Improving the Performance of Multi-engined Airplanes by Means of Idling Propellers : the "free-wheel" Propeller
This is a 1930 NASA Technical Reports Server report on improving multi-engined airplane performance with idling propellers, a technical aeronautical study prepared for aircraft engineers and propeller designers. The three plates are engineering graphs and a wing section: characteristic curves of propeller coefficients plotted against advance ratio, a lift coefficient chart for an airfoil, and an airfoil cross-section drawing. A designer might take from them the sparse, grid-based plotting style and the clean line-and-label conventions of mid-century technical diagrams.
