Le Convair B-36 Peacemaker

Le Convair B-36 Peacemaker est le premier [Vous devez être inscrit et connecté pour voir ce lien] intercontinental de l'histoire, et le plus grand avion de ce type jamais mis en œuvre par les [Vous devez être inscrit et connecté pour voir ce lien]. Son autonomie était telle qu'il pouvait voler plus de 30 heures sans escale. Il est resté en service durant toutes les années 1950.

Conception

La conception du B-36 a commencé pendant la [Vous devez être inscrit et connecté pour voir ce lien], avec le dessein de pouvoir bombarder l'[Vous devez être inscrit et connecté pour voir ce lien] en décollant d'Amérique du Nord au cas où la [Vous devez être inscrit et connecté pour voir ce lien] aurait été envahie. Malgré des premières études dès 1941, le prototype XB-36 ne vola pour la première fois qu'en [Vous devez être inscrit et connecté pour voir ce lien]. La version B-36B fut déclarée opérationnelle en [Vous devez être inscrit et connecté pour voir ce lien] au sein du [Vous devez être inscrit et connecté pour voir ce lien] de l'[Vous devez être inscrit et connecté pour voir ce lien]. La version de série B-36D, munie de 4 réacteurs additionnels en sus des 6 moteurs à piston d'origine, fut mise en service à partir de 1951.
Le B-36 ne fut pas créé avec la bombe atomique en vue. Mais, dans le contexte de la [Vous devez être inscrit et connecté pour voir ce lien], le B-36 joua d'office le rôle de bombardier nucléaire en remplacement des vétustes [Vous devez être inscrit et connecté pour voir ce lien]. Le B-36 fut le porteur de la première bombe thermonucléaire américaine, le « Mark-17 », long de 7,5 m et pesant 20 tonnes. N'ayant jamais servi au combat, le B-36 fut surnommé Peacemaker (le pacificateur).
La taille imposante et la lenteur du B-36 le rendaient vulnérable aux attaques ennemies. Un projet de chasseur intégré, le [Vous devez être inscrit et connecté pour voir ce lien], fut en conséquence envisagé, mais jamais développé. De même, certains projets expérimentaux furent menés avec des [Vous devez être inscrit et connecté pour voir ce lien].
La production du B-36 cessa en [Vous devez être inscrit et connecté pour voir ce lien] et le modèle fut retiré du service le [Vous devez être inscrit et connecté pour voir ce lien], remplacé par le [Vous devez être inscrit et connecté pour voir ce lien] qui avait été préféré au YB-60, une version du B-36 dotée de 8 réacteurs.
Les B-36 de série coûtaient 3 701 000 dollars de l'époque à l'unité. Il ne reste aujourd'hui qu'un seul exemplaire de cet avion, préservé par une association.

Engagements

Les RB-36E de reconnaissance firent un certain nombre de missions au-dessus de la République populaire de Chine et le long des frontières de l'Union soviétique.

Variantes

• XB-36, [Vous devez être inscrit et connecté pour voir ce lien] : prototype
  
• B-36A, [Vous devez être inscrit et connecté pour voir ce lien] : version d'entraînement
  
• XC-99, [Vous devez être inscrit et connecté pour voir ce lien] : projet d'avion de transport basé sur le B-36
  
• B-36B, [Vous devez être inscrit et connecté pour voir ce lien] : premier modèle opérationnel
  
• B-36D, [Vous devez être inscrit et connecté pour voir ce lien] : première version à être équipée de 4 réacteurs supplémentaires
  
• RB-36E, [Vous devez être inscrit et connecté pour voir ce lien] : version de reconnaissance équipée de 14 caméras
  
• B-36F, [Vous devez être inscrit et connecté pour voir ce lien] : amélioration du B-36D (équipé de réacteurs plus puissant)
  
• B-36H, [Vous devez être inscrit et connecté pour voir ce lien] : amélioration du B-36D (nouveau panneau de contrôle)
  
• B-36J, [Vous devez être inscrit et connecté pour voir ce lien] : version équipée des moteurs à réactions additionnels et de réservoirs supplémentaires pour accroître l'autonomie
  
