Boeing B-52 Stratofortress Variants: B-52C Thru B-52F

The next variant, the "B-52C", was very similar to the B-52B, with the same J57 engine variants and generally similar avionics. The most visible difference from the B-52B was the fit of a huge 11,365 liter (3,000 US gallon) external tank under each wing. The water-injection tank in the rear fuselage was also removed, replaced by a water-injection tank in each wing root.

The B-52C was delivered in natural metal finish, with a coat of white paint on the underside to reflect the flash of a nuclear explosion. The "anti-flash white" underbelly would also be retroactively applied to the B-52Bs. B-52s were also fitted with "flash curtains" that could be put over the windows to block out the glare or a nuclear fireball, though it is unclear when this feature was introduced into production.

The B-52C could carry a load of thermonuclear weapons or a total of 10,900 kilograms (24,000 pounds) of conventional bombs. Although most of the B-52Cs were fitted with the "improved" A-3A FCS used on late-production B-52Bs, it turned out to be not much of an improvement, and so the very last B-52C was fitted with the MD-9 FCS, which was finally a workable and effective piece of gear.

35 B-52Cs were delivered from Boeing-Seattle, making it the rarest of all production B-52s. They were all in principle compatible with the bombbay reconnaissance capsule, though none of them formally received an "RB-52C" designation. Initial flight was on 9 March 1956, with delivery in June, and all B-52C production was completed in that year. In addition, seven B-52Bs were upgraded to something close to B-52C specification under the "Sunflower" program.

The "B-52D" was nearly identical to the B-52C, with the MD-9 FCS as used on the last B-52C. The only significant difference was that the ability to carry the reconnaissance pod was deleted. 101 B-52Ds were built at Boeing-Seattle, while 69 more were made at Boeing-Wichita, the first B-52 model to be built at that plant. A Wichita-built B-52D was the first of that variant to fly, on 14 May 1956.

The "B-52E" was externally similar to the B-52D, but featured improved internal systems. Soviet air defenses had improved to the point where high-altitude bombing was no longer practical, and so SAC switched to low-level tactics. The B-52E included new systems to support the low-level mission, most significantly an IBM-integrated AN/ASQ-38 navigation & bombing system, featuring Raytheon AN/ASB-4 navigation and bombing radar and a GPL AN/APN-89 Doppler groundspeed / height indicator.

The AN/ASQ-38 would be fitted to all following B-52 variants, but it didn't prove entirely satisfactory since it often failed to perform to specification in operation and was troublesome to maintain. An upgrade program named "Jolly Well" would be implemented across most of the B-52 fleet in the early 1960s to bring the AN/ASQ-38 up to a more satisfactory level of performance and maintainability.

42 B-52Es were built at Boeing-Seattle and 58 at Boeing-Wichita. First flight of a B-52E was on 17 October 1957.

The "B-52F" was very similar to the B-52E, but featured new J57-43W engines, with 49.8 kN (5,080 kgp / 11,200 lbf) "dry" thrust and 61.2 kN (6,235 kgp / 13,750 lbf) "wet" thrust, in a revised pod configuration. Each pod had its own water-injection tank in the wing next to the pylon, and there were three inlets under the pod, two for oil coolers and one for a 40 kilowatt alternator. The alternator was powered by the left-hand engine in the pod through a Sundstrand drive in a blister on the left side of the pod. The alternator replaced the original and unreliable bleed-air turbines.

44 B-52Fs were built by Boeing-Seattle, the last B-52s to be delivered from that plant, and 45 were built by Boeing-Wichita. First flight of the B-52F was on 6 May 1958, with the last delivered in early 1959.

The Boeing B-52G

The "B-52G" was the most heavily produced Stratofortress variant. It featured substantially increased internal fuel tankage. Having eliminated the hot piping for the bleed-air turbines in the B-52F allowed Boeing to rethink the wing fuel storage scheme, leading to fit of reliable integral tanks in the wing, replacing the fuel bladders. Integral fuel increased to 176,507 liters (46,572 US gallons) and the wingtip tanks were reduced to 2,650 liters (700 US gallons), for a total fuel capacity of 181,808 liters (47,970 gallons).

