The Boeing B-52 is perhaps best known as the aircraft that went to war twice but never fired a shot in anger. The aircraft made the initial moves in two strategic thrusts against The Caliphate, one in 1965 and one in 1973 but in both cases, the aircraft were turned back. In 1965 this was due to The Caliphate caving in at the last minute while in 1973, The Caliphate ceased resistance after RB-58s and B-70s had wiped out the primary target list, the biological warfare facilities, and all effective anti-bomber defenses. Nevertheless, the B-52 was the primary long range bomber used by Strategic Air Command between 1955 and 1975, a duration only equalled by the B-70 Valkyrie.
The development of the B-52 began in June 1947, only two days before The Big One, when the Air Force directed the Air Material Command to begin the formalization of requirements for the characteristics of a new generation of postwar bombers. This resulted in a series of specifications for a bomber with an operating radius of 5000 miles and a speed of 300 mph at 34,000 feet. The crew was to be five, plus gunners for an undetermined number of 20-mm cannon turrets. A 10,000 pound bombload was specified, as well as provisions for a 6-man relief crew. The Boeing proposal the Model 462, essentially a scaled-up B-29 with a shoulder-mounted straight wing with a span of 221 feet and an area of 3250 square feet. The circular-section fuselage was 161 feet 2 inches long. Power was to be provided by six Wright XT35 Typhoon turboprop engines, each offering 5500 shaft horsepower and driving six-bladed propellers. The decision to use turboprop engines rather than pure jets was a result of the fact that the jet engines of the day were notorious fuel hogs and using them would make it impossible to meet the range requirements. Although the Model 462 fell far short of meeting that range requirement, Boeing won the competition. In mid-June, the Boeing design was assigned the designation XB-52. It quickly became apparent that the aircraft was simply too large and expensive, that it offered few performance advantages over the B-36, and that it did not offer very much in the way of growth potential.
Undaunted, Boeing went back to the drawing board and came up with the Model 464. It was a much smaller version of the Model 462, with only four Wright XT-35 turboprops and a gross weight of only 230,000 pounds. General Curtis E. LeMay, SAC Commander pointed out that the Model 464 was still not good enough. He thought that the future B-52 should have a higher cruising speed as well as a longer range. Several interim improvements failed to change the poor standing of the B-52 and General Cragie, Deputy Chief of Air Staff for Research and Development, was now solidly against the project, claiming that it offered little improvement over the B-36, and that the B-52 would likely be obsolete before it could enter service. Consequently, the Model 464 was shelved. That would ordinarily have been the end of the line for the B-52, but General LeMay urged caution, and suggested a 6-month grace period before the final decision on the future of the B-52 could be made.
Boeing designers went back to work again, and went through a succession of designs during the first few months of 1949, before they settled on the Model 464-29. This version had the same four XT-35 turboprops of previous versions, but now featured a sharply tapered wing with 20 degrees of sweepback. An extended dorsal fin was provided. The wingspan remained at 205 feet and the weight at 400,000 pounds. In May 1949, the USAF asked Boeing to explore the possibility of switching to jet engines for the B-52. The Air Force had always been interested in jet power for long-range bombers, but up to now had always ruled them out on the basis of their high fuel consumption. In response to the Air Force request, in late July of 1948, Boeing came up with the Model 464-40. The Model 464-40 was broadly similar to the Model 464, but was powered by eight Westinghouse XJ40-13-12 turbojets in underwing podded pairs. Gross weight was 280,000 pounds, and dimensions were wingspan 185 feet and length 130 feet 9 inches. The performance was nominally better than that of the Model 464-35, especially at high altitude—maximum speed was now 507 mph at 47,000 feet.
