Tennessee, June 7, 2014. A close-range study of the underside of a preserved piston-engine warbird, showing the sooted cowling and the heat-tinted exhaust collector pipe that carried gases away from a large air-cooled radial engine. Details like these, rarely visible to spectators, record the working reality of high-power piston aviation: the scorching, staining, and constant maintenance attention that engines of this class demanded. The photograph comes from the collection of Donald L. Engebretsen, a Vietnam-era A-1 Skyraider pilot whose later years were devoted to documenting the aircraft and airmen of that generation. Project: 219310