The airframe had a number of improvements that reduced its empty weight by several tonnes, though as it turned out the redesigned wing would lead to troubles. The gunner was moved forward to sit with the rest of the flight crew, next to the EWO, and used an AN/ASG-15 FCS with a TV link to control the guns. The brake chute was moved from under the tail to the top, where the gunner's position had been in earlier versions. Moving the gunner forward would eventually prove to be something of a drawback, since aircrews appreciated having someone back in the tail to keep an eye on the dangerous "six" position.

The cockpit accommodations for the crew were significantly improved relative to earlier models, making long-duration flights less tiring. One of the important improvements was better climate control, since traditionally the upper deck crew tended to roast, while the lower deck crew froze.

The nose was lengthened a bit, while the height of the vertical tailplane was cut by 2.44 meters (8 feet), making the B-52G instantly recognizable compared to early B-52 models. The short tailplane had been experimentally validated on one of the three B-52As; some sources claim this modified machine was redesignated the "XB-52G", though it was far from a full prototype of the B-52G.

If previous variants had six spoilers above each wing, as some sources claim, they were increased to the definitive seven in the B-52G, while the ailerons were eliminated, apparently to reduce weight. Roll control was now provided strictly by the spoilers. Pilots would find the lack of ailerons something of an inconvenience, particularly during midair refueling operations.

The B-52G was fitted with a pylon under each wing to carry a "GAM-77 (later AGM-28) Hound Dog" nuclear-armed turbojet-powered cruise missile. This capability was added with the 55th production B-52G and then retrofitted to early B-52Gs. The engines of the two Hound Dog could be used to provide additional thrust for the bomber on take-off, with the fuel for the missiles replenished from the B-52's own tanks in flight. The B-52G's cockpit also had a needle indicator controlled by the Hound Dog's guidance system. This was used to test the missile, essentially allowing the Hound Dog to "fly" the B-52 while still attached to the pylon.

The Hound Dog, which was for some obscure reason apparently named for the Elvis Presley hit tune "You Ain't Nothin' But A Hound Dog", was developed to help deal with the Soviet Union's extensive and growing surface-to-air missile (SAM) network. It was not a very accurate weapon, but it had a big warhead and didn't need to be right on target. It had a maximum range of 1,300 kilometers (800 miles) on a high-altitude flight profile, though much less range at low altitude. Even its shortest range allowed a B-52 to stand off out of range of Soviet SAMs and smash their launch sites from a safe distance. This would open a "hole" in the defensive barrier to allow the bomber to enter and perform precision strikes on its targets.

The B-52G also stowed four ADM-20 "Quail" decoys in the bombbay. The Quail was a little boxy aircraft that folded up for stowage; it was lowered out of the bombbay on a special rack to unfold its wings and then be released. Once in flight, it had performance and a radar cross section similar to that of the B-52. It had a sophisticated guidance system by the standards of the time, allowing it to make two course changes and one speed change.

It is unclear if any earlier versions of the B-52 were originally built with wing pylons. However, it is clear that the Hound Dog and Quail were eventually carried by many of the earlier B-52 variants.

All 193 B-52Gs were built at Boeing-Wichita, though Boeing-Seattle provided the forward fuselage. The first B-52G performed its initial flight on 31 August 1958, with deliveries beginning in that year and ending in 1961.

The Air Force was expecting to field the North American B-70 Valkyrie supersonic bomber after the B-52, and so the B-52G was supposed to have been the final production model. However, the B-70 would run into problems and only two would be built, to be operated strictly as experimental machines; and the USAF was also interested in obtaining the "GAM-87 Skybolt" air-launched ballistic missile, and so Boeing was given a contract to build the final B-52 variant, the "B-52H", as a Skybolt launch platform.

The B-52H - the last variant

The B-52H was to carry four Skybolts, with two on each underwing pylon. In fact, the Skybolt would be cancelled in December 1962 due to cost overruns, and the B-52H would never carry it operationally. It would make do with the Hound Dog, and would also carry Quails.

Since SAC had moved to low-level tactics by that time, the B-52H was given structural reinforcements. It was also fitted with the P&W TF33-3 turbofan, a derivative of the J57, with 75.6 kN (7,710 kg / 17,000 lbf) thrust. A B-52G had been temporarily fitted with these engines to validate their use for the B-52H, with some sources claiming this machine was redesignated the "YB-52H".

Although the new TF33s suffered from some flaws that would lead to a service update program in the early 1960s, they were otherwise a great improvement over the J57 all around. The TF33s eliminated the noisy and dirty water injection scheme of the J57 while providing much greater maximum thrust, and gave a smoother, quieter ride that made life easier for its crews.