In 1947, a contract had been given to Pratt & Whitney for the development of a 10,000 hp PT4 (T45) turboprop as a possible powerplant for the B-52 in case the Wright T35 engine did not work out. The PT4 had a dual axial flow compressor of 13 stages, and could easily be converted to a pure turbojet should the need arise. This was selected for the Model 464-40 with eight of the engines in pure turbojet configuration being accepted. The final design featured eight J57 engines in the podded arrangement first proposed for the 464-40. The wingspan remained at 185 feet, but the angle of sweep was increased a further 15 degrees to 35 degrees and the wing area was increased 1400 square feet to 4000 square feet, larger than any previous B-52 submission. Estimated maximum speed was 565 mph at 46,500 feet, and combat radius with a 10,000 pound bombload was estimated at 3550 miles. Gross weight was estimated at 330,000 pounds. After a final evaluation in January 1949, the Board of Senior Officers gave the new idea their approval, and decided to continue work on the Boeing proposal as a jet-powered aircraft. Boeing was informed on January 26 that the work on the jet-powered B-52 would proceed under the original contract. Range was still considered inadequate and Boeing undertook an effort to improve performance in this area. This resulted in a heaver version known as the Model 464-67. The wing remained the same, but the length of the fuselage was increased to 152 feet 8 inches, offering more space for fuel. Gross weight was estimated at 390,000 pounds. Combat radius was estimated at 3500 miles. General LeMay asked the Board of Senior Officers to accept the Boeing 464-67 in lieu of the Model 464-49. This choice was approved by the Board on March 24, 1950 and the B-52 was committed to full-scale development and production. Once the contracts were let, work on the two XB-52 prototypes proceeded rapidly and they were ready for rollout by late 1951.
The aircraft that emerged had a shoulder-mounted wing with a sweepback angle of 35 degrees. The wingspan was 185 feet, with an area of 4000 square feet. The wing was set at an angle of incidence of six degrees. This was necessary because of the tandem undercarriage layout, which did not permit the aircraft to rotate on takeoff. According to the standards of the day, the wings were quite thin. On the center line of the of the fuselage, the wing structure had a thickness ratio of 16.2 percent, declining gradually to a thickness ratio of only 8 percent at the tip. Although they were quite thin, the wings carried bladder-type cells for fuel. The thin wings had a considerable amount of flexibility, and could move up or down through a 32 foot arc at the tip without failing. The eight Pratt & Whitney J57 turbojets were carried two each in four underwing pods. The pods were suspended underneath the wings on pylons. The engines were situated beneath and ahead of the forward edge of the wing. Careful positioning of the engine pods helped to limit the drag rise at high speed and also served to alleviate load factors. The pylons also doubled as wing fences and helped to delay the onset of the stall. The wings were fitted with four segments of Fowler-type flaps, two on the trailing edge of each wing. Total flap area was 797 square feet. Only two settings were available, fully up or fully down, with the down angle being 35 degrees.
A lot of space in the fuselage was taken up by fuel tanks, with the upper sections from just behind the cockpit to just aft of the rear main undercarriage members being used almost exclusively for fuel. The weapons bay occupied almost the entire section of the lower fuselage between the forward and rear undercarriage members. It was 28 feet long and 6 feet wide, and was enclosed by double-panel doors. Three interconnected and hydraulically-actuated lower panels on each side made up the section of the bomb bay doors that could be opened in flight. While on the ground, the hinged upper panels could be swung back to provide additional clearance for loading and unloading of weapons. Defensive armament was limited to four 0.50-inch machine guns in a manned tail turret.
Normal crew was five, with pilot and copilot seated in tandem under a bubble-type canopy in the forward nose. The navigator and radar operator sat side-by-side on a lower deck in the forward nose. The tail gunner sat in a separate cockpit in the extreme tail. In an emergency, the pilot and copilot ejected upward and the navigator and radar operator ejected downward. The tail gunner jettisoned the turret by firing four explosive bolts, and he dived after it.
On the evening of November 29, 1951, the XB-52 prototype (49-230) was rolled out of the assembly hall and into the flight test hangar. It was covered with a tarpaulin to conceal its shape from prying eyes. It was subjected to a series of ground tests and checkouts. Unfortunately, the XB-52's pneumatic system failed during a full-pressure test and the resulting blow-out severely damaged the wing trailing edge, which required that the aircraft be moved back into the production hall for repair. The company and the Air Force decided to keep this news under wraps and attributed the delay to the installation of further equipment. As a result, the XB-52 did not become airborne until nearly a year later. Consequently, it was the second prototype, the YB-52, that was actually the first to get airborne. By the beginning of October 1952, the YB-52 had logged 50 hours in the air and had begun Phase 1 flight trials.