• XB-36G ou YB-60, [Vous devez être inscrit et connecté pour voir ce lien] : nouvelle version équipée de huit réacteurs à la place des moteurs à piston
  
• NB-36H, version équipée d'un réacteur nucléaire pour mesurer les effets de la radioactivité sur la cellule

Chasseur-parasite

• Un projet de chasseur eu lieu entre 1948 et 1949 pour pouvoir faire emporter trois chasseurs-parasites [Vous devez être inscrit et connecté pour voir ce lien] par un B-29
  
• En 1952 est lancé le projet FICON (FIghter CONveyor1 : un [Vous devez être inscrit et connecté pour voir ce lien] est accroché sous le ventre d'un avion de reconnaissance RB-36 destiné à lui fournir plus d'autonomie. Le Thunderjet doit être largué à proximité de l'objectif et venir s'y ré-accrocher une fois sa mission terminée. Les premiers essais commencent en janvier 1952 avec un F-84E, et donnent satisfaction au point que l'USAF demande fin 1953 de modifier 25 RF-84F et 10 RB-36.

Equipage : 15 membres

Moteure : Pratt et Whitney R-4360-25
Nombre : 6
Type : Moteurs à pistons
Puissance unitaire : 3250 cv

Envergure : 70,10 m
Longueur : 49,40 m
Hauteur : 14,22 m
Surface ailaire ;443,32 m²

Masse à vide : 61 299 kgs
Avec armemnt : 96 611 kgs
Maximale : 141 194 kgs

Vitesse maximale : 754 kmh
Plafond : 12 212 m
Rayon d'action : 12 485 km

Armement 32 688 kgs de bombes

Convair B-36 variants began in 1941 with the XB-36 to meet the [Vous devez être inscrit et connecté pour voir ce lien] needs of the [Vous devez être inscrit et connecté pour voir ce lien]; then later becoming [Vous devez être inscrit et connecté pour voir ce lien] with its [Vous devez être inscrit et connecté pour voir ce lien]. In 1948, the [Vous devez être inscrit et connecté pour voir ce lien] immediately becoming a mainstay of the American [Vous devez être inscrit et connecté pour voir ce lien]. It underwent a number of design changes before being withdrawn from service in 1959. It was also well suited to high altitude very long range [Vous devez être inscrit et connecté pour voir ce lien] missions, and several alterations were made with this mission profile in mind.

XB-36

In 1941, the fall of [Vous devez être inscrit et connecté pour voir ce lien] to a [Vous devez être inscrit et connecté pour voir ce lien] invasion seemed imminent. If the United States joined the war against the [Vous devez être inscrit et connecté pour voir ce lien], the fall of Britain would leave no bases in Europe from which the [Vous devez être inscrit et connecté pour voir ce lien] (AAC) could bomb Germany. This possibility led to AAC to seek a bomber of truly intercontinental range. On 1941 April 11, the AAC issued a design competition for an aircraft with a 275 mph (445 km/h) cruising speed, a service ceiling of 45,000 ft (14,000 m), capable of delivering 10,000 lb (4,500 kg) of bombs to targets 5,000 miles (8,000 km) away. At the time, these requirements far exceeded the best technology available.
On 1941 November, the [Vous devez être inscrit et connecté pour voir ce lien] signed a contract for two experimental aircraft under the designation XB-36, based on design studies previously submitted by [Vous devez être inscrit et connecté pour voir ce lien]. A few days later, the Engineering Division at [Vous devez être inscrit et connecté pour voir ce lien] decided that Consolidated's six-engine design, with all engines on the trailing edge of the wing, was the best option for the aircraft. The original design used vertical stabilizers and rudders, similar to those used in the [Vous devez être inscrit et connecté pour voir ce lien]. By the time the first XB-36 was delivered, the design had been changed to a huge single tail, and the wingspan increased to 230 ft (70 m), an unprecedented size.
It was clear that the B-36 needed nose guns. Adding these required a substantial rearrangement of the cockpit. In late 1944, a mockup of the new nose was approved. Though too late for the first prototype, it would be fitted to the second XB-36. Unfortunately, the new nose with its radar and radio equipment added significant weight.
The first (and only) XB-36 was completed at the Consolidated [Vous devez être inscrit et connecté pour voir ce lien] factory in late 1945. The plane sat on huge wheels 9 ft (2.8 m) in diameter; only three airfields in the USA had concrete thick enough to support the pressure exerted by wheels of that size. In 1948 June, the single-wheel undercarriage was replaced by a new undercarriage consisting of two wheels with half the diameter on each strut. This design, which would became the production standard, enabled the B-36 to operate on runways of reasonable thickness.
The maiden flight revealed problems with the [Vous devez être inscrit et connecté pour voir ce lien] actuating system, engine cooling, and the reliability of the aluminum wiring. Propeller vibration adversely affected the wing structure. Worse yet, the XB-36 failed to meet the 1941 specifications. In particular, inadequate engine cooling kept its service ceiling under 30,000 ft (9,000 m), much less than that called for in the original contract.
Following a grounding for modifications, the XB-36 was flight tested for 160 hours by pilots of the Army Air Force Air Materiel Command, then returned to Convair for further testing.