The TF33s were also much more fuel-efficient, which meant the B-52H had about 20% greater range than the B-52G. The Air Force demonstrated the increased range of the B-52H when, on 10:11 January 1962, one of them flew from Kadena AFB on Okinawa to Torrejon AFB in Spain nonstop, unrefueled, a distance of 20,177 kilometers (12,532 miles).

The old quad-fifty turret was replaced by a new turret with a single 20-millimeter GE M-61 Vulcan six-barreled Gatling-type cannon, directed by an Emerson ASG-21 fire control system. The cannon had a rate of fire of 6,000 rounds per minute and an ammunition supply of 1,242 rounds. The engine-driven alternators were also uprated to 120 kilowatts.

Late production B-52Hs featured a second stores pylon on each wing, positioned between the two engine pods. These short pylons were used to carry AN/ALE-25 chaff dispenser pods, which each containing twenty Tracor AN/ADR-8 6.35 centimeter (2.5 inch) folding-fin chaff rockets. The chaff rockets could be fired manually by the crew, or automatically by the bomber's defensive countermeasures system. The pylons were retrofitted to earlier B-52H production and to the B-52Gs.

The first B-52H performed its initial flight on 6 March 1961. Boeing-Wichita built 102, with the last rolled out on 22 June 1962, after a total production of 744 B-52s of all types at a cost of $4.5 billion USD. At its peak, the B-52 equipped 42 SAC bomber squadrons, dispersed to 38 different airbases. A production summary is listed below:

Incidentally, back in 1953 the Air Force had only contemplated obtaining a fleet of 282 B-52s, but the number kept creeping upward during the decade as the service began to realize that the B-52 was not really the "interim" machine they had expected it to be. In fact, nobody would have ever guessed in their wildest dreams how long it would remain in service.

Although most of the B-52Hs were delivered with the same wing design as used on the B-52G, the last 18 were fitted with a modified and strengthened wing. The original B-52G wing turned out to be more prone to structural fatigue from the new low-level operations than the wings of earlier B-52 models. The weakness of the wing led to the crash of a B-52G near Goldsboro, North Carolina, on 24 January 1961, and implementation of temporary fight restrictions and a high-priority program to strengthen the wing. All earlier B-52Hs and all B-52Gs were refitted with the stronger wing in the 1962:1964 timeframe. The re-winging effort was conducted more or less in parallel with a more general program of structural reinforcements for most of the B-52 fleet under the designation "High Stress".

In addition, late production B-52Hs were fitted with improved avionics for the low-level role, including modifications to existing systems and addition of radar altimeters and terrain avoidance gear. These features were retrofitted to most earlier B-52s in operational service through the "Big Four" program, which was also performed in the early 1960s.

Boeing B-52 Stratofortress Modifications

A handful of the production B-52s were modified for special applications where an aircraft with heavy hauling and high-altitude capabilities was required.

The best-known of the special modifications were three B-52s used by the US National Aeronautics & Space Administration (NASA) to launch the X-15 experimental rocket "X-plane", the NASA lifting body experimental craft, Pegasus air-launched boosters, and other payloads. The first of the NASA B-52s was one of the three B-52As, which in the late 1950s was passed on to NASA and redesignated the "NB-52A"; NASA operated the aircraft, but the Air Force retained formal ownership. It was fitted with a strengthened right stores pylon to carry the X-15 and was operated by the NASA Dryden Center.

The NB-52A was retired in 1968 to the Pima Air & Space Museum in Tucson, Arizona, having been replaced by a similarly modified B-52B, which of course became the "NB-52B". It was one of the longest-flying B-52s; it was built in 1952 and was nicknamed "Balls-8" from its tail number, "008".

Since experimental flights are an occasional sort of thing, the NB-52B didn't burn up airframe time at any great rate, but by the end of the century it was extremely difficult to maintain since all its systems were obsolete, forcing Dryden engineers to scour boneyards and museums for spares and on occasion even machining them from scratch. In 2001 NASA Dryden obtained a "new" B-52H, built in 1961, reconditioning it and modifying for the NASA drop mission. Ball's-8 was retired in December 2004, to be displayed at Edwards Air Force Base.

