B-52 Stratofortress Explained

The Boeing B-52 Stratofortress is a long-range, subsonic, jet-powered, strategic bomber operated by the United States Air Force (USAF) since 1955.

Beginning with the successful contract bid on 5 June 1946, the B-52 went through several design steps; from a straight wing aircraft powered by six turboprop engines to the final prototype YB-52, with eight turbojet engines. The aircraft made its first flight on 15 April 1952 with "Tex" Johnston as pilot.[1]

Built to carry nuclear weapons for Cold War-era deterrence missions, the B-52 Stratofortress replaced the Convair B-36. Although a veteran of a number of wars, the Stratofortress has dropped only conventional munitions in actual combat. With the longest unrefueled range of any contemporary bomber, the B-52 carries up to 70000lb of weapons.

The USAF has had B-52s in active service since 1955, initially with the Strategic Air Command (SAC), with all aircraft later absorbed into the Air Combat Command (ACC) following SAC's disestablishment in 1992. Superior performance at high subsonic speeds and relatively low operating costs have kept the B-52 in service despite proposals to replace it with the Mach 3 XB-70 Valkyrie, supersonic B-1B Lancer and stealthy B-2 Spirit. In January 2005, the B-52 became the second aircraft, after the English Electric Canberra, to mark 50 years of continuous service with its original primary operator. There are six aircraft altogether that have made this list as of 2009; the other four being the Tupolev Tu-95, the C-130 Hercules, the KC-135 Stratotanker, and the Lockheed U-2.

Design and development

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".[2] The aircraft was to have a crew of five plus turret gunners, and a six-man relief crew. It had to cruise at 300 mph (240 kn, 480 km/h) at 34,000 feet (10,400 m) with a combat radius of 5,000 statute miles (4,300 nmi, 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.[3] On 13 February 1946, the Air Force issued bid invitations for these specifications, with Boeing, Consolidated Aircraft, and Glenn L. Martin Company submitting proposals.[3]

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 combat radius of 3,110 statute miles (2,700 nmi, 5,010 km), was declared the winner.[4] On 28 June 1946, Boeing was issued a letter of contract for US$1.7 million (1946 dollars) to build a full-scale mock-up of the new XB-52 and do preliminary engineering and testing. 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.[5] 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.

Then, in November 1946, the Deputy Chief of Air Staff for Research and Development, General Curtis LeMay, expressed the desire for a cruise speed of 400 miles per hour (345 kn, 645 km/h), to which Boeing responded with a 300,000 pound (140,000 kg) aircraft.[6] 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 statute miles (10,000 nmi, 19,000 km), and the ability to carry a nuclear weapon. The aircraft could weigh up to 480,000 pounds (220,000 kg).[6] Boeing responded with two models powered by the T-35 turboprops. The Model 464-16 was a "nuclear-only" bomber with a 10,000 pound payload, while the Model 464-17 was a general purpose bomber with a 90,000 pound (40,000 kg) payload. 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.[6]

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 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.[7] As a result, the entire project was put on hold for six months. 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.[7] In September 1947, the Heavy Bombardment Committee was convened to ascertain performance requirements for a nuclear bomber. Formalized on 8 December 1947, these called for a top speed of 500 miles per hour (440 kn, 800 km/h) and an 8,000 statute mile (7,000 nmi, 13,000 km) range, far beyond the capabilities of 464-29.[8]

The outright cancellation of the Boeing contract on 11 December 1947 was staved off by a plea from its president William McPherson Allen,[9] and 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 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 (1948 dollars) proposal for design, construction, and testing of two Model 464-35 prototypes. Further revisions of specifications 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 statute miles (6,005 nmi, 11,125 km), and a 280,000 pounds (125,000 kg) gross weight which included 10,000 pounds of bombs and 19,875 US gallons (75,225 L) of fuel.

Entering the Jet Age

In May 1948 AMC asked Boeing to incorporate the previously discarded, but now more fuel-efficient, jet engine into the design. This resulted in Boeing developing yet another revision — in July 1948, Model 464-40 substituted Westinghouse J40 turbojets for the turboprops.[10] Nevertheless, on 21 October 1948, Boeing was told to create an entirely new aircraft using Pratt & Whitney J57 turbojets.

On 25 October, Boeing engineers produced a proposal and a hand-carved model of 464-49.[11] The new design built upon the basic layout of the B-47 Stratojet with 35° swept wings, eight engines paired in four underwing pods, and bicycle landing gear with wingtip outrigger wheels. A notable feature of the landing gear was the ability to pivot the main landing gear up to 20° from the aircraft centerline to increase safety during crosswind landings.[12] 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 the 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.[13] In a final attempt to increase the range, Boeing created the larger 464-67, stating that once in production, the range could be further increased in subsequent modifications.[14] Following several direct interventions by LeMay,[15] on 14 February 1951 Boeing was awarded a production contract for 13 B-52As and 17 detachable reconnaissance pods.[16] The last major design change, also at the insistence of General LeMay, 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.[17] Both XB-52 prototypes featured the original tandem seating arrangement with a framed bubble-type canopy.[18]