Specification of Boeing YB-52 Stratofortress
Engines: Eight Pratt & Whitney YJ57-P-3 turbojets, each rated at 8700 lb.s.t. Performance: Maximum speed 611 mph at 20,000 feet, 594 mph at 35,000 feet. Cruising speed 519 mph. Stalling speed 146 mph. Initial climb rate 4550 feet per minute. Combat radius 3545 miles with 10,000 pound bombload. Ferry range 7015 miles. Dimensions: Length 152 feet 8 inches, wingspan 185 feet 0 inches, height 48 feet 3.6 inches, wing area 4000 square feet. Weights: 155,200 pounds empty 405,000 pounds gross. Armanent: Not fitted with any defensive armament. Maximum offensive payload 43,000 pounds.
Boeing B-52A Stratofortress
The B-52A differed from the X/YB-52 in having a completely redesigned forward fuselage. The original bubble canopy and tandem seating arrangement for pilot and copilot were replaced by a side-by-side arrangement. Early in 1951, General LeMay told Boeing that he thought that the tandem seating arrangement featured by the XB-52 mockup was poor. General LeMay believed that side-by-side seating of pilot and copilot was superior, since it allowed more room for flight instrumentation and permitted the co-pilot to be a better assistant to the pilot. In August 1951, it was decided that the Air Force would adopt the side-by-side arrangement, but that some of the early production B-52s would still retain the tandem seating arrangement. This was later amended to stipulate that only the two prototypes would retain the tandem seating arrangement, with all production machines having side-by side seating for pilot and co-pilot. The forward fuselage was lengthened by 21 inches so as to accommodate additional equipment and an extra crew member. The crew was now six—pilot, copilot, navigator, radar operator, electronic warfare officer, and tail gunner. The pilot and co-pilot sat side-by-side in the upper deck of the forward fuselage, with the electronic warfare officer sitting behind the pilot facing to the rear. The navigator and the radar operator sat side-by side in the lower deck of the forward fuselage. The tail gunner sat all by himself in a station in the extreme tail behind the tall rudder.
The engines of the B-52A were more powerful than the largely- experimental engines of the prototypes. The powerplants were a set of eight Pratt & Whitney J57-P-1W turbojets, offering a dry thrust of 10,000 pounds. They were equipped for water injection, raising the thrust to 11,000 lb.s.t for short periods. This water was provided by a 360-gallon tank carried in the rear fuselage. A 1000-gallon auxiliary underwing fuel tank was provided outboard of the outrigger wheels. These tanks had also been fitted to both prototypes. However, it appears that the B-52As flew without these tanks more often than with them. The B-52A was fitted with an in-flight refuelling receptacle for midair refueling via the flying-boom technique. This receptacle was mounted on the upper fuselage just behind the cockpit. A couple of doors above the receptacle opened to allow the probe from the refuelling aircraft to attach itself to the B-52 for the transfer of fuel. The B-52A was the first to be fitted with defensive armament—a battery of four 0.50-inch M3 machine guns in the extreme tail. Each gun had 600 rounds of ammunition. The tail gunner, seated in the extreme rear of the plane underneath a transparent canopy, was provided with an A-3A fire control system which employed search and tracking radar antenna and which could automatically aim and fire the guns. However, the gunner also had a periscopic optical gun sight for manual operation of the guns.
The first B-52A (52-001) was rolled out at Seattle on March 18, 1954 with appropriate fanfare. Several thousand people were there for the ceremony, and USAF Chief of Staff General Nathan F. Twining addressed the crowd. It made its first flight on August 5, 1954. As was traditional, the first examples of the new Boeing bomber went to the 2nd Bomb Group, the 211th Wing of that group receiving 24 B-52A aircraft. However, controversy within the Air Force broke out over whether the B-52 would be better employed as a bomber or a reconnaissance aircraft. SAC wanted the B-52 to concentrate on the reconnaissance role with the exclusion of everything else. The RB-36s used by the strategic reconnaissance wings were hopelessly obsolete and a replacement was needed urgently. In October 1954, the Air Staff issued an order that, until further notice, all aircraft would be RB-52 reconnaissance aircraft.
