|The sole XB-28 prototype. Note the remotely operated turrets.|
|The five crew all sat in a pressurized compartment in the forward fuselage.|
|Overall configuration of the XB-28.|
|Engine run up test at Mines Field in the summer of 1942.|
By this point, however, it was realized that despite the outstanding performance of the XB-28, the realities of war showed that medium bombers already in service like the B-25 Mitchell and the Martin B-26 Marauder were most effective at low to medium altitudes flying interdiction missions where pressurization wasn't necessary. In the Pacific, B-25s equipped with extra forward firing machine guns were becoming very effective low level anti-shipping weapons while in the European theater, B-25s and B-26s operated most effectively at medium altitude (though some low level anti-shipping missions were flown in the Mediterranean against Axis vessels along the French and Italian coasts). The final nail in the XB-28's coffin was the Douglas product that was also first flown at Mines Field just a few months after the XB-28's maiden flight. The prototype Douglas XA-26 Invader first flew on 10 July 1942. It used the same engines as the XB-28, carried the same bomb load, but lacked pressurization which made it simpler to build and it only had a crew of three versus the crew of five on the XB-28. The sole XB-28 prototype was still at Wright Field at the time of the program's cancellation- it had its outer wings removed and sat out the war as a ground test article for pressurization tests before being scrapped.
Anigrand released a 1/72 resin kit of the XB-28 and this page has a great series of photos of a completed model that show the overall configuration of the XB-28. Take note of the hemispheric scanning bubbles on the upper lateral fuselage ahead of the wing for the gunners as well as the streamlined twin fairings above and below the forward fuselage for the sighting system to control the remote turrets.
Source: American Bomber Aircraft Development in World War 2 by Bill Norton. Midland Publishing, 2012, pp 66-69. Photos: USAF Museum, Anigrand