The "new" B-52H, of course redesignated "NB-52H", features an improved, strengthened pylon. It is set farther forward than the pylon on the NB-52B, which had to have its inboard flaps removed to accommodate drop payloads. The extended pylon on the NB-52H allows the flaps to be retained, reducing landing speed. Unlike its two predecessors, the NB-52H has been given a modern NASA gloss white-and-blue paint job, making it one of the best-dressed B-52s ever to fly. The Air Force intends to support the B-52H to 2040 or even beyond, and spares should not be as severe a problem.

In the late 1960s, one or more B-52s were modified under the supersecret "Senior Bowl" program to carry and launch the "D-21" high-speed reconnaissance drone on modified Hound Dog pylons. The D-21 was a ramjet powered machine, intended primarily to perform reconnaissance of the Chinese nuclear center at Lop Nor, and was originally to be launched from the back of an "M-21", a modified Lockheed SR-71 Blackbird. However, launch separation of the D-21 from the M-21 proved troublesome, leading to the fatal crash of an M-21 in 1966.

The project was then redefined for B-52 launch, with the D-21 attached to a big solid-fuel booster rocket to get it up to speed and altitude. A handful of D-21 launches were performed, including semi-operational missions over China, with dismal results. Given improved satellite reconnaissance and detente with China, the program was cancelled in the early 1970s.

One B-52E was used to test the GE XTF99 high-bypass ratio turbofan for the Lockheed C-5A Galaxy transport, with the big engine replacing one of the NB-52E's inboard engine pods. Initial flight of this machine, which was designated "NB-52E", with the XTF99 was 30 June 1968.

A second B-52E used for various test duties was also designated "NB-52E", and a B-52D used in a similar fashion was designated "NB-52D". A number of B-52s of differing variants were assigned to long-term duty as test machines and given the designation "JB-52", and some others were permanently grounded to be used for instructional duties, and given the designation "GB-52".

Boeing B-52 Stratofortress On Alert

In service, crews called the B-52 the "Buff", for "Big Ugly Fat Fella" or something close to that, and also as a contraction of sorts of "B-Fifty-Two". Well-known aviation writer Walter J. Boyne, who was an Air Force captain when he first encountered the B-52, gave a tidy pocket description of what it was like to fly the thing:

" When you took off, the wings flew before the fuselage, so the flight surfaces had to be used while the wheels were still on the ground. The crosswind landing gear took some getting used to. You could be looking out the side window while landing. The control surfaces were small so you used trim a lot, and it had a stabiliser trim not found on the B-47. Visibility was better than the B-47. Side-by-side seating was a hell of a lot better.

It gave you a very good ride at altitude. The wings flexed. Turbulence was readily dampened. But at low level ... it was like being hammered. You'd really get thrown around in your harness. You'd get knocked around. The aeroplane responded to more than one gust variation at a time and hence was never in synch. If the B-47 was a truck, the B-52 was an eighteen-wheeler [tractor-trailer rig].

Put it this way: the Buff pounded along while the B-47 cleaved the air. The spoilers took some getting used to. It wasn't like having conventional aileron control.

The B-52 was not difficult to land. You had a lot of mass coming down of the sky for a reunion with the ground. When you were lined up, you didn't have any trouble landing on the spot where you intended. You did not want to land nosewheel-first because the aircraft could porpoise [bounce fore and aft]; that could ruin your whole day, but it was almost impossible to do. Normally the rear trucks landed first."

Up until the mid-1960s, the Buff served as the first line of America's strategic nuclear deterrent, providing a bridge between the B-47 and the arrival of the US strategic nuclear missile force. As mentioned, although the B-52 had been designed for high-altitude bombing, improved Soviet defenses forced the adoption of low-level tactics. Coming in "on the deck" helped evade Soviet SAMs, though at the expense of a rough ride that was hard on aircrews and airframes.

In October 1957, the Air Force implemented an "alert" strategy for the B-52 force. A third of the force, including both bombers and their supporting Boeing KC-135 tankers, was to be always available for takeoff on a live nuclear attack mission within 15 minutes. The aircraft were set up on standby in dedicated flightline alert facilities, known as "Christmas trees" for their layout, which included "alert shacks" where the crews could reside, dashing to the aircraft when the alarm was sounded.

