Wind Tunnel Tests on Autorotation and the "Flat Spin."
This is a 1928 technical report from NASA's Technical Reports Server on wind tunnel tests of autorotation, the self-sustaining spin of aircraft wings and models, and the flat spin. It was written for aeronautical engineers and records its findings as force plots and photographs of models mounted on a test apparatus. The pictures are measured engineering graphs of lift and drag curves and grainy photographs of biplane and monoplane models hung on wires in a wind tunnel, so a designer might take from them the sparse, grid-based plotting style and the stark look of wires against a dark tunnel background.
