The variation in engine power with altitude determined from measurements in flight with a hub dynamometer
This is a 1929 NASA technical report, issued by NACA through the NASA Technical Reports Server, on how aircraft engine power falls with altitude, based on in-flight measurements with a hub dynamometer. The pictures are engineering line graphs: the first plots the ratio of brake horsepower to zero-altitude power against altitude for three curves, and the second charts pressure, temperature, engine speed and airspeed against standard altitude. A designer could draw on their plain black-line grids, labelled axes and clean scientific chart style.
