page_title: Boeing B-47 Stratojet
section_title: Variants
hierarchical_section_title: Boeing B-47 Stratojet / Variants
context_page_description: The Boeing B-47 Stratojet is a retired American long-range, six-engined, turbojet-powered strategic bomber designed to fly at high subsonic speed and at high altitude to avoid enemy interceptor aircraft. The primary mission of the B-47 was as a nuclear bomber capable of striking targets within the Soviet Union.
  Development of the B-47 can be traced back to a requirement expressed by the United States Army Air Forces in 1943 for a reconnaissance bomber that harnessed newly developed jet propulsion. Another key innovation adopted during the development process was the swept wing, drawing upon captured German research. With its engines carried in nacelles underneath the wing, the B-47 represented a major innovation in post-World War II combat jet design, and contributed to the development of modern jet airliners. Suitably impressed, in April 1946, the USAAF ordered two prototypes, designated "XB-47"; on 17 December 1947, the first prototype performed its maiden flight. Facing off competition such as the North American XB-45, Convair XB-46 and Martin XB-48, a formal contract for 10 B-47A bombers was signed on 3 September 1948. This would be soon followed by much larger contracts.
context_section_description: Section source: Baugher.
  XB-47
  Two prototype aircraft, built as Model 450-1-1 and 450-2-2 respectively,(46-065 and 46-066); powered by six Allison J-35-GE-7 turbojet engines for the first flights. The second and subsequent aircraft were built with the specified General Electric J-47-GE-3 engines, which were retrofitted to the first XB-47.
  B-47A
  The first 10 aircraft were designated "B-47A", and were strictly evaluation aircraft, the first delivered in December 1950. While the XB-47s had been built by at Boeing's Seattle plant, all B-47s were built at a government-owned factory in Wichita, Kansas that had previously built B-29s. Their configuration was close to the XB-47. They were fitted with J47-GE-11 turbojets, offering the same 5,200 lbf (23 kN) thrust as the earlier J47-GE-3, and also featured the built-in rocket-assisted-take-off (RATO) bottles. Four were fitted with the K-2 bombing and navigation system (BNS), HD-21D autopilot, an analog computer, APS-23 radar, and a Y-4 or Y-4A bombsight. Two were fitted with the tail turret mounting two 20mm cannons; one of them used an Emerson A-2 fire control system (FCS), another a General Electric A-5 FCS. The eight other B-47As lacked defensive armament.
  The B-47As were fitted with ejection seats. The pilot and copilot ejected upward, while the navigator had a downward ejection seat built by Stanley Aviation. Minimum safe ejection altitude was about 500 ft (150 m). In the 1950s, there were no suitable "dummies" to test ejection seats, thus live people were used. Several volunteers were injured testing the downward ejection seat. The first person to successfully use it was USAF Colonel Arthur M. Henderson who ejected over Choctawhatchee Bay, near Eglin Air Force Base, Florida, on 7 October 1953. Most B-47As were retired by 1952, though one performed flight tests for NACA for a few more years.
  B-47B
  In November 1949, prior to the B-47A's first flight, the USAF ordered 87 B-47Bs, the first operational model. The first flew on 26 April 1951. A total of 399 were built, including eight assembled by Lockheed and 10 assembled by Douglas using Boeing-built parts. To quickly receive B-47s in quantity, the USAF contracted both Lockheed and Douglas for additional production; Lockheed-built aircraft were designated by a "-LM (Lockheed Marietta)" suffix and Douglas-built aircraft given a "-DT (Douglas Tulsa)" suffix. Boeing production was designated by a "-BW (Boeing Wichita)" suffix, except for the Seattle-built XB-47s and B-47As, which had a "-BO" suffix.
  The initial 87 B-47Bs used the same J47-GE-11 engines as the B-47As, subsequent aircraft featured uprated J47-GE-23 turbojets with 5,800 lbf (26 kN) thrust; early production aircraft were later retrofitted. They all had a built-in RATO system, as used on the XB-47 and B-47A, along with full combat systems. Early aircraft retained the K-2 BNS installed on some B-47As, but most featured the K-4A BNS, incorporating an AN/APS-54 warning radar and an AN/APT-5 electronic countermeasures (ECM) system. The K-4A used a periscopic bombsight fitted in the nose, the transparent plexiglas nose cone of the XB-47 and B-47A being replaced by a metal nose cone with four small windows on the left side of the nose and two on the right. Another visible change on the B-47B was a vertical tailplane with a squared-off top instead of a rounded top.
  The bomb bay was shorter than that of the XB-47 and B-47A as nuclear weapons had shrunk in the interim, but the B-47B could carry a larger bombload of up to 18,000 lb (8,200 kg). All B-47Bs carried the tail turret with twin 20 mm (0.79 in) guns and the B-4 radar-guided FCS (Fire Control System). This FCS proved troublesome; on some B-47Bs, it was replaced with an N-6 optical sight. The copilot could swivel his seat to face backward and sight the guns directly. Its limited range was criticized by USAF leadership. Hence an "in-flight refueling (IFR)" receptacle was added to the nose for "flying-boom"-style refueling from KB-50 and KC-97 aircraft, necessitating the plexiglas nose cone's deletion. The B-47B was also fi
caption: A B-47A, hailed by the press as the "fastest bomber in the world" flies near Boeing's Wichita plant, 11 August 1950
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