The Boeing B-52 Stratofortress is an American nuclear-capable 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 1955 and was flown by NASA from 1959 to 2007. The bomber can carry up to of weapons and has a typical combat range of around without aerial refueling.
After Boeing won the initial contract in June 1946, the aircraft's 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 deterrence missions, the B-52 Stratofortress replaced the Convair B-36 Peacemaker. 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-52s were transferred to the new Air Force Global Strike Command (AFGSC).
The B-52's official name Stratofortress is rarely used; informally, the aircraft is commonly referred to as the BUFF (Big Ugly Fat Fucker/Fella). Superior performance at high subsonic speeds and relatively low operating costs have kept them in service despite the introduction of more advanced strategic bombers, such as the Mach-2+ Convair B-58 Hustler, the variable-geometry Rockwell B-1 Lancer, and the stealth plane Northrop Grumman B-2 Spirit. The B-52 has used conventional munitions in the Vietnam War, Gulf War, NATO bombing of Yugoslavia, Iraq War, war against the Islamic State, war in Afghanistan, and 2026 Iran war.
In its nuclear role, the B-52H is assigned only the AGM-86B cruise missile. Conventionally, it can employ the AGM-142, AGM-154, AGM-158 air-to-ground weapons, and a variety of Joint Direct Attack Munitions, and in maritime roles can employ Harpoon anti-ship missiles and Quickstrike naval mines. As a mother ship, it has deployed the D-21 reconnaissance drone, and test-launched the X-15, X-24, X-38, and X-43 experimental aircraft and various hypersonic missiles.
The US Air Force has 76 B-52s in service with 58 operated by active forces (2nd Bomb Wing and 5th Bomb Wing), 18 by reserve forces (307th Bomb Wing), and about 12 in long-term storage at the Davis-Monthan AFB Boneyard. The operational aircraft received upgrades between 2013 and 2015 and are expected to serve into the 2050s. The B-52H is the only operational variant, scheduled to be upgraded as the B-52J by 2030.
Development
Origins
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". 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 at with a combat radius of . The armament was to consist of an unspecified number of 20 mm cannons and of bombs. On 13 February 1946, the USAAF issued bid invitations for these specifications, with Boeing, Consolidated Aircraft, and Glenn L. Martin Company submitting proposals.
On 5 June 1946, Boeing's Model 462, a straight-wing aircraft powered by six Wright T35 turboprops with a gross weight of and a combat radius of , was declared the winner. On 28 June 1946, Boeing was issued a letter of contract for million to build a full-scale mockup of the new XB-52 and do preliminary engineering and testing. However, by October 1946, the USAAF was beginning to express concern about the sheer size of the new aircraft and its inability to meet the specified design requirements. In response, Boeing produced the Model 464, a smaller four-engine version with a gross weight, which was briefly deemed acceptable.
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 , to which Boeing responded with a aircraft. In December 1946, Boeing was asked to change its design to a four-engine bomber with a top speed of , range of , and the ability to carry a nuclear weapon; in total, the aircraft could weigh up to . Boeing responded with two models powered by T35 turboprops. The Model 464-16 was a "nuclear only" bomber with a payload, while the Model 464-17 was a general purpose bomber with a payload. Due to the cost associated with purchasing two specialized aircraft, the USAAF selected Model 464–17 with the understanding that it could be adapted for nuclear strikes.
In June 1947, the military requirements were updated and the Model 464-17 met all of them except for the range. It was becoming obvious to the USAAF 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. During this time, Boeing continued to perfect the design, which resulted in the Model 464–29 with a top speed of and a range. 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 and an range, far beyond the capabilities of the 464–29.
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. Allen reasoned that the design was capable of being adapted to new aviation technology and more stringent requirements. In January 1948, Boeing was instructed to thoroughly explore recent technological innovations, including aerial refueling and the flying wing. Noting stability and control problems Northrop Corporation was experiencing with its YB-35 and YB-49 flying wing bombers, Boeing insisted on a conventional aircraft, and in April 1948 presented a million (US$ today) proposal for design, construction, and testing of two Model 464-35 prototypes. Further revisions during 1948 resulted in an aircraft with a top speed of at , a range of , and a gross weight, which included of bombs and of fuel.
Design effort
In May 1948, Air Materiel Command asked Boeing to incorporate the previously discarded jet engine, with improvements in fuel efficiency, into the design. That resulted in the development of yet another revisionin July 1948, Model 464-40 substituted Westinghouse J40 turbojets for the turboprops. The USAF 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 Boeing to 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 Materiel, 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.
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 produce a proposal for a four-engine turbojet bomber. Joined by Ed Wells, Boeing's 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.
By late Friday night, they had laid out what was an essentially 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. A notable feature 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). 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 scale model. The aircraft was projected to exceed all design specifications.
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. 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. 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. Following several direct interventions by LeMay, Boeing was awarded a production contract for thirteen B-52As and seventeen detachable reconnaissance pods on 14 February 1951. 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. Both XB-52 prototypes featured the original tandem seating arrangement with a framed bubble-type canopy (see above images).
Tex Johnston noted, "The B-52, like the B-47, utilized a flexible wing. I saw the wingtip of the B-52 static test airplane travel , from the negative 1-G load position to the positive 4-G load position." The flexible structure allowed "... the wing to flex during gust and maneuvering loads, thus relieving high-stress areas and providing a smoother ride." During a 3.5-G pullup, "The wingtips appeared about 35 degrees above level flight position."
Pre-production and production
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. The YB-52, the second XB-52 modified with more operational equipment, first flew on 15 April 1952 with "Tex" Johnston as the pilot. A 2-hour, 21-minute proving flight from Boeing Field, near Seattle, Washington, to Larson Air Force Base was undertaken with Boeing test pilot Johnston and USAF Lieutenant Colonel Guy M. Townsend. The XB-52 followed on 2 October 1952. The thorough development, including 670 days in the wind tunnel and 130 days of aerodynamic and aeroelastic testing, paid off with smooth flight testing. Encouraged, the USAF increased its order to 282 B-52s.
+ Aircraft deliveries Fiscal year B-52 model Total A B C D E F G H Annual Cumulative1954 3 331955 13 13161956 355 1 41571957 23092 1241811958 7710010 1873681959 79 50 1294971960 106 1066031961 37 20576601962 68687281963 1414742Total 3 503517010089193102742742