The Air Force refused to comment on whether all B-52s on alert status were fully armed, though it is certain that at least a good proportion of them were. The standard nuclear weapon for the B-52 in the 1960s was the B28 fusion bomb. Four B28s could be carried on a "clip" that could be towed out to the flightline and quickly loaded into into the B-52's bombbay. Two clips could be accommodated in the bombbay, but it appears that usually only one was loaded, with the remaining space taken up by Quail decoys.

The B-52 could also carry the more powerful "B41" and "B53" fusion bombs, with a yield roughly an order of magnitude greater than that of the B28, and the "B57", a tactical weapon with a yield in the range of about ten kilotonnes. These three weapons were introduced in the 1960s.

An upgrade program was conducted in 1963 and 1964 to fit the engines of a number of B-52s with pyrotechnic cartridge engine starters, with the starters fired off simultaneously to get all eight engines up to speed immediately and cut the amount of time it took to get the bomber into the air. More B-52s were refitted with cartridge starters in a follow-on program a decade later.

The aircraft would get into the air as fast as possible, one following another off the runway. Such "minimum-interval takeoff (MITO)" exercises were hazardous, since there was a danger of a disastrous pileup, greatly aggravated by the clouds of black smoke pouring from water-injected J57s fitted to all Buffs except the B-52H that reduced visibility to near-zero for all but the first aircraft in the stream.

The alert system meant long and tedious work weeks, and was hard on marriages and family life. Much of the time on alert was spent reviewing mission plans and procedures and ensuring that paperwork was in order, with occasional surprise practice alerts to keep the crews on their toes. Failure to follow proper procedures was punished by severe disciplinary measures. There was also the underlying tension that the crews were really preparing for the Apocalypse. Even if they survived their missions, their bases would very likely be vaporized, along with their homes and families.

The target list of the B-52 and other nuclear strike elements in the US arsenal was outlined by a series of ultra-secret "Strategic Integrated Options Plans (SIOPs)", which determined the order in which targets would be attacked and what platform would attack them. As the US strategic missile force was built up, the B-52 were increasingly assigned to mobile targets could not be easily targeted with missiles.

SAC claimed they achieved the one-third alert level by May 1960. In March 1961, US President John F. Kennedy raised the alert level to half the force, and SAC claimed they met this goal in October 1961. In reality, it appears that some "imaginative accounting" was used to claim compliance, with the actual number of aircraft immediately available for combat falling well short of stated goals. Given the logistical difficulties involved, the alert system was still impressive.

In the spring of 1959, SAC leadership had proposed an extension of the ground alert system, the "airborne alert" system, in which a number of bombers were kept armed and in the air at all times. While SAC proposed that a sizeable percentage of the B-52 force be kept on airborne alert, in practice the expense and complexity of the scheme meant that only a handful of aircraft were assigned this duty. Formally, SAC described it as a "training effort" in this timeframe.

The airborne alert system was greatly expanded during the Cuban Missile Crisis in October 1962, with alert status raised to a "threshold of war" level. Bombers orbited outside of Soviet airspace, the crews prepared to attack the instant they received the order. After the crisis the airborne alert force was reduced to a much more modest level, with about a dozen B-52s kept in the air with a load of nuclear weapons.

The "Dirty Dozen" stayed on patrol through most of the 1960s, but the scheme had serious liabilities. On 15 October 1959, a B-52F on airborne alert had collided with a Boeing KC-135 tanker over Kentucky and crashed with two nuclear weapons on board. The weapons were recovered intact and there was no release of radioactive materials. However, on 17 January 1966, a B-52G collided with a KC-135 in a similar accident over Palomeres in Spain. The resulting crash caused the rupture of two of the four bombs on board, leading to a troublesome environmental cleanup operation. Just as bad or worse, one the bombs disappeared into the ocean off the coast, leading to an intensive search to find it and make sure it was accounted for. The weapon was discovered on 15 March and finally recovered on 7 April.

The entire incident made the front pages over all the world and was a major embarrassment. The airborne alert system stayed in place for the moment, but in late January 1968, a B-52G crashed on the Greenland ice pack while trying to perform an emergency landing at Thule AFB. There was another release of radioactive materials and consequently a big cleanup effort.

That was the end of the airborne alert system. B-52s no longer flew with nuclear weapons as a regular practice, though nuclear-armed Buffs still stood by in the alert areas. By this time, the US strategic missile force was well up to strength, and the need to keep B-52s flying around, waiting to nuke the Reds on a moment's notice, was no longer as great. Other tools were available for that job.

Author: Greg Goebel