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Preliminary Development History - IKKE OPDATERET

The B-52 Stratofortress has been the backbone of the Air Force's manned bomber strategic deterrent for the last 35 years. The B-52 entered service with the Strategic Air Command in 1955, and by 1958 it represented the most important component of America's strategic deterrent. At peak strength in 1963, SAC operated 650 B-52s, divided up among 42 squadrons at 38 different air bases. However, intercontinental ballistic missiles assumed a greater role in the strategic deterrent, but the B-52 remained important even after missiles had assumed the primary responsibility for the deterrent. The B-52 had been designed for the strategic nuclear bombardment role, but it was to assume an important conventional role in two wars -- the Southeast Asian War of 1965-1972 and Desert Storm of 1991. The Stratofortress has been periodically been upgraded over the years to make it a more capable weapons delivery platform, and had swapped roles from high-altitude nuclear bomber to low-level strike aircraft and cruise-missile carrier.

By now, budgetary limitations imposed by the end of the Cold War as well as treaty restrictions have relegated most of the B-52 fleet to the bone-yards or to museums, and many of them have been scrapped. However, the B-52H version still remains in service in substantial numbers and will remain so until the end of the century. It is possible that the B-52 could end up serving in its primary combat role for fifty years, which will probably be some sort of record for a combat aircraft.

The development of the B-52 can be said to begin back in June of 1945, at a time when the war in the Pacific was still going on. Assuming that the war in the Pacific would soon be over, the Army Air Forces directed the Air Material Command to begin the formalization of requirements for the characteristics of a new generation of postwar bombers. The seizure of forward island bases for B-29 operations against Japan at the cost of so much blood and treasure being quite recently in mind, chief among the requirements for a postwar long-range strategic bomber would be the ability to carry out its mission without the need for the reliance on advanced or intermediate bases controlled by other countries.

On November 23, 1945, a series of specifications were issued calling 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. What was sought was fundamentally a second-generation intercontinental bomber to replace the Convair B-36 which had still not yet made its maiden flight.

On February 13, 1946, the new bomber project was submitted to the aviation industry, with invitations to bid on the military characteristics laid down in the November specification. Three manufacturers -- the Boeing Airplane Company, the Glenn L. Martin Company, and the Consolidated Vultee Aircraft Corporation -- submitted cost quotations and preliminary design data.

The Boeing proposal was the Model 462. It looked a lot like a scaled-up B-29, being a fairly conventional monoplane 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 would make it difficult if not impossible to meet the range requirements. The four main wheels of the nose wheel undercarriage each retracted separately into the four inner engine nacelles. Gross weight was 360,000 pounds.

Although the Model 462 fell far short of meeting the range requirement, Boeing was informed on June 5, 1946 that it had won the competition. In mid-June, the Boeing design was assigned the designation XB-52. The letter contract issued to Boeing on June 28 (W-33-03A-ac-15065) asked for a full-scale mockup of the XB-52, plus preliminary design engineering, and the supplying of test data.

In October of 1946, less than three months after Boeing had received the Letter Contract, the USAAF was already beginning to experience misgivings about the XB-52. It was concluded that the aircraft that had been proposed by Boeing 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. Maj. Gen. Earle E. Partridge, assistant chief of Air Staff for operations, bluntly pointed out to Boeing that the Model 462 simply did not meet the range requirement.

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 XT35 turboprops and a gross weight of only 230,000 pounds.

Maj. Gen. Laurence C. Craigie, chief of the USAAF Engineering Division, recommended that the new Model 464 design be adopted. However, in November of 1946, General Curtis E. LeMay, then Deputy Chief of Air Staff for Research and Development, 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.

In December, the USAAF requested that a study be carried out for a four-engined bomber with a range of 12,000 miles, a cruising speed of 400 mph, and the ability to carry and drop the atomic bomb. Boeing came up with two separate proposals -- Models 464-16 and 464-17. Both were still powered by four Wright XT35 turboprops, but these engines now promised a significantly higher power output than was offered for the earlier 464 version, and a better performance was anticipated. The new proposals were also significantly larger and heavier than the earlier 464 version. Gross weight was now estimated at 400,000 pounds, wingspan was 205 feet, wing area was 3000 square feet, and length was 156 feet. Effective range was extended by the use of large external tanks underneath the outer wings. Top speed was estimated at 440 mph at 35,000 feet.

