The Air Force accepted the first XB-47 conditionally (minus certain equipment to be installed later by Boeing) on 29 November 1948. The second XB-47, first flown in mid 1948, was accepted the following month, under the same conditions. The Air Force took delivery of the experimental planes in December 1948, but lent them to the contractor in subsequent years. Like its predecessor, the second XB-47 was extensively tested. Boeing logged almost 100 hours of test flights; the Air Force, over 237.
p>This haste in the long run hampered both development and production. By August 1950, the Air Force had recommended some 2,000 changes, making it almost impossible to settle on an acceptable production type. Meanwhile, Boeing had begun to step up production. By mid 1951, B-47Bs were flowing in ever increasing numbers from the Wichita line but had to await the modifications and equipment that would make them suitable for combat. Despite an overall production slippage of nearly a full year, components subcontracted by Boeing as well as government furnished equipment and parts were still behind schedule. General LeMay was adamant in pointing out that failure to develop component systems in phase with production of the new bomber was an indication of bankruptcy in USAF procurement policy. The SAC Commander also thought that the USAF Armament Laboratory was not capable of satisfying the Air Force's needs.
By mid 1952, the B-47 development was still under way. Requirements kept expanding, special mission modifications were requested, and the Air Force again considered various redesigns of the aircraft's propulsion system.
In view of the B-47's sweeping new features, it was envisioned from the start that development and testing would be involved as well as lengthy. (The development and test phase, mostly completed in mid 1953 (after some 50,000 flight test hours), exceeded the original time estimate by almost 4 years) The XB-47's early flight tests quickly confirmed this expectation. Hence, the Air Force on 7 April 1950 endorsed an unusual operational suitability test, known as Project WIBAC (Wichita Boeing Aircraft Company). This meant that before the B-47 could be delivered to SAC's operational units, the aircraft and its equipment would be thoroughly tested at Wichita by Air Proving Ground Command and SAC personnel. Early WIBAC appraisals of the B-47 gave the Air Force something to think about. In mid 1951, SAC observers liked the airplane, but noted that the airframe and engines were much more advanced than the component systems. Moreover, designers and manufacturers of component parts, as well as the numerous subcontractors producing such items as relays, fuel selector valves, booster pumps, and the like, were not in tune with the sophisticated designs necessary for such a high performance aircraft. As a result, Boeing was forced to fit the B-47 with the same type of equipment that had caused so much difficulty in the B-29s and B-50s.
Besides, WIBAC promised to provide statistics on parts consumption, parts failures, and engine life. Guiding data on service testing, maintenance procedures, base facilities, and training needs were also part of the deal. The ambitious WIBAC task soon proved overwhelming. While no B-47Bs had reached WIBAC by mid 1951, the project was already in trouble. In August, WIBAC requested review of the whole B-47 program production, allocation, requirements, and operational deficiencies.
In September 1951 USAF test pilots pointed out that many of the modifications made to the B-47Bs had negatively impacted flying qualities, making the plane unstable at high altitudes and hard to manuver.
The impasse reported by WIBAC led to a conference in October 1951, attended by many top Air Force generals. Most conferees seemed to believe that WIBAC, and more specifically the office of the B-47 project officer, had been given an impossible job. Opinions differed, however, on how some of the difficulties encountered could have been avoided or at least reduced. Maj. Gen. Bryan L. Boatner, Commanding General of the Air Proving Ground, thought better results could have been secured had Air Research and Development Command and Air Materiel Command (AMC) contributed technical personnel and stationed them permanently at WIBAC as Strategic Air Command (SAC) and Air Proving Ground did. Lt. Gen. Earle E. Partridge, who headed the research and development command, commented that the concentration of all B-47 tests at Wichita had been a mistake. Generals Partridge and Boatner agreed that the B-47 was a very complicated piece of equipment and that the production problems were the greatest ever experienced. Then, General Twining (Vice Chief of Staff since October 1950) said that the B-47 problem fell to the Air Staff and that it would be solved. To this end, a so called refinement program was set to begin in early 1952 at the USAF Grand Central Plant in Tucson, Arizona. The minimum modifications to make the B-47 combat ready were lined up, SAC alone suggesting close to 50. Maj. Gen. Thomas S. Power, SAC's Vice Commander, pointed out that his command was more familiar than most with the bomber's deficiencies. He announced that an engineering operational program in the 306th Wing would get under way in early 1952. This program, General Power stated, should help significantly in speeding up progress.
Advanced procurement plans were finalized in November 1951 on the heels of the October conference by a definitive contract for 445 additional productions. This number was reduced to 395 in March 1952, after more realistic production schedules were endorsed.
As the B-47 bomb bay was designed to carry atomic bombs, no additional framework installation was required. Bomb racks, sway braces, hoists, and other equipment items were attached from the start to the airframe, specifically to the bomb bay fuel tank floor. Just the same, production and operational difficulties with the aircraft itself prompted a further cutback in the B-47B's atomic capability in April 1952. The Air Force decided at the time that the first 89 B-47Bs would not be required to carry any atomic bombs, and that the next 80 aircraft would only be expected to handle 2 specific types of bombs. While some of this early planning changed, a directive that all subsequent B-47Bs would be able to carry low density atomic bombs could not be satisified. Despite all efforts, the high speed B-47s proved unable to release subject bombs at altitudes below 30,000 feet.