References:

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• [Vous devez être inscrit et connecté pour voir ce lien]
  

YB-36

The YB-36A, a conversion of the original XB-36, was turned over to the [Vous devez être inscrit et connecté pour voir ce lien] in June 1948, a week before the production [Vous devez être inscrit et connecté pour voir ce lien] was scheduled to be delivered. The YB-36A had inadequate operation value, and the [Vous devez être inscrit et connecté pour voir ce lien] used it primarily for training missions. Later it was idle for several years, then employed in the [Vous devez être inscrit et connecté pour voir ce lien] firefighting program.
The second prototype, designated YB-36, of which only a single instance was built, was chosen as the production version in mid-1945. Its new high-visibility cockpit and redesigned nose compartment became the standard. Thanks to various design improvements, the YB-36 outperformed the XB-36, eventually reaching altitudes of 40,000 ft (12,000 m). It was essentially built to B-36A specifications; in fact, it flew six months after the B-36A. In late 1950, the YB-36 was returned to Convair and converted into a reconnaissance aircraft under the designation [Vous devez être inscrit et connecté pour voir ce lien]. In the spring of 1957, it was decommissioned and placed in the [Vous devez être inscrit et connecté pour voir ce lien] at [Vous devez être inscrit et connecté pour voir ce lien].
References:

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• [Vous devez être inscrit et connecté pour voir ce lien]
  

B-36A

The B-36A included several of the new elements developed on the YB-36, including the domed canopy and the four-wheel main landing gear (as opposed to the single-wheel landing gear used on the XB-36 and the YB-36). These new features were in a sense first seen on the B-36A rather than the YB-36, because it was the former that flew first — by six months.
The first B-36A ever built was destroyed by a series of brutal stress tests, consisting mainly of applying more and more load to various parts of the aircraft until they disintegrated.
On April 8 1948, a B-36A made a 6,922 (11,140 km) flight of 33 hours, shuttling between [Vous devez être inscrit et connecté pour voir ce lien] and [Vous devez être inscrit et connecté pour voir ce lien] three times without landing, and carrying a 10,000 lb (4,500 kg) bomb load. In May, the same aircraft did a round trip of 8,062 miles (12,970 km) lasting 33 hours.
By virtue of its designation, the B-36A was technically a production aircraft. However, it lacked defensive armament because the system wasn't ready. It was an explicitly interim plane used by the 7th Bomb Group at [Vous devez être inscrit et connecté pour voir ce lien] in Texas for the sole purpose of flight testing and transitional crew training. When the newer [Vous devez être inscrit et connecté pour voir ce lien] became available, all B-36As were converted to reconnaissance aircraft and redesignated [Vous devez être inscrit et connecté pour voir ce lien].
A total of 22 were built.
References:

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• [Vous devez être inscrit et connecté pour voir ce lien]
  

