<p>The B-58 was a combination of innovation and style which resulted in probably the classiest aircraft ever to wear Strategic Air Command's blue band. Its rapier shape and mighty J79 engines made it not only a formidable weapon, but also a world record holder with performance in excess of many fighters of the day.
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<p>Almost every part of the aircraft was new, and when it was designed each item probably had to thrust into the unknown. Even in the galloping advances of the 1950s people were still surprised to see a bomber whose height appeared to be greater than its wing span, and to see a needle-like body riding on long gatefold landing gears that resembled the tall legs of a mosquito. Flying the B-58 called for constant alertness, even though most of the time the ride was as smooth as silk. It was not unknown to travel sideways at over Mach 1, and the complexity was such that there were at least 14 major new items to go wrong. In 1964 test pilot Major Dick Johnson was asked whether the B-58's successor, the swing-wing F-111, could be landed with the wings jammed at 62.5 degree sweep; he replied, "It can be done; it's very like a B-58."
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<p>In 1949, when the UK was still writing specifications for its first subsonic jet bombers, the USAF had enough experience of such aircraft to recognize that the next step would be a supersonic bomber. It was difficult enough to build a supersonic fighter, but a supersonic bomber appeared to be impossible. The poor ratio of lift to drag was alone sufficient to destroy the practical possibilities. Put another way, a Mach 2 bomber was bound to have roughly five times the cruise drag of an equivalent size supersonic bomber, and thus would need about five times as much thrust and, give or take a few decimal places, about five times as much fuel. Alternatively, it would have one-fifth the range, which was nonsense. The USAF Air Research and Development Command (today Materiel Command) held an industry competition for GEBO-II, a GEneralized BOmber study, to see if some meaningful figures could be produced. The best submission, in January 1951, came from Convair Fort Worth, then building lumbering B-36s.
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<p>Convair's San Diego division had already gained extensive experience of transonic tailless delta aerodynamics with the XF-92A and was building the F-102 interceptor to the same formula. It alone had some basis on which to propose a tailless delta supersonic bomber, but there was no firm basis for type of engine, numbers of engines or their location. Moreover, to get anything like a useful range it was essential to cheat. One prolonged study involved parasiting, the technique of hitching a ride on a larger long-range aircraft before casting off to fly a much shorter supersonic dash across hostile territory. The obvious parent was the B-36, and in fact years later when the B-58 airframe had to be delivered to Wright-Patterson AFB for static testing, it was flown there fastened under a B-36; but parasiting never looked really practical, any more than it did for the Mach 3 North American XB-70. Almost the only other way to cheat on a big scale was to make the bomber too small to carry the fuel and bombs and then package these separately into a giant streamlined pod. Once this pod had been released the bomber reverted to a small aircraft with sufficiently low drag to fly home on the internal fuel.
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<hi style=hdr1>Breaking New Ground</hi>
<p>To cut a colossal story short, Convair Fort Worth worked their way through a succession of FZP brochures in the first quarter of 1951 and in March 1951 received a Phase I contract for MX-1626 which for most of 1951 had two monster General Electric J53 engines but sometimes three. General Electric plugged away at a completely new concept, the lightweight variable-stator engine, however, and via the X-24A this matured as the J79. Much smaller than the J53, it was more fuel-efficient and had a higher thrust/weight ratio.
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<p>MX-1626 became MX-1964 in May 1952, with a gross weight of 140,000 lb (63,504 kg) and four X-24A engines, at first in twin pods and finally, when the USAF awarded the go-ahead contract in August 1952, in four single nacelles. Throughout the study phase the managerial methods had been as radical as the project itself, and though the August 1952 contract did call for two prototype aircraft in the traditional manner, it was the first true WS (weapon system) contract. Convair was made totally responsible for two weapon systems, WS-102A (bomber) and WS-102L (reconnaissance aircraft). The latter was never built. The company's responsibility extended not only to every part of the aircraft but everything needed to build, support and maintain it, train crews and print the manuals, and included films, computer tapes and simulators.
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<hi style=hdr1>Revolutionary Engine Design</hi>
<p>The two prototypes were designated XB-58, with the serials 55660 and 55-661. Later in 1952 Convair received a letter contract for a total of 16 B-58 weapon systems (later cut to 11, designated YB-58A, serialled 55-662/671) with 31 pods. The parallel effort on the engine and its installation was enormous, because never before had anyone designed a true supersonic air-breathing engine with main and bypass flows, variable cooling flows, a variable-geometry inlet with a translating (axially sliding, computer-positioned) center-body spike, and fully variable primary and secondary nozzles. A related engine was chosen for the Lockheed F-104, and by 1975 the J79 had more time at Mach 2 than all other non-Soviet engines combined. Although the number of B-58s was trivial compared with those of the F-104, McDonnell F-4, North American A-5 and other aircraft, nearly 75 per cent of the Mach 2 time was logged by the B-58.