Specification of Boeing B-52A Stratofortress
Engines: Eight Pratt & Whitney J57-P-1W turbojets, each rated at 10,000 lb.s.t. dry and 11,000 lb.s.t with water injection. Performance: Combat radius 3590 miles. Dimensions: Length 156 feet 6.9 inches, wingspan 185 feet 0 inches, height 48 feet 3.6 inches, wing area 4000 square feet. Weights: 420,000 pounds maximum takeoff. Armament: Four 0.50-inch M3 machine guns with 600 rpg in tail turret. Maximum offensive payload 43,000 pounds.
Boeing RB-52B Stratofortress
The RB-52B was outwardly identical to the B-52A, but featured an enhanced reconnaissance capability and was fitted with a bombing/navigation system. A total of 360 were built, being issued to five Strategic Reconnaissance Groups. The RB-52Bs carried out its reconnaissance mission via a two-man pressurized capsule installed in the bomb bay which could perform electronic countermeasures or photographic reconnaissance work. Downward-firing ejector seats were provided for the crew in the case of an inflight emergency. Equipment inside the capsule could be optimized for different types of intelligence-gathering missions and included long-focal length and panoramic camers, plus photoflash bombs, mapping radars, receivers, pulse analyzers and recorders. For search operations, the pod had one AN/APR-14 low-frequency radar receiver and two AN/APR-9 high-frequency radar receivers. Each station had two AN/APA-11A pulse analyzers. The station also had three AN/ARR-88 panoramic receivers and all electronic data was recorded on an AN/ANQ-1A wire recorder. Photographic equipment could include 4 K-38 cameras at the multi-camera station plus one T-11 or K-36 at the vertical camera station. The pod could also carry three T-11 cartographic cameras.
The first RB-52B (52-8711) was delivered to the 90th Strategic Reconaissance Group at Castle AFB in California on June 29, 1955. Over the next few months, the 93rd SRG traded in its RB-36Ls for RB-52Bs. The 90th SRG was declared combat ready on March 12, 1956, but its primary mission was the training of future B-52 crews. The initial teething troubles with the B-52 included difficulties with the fuel system, imperfect water injection pumps, faulty alternators, and especially with deficient bombing and fire control systems. These took over a year to wring out of the system.
Specification of Boeing RB-52B Stratofortress:
Engines: Eight Pratt & Whitney J57-P-1W, -1WA, or -1WB turbojets, each rated at 11,400 lb.s.t with water injection. Later, Eight Pratt & Whitney J57-P-29W or -29WA turbojets, each rated at 10,500 lb.s.t dry and 12,100 lb.s.t. with water injection. Last five were fitted with eight Pratt & Whitney J57-P-19W turbojets, each rated at 10,500 lb.s.t dry and 12,100 lb.s.t. with water injection. Performance: Maximum speed 630 mph at 19,800 feet, 598 mph at 35,000 feet, 571 mph at 45,750 feet. Cruising speed 523 mph Service ceiling at combat weight 47,300 feet. Initial climb rate 4750 feet per minute. Combat radius 3590 miles with 10,000 pound bombload. Ferry range 7343 miles. Takeoff ground run 8200 feet. Takeoff over a 50-foot obstacle 10,500 feet. Dimensions: Length 156 feet 6.9 inches, wingspan 185 feet 0 inches, height 48 feet 3.6 inches, wing area 4000 square feet. Weights: 164,081 pounds empty, 272,000 pounds combat, 420,000 pounds maximum takeoff. Armament: Two 20-mm M24A1 cannon with 400 rpg or four 0.50-inch M3 machine guns with 600 rpg in tail turret.
Boeing B-52C Stratofortress
With five Strategic Reconnaissance Groups flying RB-52Bs by 1956, the only B-52 bombers in SAC were the 24 B-52As in the 2nd Bomb Group. Despite the arrival of the B-60, most of SAC was still flying the increasingly vulnerable B-36. A switch back to B-52 bomber production was required. The first step was to order 48 B-52C bombers that would equip the remaining two Bomb Wings of the 2nd. The B-52C was essentially a RB-52B with its reconnaissance equipment removed. The primary difference between the B-52C and the earlier A and B models was that the B-52C featured much larger auxiliary underwing fuel tanks, with the 1000-gallon units of the B-52A and B being replaced by 3000-gallon tanks. This increased the total fuel capacity to 41,700 US gallons, which significantly extended the aircraft's unrefuelled range. All 48 B-52Cs were delivered in 1956.
