Boeing B-47B Rocket-Assisted Take Off: World's 1st Swept-Wing bomber HD Strategic Air Command (1955)

RATO rocket-assisted take off of Boeing B-47B - Black smoke from engines indicates water-methanol injection is in use
SAC B-47s, the world's first swept-wing bomber
The Boeing B-47 Stratojet (Boeing company designation Model 450) 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.

The Boeing B-47 Stratojet gets a secondary role in Paramount's 1955 film Strategic Air Command (SAC), starring James Stewart, as the new jet that is nothing like the old Convair B-36 he is used to.[135] The film features good aerial footage of both the B-47 and the B-36. The majority of B-47 scenes were filmed at MacDill Air Force Base, Florida, using aircraft from the 306th Bombardment Wing.

Development of the B-47 can be traced back to a requirement expressed by the United States Army Air Forces (USAAF) 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.

During 1951, the B-47 entered operational service with the United States Air Force's Strategic Air Command (SAC), becoming a mainstay of its bomber strength by the late 1950s. Over 2,000 were manufactured to meet the Air Force's demands, driven by the tensions of the Cold War. The B-47 was in service as a strategic bomber until 1965, at which point it had largely been supplanted by more capable aircraft, such as the Boeing B-52 Stratofortress. The B-47 was also adapted to perform a number of other roles and functions, including photographic reconnaissance, electronic intelligence, and weather reconnaissance. While never seeing combat as a bomber, reconnaissance RB-47s would occasionally come under fire near or within Soviet air space. The type remained in service as a reconnaissance aircraft until 1969. A few served as flying testbeds up until 1977

Engines and performance
B-47B using JATO bottles to reduce takeoff distance

During the late 1940s, the bomber was hailed as the fastest of its class in the world.[42] The first prototypes were fitted with General Electric J35 turbojets, the production version of the TG-180, with 3,970 lbf (17.7 kN) of thrust. Early jet engines did not develop good thrust at low speeds, so to assist take off when heavily loaded, the B-47 had provisions for fitting solid-fuel rocket-assisted takeoff (RATO) rockets, each generating roughly 1,000 lbf (4.4 kN) of static thrust.[43] Early aircraft had mounts for nine RATO units built into each side of the rear fuselage, arranged in three rows of three bottles. Most of the space within the upper fuselage was taken up by self-sealing fuel tanks, the wing having been deemed unsuitable for storing fuel.[44]

The performance of the Model 450 was projected to be so good that the bomber would be as fast as fighters then on the drawing board;[45] thus the only defensive armament was to be a tail turret with two .50 in (12.7 mm) AN/M2 Browning machine guns, which would in principle be directed by an automatic fire-control system.[46] The two XB-47s were neither fitted with combat equipment nor tail turrets as they were engineering and flight test aircraft only. The total bombload capacity was to be 25,000 lb (11 t). Production aircraft were to be equipped with modern electronics for navigation, bombing, countermeasures and turret fire control. Navigation was more difficult than on earlier aircraft due to the higher speed involved

One problem with the aircraft was that at higher altitudes, where the pure turbojet engines could produce good fuel economy, the wing was very compromised. At the top of the B-47's envelope, about 35,000 feet (11,000 m), it was in "coffin corner".[48] That means that at this level, which produced the most range at most weights due to fuel consumption, there was an envelope of 5 kn (9.3 km/h) between maximum mach and stall speed. For the B-47 to cross the Atlantic Ocean, it had to be flown this high. Due to its rudimentary autopilot, the pilot had to leave it turned off and spend up to eight hours diligently mon