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Boeing B-47 Stratojet

History of the Boeing B-47 Stratojet

Boeing's swept-wing B-47 stratojet was in many ways a milestone in American bomber design. The system pioneered the traditional bomber layout of many of today's bombers and delivers performance unmatched to date.

The system is a postwar/Cold War aircraft design that embodies the advanced penetration systems that the U.S. military is seeking to enable nuclear strikes deep within enemy territory.

Proposed as early as 1945 (the last year of WWII), the XB-47 beat the extraordinary flying-wing design proposed by Northrop Aerospace. Two XB-47 prototypes were built as SN 46-065 and 46-066. Each prototype was initially powered by six Allison J35-GE-7 turbojets mounted under each swept wing, with both prototypes eventually powered by General Electric J47-GE-3 turbojets. The engines were split into pairs and single mounted as separate nacelles. The plane was flown by a crew of three, including two pilots and a bombardier.

From there, the first XB-47 flew for the first time in 1947.

The B-47 is massive, uses no less than 18 rocket boosters to aid its flight, and displays a dizzying amount of power and smoke on takeoff. In order to shorten the runway landing distance, the Stratojet employed a drag chute to significantly slow down the fuselage on landing - a practice still used today in modern aircraft types.

Impressive inherent range means the B-47 is ideal for forward and reverse operating bases in Europe and the United States. Until precise surface-to-air missile systems became the norm, the B-47 was really only threatened by the Soviet Union's newest delta-wing interceptors.

Since the rear of each bomber was vulnerable to interceptors, the B-47 was fitted with two remote-controlled 12.7mm machine guns (later upgraded to 20mm) in its rear. As for its exterior design, the B-47 is conventional, with a forward-mounted cockpit (including a glass nose cone), a cylindrical fuselage, and a conventional empennage to which a vertical fin and corresponding horizontal plane are attached. At rest, the aircraft assumes a pronounced "nose up" position, which requires the use of a taxi platform to board the crew. The landing gear consists of a pair of twin-tire landing gear legs along the centerline of the fuselage and a pair of smaller single-tire legs below the internal engine nacelles.

With the advent of the improved Soviet surface-to-air missile (SAM) system, the B-47 was forced to take on more low-altitude bombing missions and was therefore optimized for the rigors of this flight. Internal ammunition was finalized as the B-47E model, which could carry 25,000 lbs of ammunition in the form of 2 x Mk 15 nuclear throwing bombs or up to 28 x 500 lb conventional throwing bombs.

The B-47A was the first production variant to be used as an evaluation aircraft, with 10 examples in total. The first unit was delivered in December 1950, following the initial XB-47 prototypes, which were equipped with 5,200 lbf J47-GE-11 series turbojets. At least four are equipped with autopilots and their navigational attack systems and radars. Ejection seats were awarded to both the pilot and the bombardier - the former with the seat up, the latter with the seat down.

The B-47A model remained in service until 1952, followed by the improved B-47B model.

The B-47B was the first true operational form of the Stratojet, and the USAF ordered about 87 of them. The first flight took place on April 26, 1951, and the USAF desperately needed to deploy the B-47 to ensure a total of 399 B-47Bs were delivered.

The first production runs were equipped with the J47-GE-11 engine, followed by deliveries of the J47-GE-23 series turbojets that received 5,800 lbf. Due to the short range of the B-47 series so far, an aerial refueling arm was added on the right side of the nose to increase range, as well as a jettisonable external fuel tank between the outboard and inboard engine pairings.

Added glass nose cone that eliminates Bombardier. The resulting changes resulted in the final product being heavier than the XB-47 and B-47A that preceded it, and some weight-saving measures were takenincluding the removal of the ejection seat.