Specification of Boeing B-52C Stratofortress
Engines: Eight Pratt & Whitney J57-P-29WA or -19W turbojets, each rated at 12,100 lb.s.t with water injection. Performance: Maximum speed 636 mph at 20,200 feet, 570 mph at 45,000 feet. Cruising speed 521 mph. Stalling speed 169 mph. Initial climb rate 5125 feet per minute. Service ceiling at combat weight 45,800 feet. Combat radius 3475 miles with 10,000 pound bombload. Ferry range 7856 miles. Takeoff ground run 8000 feet. Takeoff over 50 foot obstacle in 10,300 feet. Dimensions: Length 156 feet 6.9 inches, wingspan 185 feet 0 inches, height 48 feet 3.6 inches, wing area 4000 square feet. Weights: 164,486 pounds empty, 293,100 pounds combat, 450,000 pounds maximum takeoff. Armament: Four 0.50-inch M3 machine guns with 600 rpg in tail turret. Maximum offensive payload 43,000 pounds.
Boeing B-52D Stratofortress
The first large-scale production bomber version of the Stratofortress was the B-52D, of which 720 were built between June 1956 and November 1959. The B-52D was externally indistinguishable from the B-52C which preceded it. The only significant internal difference was the adoption of the MD-9 fire control system. The powerplants were the J57-P-19W or -29W. The B-52Ds were also fitted with the ability to carry Hound Dog cruise missiles and Quail decoys and received an improved electronic warfare outfit. Performance of the B-52D was identical to that of the B-52C. The first B-52s were received by the 100th Bomb Group in December 1956.
Boeing B-52E Stratofortress
The next production version of the Stratofortress was the B-52E which was externally identical to the B-52D. The differences were entirely internal, and featured a more sophisticated suite of bombing and navigation avionics, and led to the development of the AN/ASQ-38 system which was fitted to the B-52E and to subsequent Stratofortress versions. In the B-52E, some internal equipment was relocated and a slight redesign of the navigator-bombardier station increased crew comfort. Some experiments were made with low-altitude penetration but it was quickly discovered that the risks from light anti-aircraft guns and shoulder-fired missiles were too severe to be acceptable (let alone the added dangers of high-speed flight at low altitude and the strain on the aircraft's airframe) and the experiments were abandoned. 360 B-52Es were built, bringing the planned B-52 fleet up to 15 fully-equipped groups. The last B-52E was delivered in early 1960.
Boeing B-52F Stratofortress
With the 1960 decision to withdraw the B-60 from service, additional B-52s were ordered to equip five Bomb Groups that had operated B-60s. The aircraft were the B-52F version which differed from the E primarily in being equipped with more powerful J57-P-43W, -P-43WA, or P-43WB turbojets, which each offered a normal rating of 11,200 lb.s.t dry and 13,750 lb.s.t. with water injection. Incorporation of these new engines required some internal changes, and a slight modification had to be made to the wing structure in order to incorporate two additional water tanks in the wing. 480 B-52Fs were ordered and were delivered by mid-1962 (100 being replacements for B-52A/C aircraft and attrition replacements) and it was assumed that these would end B-52 production, a total of 1,952 aircraft having been produced.
Specification of Boeing B-52F Stratofortress:
Engines: Eight Pratt & Whitney J57-P-43WA turbojets, each rated at 11,200 lb.s.t dry and 13,750 lb.s.t. with water injection. Performance: Maximum speed 638 mph at 21,000 feet, 570 mph at 46,500 feet. Cruising speed 523 mph. Stalling speed 169 mph. Initial climb rate 5600 feet per minute. Service ceiling at combat weight 46,700 feet. Combat radius 3650 miles with 10,000 pound bombload. Ferry range 7976 miles. Takeoff ground run 7000 feet. Takeoff run over 50-foot obstacle 9100 feet. Dimensions: Length 156 feet 6.9 inches, wingspan 185 feet 0 inches, height 48 feet 3.6 inches, wing area 4000 square feet. Weights: 173,599 pounds empty, 291,570 pounds combat, 450,000 pounds maximum takeoff. Armament: Four 0.50-inch M3 machine guns with 600 rpg in tail turret. Maximum offensive payload 43,000 pounds.
