Boeing B-52 Stratofortress

B-52 Stratofortress
Aerial top/side view of gray B-52H flying over barren desert land.
A B-52H from Barksdale AFB flying over desert
RoleStrategic bomber
National originUnited States
ManufacturerBoeing
First flight15 April 1952; 67 years ago (1952-04-15)
IntroductionFebruary 1955
StatusIn service
Primary usersUnited States Air Force
NASA
Produced1952–1962
Number built744[1]
Unit cost
B-52B: US$14.43 million (1956);[2]($104 million in 2018)[3]
B-52H: US$9.28M (1962);[4] ($60.2 million in 2018)[3]
Developed intoConroy Virtus

The Boeing B-52 Stratofortress is an American long-range, subsonic, jet-powered strategic bomber. The B-52 was designed and built by Boeing, which has continued to provide support and upgrades. It has been operated by the United States Air Force (USAF) since the 1950s. The bomber is capable of carrying up to 70,000 pounds (32,000 kg) of weapons,[5] and has a typical combat range of more than 8,800 miles (14,080 km) without aerial refueling.[6]

Beginning with the successful contract bid in June 1946, the B-52 design evolved from a straight wing aircraft powered by six turboprop engines to the final prototype YB-52 with eight turbojet engines and swept wings. The B-52 took its maiden flight in April 1952. Built to carry nuclear weapons for Cold War-era deterrence missions, the B-52 Stratofortress replaced the Convair B-36. A veteran of several wars, the B-52 has dropped only conventional munitions in combat. The B-52's official name Stratofortress is rarely used; informally, the aircraft has become commonly referred to as the BUFF (Big Ugly Fat Fucker/Fella).[7][8][9][Note 1]

The B-52 has been in active service with the USAF since 1955. As of December 2015, 58 were in active service with 18 in reserve.[11] The bombers flew under the Strategic Air Command (SAC) until it was disestablished in 1992 and its aircraft absorbed into the Air Combat Command (ACC); in 2010 all B-52 Stratofortresses were transferred from the ACC to the newly created Air Force Global Strike Command (AFGSC). Superior performance at high subsonic speeds and relatively low operating costs have kept the B-52 in service despite the advent of later, more advanced aircraft, including the Mach 2+ B-58 Hustler, the canceled Mach 3 B-70 Valkyrie, the variable-geometry B-1 Lancer, and the stealth B-2 Spirit. The B-52 completed sixty years of continuous service with its original operator in 2015. After being upgraded between 2013 and 2015, it is expected to serve into the 2050s.[Note 2]

Development

Origins

Models 462 (1946)[16] to 464–35 (1948)[16]
Models 464-49 (1949)[16] to B-52A (1952)

On 23 November 1945, Air Materiel Command (AMC) issued desired performance characteristics for a new strategic bomber "capable of carrying out the strategic mission without dependence upon advanced and intermediate bases controlled by other countries".[17] The aircraft was to have a crew of five or more turret gunners, and a six-man relief crew. It was required to cruise at 300 mph (260 knots, 480 km/h) at 34,000 feet (10,400 m) with a combat radius of 5,000 miles (4,300 nautical miles, 8,000 km). The armament was to consist of an unspecified number of 20 mm cannon and 10,000 pounds (4,500 kg) of bombs.[18] On 13 February 1946, the Air Force issued bid invitations for these specifications, with Boeing, Consolidated Aircraft, and Glenn L. Martin Company submitting proposals.[18]

On 5 June 1946, Boeing's Model 462, a straight-wing aircraft powered by six Wright T35 turboprops with a gross weight of 360,000 pounds (160,000 kg) and a combat radius of 3,110 miles (2,700 nmi, 5,010 km), was declared the winner.[19] On 28 June 1946, Boeing was issued a letter of contract for US$1.7 million to build a full-scale mockup of the new XB-52 and do preliminary engineering and testing.[20] However, by October 1946, the Air Force began to express concern about the sheer size of the new aircraft and its inability to meet the specified design requirements.[21] In response, Boeing produced Model 464, a smaller four-engine version with a 230,000 pound (105,000 kg) gross weight, which was briefly deemed acceptable.[21][22]

