The B-52H did not differ outwardly from the B-52G, except for the shape of its nacelles, slightly altered because of the new engine's larger inlets. Internally, however, there were several important changes. The B-52H featured Pratt and Whitney's 17,000-pound thrust TF-33-P-3 turbofan engines (without water injection system), new engine-driven generators, ECM equipment improved up to the state of the art, and an enhanced fire-control system-the AN/ASG-21. This new system operated a Gatling gun-type of multi-barrel cannon in a remote-controlled tail mounting for rear defense. The Galling gun, the world's first practical machine gun, dated back to the Civil War. The B-52H's ultra-modern version of this 100-year-old weapon was hydraulically operated and electronically controlled. The 6-barreled gun could spew out a stream of 20-mm shells at the rate of 4,000 rounds per minute. The AN/ASG-21 also controlled forward-firing penetration rocket launchers. In addition, the B-52H had better cabin arrangements for low-level penetration flights and was equipped to carry the never-to-be GAM-87 Skybolts. Instead of Skybolts, the B-52Hs carried decoys and missiles identical to those of the B-52Gs.
An outgrowth of the B-52G, the B-52H design was initiated in January 1959, 1 month before SAC received its first B-52G. Although no great innovations resulted, some airframe changes had to be made to take care of the new model's special features. The B-52H was due from the start to incorporate the TF-33 turbofan engine, a modified J57 already adopted by commercial jet transports. The new aircraft was also designed to carry 4 Douglas GAM-87A Skybolts, which would be a marked improvement over previous B-52s. Had the Skybolt survived, it would have characterized the B-52H as the first manned bomber capable of serving as a flying platform for launching 2-stage solid propellant ballistic missiles with a range of 1,150 miles, fitted with nuclear warheads.
Like the B-52Gs, the B-52Hs were bought under individual contracts. Two FPI contracts-AF33(600)-38778, funded in FY 60, and AF33(600)41961, funded in FY 61-accounted for the entire B-52H lot. The first procurement, initiated by letter contract on 2 February 1959, was finalized the following year, on 6 May 1960. It covered 62 B-52Hs. The second B-52H contract was started by a letter contract on 28 July 1960, but was not finalized until the latter part of 1962. There were good reasons for the delay. This was the end of the B-52 procurement and the contract only purchased 40 more B-52Hs. The Air Force could not be sure this would be enough. These were difficult times. In September 1962, an Air Force recommendation to expand the North American XB-70 program into a full-scale weapon system development was rejected by Secretary of Defense McNamara. In December, President John F Kennedy confirmed that further development of the Skybolt, an air-to-surface ballistic missile earmarked for the B-52H, was definitely cancelled.
The YB-52H's first flight was entirely successful. Ensuing flight tests showed that the new TF-33 turbofan engines would allow the new plane to surpass the B-52G's range. Take-off would also be improved and require about 500 feet less ground roll than the B-52G.
The Air Force accepted the first B-52H in the same month the plane initially flew, but left it with Boeing for testing. By the end of June 1961, B-52H flight tests had confirmed that the TF-33-P-3 engines were working even better than expected. Moreover, even though the new Emerson ASG-21 fire-control system and the Sunstrand 120 KVA constant speed alternator drive needed perfecting, they both were tactically operable.
The B-52H entered operational service with the 379th Bomb Wing, at Wurtsmith AFB, Michigan. The first plane (Serial #60-001) was received by the 379th on 9 May 1961. By the end of June, 20 B-52Hs were in operation. In contrast to all other B-52Hs, 18 of those early planes had not been equipped during production for all-weather, low-level flying. However, modifications accomplished between April and September 1962 brought them up to standard.
While both the B-52F and B-52G had failed to live up to original range estimates, the B-52H's new TF-33-P-3 turbofan engines gave the aircraft a better range increase than anticipated. Moreover, as indicated by recent B-52H flight tests, some of the new engine's problems appeared to be solved, and remaining malfunctions were being worked out. Yet, despite several engineering fixes, the TF-33 in late 1961 still created difficulties. Throttle creep, hang or slow start, flameout, and uneven throttle alignment were some of the most frequent troubles. In addition, the engine consumed too much oil, turbine blades failed and inlet cases often cracked. By mid-1962, even though most of these early problems had been corrected, Hot Fan, a depot maintenance and overhaul project, was underway. This $15 million modernization effort, involving the accomplishment of 35 technical orders, had 2 essential purposes. The Air Force wanted the TF-33 to be more reliable, and it did not want the engine to fail before 600 hours of operation. Curtailed by the Cuban Missile Crisis of October 1962, when all B-52s stood on alert, Hot Fan was not resumed until January 1963. However, the Oklahoma City Air Materiel Area accelerated its overhaul schedule, and although Hot Fan covered 894 TF-33 engines, the project was practically completed before the end of 1964.
