Investigation in the 7-By-10 Foot Wind Tunnel of Ducts for Cooling Radiators Within an Airplane Wing, Special Report
This is a 1938 NACA technical report by NASA Technical Reports Server, examining wind-tunnel tests of ducts that cool radiators housed inside an airplane wing, prepared for aeronautical engineers. The pictures are engineering line drawings and graphs: wing cross-section profiles with duct geometry and plotted efficiency, flow-ratio and angle curves against section lift coefficient, which a designer could use as a clean diagrammatic reference for airfoil and cutaway forms.