Explosive decompression tests in 1951 proved the B-47's original canopy unsafe for high altitude combat operations. A sectionalized canopy was the answer, but would not be available for some time. Another major problem was the lack of ejection seats in the B-47B. SAC long believed that ejection type seats were the safest method of egress from high speed aircraft. Boeing studies on the subject had shown it would be impossible to get out of an uncontrolled B-47 without ejection seats. Escaping under controlled flight conditions would even be hazardous without them. Although the 10 B-47As had ejection seats, these were operationally marginal. Therefore, in the interest of saving weight at least until the B-47 reached a 4,000 nautical mile range a group of senior officers (including some from SAC) had decided to dispense with the seats. SAC's ensuing objections were to no avail, but its request in mid 1950 for reinstatement of the seats was finally approved. Still it became obvious in December 1951 that ejection seats would not be incorporated in production for quite a while.
Providing satisfactory ejection seats for the B-47's 3 man crew entailed the relocation of important pieces of equipment. Air Material Command estimated this might require as many as 26,000 engineering manhours. In addition, much more was involved to ensure crew safety. In fact, high speed testing of the approved seats (upward for pilot and co pilot; downward for the navigator) was still going on in December 1952.
As many as 400 B-47s would not have any ejection seats, and this was far more than SAC had been prepared to accept. Since retrofit of the aircraft then seemed economically impossible, the only alternative was to settle for the next best means of egress. To begin with, this called for development of a redesigned dinghy. It was difficult to maneuver from the crew positions to the escape hatch with the present dinghy attached to the parachute harness. Yet, in an emergency, there seldom was time to attach the raft after leaving one's seat.
The K-2 bombing and navigation system, like the early K-1 of many B-36s, was unreliable and hard to maintain. The 1,600 pound K-2 counted 41 major components, totaling some 370 vacuum tubes and close to 20,000 separate parts. Since the B-47 was compact, the K-2 equipment had been scattered throughout the aircraft. Many of the system's parts were outside of the plane's pressurized area. Hence, no inflight maintenance was possible and high abort rates wen; to be expected. Maintenance on the ground was nearly as difficult. Pre flight checking took too long 8 hours, compared to 1 hour for checking almost the same system on the B-36.
By mid 1952 the K-2 had been made to work somehow, but still needed improvement even after additional modifications had brought about its redesignation as the K-4. The Emerson A-2 tail defense system, earmarked for the B-47; was canceled before the end of the year in favor of the General Electric A-5. Development of the system could be traced back to 1946, when the XB-47 was first reviewed by the AMC's armament laboratory the same laboratory General LeMay still took to task in 1951. Engineers believed that the Emerson built tail turret, referred to as the A-1 fire control system and intended for the North American B-45, could be fitted into the B-47 without altering the turret's basic mechanism. With Boeing's concurrence, the Air Force in June 1948 asked Emerson to design for the B-47 a turret gunner cab similar to that of the B-45, but providing sufficient comfort for missions of long duration. The project quickly became so complicated that it was given up. A remote controlled system that would be operated by one of the flight crew members appeared more feasible. This gave way to the A-2 fire control system, a system eliminating the need for a tail gunner. This A-2 was due to provide accurate defensive fire for protection of the B-47 and to perform, although not simultaneously, both search and track. The A-2, after being fitted into the tail of a B-29, was successfully tested under Project Hornet. Moreover, in theory, the A-2 was superior to the APG-32 built by the General Electric Company for the B-36. In practice, however, while major APG-32 problems could be solved, the A-2's basic suitability for the B-47 remained too questionable to warrant its retention.
The decision, based on Project WIBAC's recommendation, proved sound but posed an immediate problem. No A-5 fire control systems were available and none were to be expected much before 1953. In the meantime, it was mandatory for SAC that a makeshift system be devised. Retrofit of early B-47s with a 2 gun turret and an N-6 optical sight was the chosen solution. This would at least give the aircraft some kind of defense. Although contrary to plans, the extra modification was included in the refinement program that had been endorsed during the conference of October 1951. Not surprisingly, further pioneer difficulties were encountered. One was fuel boil off and fuel purging, found more critical in jet bombers. The B-47 was designed for maximum speed and range at a high altitude, and the sooner it reached that altitude, the better. Yet, at high altitudes fuel boil and loss of fuel occurred, reducing the aircraft's range which, in any case, remained far shorter than required in early 1944. Development of JP-4 fuel, after numerous experiments, appeared to solve much of the problem, but production quantities would not be available until January 1952. Again, purging fuel tanks required the use of dry ice, which would be difficult to purchase in areas where the B-47s were expected to operate, especially when the aircraft would be operating overseas. Development of portable dry ice manufacturing equipment was a partial answer. A new exhaust gas purging system, being devised by AMC, would be more dependable and less hazardous. It would require no additional maintenance and provide greater and longer protection for more fuel volume than the dry ice system. This was all for the best but, as with every new system, the AMC development would take time.
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