Boeing XB-38 Flying Fortress The XB-38 was destroyed and the project was canceled, in part because the V-1710 engines were needed for other projects such as the Lockheed P-38 Lightning, Bell P-39 Airacobra, Curtiss P-40 Warhawk, North American P-51A Mustang, and Bell P-63 Kingcobra fighters. Boeing XB-38 Flying Fortress The XB-38 Flying Fortress was a single example conversion of a production B-17E Flying Fortress, testing whether the Allison V-1710 V type engine could be substituted for the standard Wright R-1820 radial engine during early World War II. The XB-38 was the result of a modification project undertaken by Boeing and Vega (a subsidiary of
RAF Bomber Command aircrew of World War II aircrew were given the task of flying a required number of operations, an "operational tour", usually of about 30 operations (missions in USAAF terminology). On completion of an operational tour the airman (and often his complete crew as they tended to remain very tight-knit, always flying together) would be "screened" (taken off operational flying) and split up as they received their future postings which would frequently be serving at Operational Training Units or Heavy Conversion Units preparing the next groups of young bomber crews for their postings to operational squadrons. Between March 1943 and the early summer of 1944 the