Other variants

B-36B
As the B-36A with R-4360-41 engines and full armament installed (sixteen 20mm cannon in eight barbettes), 73 built.
RB-36B
Designation given to 30 B-36Bs temporarily flown with camera installations.
YB-36C
Projected version of the B-36B with six 4300hp R-4360-51 engines driving tractor airscrews, not built and the prototype on order was cancelled.
B-36C
Production version of the YB-36C, variant cancelled and the 34 on order were completed as B-36Bs.
B-36D
As the B-36B but with four 5200 lbst J-47 engines in paired underwing pods, 22 built.
RB-36D
Strategic reconnaissance variant of the B-36D with two of the four bomb-bays housing camera installations, 17 built.
RB-36E
The YB-36A and 21 B-36As converted to RB-36D standard.
B-36F
As the B-36D but with six R-4360-53 and four J-47 engines, 34 built.
RB-36F
Strategic reconnaissance variant of the B-36F with additional fuel, 24 built.
GRB-36F
One RB-36F (serial 49-2707) converted to carry a GRF-84F Thunderstreak on a central trapeze as part of the FICON (Fighter Conveyor) programme, other machines were also converted and used for trials including launching stand-off missiles.
YB-36G
Initial designation of a jet powered version that was developed as the YB-60.
B-36H
As the B-36F but with an improved flightdeck layout and equipment changes, 83 built.
NB-36H
One B-36H (serial 51-5712) with a nuclear reactor installed in the rear fuselage for tests.
RB-36H
Strategic reconnaissance version of the B-36H, 73 built.
B-36J
As B-36H but with strengthened undercarriage and increased fuel tankage, 33 built, some aircraft flew with a reduced crew and no armament apart from the tail guns for high altitude missions
GRB-36J
Designation of a few B-36Js used for FICON testing.
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Modified version of the B-36 with swept wings and tail surfaces and powered by eight J-57-P-3 engines for evaluation against the B-52, two built.
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Transport version of the B-36 using the wings, tail surfaces and six R-4360-41 pusher engines with a two-deck fuselage for 400 troops. One built and used for trials and research from 1949 to 1957.
X-6
Projected conversion of the B-36 intended for airborne nuclear powerplant testing, following the NB-36H programme. Cancelled and none built.

Rxemplaires construites selon les variantes

XB-36 : 1
YB-36 : 1
B-36A : 21
B-36B : 62
B-36D : 26
RB-36D : 24
B-36F : 36
RB-36F : 24
B-36H : 83
RB-36H :73
B-36J : 33

Soit un total de 384

By the end of World War II, the United States had obtained nuclear weapons. There was a need for a bomber with intercontinental range to carry such weapons; fortunately, work had been conducted from even before Pearl Harbor on the development of such an aircraft. The result was the enormous Convair B-36 "Peacemaker", which was the mainstay of the American strategic deterrent in the early years of the Cold War. This document provides a history and description of the B-36.