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<p>The number of major studies, investigations and voluminous reports in the early years of the B-58 was incredible. Some were concerned with reconnaissance or LRI (long-range interceptor) versions, and a major hiccup in March 1953 was injected by the timely discovery of the 'area rule' (with Convair's own F-102, which refused to exceed even Mach 1). The B-58 was reprofiled just in time to avoid similarly embarrassing problems, and from 1954 the biggest effort was by Sperry on the enormously large and complicated navigation and bombing system, by Bendix on the fully powered flight controls and by Hamilton Standard on the unprecedented air-conditioning. There were only three flight control surfaces, but they were the most powerful ever built. Each elevon had a chord of 7 ft (2.13 m) and an area more than one-eighth that of the whole wing; the power units could drive them at 20 degrees per second with a hinge-moment of over 120,000 Ib-ft (162 kN-m), roughly 100 times that for similar surfaces on fighters of the day.
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<p>At last, on 31 August 1956, the incredible XB-58 was pushed out of the mile-long plant, and a sneak picture appeared from a news agency. It revealed something that looked like a praying mantis, and was remarkably small for the task it had to do. This aircraft was flown by chief engineering test pilot B. A. Erickson on 11 November 1956, still with no pod. Initial flying was encouraging and confirmed several very large decisions that had been taken on the basis of not much better than educated guesses. Convair proposed five far-sighted spin-off aircraft at this time, including a dedicated low-level B-58, a version carrying an ALBM (air-launched ballistic missile), a parent for a manned USAF Mach 4 system looking like a small Shuttle Orbiter, a B-58MI version to fly the 1957 WS-110 mission (for which the XB-70 was eventually chosen) and a commercial SST.
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<hi style=hdr1>Thin Wing</hi>
<p>The B-58, named Hustler in 1956, had a 60 degree delta wing, but with the trailing edge swept forward to give exact area-rule volume distribution. Thickness was only 3.46 per cent at the root, which meant there was hardly any room inside for structure or fuel. Like most of the B-58 the structure was mainly a light alloy sandwich using organic adhesive; hot or blast-buffeted areas, including the giant elevons, were again of sandwich construction, but this time of brazed stainless steel. The airframe came out at the amazingly low percentage weight of 13.8, and the equipped empty weight of the production aircraft was only 31 per cent of the gross weight, although other companies would point out that you can do better if you make your bomb bay as part of a pod that is not counted as part of the aircraft.
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<p>Altogether, a test fleet of 30 aircraft was needed to solve all the problems and clear the complicated and difficult B-58A for service with Strategic Air Command. The 30 comprised the two XB-58s, the 11 YB-58s and 17 extra YB-58s (58-1007/1023) which much later were rebuilt as RB-58A-10 reconnaissance aircraft with MB-1 single-unit pods with the lower bays filled with photo and linescan equipment. These never saw combat duty. A total of 35 MB-1 pods accompanied the 30-strong test fleet, which was run by the 6592nd Test Squadron and the 3958th Operational Evaluation and Training Squadron, both adjacent to the plant at Carswell AFB. Gradually the USAF formed B-58 crews to help share the load, each being made up of a pilot, a navigator/bombardier and a DSO (defense systems operator). Although the selected men were 'grizzled veterans', all doubly or triply rated (so that they could each do another's or two others' job), the B-58 was a new vehicle for SAC in that each man sat in his own cubicle and could not even stand up. What was less obvious was that each cockpit was inside a capsule which, in emergency, could be bodily ejected from the stricken aircraft to screen the occupant from the possible Mach 2 blast, and after landing act as a buoyant survival shelter. The problems of providing such capsules around fully instrumented cockpits packed with controls and avionics can perhaps be imagined; and each capsule dispensed chaff to aid radar tracking and contained a host of items of its own including sunburn lotion and a fishing kit.
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<hi style=hdr1>The Noisiest Take-Off</hi>
<p>Early aircraft had the J79-GE-1 engine, rated at 14,300 lb (63.61 kN) thrust, but the production engine was the J79-5B of 15,600 lb (69.4 kN) thrust with maximum afterburner. Full power was used for take-off, because a very heavy aircraft with a small and thin delta wing has to reach speeds higher than any previously known before leaving the ground. Most people thought a B-58 take-off the noisiest in their experience. A typical decision speed was 192 mph (309 km/h), and after rotation to 17 degree angle of attack the aircraft would become airborne at about 248 mph (400 km/h) and climb away at 17,000 ft (5,180 m) per minute. A light B-58 could climb at 46,000 ft (14,020 m) per minute. As the main wheels carried a total of 16 tires, each of only 22-in (56-cm) diameter, the wheel rpm was amazing; limit for tire integrity was 306 mph (492 km/h). Despite this very small tire size, large boxes were needed to house the retracted main gears inside the wing. The long nose unit had a double-kinked action to take it up past the nose of the pod.
