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Cold War: Boeing B-47 Stratojet

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Cold War: Boeing B-47 Stratojet

B-47 Stratojet

Photograph Courtesy of the US Air Force

B-47E Stratojet - Specifications:

General

  • Length: 107 ft., 1 in.
  • Wingspan: 116 ft.
  • Height: 28 ft.
  • Wing Area: 1,428 sq. ft.
  • Empty Weight: 79,074 lbs.
  • Loaded Weight: 133,030 lbs.
  • Maximum Takeoff Weight: 230,000 lbs.
  • Crew: 3

Performance

  • Maximum Speed: 607 mph
  • Combat Radius: 2,013 miles
  • Rate of Climb: 4,660 ft./min.
  • Service Ceiling: 33,100 ft.
  • Power Plant:6 × General Electric J47-GE-25 turbojets

Armament

  • 2 × 20 mm M24A1 autocannons in a remote controlled tail turret
  • Bombs: 25,000 lbs. of ordnance

  • B-47 Stratojet - Background:

    With World War II raging, both sides commenced research into jet engines. While these initiatives produced early jet fighters such as the Messerschmitt Me 262 and Gloster Meteor, effort also went into developing effective jet-powered bombers. In 1943, the US Army Air Forces requested designs for a jet-powered reconnaissance bomber. Responding, Boeing created the Model 424 which essentially consisted of a scaled-down B-29 Superfortress with four jet engines. A year later, the USAAF formally requested proposals for a jet bomber capable of 550 mph with a range of 3,500 miles. That December, Boeing was one of four companies to offer a design. As testing of the Model 424 had shown it incapable of the required speed, a modified design, the Model 432, was created which placed the four engines in the fuselage. Electing to develop several options, the USAAF directed Convair and North American to pursue four engine designs while Boeing and Martin were to create six-engine aircraft.

    B-47 Stratojet - Design & Development:

    With end of World War II the following year, Boeing engineer George S. Schairer began to study captured German reports regarding the advantages of swept wings. Believing this information could be useful in developing the bomber design, he sent it back to the United States. There the Boeing team elected to alter the Model 432 to incorporate swept wings. Redesignated the Model 448, this aircraft was powered by six engines with two in the forward fuselage and two aft. Shown to the USAAF that September, the reviews were mixed as the service frowned on the fuselage mounted engines due to concerns over fire. Responding, Boeing shifted the engines to the wings with two engines mounted in a twin pod one-third of the way outboard and a third at the wingtip. As the USAAF responded positively to this innovation, Boeing refined the design with the third engine ultimately moving inboard a short distance.

    Dubbed the XB-47, the prototype of the Boeing design featured 35-degree swept wings and was powered by six General Electric J35 turbojets. Due to the thinness of the wings, the aircraft's landing gear was mounted in the fuselage in a tricycle configuration. As the design's projected speed matched or exceeded that of existing and planned fighters, its only defensive armament was a pair of .50 cal. machine guns mounted in a remote-controlled tail turret. Manned by a crew of three, the pilot and copilot sat in a tandem cockpit under a bubble canopy, while the navigator/bombardier occupied a station inside the nose. From this position, a K-series bombsight provided targeting. The first prototype emerged on September 12, 1947, a few days before the US Air Force became a separate service.

    Excited about the new aircraft, the USAAF believed the design had the potential to be revolutionary. On December 17, 1947, the anniversary of Wright Brothers' first flight, the XB-47 first took to the sky with test pilots Robert Robbins and Scott Osler at the controls. As testing moved forward, a canopy malfunction led to Osler's death and necessitated the hiring of famed test pilot Tex Johnston. The following summer, a second prototype, powered by General Electric J47-GE-3 turbojets, commenced testing. Though plagued by minor performance issues, these were corrected and the XB-47 became an excellent performer which proved capable of outrunning its chase planes. In final testing, the XB-47 defeated the Martin XB-48 and a contract for ten aircraft was issued on September 3, 1948.

    B-47 Stratojet - Operational History:

    Final development of the aircraft continued over the next three years and in 1951 the first B-47B Stratojets were introduced to units of General Curtis Lemay's Strategic Air Command. The first line of the United States' nuclear defense, B-47 units were tasked with penetrating Soviet air defenses in the case of war and delivering nuclear weapons against a variety of targets. As a result, squadrons generally operated from forward bases in Great Britain, Greenland, Guam, Alaska, and Morocco. Due to the aircraft's strategic mission, it did not see action in the Korean War which was ongoing at the time of its introduction. The first two years of the B-47's career saw it continue to suffer from problems relating to takeoff/landing and low-altitude performance. Addressing these with the definitive B-47E, Boeing also added more powerful engines, improved avionics, ejection seats, and a stronger defensive armament. In addition, the aircraft's built-in jet-assisted takeoff (JATO) system was eliminated in favor of an expendable, external JATO rack.

    Fully operational by 1953, the B-47 became a favorite of pilots who appreciated its fighter-like controls and performance. Due to their nuclear deterrence role, B-47 squadrons typically operated on one-third alert. This meant that one third of the aircraft were always armed, fueled, and ready for an immediate strike against the Soviet Union. By the late 1950s, the type began to suffer a series of wing failures due to fatigue and stress on the airframes. This led to a large-scale refit program in 1958 to strengthen the B-47's wing mountings. That same year, a B-47 famously lost an unarmed Mark 15 nuclear bomb after sustaining damage during a training exercise with a F-86 Sabre off Tybee Island, GA. Though the B-47 safely returned to base, the bomb was never located. In 1959, the B-47 began to be phased out in favor of the new, larger Boeing B-52 Stratofortress. This transition continued until the last B-47 departed frontline service in 1965. The type continued in secondary roles with the USAF until 1969 and the US Navy until 1976.

    B-47 Stratojet - Reconnaissance Variants:

    In addition to the bomber variants of the B-47, several reconnaissance types were also developed. The initial model, the RB-47B, commenced overflights of Soviet airspace in October 1952. These flights continued into the mid-1960s and RB-47s frequently were forced evade Soviet and North Korean fighters such as the MiG-15 and MiG-17. In the course of these operations, three aircraft were lost. During the early years of the Vietnam War, some RB-47s saw service over Southeast Asia where they performed a variety of special, electronic warfare roles. Retired in 1967, the type was replaced by Boeing RC-135s.

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