Boeing B-52G Stratofortress
The B-52G design was officially begun in June 1960. At that time, the North American B-70 Valkyrie program seemed to be in trouble, and the development of the B-52G was initiated as a safety measure intended to prevent possible technical obsolescence of the strategic bomber force in the 1960s. In the design of the B-52G, considerable attention was paid to reducing the structural weight. Different materials were used in the construction of the airframe, and the wing structure was extensively redesigned. The B-52G featured a "wet" wing which resulted in it being able to carry 48,030 gallons of fuel as opposed to the 41,553 gallons of the B-52F. Each wing had three integral fuel tanks which replaced the rubber bladder-type tanks in the wings of previous versions. This called for a complete structural redesign. The new wing required the machining of long alloy wing skins so that stiffeners were an integral part of the structure. This resulted in a surface with a minimum of chordwise joints which, it was hoped, would reduce the possibility of fuel leaks and fatigue.
The familiar jettisonable 3000-gallon underwing auxiliary fuel tanks of earlier versions were replaced by smaller, fixed 700-gallon tanks. These were actually fitted not so much for the additional fuel capacity but more for their role as bob weights to help prevent wing flutter. According to SAC legend, the primary use for these tanks was to carry the crew's personal luggage. In spite of the weight reduction program, the gross weight of the B-52G was up to 488,000 pounds because of the increased fuel capacity. Total internal fuel tankage was 46,575 gallons. With the two external tanks fitted, total fuel capacity was 47,975 gallons. This offered greatly enhanced range performance.
In the B-52G, the gunner was moved from the extreme rear of the aircraft to a position beside the electronic warfare officer in the forward part of the fuselage. He was provided with a rearward-facing upward-firing ejector seat. The locations of the other four crew members (pilot, copilot, bombardier and radar navigator) were unchanged. A new Avco-Crosley AN/ASG-15 fire control system was fitted in the extreme tail to support the now remotely-operated rearward-firing gun turret. Like earlier versions of the fire control system, the AN/ASG-15 featured separate radar dishes for search and track, but it also carried a television camera, although the camera was later replaced by ALQ-117 countermeasures gear. The gunner could operate the tail guns either by using the AGS-15 fire-contol system or by using a remote control system which he monitored approaching threats either by radar or by closed-circuit television. The ammunition capacity of the tail gun was altered. The removal of the rear gunner's position made it possible to move the stowage location for the braking parachute from below to above the extreme aft fuselage section.
In the design of the B-52G, considerable attention was paid to improvements in crew comfort. In previous B-52s, pilots had often roasted while the bombardier and radar navigator froze, leading to lots of arguments over the cabin temperature control setting. The seats were redesigned to lessen the fatigue of 20-hour missions. The B-52G retained the AN/ASQ-38 bombing navigation system of the B-52F. However, the nose radome was enlarged, and was now of one-piece construction.
A total of 720 B-52Gs were ordered to replace the older B-52D and E models. These were delivered between 1963 and 1966.
Specification of Boeing B-52G Stratofortress:
Engines: Eight Pratt & Whitney J57-P-43WB turbojets, each rated at 13,750 lb.s.t with water injection. Performance: Maximum speed 636 mph at 20,800 feet, 570 mph at 46,000 feet. Cruising speed 523 mph. Stalling speed 169 mph. Initial climb rate 5450 feet per minute. An altitude of 33,400 feet could br reached in 19 minutes. Cruising speed 523 mph. Service ceiling at combat weight 47,000 feet. Combat radius 4100 miles with 10,000 pound bombload. Ferry range 9,976 miles. Takeoff ground run 8150 feet. Takeoff over 50-foot obstacle 10,400 feet. Dimensions: Length 157 feet 7 inches (later increased to 160 feet 10.9 inches), wingspan 185 feet 0 inches, height 40 feet 8 inches, wing area 4000 square feet. Weights: 168,445 pounds empty, 302,634 pounds combat, 488,000 pounds maximum takeoff. Armament: Four 0.50-inch M3 machine guns with 600 rpg in tail turret. Maximum offensive payload 50,000 pounds.
