was revised. Referred to as the "Cheyenne" configuration (after the modification center where it was introduced, the United Airlines Modification Center in Cheyenne, Wyoming), its guns were mounted in a new turret with a reflector sight and a much greater field of fire. Some 8,680 were built, and dozens were converted for several different uses: CB-17G: Troop transport version, capable of carrying 64 troops. DB-17G: Drone variant DB-17P: Drone director JB-17G: Engine test-bed MB-17G: Missile launcher QB-17L: Target drone QB-17N: Target drone RB-17G: Reconnaissance variant SB-17G: Rescue version, later redesignated B-17H: Featured A-1 lifeboat under fuselage. After World War II, armament on the B-17Hs was removed; it was reinstated when the Korean War began. TB-17G: Special duty training version TB-17H: Training version of B-17H VB-17G: VIP transport PB-1: This designation was given to one B-17F and one B-17G. They were used by the U.S. Navy for various test projects. PB-1G: This designation was given to 17 B-17Gs used by U.S. Coast Guard as air-sea rescue aircraft. PB-1W: This designation was given to 31 B-17Gs used by the U.S. Navy as the first airborne early warning aircraft (AWACS). Fortress III Eighty-five B-17Gs were transferred to the RAF, where they received the service designation Fortress III. Three were assigned to Coastal Command in the Azores and were fitted with radar before being reused by meteorological survey squadrons. The rest were operated from February 1944 by two squadrons of Bomber Command's No. 100 Group RAF at RAF Sculthorpe, where they were used to carry electronic countermeasures to confuse and jam enemy radar in support of bombing missions. These Fortress III (SD) would carry an extensive array of equipment: the Monica tail-warning receiver, the Jostle VHF jammer, airborne Grocer air-interception jammers, Gee and LORAN for navigation, and the H2S radar in the lower nose position, replacing the chin turret. They were also used as decoys during night bombing attacks. Fortress IIIs took part in various such operations until the units were disbanded in July 1945. XB-38 The XB-38 was a modification project undertaken primarily by the Vega division of Lockheed on the ninth B-17E built. Its primary purpose was testing the feasibility of liquid-cooled Allison V-1710-89 engines. It was meant as an improved version of the B-17, and a variant that could be used if the Wright R-1820 engine became scarce. Completing the modifications took less than a year, and the XB-38 made its