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B-36 ORIGINS / XB-36 & YB-36 / B-36A / B-36B
* As America was preparing for World War II in early 1941, there was a fear that Britain would be overrun by Hitler, depriving the US of a forward staging area for Europe. One of the consequences of this mindset was that the US Army Air Corps believed that America might need a bomber that had true intercontinental range, able to fly from North America, attack targets in Europe, and return home without refueling. The Air Corps issued a secret request for proposals on 11 April 1941, specifying a true intercontinental bomber with a range of 16,100 kilometers (10,000 miles); a bombload of 4,540 kilograms (10,000 pounds); a speed of 385 to 485 KPH (240 to 300 MPH); and a ceiling of 10,700 meters (35,000 feet). The bomber would be able to carry a much larger bombload over short distances.
Four companies returned proposals, the winner being the Consolidated "Model 36" -- basically an enlarged version of the Consolidated B-32, a heavy bomber that would be produced in small quantities. Consolidated was given a contract for two prototypes of the Model 36 on 15 November 1941. The Model 36 was a huge aircraft, with a wingspan of 70.1 meters (230 feet) and driven by six big radial engines, driving pusher propellers on the back of the wings. The wings were 1.8 meters (6 feet) thick at the roots. The aircraft had a tubular fuselage to ease pressurization, and a twin-fin tail.
By late 1941, the threat of a German invasion of the British Isles had all but vanished. With the Japanese attack on Pearl Harbor on 7 December 1941, work on the Model 36 went on the back burner while Consolidated churned out PBYs and B-24s that were required to fight the war in the here and now. Although a hundred production aircraft were ordered on 23 July 1943 -- the need for a long-range bomber to attack Japan brought the Model 36 off the back burner for a time -- the first prototype Model 36, the "XB-36", wasn't rolled out until 8 September 1945, and it didn't fly for almost a year, performing its first flight on 8 August 1946, with test pilot Beryl A. Erickson at the controls and eight other aircrew on board.
Officially speaking, the B-36 was named the "Peacemaker", but nobody actually liked that name; the B-36 would sometimes be called the "Big Stick", or the "Magnesium Cloud" as a reference to its construction and high-altitude capabilities. By this time, it wasn't a Consolidated product, since the company had merged with Vultee in 1943 to become the "Consolidated Vultee Aircraft Company". The name was normally abbreviated to just "Convair", though that wouldn't be the "official" name until 1954.
The XB-36 was generally much like the original Model 36 proposal, differing mainly in being fitted with a conventional single-fin tail assembly instead of the twin fins envisioned at first. The prototype was unarmed and not fitted with operational kit. It had tricycle landing gear, with single-wheel main gear. The main gear tires were ridiculously huge, with a diameter of 2.8 meters (9 feet 2 inches), and landings were hard on both tires and tarmac. It was experimentally fitted with tracked landing gear, but it only flew once in that configuration, the landing gear not holding up well to the exercise.
The second prototype performed its initial flight on 4 December 1947, again with Beryl Erickson at the controls. It was designated "YB-36", which initially had the single-wheel main gear but was later refitted with much more practical four-wheel bogies. The YB-36 also had a raised "bugeye" cockpit instead of the conventional cockpit of the XB-36.
The two prototypes were followed by 22 unarmed evaluation machines designated "B-36A". They weren't all that close to operational spec -- in fact, the first B-36A performed its initial flight on 28 August 1947, well before the YB-36 took to the air. After some misgivings, the Air Force -- the service having become independent from the Army in that year -- ordered "B-36B" production variants. Initial flight of the B-36B was on 8 July 1948 and 62 were built. Incidentally, sources tend to be confused on the number of B-36Bs, mostly because some of those ordered ended up being built as other variants.

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By the end of 1948, an operational group of B-36Bs had been formed up at Carswell Air Force Base (AFB) in Texas, right next to the Convair plant. Lacking hangars big enough to accommodate the huge B-36s at the time, ground crews were forced to freeze in the winter and roast in the summer as they tried to keep the aircraft flying. Later, mobile shelters were built that could be rolled over the wings to provide some protection from the elements when hangars of adequate size were not available.
To demonstrate the machine's capabilities, on 7 December 1948 the Air Force decided to commemorate Pearl Harbor by flying a B-36B from Carswell to Hawaii, dropping a 4,500 kilogram (10,000 pound) bomb load, and then coming back home, nonstop and unrefueled. The mission took 35 hours 30 minutes of flight time, covering 13,000 kilometers (8,100 miles) at an average speed of less than 370 KPH (240 MPH). On 20 January 1949, five B-36Bs flew from Carswell to overfly Washington DC as part of the inaugural ceremony for President Harry Truman.
* The B-36B might well have been the end of the road, since in the summer of 1949, it was at the center of a storm of political controversy that threatened the program with cancellation. The Truman Administration had just appointed a new secretary of defense, an attorney named Louis A. Johnson; when Johnson was told to make defense cuts, he did so, giving the axe to a US Navy supercarrier named, somewhat redundantly, the USS UNITED STATES.
The Navy did not take kindly to this act. The USS UNITED STATES was the Navy's gambit to give the service a strategic nuclear strike capability, and to aggravate their frustration, the admirals were not consulted on the cancellation ahead of time. The Air Force wanted to keep control of this mission, with the B-36 as the long-range delivery platform. To complicate matters, Johnson had once been a Convair official -- a conflict of interest that would be grossly unacceptable now, though few paid it much mind then.
The Navy produced a memo that called the B-36 an "obsolete and unsuccessful aircraft" and claimed that Convair had paid off Democratic politicians with millions of dollars. The memo was internal, but by accident or design it ended up in public hands. Navy boosters blasted the B-36 program as a "billion dollar blunder", calling the aircraft a "lumbering cow", saying that all the latest Navy jet fighters could fly rings around it. That was not the case; the B-36 was slow, but with its huge wings, it could fly at altitudes above the effective ceiling of most jet fighters. Even if they reached it, they had no maneuverability and the big bomber could easily dodge them.
The USAF hit back, with Secretary of the Air Force Stuart Symington publicly defending the B-36. A Congressional committee investigated the matter, with the Air Force making a thorough case for the B-36, while the Navy fumbled their argument. The conveniently leaked Navy memo backfired when the committee subpoenaed the officials behind it and tore them to ribbons on the witness stand. That was about as far as the committee could go without revealing military secrets, but that was of little consequence. The "revolt of the admirals", as it was called, had led to a nasty public confrontation with insults and accusations traded back and forth in the press, but the USS UNITED STATES stayed cancelled.
Relations with the USSR had been deteriorating to the point of blatant hostility -- the Soviet blockade of West Berlin beginning in June 1948 had been a real wake-up call -- and the USA needed a long-range bomber to threaten the Soviets. The B-36 was the only weapon available to do the job at the time, and so it would be the backbone of the Air Force's Strategic Air Command (SAC) until better weapons then in the pipeline arrived. The Navy would continue to be frustrated by the strategic nuclear strike issue until the late 1950s, when the service began development of the Polaris ballistic missile submarine, a weapon that gave the admirals all the nuclear offensive power they could seriously want. But that is another story.