Subsequently, in November 1946, the Deputy Chief of Air Staff for Research and Development, General Curtis LeMay, expressed the desire for a cruising speed of 400 miles per hour (345 kn, 645 km/h), to which Boeing responded with a 300,000 lb (136,000 kg) aircraft.[23] In December 1946, Boeing was asked to change their design to a four-engine bomber with a top speed of 400 miles per hour, range of 12,000 miles (10,000 nmi, 19,300 km), and the ability to carry a nuclear weapon; in total, the aircraft could weigh up to 480,000 pounds (220,000 kg).[24] Boeing responded with two models powered by T35 turboprops. The Model 464-16 was a "nuclear only" bomber with a 10,000 pound (4,500 kg) payload, while the Model 464-17 was a general purpose bomber with a 9,000 pound (4,000 kg) payload.[24] Due to the cost associated with purchasing two specialized aircraft, the Air Force selected Model 464-17 with the understanding that it could be adapted for nuclear strikes.[25]

In June 1947, the military requirements were updated and the Model 464-17 met all of them except for the range.[26] It was becoming obvious to the Air Force that, even with the updated performance, the XB-52 would be obsolete by the time it entered production and would offer little improvement over the Convair B-36 Peacemaker; as a result, the entire project was postponed for six months.[27] During this time, Boeing continued to perfect the design, which resulted in the Model 464-29 with a top speed of 455 miles per hour (395 kn, 730 km/h) and a 5,000-mile range.[28] In September 1947, the Heavy Bombardment Committee was convened to ascertain performance requirements for a nuclear bomber. Formalized on 8 December 1947, these requirements called for a top speed of 500 miles per hour (440 kn, 800 km/h) and an 8,000 mile (7,000 nmi, 13,000 km) range, far beyond the capabilities of 464–29.[27][29]

The outright cancellation of the Boeing contract on 11 December 1947 was staved off by a plea from its president William McPherson Allen to the Secretary of the Air Force Stuart Symington.[30] Allen reasoned that the design was capable of being adapted to new aviation technology and more stringent requirements.[31] In January 1948 Boeing was instructed to thoroughly explore recent technological innovations, including aerial refueling and the flying wing.[32] Noting stability and control problems Northrop was experiencing with their YB-35 and YB-49 flying wing bombers, Boeing insisted on a conventional aircraft, and in April 1948 presented a US$30 million (US$313 million today[33]) proposal for design, construction, and testing of two Model 464-35 prototypes.[34] Further revisions during 1948 resulted in an aircraft with a top speed of 513 miles per hour (445 kn, 825 km/h) at 35,000 feet (10,700 m), a range of 6,909 miles (6,005 nmi, 11,125 km), and a 280,000 pounds (125,000 kg) gross weight, which included 10,000 pounds (4,500 kg) of bombs and 19,875 US gallons (75,225 L) of fuel.[35][36]

Design effort

XB-52 Prototype on flight line (X-4 in foreground). Note original tandem-seat "bubble" style canopy, similar to Boeing's earlier B-47 Stratojet.
Side view of YB-52 bomber, still fitted with tandem cockpit, in common with other jet bombers in US service, such as the B-45 Tornado, B-47 Stratojet and B-57 Canberra

In May 1948, AMC asked Boeing to incorporate the previously discarded, but now more fuel-efficient, jet engine into the design.[37] That resulted in the development of yet another revision—in July 1948, Model 464-40 substituted Westinghouse J40 turbojets for the turboprops.[38] The Air Force project officer who reviewed the Model 464-40 was favorably impressed, especially since he had already been thinking along similar lines. Nevertheless, the government was concerned about the high fuel consumption rate of the jet engines of the day, and directed that Boeing still use the turboprop-powered Model 464-35 as the basis for the XB-52. Although he agreed that turbojet propulsion was the future, General Howard A. Craig, Deputy Chief of Staff for Material, was not very enthusiastic about a jet-powered B-52, since he felt that the jet engine had not yet progressed sufficiently to permit skipping an intermediate turboprop stage. However, Boeing was encouraged to continue turbojet studies even without any expected commitment to jet propulsion.[39][40]