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<p>Not least of the on-board complexities was the ASQ-42(V) nav/bomb system, managed by Sperry but incorporating items from 38 other manufacturers. It was certainly the biggest avionic challenge of the early 1950s, and in a nutshell it had to do everything. The seven main sub-systems were in the main radar in the nose (whose enormous radome had to withstand hailstones at Mach 2, which even today is no easy requirement), the midships inertial system and astro tracker, radar altimeters at each end of the fuselage and Doppler at the tail alongside major units of the very extensive ECM systems. The whole lot was tied by the first major computer ever designed for airborne use, and the outputs included automatic control of bombing, photography or radar mapping, precise aircraft velocity (in three planes) and attitude at weapon release, atmospheric densities and winds at various heights, and all the many factors concerned with freefall nuclear weapons.
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<p>To show it all worked, the B-58A was declared operational with the 43rd Bomb Wing at Carswell on 1 August 1960, and only five weeks later a crew from the 43rd BW easily won the annual SAC bombing competition with phenomenal scores far ahead of the experienced veterans with B-47s and B-52s. Subsequently, the 43rd BW, based at Little Rock from 1962, set an unprecedented 18 world records, all of them in realms of speed and height never before achieved even by a fighter, let alone a strategic bomber. Major H. E. Confer's crew gained a Thompson Trophy for a 621-mile (1,000-km) circuit with 4,409-lb (2,000-kg) payload at 1,284.73 mph (2,067.6 km/h). Major E. E. Murphy's crew won the trophy donated in 1930 by Louis Bleriot for the first pilot to fly at 1,242.8 mph (2,000 km/h) for 30 minutes (then thought as likely as flying to the moon); Murphy just set up ASQ-42(V) to describe a circle of the required diameter and put on full afterburner, and the result was 669.43 miles (1,073 km) in 30 minutes 43 seconds, an average for the half-hour of 1,302.7 mph (2,095 km/h). This was in May 1961, and in the same month Major W. R. Payne's crew flew from Carswell to Paris setting averages far over 1,000 mph (1,609 km/h) from Washington onwards (the same timings as Concorde, in fact). Sadly, this aircraft (59-2451, the same as used by Murphy) later disintegrated in cloud during the Paris air show. In March 1962 a 43rd BW aircraft flew from Carswell to a computed point over the Pacific, raced east around New York, back over the Pacific and then home (easily beating the sun westbound). Another crew took a 11,023-lb (5,000-kg) load to 85,360.84 ft (26,018 m).
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<p>In late 1961 the 305th BW became operational at Bunker Hill (later called Grissom) AFB, near Peru, Indiana, and its first record was a tough mission from Tokyo to London (for record purposes the distance was computed as the perfect great circle of 8,028 miles/12,919 km, flown in 8 hours 35 minutes, but the distance actually flown was more than 9,100 miles/14,645 km). By this time the B-58A was a mature aircraft, still an awesome challenge and with a relatively high accident rate but a fantastic performer that, on the whole, was regarded not only with respect but also affection. The backseaters had only two tiny windows but were simply too busy to feel claustrophobia. The pilot had a fine view, and on a KC-135 hook-up was not behind but under the tanker, with the latter's formation lights directly above the bomber's needle nose and the turbulent wash going past the tip of the B-58's fin. Scrambles in five minutes were common from the 'cocked' ground alert posture, in most cases with the two-component pod carrying five nuclear bombs. In addition to this 62-ft (18.9-m) payload four wing pylons were added for small nuclear bombs or other payloads grossing 7,000 lb (3,402 kg). Increasingly from 1961, a proportion of missions were at very low level, in which mode the ride at Mach 0.93 was reputedly better than that of any other known aircraft (Convair pilot Erickson flew Carswell to Edwards faster than a pistol bullet, staying at all times below 500 ft/152 m, and was never once detected by air-defense radars).
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<p>Throughout the 1960s the two B-58A bomb wings remained on alert, each with individual aircraft assigned targets attainable with a single air refueling. ECM equipment was almost the only hardware that needed any updating, and there was abundant proof in countless 'hairy' incidents that suspected weakness of the airframe was unfounded. Doubtless the B-58s would have gone on as long as the B-52s, but their extremely high operating cost was the chief reason for their withdrawal from the active inventory on 31 January 1970. Survivors were sent to the 'boneyard', where even their gutted hulks still retained a whiff of their once unequalled activity.
<item><hi format=bold>Powerplant:</hi> four General Electric J79-5B augmented turbojets, each rated at 15,600 lb (69.4 kN) with maximum afterburner
<item><hi format=bold>Performance:</hi> maximum speed at sea level 701 mph (1,128 km/h), and at high altitude 1,322 mph (2,128 km/h); range 5,125 miles (8,248 km) without refueling
<item><hi format=bold>Weights:</hi> empty without pod 55,560 Ib (25,202 kg); maximum take-off 163,000 Ib (73,937 kg); after inflight refueling 177,120 lb (80,342 kg)
<item><hi format=bold>Dimensions:</hi> span 56 ft 10 in (17.32 m); length 96 ft 9 in (29.49 m); height 31 ft 5 in (9.58 m); wing area 1,543 sq ft (143.35 m<su>2</su>)
<item><hi format=bold>Armament:</hi> maximum drop weight 19,450 lb (8,823 kg) including pod(s), with any six types of nuclear bomb including B43 and B61; one 20-mm T-171 tail gun