The YB-52 (actually, the second XB-52 with more operational equipment) first flew on 15 April 1952,[19] a 2 hour 21 minute flight from Renton Field in Renton, Washington to Larson AFB with Boeing test pilot Alvin M. Johnston and Air Force Lieutenant Colonel Guy M. Townsend.[20] [21] The XB-52 followed on 2 October 1952. The thorough development,[22] 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.[23]

Only three of the 13 B-52As ordered were built. All were returned to Boeing, and used in their test program.[24] On 9 June 1952 the February 1951 contract was updated to order the aircraft under new specifications. The final ten - the first aircraft to enter active service - were completed as B-52Bs.[24] At the roll out ceremony on 18 March 1954, Air Force Chief of Staff, General Twining said:

In informal circumstances, the official name Stratofortress was rarely used; personnel involved with the aircraft most commonly referred to it as BUFF (Big Ugly Fat Fucker).[25] [26]

Operational history

See also: List of B-52 Units of the United States Air Force. Although the B-52A was the first production variant, these aircraft were used only in testing. The first operational version was the B-52B which had been developed in parallel with the prototypes since 1951. First flying in December 1954, B-52B, AF Serial Number 52-8711, entered operational service with 93rd Heavy Bombardment Wing at Castle Air Force Base, California, on 29 June 1955. The wing became operational on 12 March 1956. The training for B-52 crews consisted of five weeks of ground school and four weeks of flying, accumulating 35–50 hours in the air. The new B-52Bs replaced operational B-36s on a one-to-one basis.

Early operations were complicated by lack of spares and ground facilities while ramps and taxiways deteriorated under the weight of the aircraft. The fuel system was prone to leaks and icing, and bombing and fire control computers were unreliable. The two-story cockpit presented a unique climate control problem – the pilots' cockpit was heated by sunlight while the observer and the navigator on the bottom deck sat on the ice cold floor. Thus, comfortable temperature setting for the pilots caused the other crew members to freeze, while comfortable temperature for the bottom crew caused the pilots to overheat. The J57 engines were still new and unreliable. Alternator failure caused the first fatal B-52 crash in February 1956, which resulted in a brief grounding of the fleet. In July, fuel and hydraulic system problems again grounded the B-52s. To avoid maintenance problems, the Air Force set up Sky Speed teams of 50 maintenance contractors at each B-52 base. In addition to maintenance, the teams performed routine checkups which took one week per aircraft.

On 21 May 1956, a B-52B (52-0013) dropped its first live hydrogen bomb (a Mk.15) over the Bikini Atoll.[27] On 24–25 November 1956, four B-52Bs of the 93rd BW and four B-52Cs of the 42nd BW flew nonstop around the perimeter of North America in Operation Quick Kick, covering 15,530 statute miles (13,500 nm, 25,000 km) in 31 hours 30 minutes (493.0 smph). SAC noted that the flight time could have been reduced by 5-6 hours if the four inflight refuellings were done by fast jet-powered tanker aircraft rather than propeller-driven KC-97 Stratotankers. In a demonstration of the B-52s global reach, on 16–18 January 1957, three B-52Bs made a nonstop flight around the world during Operation Power Flite, covering 24,325 statute miles (21,145 nm, 39,165 km) in 45 hours 19 minutes (536.8 smph) with several in-flight refuelings by KC-97s. The 93rd Bomb Wing received the Mackay Trophy for their accomplishment.

The B-52 set many records over the next few years. On 26 September 1958, a B-52D set a world speed record of 560.705 miles per hour (487 kn, 902 km/h) over a 10,000 kilometers (5,400 nm, 6,210 mi) closed circuit without a payload. The same day, another B-52D established a world speed record of 597.675 miles per hour (519 kn, 962 km/h) over a 5,000 kilometer (2,700 nmi, 3,105 mi) closed circuit without a payload.[28] On 14 December 1960, a B-52G set a world record by flying unrefueled for 10,078.84 statute miles (8,762 nm, 16,227 km). The flight lasted 19 hours 44 minutes (510.75 smph). On 10–11 January 1962, a B-52H set a world record by flying unrefuelled from Kadena Air Base, Okinawa, Japan, to Torrejon Air Base, Spain, covering 12,532.28 statute miles (10,895 nmi, 20,177 km).

During this time, at the Strategic Air Command's peak strength in 1963, 650 B-52s were in operation in 42 squadrons at 38 air bases.[29]

Vietnam War

See main article: Vietnam War. With the escalating situation in Southeast Asia, in June 1964 28 B-52Fs were fitted with external racks for 24× 750 pound (340 kg) bombs under project South Bay. An additional 46 aircraft received similar modifications under project Sun Bath. In March 1965, the United States commenced Operation Rolling Thunder, and the first combat mission of Operation Arc Light was flown by B-52Fs on 18 June 1965, when thirty bombers of the 9th and 441st Bombardment Squadrons struck a communist stronghold near Ben Cat in South Vietnam. The first wave of bombers arrived too early at a designated rendezvous point, and while maneuvering to maintain station, two B-52s collided, resulting in the loss of both bombers and eight crewmen. The remaining bombers, minus one more which turned back due to mechanical problems, continued on towards the target, which was bombed successfully.[30]

