The Pratt & Whitney R-1340 Wasp Engine was built to US Navy (USN) specifications for a 400 hp engine weighing less than 650 lb. It had a conventional layout but introduced a significant innovation in the form of a forged aluminum crankcase. The R-1340 Wasp first ran in late 1925 and was quickly developed to 380 hp, rising to 425 hp by the third version.  This prompted the USN to order 200 engines. By the beginning of World War II, the R-1340 had a 600 hp take-off power rating at 2,250 rpm and a weight of 684 lb. This version was widely used in the T6 Texan training aircraft, which was capable of 205 mph and a ceiling of 21,500 ft. One of the most successful aircraft engines ever designed, there were 34,966 R-1340 Wasps built between 1925 and 1960.