Wind tunnel tests on airfoil boundary control using a backward opening slot
This is a 1929 NACA technical note from the NASA Technical Reports Server, a wind tunnel report on airfoil boundary control using a backward opening slot, written for aeronautical engineers. Its pictures are plain engineering line graphs of lift, drag and pressure against angle of attack and slot width, drawn in black ink on white with gridded axes and labelled curves. A designer might take from them only the clean chart conventions of stepped labels, dense gridlines and minimal colour, rather than any imagery of aircraft.