In December 1965, a number of B-52Ds underwent Big Belly modifications to increase bomb capacity for carpet bombings. While the external payload remained at 24× 500 pound (227 kg) or 750 pound (340 kg) bombs, the internal capacity increased from 27 to 84× 500 pound bombs or from 27 to 42× 750 pound bombs.[31] The Big Belly modification now created enough capacity for a total of 60,000 pounds (27215 kg) in 108 bombs. Thus modified, B-52Ds could carry 22,000 pounds (9,980 kg) more than B-52Fs.[32] Replacing B-52Fs, modified B-52Ds entered combat in April 1966 flying from Andersen Air Force Base, Guam. Each bombing mission lasted ten to 12 hours with an aerial refueling by KC-135 Stratotankers.[19] In spring 1967, the aircraft began flying from U Tapao Airfield in Thailand which had the advantage of not requiring in-flight refueling.[31] These missions lasted only 2 to 3 hours. On 15 April 1968, a Replacement Training Unit was established at Castle AFB which converted B-52E through B-52H crews to B-52Ds so they could participate in combat in Southeast Asia.[33]

On 22 November 1972, a B-52D (55-0110) from U-Tapao was hit by a SAM while on a raid over Vinh. The crew was forced to abandon the damaged aircraft over Thailand. This was the first B-52 to be destroyed by hostile fire in Vietnam.[28]

The zenith of B-52 attacks in Vietnam was Operation Linebacker II which consisted of waves of B-52s (mostly D models, but some Gs without jamming equipment and with a smaller bomb load). Over 12 days B-52s flew 729 sorties,[34] dropping 15,237 tons of bombs on Hanoi, Haiphong, and other targets.[35] In total, ten B-52s were shot down over North Vietnam and five others were damaged and crashed in Laos or Thailand.[36]

B-52D tail gunners were credited with shooting down two MiG-21 "Fishbeds"; one on 18 December 1972, by SSgt Samuel O. Turner, and one on 24 December 1972, by A1C Albert E. Moore. Turner was awarded a Silver Star for his actions.[37] The last Arc Light mission took place on 15 August 1973 and all B-52s left Southeast Asia shortly after.[28]

Cold War

See main article: Cold War. During the Cold War, B-52s performed airborne alert duty under code names such as Head Start, Chrome Dome, Hard Head, Round Robin, and Giant Lance. Bombers loitered near points outside the Soviet Union to provide rapid first strike or retaliation capability in case of nuclear war.[38] [39]

See main article: 1966 Palomares B-52 crash.

On 17 January 1966, a fatal collision occurred between a B-52G and a KC-135 Stratotanker over Palomares, Spain. The four B-28 FI 1.45-megaton-range nuclear bombs on the B-52 were eventually recovered. Two of the four bombs had a minor detonation, as the warheads' conventional explosives were set off, with serious dispersion of both plutonium and uranium. The main fuse safety withstood the violent impact and explosion, preventing a nuclear disaster. After the crash, 1,400 tons of contaminated soil was sent to the United States. The crash and the decontamination were too expensive to risk again and ended the airborne alert program. In 2006, an agreement was made between the U.S. and Spain to investigate and clean the pollution still remaining as a result of the accident.[40]

See main article: 1968 Thule Air Base B-52 crash. On 21 January 1968, another B-52G, with four nuclear bombs aboard as part of Operation Chrome Dome, crashed on the ice of the North Star Bay while attempting an emergency landing at Thule Air Base, Greenland.[41] The resulting fire caused extensive radioactive contamination, the cleanup of which lasted until September of that year.

The Yom Kippur War in October 1973 saw the Soviet Union threaten to intervene on behalf of Egypt and Syria. To stop the Soviets, President Richard M. Nixon called on the military to raise its alert level to DEFCON 3. Secretary of Defense Melvin Laird ordered the B-52s to an immediate war footing and fully armed and fueled B-52s were circling Greenland. The Soviet Union did not become directly involved in the war.

B-52Bs reached the end of their structural service life by the mid-1960s and all were retired by June 1966, followed by the last of the B-52Cs on 29 September 1971; except for NASA's B-52B "008" which was eventually retired in 2004 at Edwards AFB, California.[42] Another of the remaining B Models, "005" is on display at the Wings Over the Rockies Air and Space Museum in Denver, Colorado.

A few time-expired E models were retired in 1967 and 1968, but the bulk (82) were retired between May 1969 and March 1970. Most F models were also retired between 1967 and 1973, but 23 survived as trainers until late 1978.

The fleet of D models served much longer. Eighty D models were updated under the Pacer Plank program (ECP 1581) at Boeing's Wichita plant. Skinning on the lower wing and fuselage was replaced, and various structural components were renewed. Work was completed in 1977. The fleet of D models stayed largely intact until late 1978, when 37 were retired. The remainder were retired between 1982 and 1983.

The remaining G and H models were used for nuclear standby ("alert") duty as part of the United States' nuclear triad. This triad was the combination of nuclear-armed land-based missiles, submarine-based missiles and manned bombers. The B-1B Lancer which was intended to supplant the B-52, replaced only the older models and the supersonic FB-111.

After the fall of the Soviet Union, the B-52Gs were destroyed per the terms of the Strategic Arms Reduction Treaty (START). AMARG was tasked with eliminating 365 B-52 bombers. The progress of this task was to be verified by Russia via satellite and first-person inspection at the AMARG facility. Initially, the B-52s were chopped into pieces with a 13,000 pound guillotine.

