Pratt & Whitney X-1800
The Pratt & Whitney X-1800 was the project of a US water-cooled 24-cylinder H-engine . The intended military designation was Pratt & Whitney H-2600. It was intended for the Vultee XP-54 , Curtiss-Wright XP-55 , Northrop XP-56 and Lockheed XP-49 aircraft and had a projected output of 1850 to 2200 hp with a displacement of 42.6 liters. It was equipped with turbochargers to ensure good altitude performance .
The engine was to be mass-produced from 1942. However, as early as 1940, when the test bench runs were not passed, it became apparent that there was considerable further development need. Pratt & Whitney then decided to focus on radial engines and stopped developing the X-1800 in October 1940.