This restricted War Department “official training film” was produced in 1940 by the United States Army Signal Corps in collaboration with the Chief of the Air Corps. The purpose is made clear within the first 30 seconds of the black-and-white picture, thanks to a title card: “This film presents some elementary principles of carburetor functioning, the understanding of which will assist the pilot in making proper use of the carburetor and effecting good engine performance. Improper handling of carburetors is conductive to engine failure.” With that, the decidedly mundane and straightforward film launches into “Aircraft Engines — Part 3 — Carburetion” and an engine diagram, accompanied by a voiceover describing the operation and function of a carburetor in painstaking detail. The announcer also explains the function of such pieces as intake pipes, the intake manifold, and the exhaust manifold, all of which are accompanied by illustrated diagrams. At mark 03:40, the viewer is told the correct pound mixture (Gasoline 1 Air 15) for the combustion of gasoline, along with a discussion on the rate of burning and imperfect distribution of fuel to the various cylinders (caused by excess oxygen), which is illustrated beginning at mark 05:18. Mark 06:27 offers the viewer a graph along with a discussion of an aircraft’s potential horsepower based on its fuel mixture ratio. “Maximum power is obtained with a mixture of 12 to 14 parts of air to one of fuel,” it is noted. “Too lean a mixture makes an engine too hot.” By mark 10:15, the presentation continues with a discussion of various systems including main metering, idling, accelerating, economizer, and mixture control. What follows, starting at mark 11:00, is a detailed discussion of the main metering system, and continues with in-depth discussion on the other systems previously introduced in the film and continues through the end of the film.