Effect of altitude on power of aviation engines
A 1924 technical report on how altitude reduces aviation engine power, issued by NASA's Technical Reports Server as a digitised government document. Its three charts plot atmospheric pressure, a second altitude-related ratio, and the change in effective horsepower against altitude in metres, with plain black curves on gridded paper. A designer could take their clean scientific graph style, with sparse labels and simple curved lines, as a model for minimal data visuals.
