The Stipa-Caponi "Flying Barrel" is one of history's most interesting flying oddities. It was an experimental Italian aircraft designed in 1932 by Luigi Stipa (1900–1992) and built by Caproni. It featured a hollow, barrel-shaped fuselage with the engine and propeller completely enclosed by the fuselage—in essence, the whole fuselage was a single ducted fan. Stipa 's basic idea—which he called the "intubed propeller"—was to mount the engine and propeller inside a fuselage that itself formed a tapered duct, or venturi tube, and compressed the propeller's airflow and the engine exhaust before it exited the duct at the trailing edge of the aircraft, essentially applying Bernoulli's principle of fluid movements to make the aircraft's engine more efficient. Although the Regia Aeronautica (Italian Royal Air Force) was not interested in pursuing development of the Stipa-Caproni, its design was an important step in the development of jet propulsion.
