Testing a Windmill Airplane ("autogiro")
This NACA technical memorandum, issued in 1927 by the National Advisory Committee for Aeronautics and later digitized by NASA's Technical Reports Server, reports wind-tunnel and test-rig work on an early rotary-wing autogiro for engineers and aviation researchers. Its plates are graphs of velocity, angle, and coefficient curves, an airfoil polar diagram with labelled test profiles, and a photograph of a small instrument rig with angled blades on a pivot, which give designers a sparse, diagrammatic record of technical measurement rather than ornament.