There exists a specialized reconnaissance version of the B-47 - aptly named the RB-47 - with extensive electronic countermeasures (ECM) equipment onboard. The similarities between the B-47 and RB-47 are consistent, all RB-47s can be modified to carry bombs if necessary. Despite the inherently limited internal carrying capacity of the base aircraft - both ammunition and electronics - the B-47 made up for this in numbers, with more than 2,000 prototypes produced in one form or another - many ended up Served in Strategic Air Command (Sac). The RB-47B consists of 24 B-47B airframes modified for reconnaissance missions - these airframes are mounted in the forward bomb bay with 8 internal cameras.

It should be noted that these airframes are only suitable for daytime operations.

The TB-47B is a modified version of the B-47B production trainer. At least 66 B-models have undergone such modifications, which saw their rear defense weapons lost, as well as the addition of a fourth position for the instructor.

The Stratojet existed in several short-lived forms, including the YDB-47B missile launch platform, the WB-47B weather reconnaissance platform, the KB-47B tanker, and the Air Canada CL-52, designed to be used as a test aircraft Orenda Iroquois- The engine that powered their (eventually) cancelled Avro CF-105 Arrow interceptor. Likewise, a B-47E was loaned to the U.S. Navy to test the GE TF34-2 turbofan engine that would be used in the Lockheed S-3 Viking anti-submarine aircraft and was designated NB-47E. There are several specialized ECM conversion models known by their "E" designations, such as EB-47E, EB-47E (TT), and ETB-47E.

The JB-47E was used to test early fly-by-wire systems, while the QB-47E was a radio-controlled target drone.

Boeing also proposed a four-engine variant of the B-47, powered by four Allison J35-A-23 turbojets, each with 10,090 thrust. Engine problems eventually delayed this Stratojet version, and it was eventually cancelled in December 1952.

The XB-47D was an experimental Wright turboprop platform for the U.S. Air Force, but was never further developed as it failed to outperform the original turbojet.

The B-47C and B-47D designations were assigned to specialized B-47 variants that were never selected by the USAF for serial production.

The final B-47 became the B-47E model. The first flight was recorded on January 30, 1953, with a J47-GE-25 turbojet engine rated at 5,970 lbf. These were then upgraded to J47-GE-25A series engines with a water-methanol injection system for extra boost on takeoff.

The original 18 JATO packets are further increased to 33, which can be discarded after use. The ejection seat was brought back folded. The defensive rear weapons are upgraded to a pair of 20mm cannons. The second B-47E production module was little different from the first, while the third added an electronic countermeasures (ECM) kit and chaff dispenser, the former known as a bulge under the fuselage.

The fourth production area features a strengthened fuselage and landing gear, and increased internal fuel capacity for greater range. The internal bomb load was also slightly increased (25,000 lbs), but was smaller to accommodate the smaller technology of the updated nuclear bomb.

A total of 1,341 prototypes of the B-47E were built, with production at Boeing, Lockheed and Douglas plants.

Like the B-47B before it, the B-47E was converted for reconnaissance missions to become the RB-47E, of which approximately 240 prototypes were built. These are known for their slender head assemblies that can hold up to 11 cameras. Night reconnaissance is now possible with the newer RB-47E.

The B-47E was also converted to the WB-47E for weather reconnaissance, and 34 were produced.

RB-47H is an ELINT platform (ELectronic INtelligence) complemented by another variant called ERB-47H. These are known for the airbag-covered nose and pressurized bomb bay (used as a crew compartment), and for the antenna fairing under the nose of the latter.

The RB-47K was used for weather reconnaissance until 1963. The EB-47L has been used as an airborne communications relay platform since 1963, when total nuclear war broke out.

By 1965, the B-47 program was nearly complete and has now been replaced by the Convair B-58 Hustler and Boeing B-52 Stratofortress series of bombers (both of which are described elsewhere on this site). Although somewhat average in service life, the B-47 made a significant contribution to the U.S.

Air Force's strategic defense and deterrence. Being a capable high- or low-altitude bomber and reconnaissance platform ensured the system's historical stature and paved the way for future American bomber designs that would capitalize on the breakthrough B-47's success.