In 1991, B-52s ceased continuous 24-hour SAC alert duty.

Gulf War and later

See also: Gulf War. On 16 February 1991 a flight of B-52Gs launching from and returning to Barksdale AFB, in Louisiana, struck targets inside Iraq. This was at the time the longest distance combat mission in history: 35 hours and 14,000 statute miles round trip.[43] [44] Over the next months, B-52Gs operating from bases in Saudi Arabia, the United Kingdom, Spain and on the island of Diego Garcia flew low level bombing missions. The B-52s moved to high level missions after Coalition forces ensured air superiority and were able to suppress air defense systems capable of reaching bombers at a higher altitude. B-52s were an important part of the air war during Operation Desert Storm as they could be employed with impunity. The conventional strikes were carried out by three bombers dropping 153 750 pound bombs at a time, covering an area one and a half miles long by one mile wide. The bombings demoralized the defending Iraqi troops, and they could be induced to surrender rather than be destroyed.[45] Flying approximately 1620 sorties in the Gulf War, B-52s delivered 40% of the weapons dropped by coalition forces,[46] while suffering only one aircraft loss, with several receiving minor damage from enemy action.

On 2–3 September 1996, two B-52H struck Baghdad power stations and communications facilities with 13 AGM-86C air-launched cruise missiles (ALCM) as part of Operation Desert Strike, a 34-hour, 16,000 statute mile round trip mission from Andersen AFB, on Guam - the longest distance ever flown for a combat mission.[47] Only two days prior, the crews had completed a 17-hour flight from Louisiana to Guam.

Since the mid-1990s, the B-52H has been the only variant still in service; it is currently stationed at:

The B-52 also contributed to the US success in Operation Enduring Freedom in 2001 (Afghanistan/Southwest Asia), providing the ability to loiter high above the battlefield and provide Close Air Support (CAS) through the use of precision guided munitions, a mission which previously would have been restricted to fighter and ground attack aircraft.

B-52s also played a role in Operation Iraqi Freedom, which commenced on 20 March 2003 (Iraq/Southwest Asia). On the night of 21 March 2003, B-52Hs launched at least 100 AGM-86 ALCMs.[48]

In August 2007, a B-52H ferrying AGM-129 ACM cruise missiles from Minot air force base to Barksdale Air Force Base for dismantling was mistakenly loaded with six missiles from which the nuclear warhead had not been removed. The weapons did not leave USAF custody and were recovered at Barkesdale.

, 94 of the original 744 B-52 aircraft were still operational within the U.S. Air Force.[49] Four of 18 B-52Hs from Barksdale AFB that are currently being retired are in the "boneyard" of 309th AMARG at Davis-Monthan AFB as of 8 September 2008.

On 21 July 2008, a B-52H, deployed from Barksdale AFB, crashed approximately 25 miles off the coast of Guam.[50]

Future of the B-52

The Air Force intends to keep the B-52 in service until at least 2040, an unprecedented length of service for a military aircraft.[46] [51] B-52s are periodically refurbished at the USAF maintenance depots such as Tinker Air Force Base, Oklahoma.

The USAF continues to rely on the B-52 because it remains an effective and economical heavy bomber, particularly in the type of missions that have been conducted since the end of the Cold War, mainly against nations that have limited air defense capabilities. The B-52's capacity to "loiter" for extended periods over (or even well outside) the battlefield, while delivering precision standoff and direct fire munitions, has been a valuable asset in conflicts such as Operation Enduring Freedom in Afghanistan.

The speed and stealth of the B-1 Lancer and B-2 Spirit have only been useful until enemy air defenses were destroyed, a task that has been swiftly achieved in recent conflicts. The B-52 boasts the highest mission capable rate of the three types of heavy bombers operated by the USAF. Whereas the B-1 averages a 53% ready rate, and the B-2 achieved a 26%, the B-52 averages 80% as of 2001.[52]

Upgrades and modifications

In November 1959, SAC initiated the Big Four modification program (also known as Modification 1000) for all operational B-52s except early B models. The program was completed by 1963.[53] The four modifications were:

  1. Ability to perform all-weather, low-altitude (below 500 feet (150 m)) interdiction as a response to advancements in Soviet Union's missile defenses. The low-altitude flights were estimated to accelerate structural fatigue by at least a factor of eight, requiring costly repairs to extend service life.
  2. Ability to launch AGM-28 Hound Dog standoff nuclear missiles
  3. Ability to launch ADM-20 Quail decoys
  4. An advanced electronic countermeasures (ECM) suite

The ability to carry up to 20 AGM-69 SRAM nuclear missiles was added to G and H models starting in 1971.[54] Fuel leaks due to deteriorating Marman clamps continued to plague all variants of the B-52. To this end, the aircraft were subjected to Blue Band (1957), Hard Shell (1958), and finally QuickClip (1958) programs. The latter fitted safety straps which prevented catastrophic loss of fuel in case of clamp failure.[55]

Ongoing problems with advanced avionics were addressed in the Jolly Well program, completed in 1964, which improved components of the AN/ASQ-38 bombing navigational computer and the terrain computer. The MADREC (Malfunction Detection and Recording) upgrade fitted to most aircraft by 1965 could detect failures in avionics and weapons computer systems, and was essential in monitoring the Hound Dog missiles. The electronic countermeasures capability of the B-52 was expanded with Rivet Rambler (1971) and Rivet Ace (1973).[56]