On Thursday, 21 October 1948, Boeing engineers George S. Schairer, Art Carlsen and Vaughn Blumenthal presented the design of a four-engine turboprop bomber to the chief of bomber development, Colonel Pete Warden. Warden was disappointed by the projected aircraft and asked if the Boeing team could come up with a proposal for a four-engine turbojet bomber. Joined by Ed Wells, Boeing vice president of engineering, the engineers worked that night in The Hotel Van Cleve in Dayton, Ohio, redesigning Boeing's proposal as a four-engine turbojet bomber. On Friday, Colonel Warden looked over the information and asked for a better design. Returning to the hotel, the Boeing team was joined by Bob Withington and Maynard Pennell, two top Boeing engineers who were in town on other business.[41]

By late Friday night, they had laid out what was essentially a new airplane. The new design (464–49) built upon the basic layout of the B-47 Stratojet with 35-degree swept wings, eight engines paired in four underwing pods, and bicycle landing gear with wingtip outrigger wheels.[42] A notable feature of the landing gear was the ability to pivot both fore and aft main landing gear up to 20° from the aircraft centerline to increase safety during crosswind landings (allowing the aircraft to "crab" or roll with a sideways slip angle down the runway).[43] After a trip to a hobby shop for supplies, Schairer set to work building a model. The rest of the team focused on weight and performance data. Wells, who was also a skilled artist, completed the aircraft drawings. On Sunday, a stenographer was hired to type a clean copy of the proposal. On Monday, Schairer presented Colonel Warden with a neatly bound 33-page proposal and a 14-inch scale model.[41] The aircraft was projected to exceed all design specifications.[44]

Although the full-size mock-up inspection in April 1949 was generally favorable, range again became a concern since the J40s and early model J57s had excessive fuel consumption.[45] Despite talk of another revision of specifications or even a full design competition among aircraft manufacturers, General LeMay, now in charge of Strategic Air Command, insisted that performance should not be compromised due to delays in engine development.[46][47] In a final attempt to increase range, Boeing created the larger 464-67, stating that once in production, the range could be further increased in subsequent modifications.[48] Following several direct interventions by LeMay,[49] Boeing was awarded a production contract for thirteen B-52As and seventeen detachable reconnaissance pods on 14 February 1951.[50] The last major design change—also at General LeMay's insistence—was a switch from the B-47 style tandem seating to a more conventional side-by-side cockpit, which increased the effectiveness of the copilot and reduced crew fatigue.[51] Both XB-52 prototypes featured the original tandem seating arrangement with a framed bubble-type canopy (see above images).[52]

Pre-production and production

The YB-52, the second XB-52 modified with more operational equipment, first flew on 15 April 1952 with "Tex" Johnston as pilot.[53][54] During ground testing on 29 November 1951, the XB-52's pneumatic system failed during a full-pressure test; the resulting explosion severely damaged the trailing edge of the wing, necessitating considerable repairs. A two-hour, 21-minute proving flight from Boeing Field, King County, in Seattle, Washington to Larson Air Force Base was undertaken with Boeing test pilot Johnston and Air Force Lieutenant Colonel Guy M. Townsend.[55] The XB-52 followed on 2 October 1952.[56] The thorough development,[Note 3] including 670 days in the wind tunnel and 130 days of aerodynamic and aeroelastic testing, paid off with smooth flight testing. Encouraged, the Air Force increased its order to 282 B-52s.[58]

Aircraft deliveries
 Fiscal
Year
B-52 model   Annual
Total  
  Cumulative
Total  
  A  
[59]
  B  
[2]
  C  
[60]
  D  
[61]
  E  
[62]
  F  
[63]
  G  
[64]
  H  
[4]
1954 3 3 3
1955 13 13 16
1956 35 5 1 41 57
1957 2 30 92 124 181
1958 77 100 10 187 368
1959 79 50 129 497
1960 106 106 603
1961 37 20 57 660
1962 68 68 728
1963 14 14 742
Total 3 50 35 170 100 89 193 102 742 742

Only three of the 13 B-52As ordered were built.[65] All were returned to Boeing, and used in their test program.[59] On 9 June 1952, the February 1951 contract was updated to order the aircraft under new specifications. The final 10, the first aircraft to enter active service, were completed as B-52Bs.[59] At the roll-out ceremony on 18 March 1954, Air Force Chief of Staff General Nathan Twining said:

The long rifle was the great weapon of its day. ... today this B-52 is the long rifle of the air age.[66][67]

The B-52B was followed by progressively improved bomber and reconnaissance variants, culminating in the B-52G and turbofan B-52H. To allow rapid delivery, production lines were set up both at its main Seattle factory and at Boeing's Wichita facility. More than 5,000 companies were involved in the huge production effort, with 41% of the airframe being built by subcontractors.[68] The prototypes and all B-52A, B and C models (90 aircraft)[69] were built at Seattle. Testing of aircraft built at Seattle caused problems due to jet noise, which led to the establishment of curfews for engine tests. Aircraft were ferried 150 miles (240 km) east on their maiden flights to Larson Air Force Base near Moses Lake, where they were fully tested.[70]

As production of the B-47 came to an end, the Wichita factory was phased in for B-52D production, with Seattle responsible for 101 D-models and Wichita 69.[71] Both plants continued to build the B-52E, with 42 built at Seattle and 58 at Wichita,[72] and the B-52F (44 from Seattle and 45 from Wichita).[73] For the B-52G, Boeing decided in 1957 to transfer all production to Wichita, which freed up Seattle for other tasks, in particular, the production of airliners.[74][75] Production ended in 1962 with the B-52H, with 742 aircraft built, plus the original two prototypes.[76]

Upgrades

A proposed variant of the B-52H was the EB-52H, which would have consisted of 16 modified and augmented B-52H airframes with additional electronic jamming capabilities.[77][78] This variant would have restored USAF airborne jamming capability that it lost on retiring the EF-111 Raven. The program was canceled in 2005 following the removal of funds for the stand-off jammer. The program was revived in 2007, and cut again in early 2009.[79]

In July 2013, the Air Force began a fleet-wide technological upgrade of its B-52 bombers called Combat Network Communications Technology (CONECT) to modernize electronics, communications technology, computing, and avionics on the flight deck. CONECT upgrades include software and hardware such as new computer servers, modems, radios, data-links, receivers, and digital workstations for the crew. One update is the ARC-210 Warrior beyond-line-of-sight software programmable radio able to transmit voice, data, and information in-flight between B-52s and ground command and control centers, allowing the transmission and reception of data with updated intelligence, mapping, and targeting information; previous in-flight target changes required copying down coordinates. The ARC-210 allows machine-to-machine transfer of data, useful on long-endurance missions where targets may have moved before the arrival of the B-52. The aircraft will be able to receive information through Link-16. CONECT upgrades will cost $1.1 billion overall and take several years. Funding has been secured for 30 B-52s; the Air Force hopes for 10 CONECT upgrades per year, but the rate has yet to be decided.[80]

Weapons upgrades include the 1760 Internal Weapons Bay Upgrade (IWBU), which gives a 66 percent increase in weapons payload using a digital interface (MIL-STD-1760) and rotary launcher. IWBU is expected to cost roughly $313 million.[80] The 1760 IWBU will allow the B-52 to carry eight[81] JDAM 2000 lb bombs, AGM-158B JASSM-ER cruise missile and the ADM-160C MALD-J decoy missiles internally. All 1760 IWBUs should be operational by October 2017. Two bombers will have the ability to carry 40 weapons in place of the 36 that three B-52s can carry.[82] The 1760 IWBU allows precision-guided missiles or bombs to be deployed from inside the weapons bay; previous aircraft carried these munitions externally on wing hardpoints. This increases the number of guided weapons a B-52 can carry and reduces the need for guided bombs to be carried on the wings. The first phase will allow a B-52 to carry twenty-four 500-pound guided JDAM bombs or twenty 2,000-pound JDAMs, with later phases accommodating the JASSM and MALD family of missiles.[83] In addition to carrying more smart bombs, moving them internally from the wings reduces drag and achieves a 15 percent reduction in fuel consumption.[84]

Air Force scientists are working to arm the B-52 with defensive laser weapons able to incinerate attacking air-to-air or surface-to-air missiles.[85]

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