Boeing B-52H Stratofortress
The last new production version of the Stratofortress was the B-52H, a total of 720 being built so that the 20 B-52 Bomb Groups could all be equipped with B-52G or H aircraft. The most noticeable difference between the B-52H and earlier versions was the replacement of the water-injected J57 turbojet engines by Pratt & Whitney TF33-P-3 turbofans. The TF33 was a military adaptation of the JT3D turbofan, which had originally been produced as an adaptation of the J57 to the commercial market. The TF33 engines of the B-52H offered 30 percent more thrust than the J57s of the G-model, even when the J57s were using water injection. A maximum thrust of 17,100 pounds could be delivered, producing much better airfield performance and an extra margin of safety during heavyweight takeoffs. For the B-52H, the ground roll was about 500 feet less than that of the B-52G. In addition, the TF33 was much cleaner and quieter when operating at full power. It was much more environmentally-friendly than the water-injected J57, and did not leave behind it the same trail of noxious black smoke. The TF33 engine is much quieter, which results in a less-noisy cabin and a corresponding reduction in crew fatigue. The deletion of the water injection made it unnecessary to maintain large stocks of (prepositioned) distilled water, which had hindered the rapid deployment of the B-52G and earlier versions. The TF33 was also much more economical, offering a notable improvement in range.
The defensive tail armament was changed. The quartet of 0.50-inch machine guns carried by earlier versions was replaced by a single General Electric M61 20-mm six-barreled rotary cannon. The maximum firing rate was 4000 rounds per minute. The magazine carried 1242 rounds of ammunition. The Emerson AN/ASG-21 fire control system was installed as standard. The gunner was still seated in the main crew compartment forward of the wing leading edge, sitting in an upward-firing rearward-facing ejector seat beside the electronic warfare officer. The B-52H had originally been expected to carry four Douglas GAM-87 Skybolt air-to-surface missiles as the main offensive weapon. These were to be carried two each on an inverted Y pylon underneath each wing. The Skybolt was an air-launched ballistic missile that would have carried a W59 nuclear warhead inside a Mk 7 re-entry vehicle. Development was initiated in the latter half of the 1950s. Decision to proceed with the Skybolt was reached in February of 1960, with initial deployment scheduled to begin in 1964. In fact, Skybolt development ran late and the missile did not enter service until 1969. As a result, its deployment on the B-52H was limited.
The first B-52Hs were issued to combat groups in late 1966 and the last were delivered in 1969.
Specification of Boeing B-52H Stratofortress
Engines: Eight Pratt & Whitney TF33-P-3 turbofans, each rated at 17,000 lb.s.t. for takeoff. Performance: Maximum speed 632 mph at 23,800 feet, 603 mph at 35,000 feet, 560 mph at 46,650 feet. Cruising speed 525 mph. Stalling speed 169 mph. Initial climb rate 6270 feet per minute. Service ceiling at combat weight 47,700 feet. Combat radius 4825 miles with 10,000 pound bombload. Ferry range 10,145 miles. Takeoff ground run 7240 feet. Takeoff over 50-foot obstacle 9580 feet. Dimensions: Length 156 feet 0 inches, wingspan 185 feet 0 inches, height 40 feet 8 inches, wing area 4000 square feet. Weights: 172,740 pounds empty, 306,358 pounds combat, 488,000 pounds maximum takeoff. Fuel: Internal fuel 299,434 pounds, plus provision for 9114 pounds in two 700-US gallon non-jettisonable underwing tanks. Armament: One 20-mm M61 cannon with 1242 rounds in tail turret. Maximum offensive payload 50,000 pounds.
Boeing B-52J Stratofortress
By 1971 it was becoming apparent that the B-60F bombers were rapidly running out of airframe life. Their replacement, the B-74 Dominator was far from being ready to enter service and an interim solution was needed. Fortunately, the B-70 Valkyrie was finally starting to trickle into service with two Bomb Groups, the 35th and 100th already receiving their aircraft. This lead to a shuffle by which the B-52Gs from the 35th and 100th were transferred to B-52H equipped groups and the B-52Hs were modified for conventional bombing and issued to B-60 groups. The modifications involved redesigning the stowage of bombs in the bomb bay and the provision of underwing racks so that a total of up to 72,000 pounds of conventional bombs could be carried. As more B-70s entered service, the B-52s made available by them were similarly converted until all the B-60s had been replaced.