In order to improve the ability to operate safely at low level during both day and night, the AN/ASQ-151 Electro-Optical Viewing System (EVS), consisting of a Low Light Level Television (LLLTV) and a Forward Looking Infra-Red (FLIR) system mounted in blisters under the noses of B-52Gs and Hs between 1972 and 1976.[57] In order to further improve the B-52s offensive ability, it was decided to fit Air Launched Cruise Missiles (ALCMs). After testing of both the Air-Force backed Boeing AGM-86 and the Navy backed General Dynamics AGM-109 Tomahawk, the AGM-86B was selected for operation by the B-52 (and ultimately by the B-1 Lancer). A total of 194 B-52Gs and Hs were modified to carry AGM-86s, carrying 12 missiles on underwing pylons, with 82 B-52Hs further modified to carry another eight missiles on a rotary launcher fitted in the aircraft's bomb-bay. In order to conform with the requirements of the SALT II Treaty for cruise missile capable aircraft to be readily identified by reconnaissance satellites, the cruise missile armed B-52Gs were modified with a distinctive wing root fairing. As all B-52Hs were assumed to be modified, no visual modification of these aircraft was required.[58] In 1990, the stealthy AGM-129 ACM cruise missile entered service. Although originally intended to replace the AGM-86 its high cost and the end of the Cold War stopped production after only 450 had been made. Unlike the AGM-86, no conventional (i.e. non-nuclear) armed version was built.[59]

Structural fatigue, exacerbated by the change to low-altitude missions, was first dealt with in the early 1960s by the three-phase High Stress program which enrolled aircraft at 2,000 flying hours.[60] This was followed by a 2,000-hour service life extension to select airframes in 1966-1968, and the extensive Pacer Plank reskinning completed in 1977. The wet wing introduced on G and H models was even more susceptible to fatigue due to experiencing 60% more stress during flight than the old wing. The wings were modified by 1964 under ECP 1050.[61] This was followed by a fuselage skin and longeron replacement (ECP 1185) in 1966, and B-52 Stability Augmentation and Flight Control program (ECP 1195) in 1967.[61]

Boeing has suggested re-engining the B-52H fleet with the Rolls-Royce RB211 534E-4. This would involve replacing the eight Pratt & Whitney TF33s (total thrust 8 × 17,000 lb) with four RB211s (total thrust 4 × 37,400lb). The RR engines will increase the range and payload of the fleet and reduce fuel consumption. However, the cost of the project would be significant. Procurement would cost approximately US$2.56 billion (US$36 million × 71 aircraft). A Government Accountability Office study of the proposal concluded that Boeing's estimated savings of US$4.7 billion would not be realized. They found that it would cost the Air Force US$1.3 billion over keeping the existing engines.[62] This was subsequently disputed in a Defense Sciences Board report in 2003 and revised in 2004 that identified numerous errors in the prior evaluation of the Boeing proposal, and urged the Air Force to re-engine the aircraft without delay. Further, the DSB report stated the program would save substantial funds, reduce greenhouse gas emissions, and increase aircraft range and endurance, duplicating the results of a Congressionally funded US$3M program office study conducted in 2003.[63] However, the re-engining has been approved as of 2009.

In 2007 the LITENING targeting pod was fitted and commissioned increasing the combat effectiveness of the aircraft during day, night and under-the-weather conditions in the attack of ground targets with a variety of standoff weapons under the guidance of LASERs and the help of high resolution forward-looking infrared sensor (FLIR) for visual display in the infrared portion of the electromagnetic spectrum and charged coupled device (CCD-TV) camera used to obtain target imagery in the visible portion, this technology could also be used in real-time transmission to ground communications networks and government agencies to gather battlefield intelligence, assess battlefield damage, assess terrorist activities and counter drug activity, further advancing the B-52H's capabilities and uses.

Fuel research platform

In September 2006, the B-52 became one of the first US military aircraft to fly using 'alternative' fuel. Syntroleum Corporation, a leader in Fischer-Tropsch process (FT) technology, announced that its Ultra-Clean jet fuel had been successfully tested in a B-52. It took off from Edwards Air Force Base with a 50/50 blend of FT and traditional JP-8 jet fuel which was burned in two of the eight engines on the aircraft. This marked the first time that FT jet fuel was tested in a military flight demo, and is the first of several planned test flights.[64]

On 15 December 2006, tail number 61-0034, Wise Guy took off from Edwards with the synthetic fuel blend powering all eight engines, the first time an Air Force aircraft was completely powered by the mixture. The test flight was captained by Major General Curtis Bedke, commander of the Edwards Flight Test Center, the first time in 36 years that the installation's commander performed a first flight in a flight test program. The flight lasted seven hours, reached an altitude of 48,000 feet, and was considered a success.[64]

On 8 August 2007, Air Force Secretary Michael Wynne certified the B-52H as fully approved to use the FT blend, marking the formal conclusion of the test program.[65]

This program is part of the Department of Defense Assured Fuel Initiative, an effort to develop secure domestic sources for the military energy needs. The Pentagon hopes to reduce its use of crude oil from foreign producers and obtain about half of its aviation fuel from alternative sources by 2016.[64] With the B-52 now approved to use the FT blend, the USAF will use the test protocols developed during the program to certify the C-17 Globemaster III and then the B-1B to use the fuel (the first B-1 test flight took place in March, 2008). The Air Force intends to test and certify every airframe in its inventory to use the fuel by 2011.[65]

Costs

The costs are in approximate 1955 United States dollars and have not been adjusted for inflation.

