from them only a sparse, technical scientific chart style of thin black lines on a fine grid.
