Preliminary Model Tests of a Wing-Duct Cooling System for Radial Engines, Special Report
This NACA special report from 1939, issued by the National Advisory Committee for Aeronautics, documents preliminary wind-tunnel model tests of a wing-duct cooling system intended for radial aircraft engines. Its pictures are plain engineering photographs and graphs: one shows a propeller-driven model mounted on struts inside a test section, the other plots pressure and drag coefficients as line charts on gridded paper. A designer might take from them the clean monochrome technical-drawing look, with grid lines, axis labels and tidy numerals.