X/YB-52B-52AB-52BB-52CB-52DB-52EB-52FB-52GB-52H
Unit R&D cost100 million
Airframe26,433,51811,328,3985,359,0174,654,4943,700,7503,772,2475,351,8196,076,157
Engines2,848,1202,547,4721,513,2201,291,4151,256,5161,787,1911,427,6111,640,373
Electronics50,76161,19871,39768,61354,93360,11166,37461,020
Armament47,874482,284293,346548,353931,665862,839840,0001,501,422
Ordnance9,19311,52010,98317,9284,6263,0166,8096,804
Flyaway cost28.38 million14.43 million7.24 million6.58 million5.94 million6.48 million7.69 million9.29 million
Maintenance cost per flying hour9251,0251,0251,182

Variants

Production numbers! Variant !! Produced !! Entered Service
XB-522 (1 redesignated YB-52)prototypes
B-52A3
NB-52A1 Modified B-52A
B-52B5029 June 1955
RB-52B27 Modified B-52Bs
NB-52B1 Modified B-52B
B-52C35June 1956
B-52D170December 1956
B-52E100December 1957
B-52F89June 1958
B-52G19313 February 1959
B-52H1029 May 1961
Grand total744 production

The B-52 went through several design changes and variants over its 10 years of production.

B-52A :
Only three of the first production version, the B-52A, were built, all loaned to Boeing for flight testing.[19] The first production B-52A differed from prototypes in having redesigned forward fuselage. The bubble canopy and tandem seating was replaced by a side-by-side arrangement and a 21 inch (53 cm) nose extension accommodated more avionics and a new 6th crew member.[66] [67] In the rear fuselage a tail turret with four 0.50 inch (12.7 mm) machine guns with a fire-control system, and a water injection system to augment engine power with a 360 US gallon (1,363 L) water tank was added. The aircraft also carried a 1,000 US gallon (3,785 L) external fuel tank under each wing.[66] [67] The tanks acted as dampeners to reduce wing flex and also kept wingtips close to the ground for ease of maintenance.
NB-52A :
The last B-52A (serial 52-0003) was modified and redesignated NB-52A in 1959 to carry the North American X-15. A pylon was fitted under the right wing between the fuselage and the inboard engines with a 6 feet x 8 feet (1.8 m x 2.4 m) section removed from the right wing flap to fit the X-15 tail. Liquid oxygen and hydrogen peroxide tanks were installed in the bomb bays to fuel the X-15 before launch. First flight with X-15 was on 19 March 1959, with the first launch on 8 June 1959. The NB-52A, named "The High and Mighty One" carried the X-15 on 93 of the program's 199 flights.[68]
B-52B/RB-52B :
The B-52B was the first version to enter service with the USAF on 29 June 1955, with the 93rd Bombardment Wing at Castle AFB in California.[67] This version included minor changes to engines and avionics in the attempt to fix minor problems. Temporary grounding of the aircraft after a crash in February 1956 and again the following July caused training delays, and at mid-year there were still no combat-ready B-52 crews.[69]

Of the 50 B-52Bs built, 27 were capable of carrying a reconnaissance pod as RB-52Bs (the crew was increased to eight in these aircraft).[19] The 300 pound (136 kg) pod contained radio receivers, a combination of K-36, K-38, and T-11 cameras, and two operators on downward-firing ejection seats. The pod required only four hours to install.[69]

Seven B-52Bs were brought to B-52C standard under Project Sunflower.[70]

NB-52B :
The NB-52B was B-52B number 52-0008 converted to an X-15 launch platform. It subsequently flew as the "Balls 8" in support of NASA research until 17 December 2004, making it the oldest flying B-52B. It was replaced by a modified B-52H.[71]
B-52C :
In the B-52C the fuel capacity (and range) was increased to 41,700 US gallons by adding larger 3000 US gallon underwing fuel tanks. The gross weight was increased by 30,000 pounds (13,605 kg) to 450,000 pounds. The belly of the aircraft was painted with antiflash white paint, which was intended to reflect thermal radiation away after a nuclear detonation.[72]
RB-52C :
The RB-52C was the designation given, but seldom used, to B-52Cs converted for reconnaissance duties in a similar manner to RB-52Bs.[72]
B-52D :
The B-52D was a dedicated long-range bomber without a reconnaissance option. The Big Belly modifications allowed the B-52D to carry heavy loads of conventional bombs for carpet bombing over Vietnam. Aircraft assigned to Vietnam were painted camouflage with black bellies to defeat searchlights.[73]
B-52E :
In the B-52E the aircraft had an updated avionics and bombing navigational system, which was eventually debugged and included on following models.[74]

