page_title: Boeing B-47 Stratojet
section_title: Early years
hierarchical_section_title: Boeing B-47 Stratojet / Operational history / Early years
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: The USAF Strategic Air Command operated multiple B-47 models (B-47s, EB-47s, RB-47s and YRB-47s) from 1951 through 1965. Upon entry to service, its performance was closer to that of contemporary fighters than SAC's extant B-36 Peacemaker bomber, setting multiple records with ease. It handled well in flight, the controls having a fighter-like light touch. The large bubble canopy enhanced the flying crew's vision and gave a fighter-like feel, but also caused internal temperature variations for the crew. The three-man crew consisted of the commander, copilot, and a navigator/bombardier or a crew chief.
  In 1953 the B-47 became operational. It was sluggish on takeoff and too fast on landings, an unpleasant combination. If landed at the wrong angle, the B-47 would "porpoise", bouncing fore-and-aft. If the pilot did not lift off for another go-around, instability would quickly cause it to skid onto one wing and cartwheel. Because the wings and surfaces flexed in flight, low-altitude speed restrictions were necessary to ensure effective flight control. The B-47 was regarded as a maintenance "hog". General reliability was good, the only major issuing relating to the avionics, typical of the vacuum tube technology used and the placement of equipment outside the pressurized crew compartment. Much work was done to improve avionics reliability, but avionics remained troublesome throughout the B-47's operational life.
  Starting in 1950, several models of the B-47 included a fuel tank inerting system, in which dry ice was sublimed into carbon dioxide vapor while the fuel pumps operated or while the in-flight refueling system was in use. The carbon dioxide was pumped into both the fuel tanks and the fuel system to ensure low oxygen levels throughout. It was implemented largely to reduce the probability of an explosion from static electricity discharges.
  Initial mission profiles included the loft bombing of nuclear weapons. As the training for this imposes repeated high stress on the aircraft, the airframe lifetime would have been severely limited by metal fatigue, and this maneuver was eliminated. Improved training led to a good safety record, and few crews felt the aircraft was unsafe or too demanding, but apparently there were some aircrews who had little affection for the B-47. Crew workload was high, having only three crew members to operate it. Boeing's B-52 Stratofortress, in contrast, generally had six crewmen, five officers and one enlisted, with more internal cabin space.
caption: B-47Es on a SAC base flight line
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