B-52Hs were still being assigned to SAC when a serious and ill-timed problem came to light. In August 1962, again shortly before the Cuban Missile Crisis, 2 of the B-52Hs at Homestead AFB, Florida, developed cracks where wings and fuselage joined. Boeing and the Air Force focused attention on the taper lock fasteners, which under high stress and in the B-52's operational environment were susceptible to corrosion. They soon determined that the "primary contributing cause for these cracks was the use of taper lock fasteners throughout the forging." In September, Boeing came up with a repair and rework package to take care of the problem. The next month, engineers of Air Force System Command's Aeronautical Systems Division set up requirements to evaluate the impact of stress corrosion on all primary structural materials. Project Straight Pin, the modification package developed by Boeing, was not allowed to linger. Rework centers were immediately established at Moses Lake, Washington; Wichita, Kansas; and at the San Antonio Air Materiel Area's shops. There, maximum interference wing terminal fasteners were replaced with those having extremely low interference, and cracked fitting holes were "cleaned up" by oversize reaming. Although SAC suspended diversion of its airplanes to the modification centers during the Cuban Crisis, Straight Pin was virtually completed by the end of 1962.
An older stress corrosion problem came to life again in August 1962. Two main landing gear outer cylinders failed on B-52D and B-52F aircraft, the latest in a series of similar incidents with B-52Gs and B-52Hs since the end of 1959. While SAC asked for redesigned cylinders, Air Force engineers noted that a quicker and safer alternative would be to make use of another alloy, one that would be less susceptible to stress corrosion. This gave way to a new study and test program to further investigate current and potential stress corrosion problems. Meanwhile, to prevent other incidents, anticorrosion coating was applied to all components of the landing gear. Progress was also made to cure most of the B-52H's other early ills. By mid-1962, failure of the aircraft's Sunstrand constant speed drive was becoming a problem of the past. During the same period, a long-standing SAC requirement, only endorsed for the B-52Hs, was finally extended to all B-52s. Started in January 1963 and completed in March of the following year, this retrofit project put 2 cartridge starters in every B-52. The installation of cartridge starters was not simple. The aircraft's electrical system had to be modified to accommodate the new starters and new valves. In addition, duct covers had to be redesigned and nickel cadmium batteries had to be added. The modification was expensive, which accounted for SAC's difficulties in getting it approved for the entire B-52 force, but it was important. Besides giving crews the means to start their engines faster, it would allow dispersed or post-strike B-52s to take off from airfields lacking certain ground support equipment, electrical power carts in particular.
As already noted, all B-52G structural modifications were extended to the B-52Hs. These aircraft were also included in the many B-52G modernization programs of the early seventies. Like the Gs, the B-52Hs were being equipped to carry the new SRAMs; they were being fitted with electrooptical viewing systems, low-light television cameras, and forward-looking infrared scanners. Finally, they were due to receive better electronics and more sophisticated components to improve both their offensive and defensive systems. A new project, initially triggered by the relatively slow start of the B-52H's TF-33 engines, was also underway. Despite the cartridge starter retrofit that had been accomplished between 1963 and 1964, SAC was still dissatisfied with the time it took for the B-52 to take off. The recently approved Quick Start project, now only concerned with the B-52G and H bombers, would make the ground alert force far less vulnerable to surprise attacks. Quick Start specifically consisted of putting a quick start device on each of the aircraft's 8 engines, thereby ensuring take-off in almost no time.
Production ended in the fall of 1962, SAC receiving on 26 October the last B-52H (Serial #61-040). This plane went to the 4137th Strategic Bomb Wing at Minot AFB, North Dakota. This marked the end of a production run which had begun some 9 years before. Wanting to keep the production door ajar, at least for a white, the Air Force negotiated with Hoeing a supplemental agreement to the final B-52H production contract-AF33(600)-41961. Signed on 17 October 1962, this $770,283 agreement ensured that Boeing, the prime contractor, would store the Wichita B-52H tooling until July 1963. Selected B-52 subcontractors, using government-owned facilities, would do the same.
The 102 B-52Hs accepted by the Air Force, like the B-52Gs, were built in Wichita. The Air Force accepted 20 B-52Hs in FY 61 (from March through June 1961); 68 in FY 62 (between July 1961 and June 1962); and 14 in FY 63 (the last 5 during October 1962). Cost per aircraft was: $9.28 million: Airframe, $6,076,157; engines (installed), $1,640,373; electronics, $61,020; ordnance, $6,804; armament (and others), $1,501,422.
The Air Force inventory in July 1973 still counted 99 B-52Hs-against an initial contingent of 102. Like the B-52Gs, B-52Bs were undergoing modifications to extend their service-life as well as their efficiency.
On 10-11 January 1962, a B-52H of the 4136th Strategic Wing, Minot AFB, North Dakota, completed a record-breaking 12,532.28-mile unrefueled flight from Kadena Air Base, Okinawa, to Tbrrejon Air Base, Spain. This flight broke the old "distance in a straight line" world record of 11,235.6 miles held by the U.S. Navy's propeller-driven "Truculent Turtle." Weighing 488,000 pounds at takeoff, the B-52H flew at altitudes between 40,000 and 50,000 feet with a top speed of 662 miles per hour on the Kadena-Tbrrejon flight route.
On 7 June 1962, a B-52H of the 19th Bomb Wing, Homestead AFB, Florida, broke the world record for distance in a closed course without landing or refueling. The closed course began and ended at Seymour Johnson AFB, North Carolina, with a validated distance of 11,336.92 miles. The old record of 10,078.84 miles had been held by a B-52G of the 5th Bomb Wing since 1960.
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