One E aircraft (AF Serial No. 56-0631) modified as a testbed for various B-52 systems. Redesignated NB-52E, the aircraft was fitted with canards and a Load Alleviation and Mode Stabilization system (LAMS) which reduced airframe fatigue from wind gusts during low level flight. In one test, the aircraft flew 10 knots (11.5 mph, 18.5 km/h) faster than the never exceed speed without damage because the canards eliminated 30% of vertical and 50% of horizontal vibrations caused by wind gusts.[74] [75]

B-52F:
In the B-52F, the aircraft was given J57-P-43W engines with a larger capacity water injection system and new alternators.[76] The aircraft had a problem with fuel leaks, which were eventually solved by service modifications Blue Band, Hard Shell, and QuickClip.[55]
B-52G :
The B-52G was proposed to extend the B-52's service life during delays in the B-58 Hustler program. At first, a radical redesign was envisioned with a completely new wing and Pratt & Whitney J75 engines. This was rejected to avoid slowdowns in production, although changes were implemented. The most significant of these was the brand new "wet" wing with integral fuel tanks which considerably increased the fuel capacity — gross aircraft weight went up by 38,000 pounds (17,235 kg) compared with prior variants. In addition, a pair of 700 US gallon (2,650 L) external fuel tanks was fitted under the wings. The wing also had the traditional ailerons eliminated, instead utilizing spoilers for roll control. The tail fin was shortened by 8 feet (2.4 m), water injection system capacity was increased to 1,200 US gallons (4,540 L), and the nose radome was enlarged. The tail gunner was provided with an ejection seat and moved to the main cockpit. Dubbed the "Battle Station" concept, the offensive crew (pilot and copilot on the upper deck and the two bombing navigation system operators on the lower deck) faced forward, while the defensive crew (tail gunner and ECM operator) on the upper deck faced aft. The B-52G entered service 13 February 1959 (a day earlier, the last B-36 was retired, making SAC an all-jet bomber force). Nearly all B-52Gs were destroyed in compliance with the Strategic Arms Reduction Treaty of 1992. A few examples remain in museums and as static displays at various air force bases.[77]
B-52H :
The B-52H had the same crew and structural changes as the B-52G. The most significant upgrade was the switch to TF33-P-3 turbofan engines which, despite the initial reliability problems (corrected by 1964 under the Hot Fan program), offered considerably better performance and fuel economy than the J57 turbojets. The ECM and avionics were updated, a new fire control system was fitted, and the rear defensive armament was changed from machine guns to a 20 mm M61 Vulcan cannon. A provision was made for four AGM-48 Skybolt ballistic missiles. First flight 10 July 1960, entered service 9 May 1961. This is the only variant still operational.[78] A total of 744 B-52s were built. The last production aircraft, B-52H AF Serial No. 61-0040, left the factory on 26 October 1962.[79] [80]
EB-52H :
Was a proposed variant of the B-52H that would have modified 16 aircraft with electronic jamming capabilities.[81] It would have given the USAF an airborne jamming capability that it has lacked since retiring the EF-111 Raven. The program was cancelled in 2005 following removal of funding for the stand-off jammer, it was revised in 2007 but funding was removed again in early 2009.[82]

Popular culture

The B-52 has been featured in a number of major films and other media:

Survivors

See main article: Boeing B-52 Survivors.

There are many B-52s on static display at USAF air bases and museums around the world.

References

Bibliography

All websites re-accessed: 29 November 2007.

