The Pratt & Whitney R-2800 is a twin-row, 18-cylinder, air-cooled radial aircraft engine with a displacement of 2,800 in³ (46 L), and is part of the long-lived Wasp family. The R-2800 is considered one of the premier radial piston engines ever designed and is notable for its widespread use in many important American and foreign aircraft during and after World War II. Although much smaller than the world’s only other modern eighteen cylinder engine, the 3,442 cu in. (56.4 L) Gnome-Rhone 18L, it was more powerful. During the war years, Pratt & Whitney continued to develop new ideas to upgrade this already powerful workhorse, most notably water injection for takeoff in cargo and passenger planes and to give emergency power in combat.
Heat dissipation was a problem for radial engines. This meant that for the R-2800, the cast or forged cooling fins of previous designs had to be discarded. Cooling fins needed to be so thin and of such a fine pitch that they had to be machined from a solid metal forged head. The fins were cut together by a gang of automatically guided milling saws that rose and fell following the head contour. The Double Wasp’s efficient baffling system directed the flow of cooling air and was considered better than the arrangements on the Ranger inline air-cooled engines.