Martin XB-48

The Martin XB-48 was an American medium jet bomber developed in the mid-1940s. It competed with the Boeing B-47 Stratojet, which proved to be a superior design, and was largely considered as a backup plan in case the B-47 ran into development problems. It never saw production or active duty, and only two prototypes, serial numbers 45-59585 and 45-59586, were built.

Design and development

In 1944, the U.S. War Department was aware of aviation advances in Germany and issued a requirement for a range of designs for medium bombers weighing from 80,000 pounds (36,000 kg) to more than 200,000 pounds (91,000 kg). Other designs resulting from this competition, sometimes nicknamed "The Class of '45", included the North American XB-45 and the Convair XB-46.

All of the bombers comprising the Class of '45 were transitional aircraft, which combined the power of turbojets with the aeronautical design of World War II, notably the unswept wings and tail surfaces. The XB-48 was no exception, as its round fuselage and unswept wings showed a distinct influence of Martin's B-26 Marauder medium bomber.

At the time of the XB-48's design, jet propulsion was still in its infancy. While the B-26 had enough thrust with two massive 18-cylinder radial engines, the XB-48 needed no less than six of the low-thrust turbojets available at the time. And, although it appeared superficially to have six separate engine nacelles – that is, three under each wing – the XB-48 actually had only two, unusually wide, three-engined nacelles.