The difference between the two models was that the 464-16 was a "specialized" version (i.e. intended for the delivery of nuclear weapons) that could carry only a 10,000 pound bombload over a long range and the 464-17 was optimized for conventional warfare and was capable of carrying a bombload as high as 90,000 pounds over a much more restricted range.

The USAAF clearly could not afford to fund both projects simultaneously, and they opted for the conventional-warfare Model 464-17. Apart from the range, the Model 464-17 appeared to meet the requirements. However, with the advent of mid-air refuelling, the shortfall in range did not now appear to be all that critical a disadvantage. However, General LeMay was still not happy, since he felt that this version of the XB-52 would still be too large and costly -- perhaps limiting procurement to only 100 aircraft. To make matters worse, General Craigie 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 464-17 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 XT35 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. A major change was the adoption of a centerline landing gear underneath the fuselage similar to that fitted to the B-47 but with forward and aft units much closer together, plus a set of outrigger wheels which retracted into the outer engine nacelles. The estimated maximum speed was 445 mph.

In the latter half of 1947, the Air Force was still looking for more effective means of delivering nuclear weapons. A Heavy Bombardment Committee was established to explore alternatives. Speed and altitude were found to be crucial qualities required of an aircraft capable of delivering the atomic bomb. This was particularly true when the bomber reached the combat zone. A new set of requirements was drawn up, calling for a special-purpose bomber with an 8000-mile range and a 550-mph cruising speed. These new requirements were officially issued on December 8, 1947, although at that time the cruising speed requirement was lowered to only 500 mph.

Under the new set of requirements, both the range and speed of the Model 464-29 would clearly be inadequate. During the winter of 1947-48 things looked so unpromising that the entire B-52 project was on the verge of cancellation. On December 11, 1947, the Air Materiel Command had actually been directed to cancel the Boeing contract, but a protest from Boeing chairman William M. Allen persuaded Secretary of the Air Force Stuart Symington to grant a stay of execution. Nevertheless, in January of 1948 Symington informed Boeing that the existing proposal was not suitable, but that no final decision would be made until other possibilities (such as the Northrop YB-49 flying wing) had been explored.

During this period of uncertainty, Boeing engineers had been at work in attempting to improve the performance of their design. The result was the Model 464-35, which first appeared in January 1948. It had the same four Wright XT35 turboprops, but the engines now drove a set of coaxial propellers. The wingspan was reduced to 185 feet, wing area to 2600 square feet, and length to 131 feet 4 inches. Considerable attention had been paid to weight reduction, and gross weight was now down to 280,000 pounds. Maximum speed was estimated at 500 mph at 41,000 feet. Maximum range was 11,635 miles.

The performance of the Model 464-35 now appeared to be closer to what the Air Force wanted. In April 1948, Boeing presented a complete Phase II proposal for the design, development and testing of two XB-52s based on the Model 464-35. Although the Model 464-35 was still not all the Air Force wanted, the blockade of Berlin by Soviet forces which began in late June gave a new sense of urgency, and the Air Force endorsed Boeing's Phase II proposal in July.

The B-52 project was now well on its way, and work began on a mockup. However, things were to change yet again, this time even more drastically. In May of 1948, 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 464-35, 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.

The Boeing engineers took the Model 464-40 study to the Air Force Project Officer, who was favorably impressed, especially since he had already been thinking along similar lines. Nevertheless, the government was still 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 of its two XB-52s. Although he agreed that turbojet propulsion was definitely the wave of the future, General Howard A. Craig, Deputy Chief of Staff for Material, was not very keen on a jet-powered B-52, since he felt that the jet engine had still not progressed sufficiently far to permit the skipping of the intermediate turboprop stage. However, Boeing was encouraged to continue with turbojet studies even though no commitment to jet propulsion could be expected at present.

Within only a couple of months, everything was to change. On October 21, 1948, a group of Boeing engineers arrived at Wright Field to confer with Air Force officials about the future of the turboprop-powered B-52. The Boeing team had arrived with reams of drawings and figures in preparation for discussions on the progress of their design. They were shocked when Col. Henry Warden of the Wright Air Development Center told them that the turboprop design should be scrubbed and that the turbojet was definitely the way to go. Warden had been pushing Pratt & Whitney to develop the JT3 (J57), a pure jet adaptation of the 10,000 hp T45 turboprop, as a powerplant for the B-52.

