Aerodynamic Characteristics of NACA 23012 and 23021 Airfoils with 20-Percent-chord External-Airfoil Flaps of NACA 23012 Section
This is a 1937 NASA technical report, published by NACA, on wind-tunnel tests of wing sections and their external flaps, for aeronautical engineers. Its single plate shows photographs of metal airfoil models, one long wing section with a flap hinged beneath and a close-up of a flap model in cross-section, both shot in plain light against white.