B-36B DESCRIBED
* The B-36B was built primarily of aircraft aluminum and magnesium. It was powered by six Pratt & Whitney (P&W) R-4360-41 Wasp Major engines -- the spectacular "corncob" air-cooled radials, with 28 cylinders consisting of four banks of seven cylinders in a spiral. The engines provided 2,610 kW (3,500 HP) each. The prototypes and B-36As had featured the less powerful R-4360-25 variant of the engine, with only 2,240 kW (3,000 HP). The Wasp Majors drove oversized three-bladed pusher props with a diameter of 5.8 meters (19 feet) through driveshafts, with a reduction gearing system cutting prop RPM to half that of the engine to keep the proptips from going supersonic. The props were still said to have a rumbling drone that could shake windows when the aircraft was flying far overhead. To support operations from forward airbases, the USAF obtained a special carrier to allow B-36s to haul two spare Wasp Majors. The carrier was fitted into the forward bomb, with a pod sticking out to each side of fuselage to accommodate an engine.
The scale of the B-36 could be considered by realizing that the total area of its control surfaces alone -- flaps, ailerons, rudder, elevators -- was more than the wing area of a B-24 Liberator. The flight control surfaces were, surprisingly, all manually operated, with the pilot shifting small "servo tabs" that drove actuators to move the control surfaces. The B-36B had four bombbays, with a tunnel on top through which a crewman could roll prone on a trolley to move between the front and back crew sections, pulling himself on a overhead rope.
The B-36B had an optical bombsight, as well as an AN/APQ-23 bombing-navigation radar in a blister under the forward fuselage, integrated with the optical bombsight and an electromechanical analog computer in the K-1 bombing system. As mentioned, the B-36 fleet was tasked with the nuclear strike mission and could carry several fission bombs; from 1953, fusion weapons were available, with the B-36 carrying two Mark 17 "Runts", with a weight of 19,050 kilograms (42,000 pounds). B-36s performed several "live drops" of nuclear weapons in test programs. In principle, the B-36 could perform conventional bombing, with stores arrangements running from 132 225 kilogram (500 pound) bombs to two 19,505 kilogram (43,000 pound) T-12 bombs.
The bomber could not only carry a big bombload over long distances, it was also fitted with heavy defensive armament. There were twin M24A1 20 millimeter cannon in both nose and tail positions, with an AN/APG-3 gun-laying radar in a small radome above the tail turret, and six remotely-controlled turrets, again with twin 20 millimeter cannon. Each cannon had an ammunition supply of 600 rounds.
The turrets were retractable, hidden in pairs under doors in normal flight, popping up with one turret to cover the left side of the aircraft and the other to cover the right. There were three of these dual-turret installations on the bomber, with two installations on the top, one behind the cockpit and the other behind the wing, and one installation on the belly, just underneath the rear top gun positions. The gunners sighted the guns from six blister positions, two in front, four in the rear. There was no provision for switching control of the turrets between gunners; each gunnery station was dedicated to the control of a particular turret. It seems the cannon system was overcomplicated and not very reliable.