Pratt & Whitney had not been a pioneer in jet engine development, the US government having chosen not to divert this manufacturer from its primary task of making its fine series of air-cooled piston engines. P & W's first successful effort in the field of turbine propulsion had been the PT2, which had evolved as the successful T34 turboprop. 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.

After giving the idea consideration throughout the afternoon and evening of October 21, the Boeing team called Col. Warden the next morning and told him that they would have a fresh proposal ready by the next Monday. The team went back to the Van Cleeve Hotel in Dayton and worked around the clock all weekend long. Their colleagues back in Seattle were told to stand by to provide data by phone if needed. The Model 464-49 was the result. It 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. It was felt that the use of jet engines would eliminate the need to tackle the unsolved problems with propeller aerodynamics and control, and a jet-powered B-52 would probably be available almost as quickly as the turboprop variant then under development.

An engineer converted this new design into model form by using balsa wood purchased from a local hobby shop. On Monday morning, the Boeing team delivered their new proposal to the Air Force. Colonel Warden was immediately convinced, and decided that the B-52 would henceforth proceed as a jet-powered aircraft. Boeing immediately halted all work on the Model 464-35 mockup, which was then almost ready. At the same time, Pratt & Whitney was instructed to proceed with the J57 engine.

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.

Although the jet-powered B-52 showed considerable promise, the severe budgetary squeeze enforced by the Truman administration on the Defense Department in late 1948 endangered the whole B-52 program. There was also some internal Air Force resistance to the project at several levels, since the decision to proceed with a jet-powered B-52 had leapfrogged over powerplant, armament and propeller divisions at Wright Field.

The swept-wing turbojet-powered XB-52 mockup was inspected on April 26-29, 1949. The Air Force still had some reservations about the range, since the J57 engine at its current stage of development promised a combat radius of only 2700 nautical miles. General Orville R. Cook, the AMC Director of Procurement and Industrial Planning, was very unhappy about the low range and favored a review of the entire program and perhaps the scheduling of another competition. However, General LeMay, now the commander of the Strategic Air Command, was now thoroughly convinced and strongly backed the B-52, and suggested that the answer to the range problem lay in engine development and that it was unnecessary to accept inferior performance in either speed or range.

In November 1949, convinced that the inadequate range of the Model 464-49 could seriously jeopardize the future of the entire project, Boeing undertook an effort to improve the range. As an answer, Boeing offered a heavier 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.

The Model 464-67 was looked upon favorably by SAC personnel, including General LeMay. On January 26, 1950, a conference was held at USAF Headquarters to consider once again the future of the B-52. Alternatives were considered once again, including new proposals from Douglas and Republic, Fairchild Aircraft Corporation's idea for a rail-launched flying wing, the swept-wing Convair YB-60, a Rand turboprop aircraft, two new designs based on the B-47, plus several missile aircraft. Although the meeting adjourned without reaching any firm decision, General LeMay still backed the B-52 as providing the best solution for SAC's strategic mission.

In February 1950 the Air Staff requested performance and cost data for all the strategic vehicles so far proposed. In the same month, however, 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, but there was still no definitive commitment to production.

It was not until early 1951 that the decision was finally taken to commit the B-52 to production. By this time, the Korean War was in full fury, and the relations between the USA and the USSR were at a new low. General LeMay forcefully argued for the modernization of the strategic bombing force with the B-52. On January 9, 1951, USAF Chief of Staff General Hoyt S. Vandenberg approved a proposal that the B-52 be acquired as a replacement for the B-36. Letter Contract AF33(038)-21096, signed on February 14, 1951, was the first contract authorizing production. It called for an initial batch of 13 B-52As (with serials 52-0001/0013), with first delivery slated for April of 1953.

Still more controversy broke out among the USAF hierarchy as to whether the B-52 would be better employed as a bomber or a reconnaissance aircraft. SAC wanted a dual-role aircraft which could accommodate a pod-mounted set of reconnaissance sensors that were easily removable so that the aircraft could quickly be reconfigured as a straightforward bomber. USAF Headquarters wanted the B-52 to concentrate on the reconnaissance role with the exclusion of everything else. In October of 1951, the Air Staff issued an order that all aircraft would be RB-52 reconnaissance aircraft. This directive was actually misleading, since it was agreed that the aircraft would retain the ability to be converted for bombardment operations.

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 copilot 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 copilot.


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