External links

Notes and References

  1. http://www.boeing.com/history/chronology/chron08.html "The Boeing Logbook: 1952–1956 15 April 1952"
  2. Knaack 1988, pp. 206–207.
  3. Knaack 1988, p. 207.
  4. Knaack 1988, pp. 207-208.
  5. Knaack 1988, p. 208.
  6. Knaack 1988, p. 209.
  7. Knaack 1988, p. 210.
  8. Knaack 1988, pp. 210–211.
  9. Knaack 1988, p. 212.
  10. Knaack 1988, pp. 214–215.
  11. Knaack 1988, p. 215.
  12. http://www.globalsecurity.org/wmd/systems/b-52d.htm Global Security: B-52D
  13. Knaack 1988, pp. 217–218.
  14. Knaack 1988, p. 218.
  15. Knaack 1988, p. 217–219.
  16. Knaack 1988, p. 219.
  17. Knaack 1988, p. 221.
  18. Cooke 1956, pp. 24–28.
  19. Donald 1997, p. 161-162. Note: Ground tests and checkouts carried out on 29 November 1951 resulted in the XB-52's pneumatic system's failure during a full-pressure test with the resulting explosion severely damaging the wing trailing edge. The prototype was returned to the production hall for repairs.
  20. Knaack 1988, p. 222.
  21. http://www.vectorsite.net/avb52_1.html#m1 Vectorsite: B-52 Evolution
  22. Knaack 1988, p. 227. "Designing the B-29 had required 153,000 engineering hours; the B-52, 3,000,000."
  23. Knaack 1988, p. 229.
  24. Knaack 1988 p. 230.
  25. http://www.wordorigins.org/index.php/more/896/ Wordorigins.org "BUF"
  26. Flynn 1997, p. 138.
  27. http://www.globalsecurity.org/wmd/systems/b-52b.htm Global Security: B-52B
  28. Baugher, Joe. Service of Boeing B-52D Stratofortress. Retrieved: 12 October 2007
  29. Baugher, Joe. Origin of the B-52. Retrieved: 9 October 2007.
  30. Baugher, Joe. Service of Boeing B-52F Stratofortress. Retrieved: 12 October 2007.
  31. Dick and Patterson 2006, p. 161.
  32. Knaack, 1988, p. 256.
  33. http://www.globalsecurity.org/wmd/systems/b-52d.htm B-52 D
  34. Dick and Patterson 2006, p. 187.
  35. Budiansky 2004, p. 394.
  36. McCarthy & Allison, p. 173.
  37. Futrell 1976
  38. http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=1851 "SAC AIRBORNE ALERT"
  39. http://www.nautilus.org/archives/nukepolicy/Denmark/index.html US Nuclear Weapons Deployments Disclosed, Nautilus Institute
  40. http://www.foxnews.com/story/0,2933,218559,00.html "Spain, U.S. Agree to Radioactivity Cleanup 40 Years After Atomic Accident."
  41. http://www.nukestrat.com/dk/ButterknifeV012168.PDF "Butterknife V Thule Route."
  42. http://www.nasa.gov/vision/earth/improvingflight/B-52B_retires.html NASA's B-52B Retires
  43. Willis Air Enthusiast November/December 2005, p.50.
  44. Baugher, Joe. Service of Boeing B-52G Stratofortress. Retrieved: 12 October 2007.
  45. Dick and Patterson 2006, p. 225.
  46. http://www.af.mil/factsheets/factsheet.asp?fsID=83 B-52 Stratofortress
  47. Dick and Patterson 2006, p. 222.
  48. Dick and Patterson 2006, p. 242.
  49. Hopper, David. "Upgraded B-52 still on cutting edge". Air Combat Command Public Affairs, 31 March 2008. Retrieved: 21 July 2008.
  50. Song, Jaymes. "B-52 bomber carrying 6 crashes off Guam". Associated Press, 21 July 2008. Retrieved: 21 July 2008.
  51. http://www.afa.org/magazine/feb2007/0207force.asp B-52 Factsheet
  52. Arana-Barradas, Louis A. 'BUFF' and Tough - the B-52 bomber has been a valuable and effective member of the Air Force since 1955. Airman, June, 2001. Retrieved: 16 October 2007.
  53. Knaack 1988, p. 252–254.
  54. Knaack 1988, pp. 277–278.
  55. Knaack 1988, pp. 266–267.
  56. Knaack 1988, pp. 279–280.
  57. Willis Air Enthusiast November/December 2005, pp.41-43.
  58. Willis Air Enthusiast November/December 2005, pp.44-45.
  59. Dorr and Rogers 1996, pp.65-66.
  60. Knaack 1988, pp. 254–255.
  61. Knaack 1988, pp. 276–277.
  62. http://www.globalsecurity.org/wmd/systems/b-52-upgrade.htm B-52 Stratofortress Upgrades
  63. http://www.acq.osd.mil/dsb/reports/2004-06-b52h_re-engining.pdf "Defense Science Board Task Force on B-52H Re-Engining"
  64. Zamorano, Marti, "B-52 synthetic fuel testing: Center commander pilots first Air Force B-52 flight using solely synthetic fuel blend in all eight engines", Aerotech News and Review, 22 December 2006
  65. Hernandez, Jason, "SECAF certifies synthetic fuel blends for B-52H", Aerotech News and Review, 10 August 2007.
  66. Baugher, Joe. Boeing B-52A Stratofortress. Retrieved: 10 October 2007. Note: The electronic warfare officer sat behind the pilot facing to the rear.
  67. Dorr 1990, p.26.
  68. Willis Air Enthusiast September/October 2005, p.70.
  69. Baugher, Joe. Boeing RB-52B/B-52B Stratofortress. Retrieved: 10 October 2007.
  70. Willis Air Enthusiast September/October 2005, p.59.
  71. NASA "Balls 8".B-52B "Mothership" Launch Aircraft Retrieved: 2 October 2007.
  72. Baugher, Joe. Boeing B-52C Stratofortress. Retrieved: 11 October 2007.
  73. Baugher, Joe. Boeing B-52D Stratofortress. Retrieved: 12 October 2007.
  74. Baugher, Joe. Boeing B-52E Stratofortress. Retrieved: 12 October 2007.
  75. Hewitt Phillips, W. "Chapter 13: Gust Alleviation" JOURNEY IN AERONAUTICAL RESEARCH: A Career at NASA Langley Research Center, Monographs in Aerospace History, Number 12. Washington, D.C: NASA Historical Office,November 1998. p.132.
  76. Baugher, Joe. Boeing B-52F Stratofortress. Retrieved: 12 October 2007.
  77. Baugher, Joe. Boeing B-52G Stratofortress. Retrieved: 12 October 2007.
  78. Baugher, Joe. Boeing B-52H Stratofortress. Retrieved: 12 October 2007.
  79. Dorr 1990, p.27.
  80. Baugher, Joe. Service of Boeing B-52H Stratofortress. Retrieved: 12 October 2007.
  81. http://proxify.org/p/011010A1000100/687474703a2f2f7777772e646566656e7365746563682e6f72672f61726368697665732f3030313930392e68746d6c Jamming with the B-52s
  82. Trimble, Stephen. "US Air Force cancels SAM-jamming EB-52 for second time". Flight International, 3 March 2009.