The XB-28 (NAA model NA-63) was originally conceived as a high altitude version of the B-25 medium bomber; however, the final design of the aircraft was entirely new and bore little resemblance to the Mitchell. The aircraft featured a cylindrical pressurized fuselage and a conventional tail. The XB-28 could carry a 4,000-pound bomb load as high as 34,600 feet. The armament consisted of three remote-controlled and remotely-sighted power turrets with a pair of .50-cal. machine guns in each.
Although the XB-28 was a successful design, the aircraft never went into production. One reason for this was high-altitude bombing was too susceptible to errors caused by wind, cloud cover, etc., especially in the Pacific Theater of Operations. Another was the increasing effectiveness of medium bombers at low and medium levels along with improved tactics. Finally, the performance gains were not considered great enough to interrupt production of proven combat models.
Performance was impressive enough for the Army to order a second prototype built as a high-altitude photo reconnaissance aircraft. This plane was designated XB-28A but never progressed past the prototype phase.
High-altitude medium bomber
High-altitude photo recon aircraft
TECHNICAL NOTES: Armament: Six .50-cal. machine guns and 4,000 lbs. of bombs Engines: Two Pratt & Whitney R-2800-27 Double Wasp radials of 2,000 hp each (takeoff power) Maximum speed: 372 mph Cruising speed: 255 mph Range: 2,040 miles Service ceiling: 33,500 ft. Span: 72 ft. 7 in. Length: 56 ft. 5 in. Height: 14 ft. 0 in. Weight: 35,740 lbs. (gross)
Crew: Five Serial numbers: 40-3056 (XB-28) and 40-3058 (XB-28A)