6In 1944, the Army issued requirements for a jet-propelled medium bomber which eventually spawned four aircraft. These were the North American B-45 (see Air Force Legends 224), Convair XB-46 (see Air Force Legends 221), Boeing B-47, and the Martin XB-48 the sudject of this book. Specifications were somewhat general and called for an 80,000 to 200,000 lb aircraft with a 45,000 ft ceiling, range of 3,000 miles and a maximum speed of 550 mph. The Martin designwas a three-place, straight wing, six-jet, high wing, all metal medium bomber. The unique landing gear developed by Martin consisted of dual wheel main gear located in tandem with outrigger single type wing gear. This gear arrangement allowed for a huge continuance bomb bay with quick acting doors capable of carrying a 22,000 lb "Grand Slam" bomb. The other unique feature of the airplane was instalation of the six J35 engines. Each engine (three on a wing) had its own squarish nacelle seperated with by-pass ducts framed by a thin airfoil plate across the bottom of the three engines mounted under each wing. Two aircraft were produced and were tested at the Naval air Test Center, NAS Patuxent River, MD, about 70 miles from Martin's New River plant before being accepted by the Air Force. The XB-48 was not accepted for production, those contracts going to the B-45 and B-47. The second XB-48 finished its life as a landing pilot training plane for future B-47 pilot's.