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B-36C / B-36D, RB-36D, & RB-36E

* Complaints about the B-36's performance led Convair engineers to come up with possible tricks to improve performance. A "B-36C" was considered, to be fitted with uprated R-4360-51 engines, which provided an auxiliary "jet exhaust" to increase speed. The new engines would have required changing the configuration from pusher to conventional tractor. However, analysis showed that the performance increase would have been too trivial to be worth the effort, and the B-36C was never built.
The better solution was to add four jet engines along with the six piston engines, resulting in the "B-36D". The prototype converted from a B-36B, performing its initial flight in its "mixed power" configuration on 26 March 1949. The jet engines were fitted in pairs in pods, with a single pod outboard on each wing. The jet engine pod was basically lifted from the Boeing B-47 Stratojet. It used General Electric J47-GE-19 turbojets, providing 23.1 kN (2,360 kgp / 5,200 lbf) thrust each. The prototype had used similar but less powerful Allison J35 engines.

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The jet engines were only used on takeoff and for boost performance in hostile airspace; they provided a significantly shorter takeoff run, as well as a useful increment of speed and ceiling. When all the engines were running, aircrews described it as "six turning and four burning". The jet intakes were fitted with an "iris" that closed the engines off to reduce drag from "windmilling" when the turbojets were not in use. Interestingly, in long-range cruise it was not unusual to shut down two, or even three, of the piston engines as well.
The B-36D also featured an astrodome blister on top of the canopy, and "snap action" bombbay doors, made up of four hinged panels that folded up on themselves, replacing the roll-open bombbay doors of earlier models. Although the B-36Ds were initially fitted with the K-1 bombing system, they were later refitted with the more sophisticated and reliable K-3A bombing system. The optical bombsight was regarded as redundant and eliminated, with the bombsight panel in the nose faired over with a metal plate. Similarly, the B-36Ds were originally fitted with AN/APG-3 tail radar but were later upgraded to AN/APG-32 tail radar, featuring a "chicklet" style radome. 26 new-build B-36Ds were produced, and 59 of the B-36Bs were rebuilt to B-36D standard. Initial service delivery was on 17 August 1950, to Carswell.
* A strategic reconnaissance version of the B-36D, the "RB-36D", was also built, with a manned pressurized module with 14 cameras in the forward bombbay, up to 80 photoflash bombs in the second bombbay, a fuel tank in the third bombbay, and electronic intelligence (ELINT) gear, revealed by an additional antenna fairing under the nose and three fairings under the rear bombbay. There was some variation in bombbay configurations among the RB-36 machines; they could also in principle carry bombloads.
24 new-production RB-36Ds were delivered -- some sources mention conversions from B-36Bs, but these were merely machines that had been ordered as B-36Bs and not built as them. Initial delivery of the RB-36D was on 3 June 1950.
* In addition, 21 B-36As and the YB-36A were upgraded to a standard similar to that of the RB-36D, and given the designation "RB-36E", the first being flown on 18 December 1950. The reconnaissance variants tended to carry large crews, of up to 22, to handle the photographic and ELINT systems.
From the mid-1950s, a "Featherweight" program was conducted to strip out gear from selected B-36s to improve their ceiling. There were "class II" Featherweights that retained their defensive armament, and "class III" Featherweights in which all the defensive armament except for the tail position, with the gunner's blisters either faired over or replaced with flush windows.

B-36F & RB-36F / B-36H & RB-36H / B-36J / B-36 IN SERVICE

* The "B-36F" was similar to the B-36D, but with uprated P&W R-4360-53 engines with 2,835 kW (3,800 HP) each. The K-3A bombing system and AN/APG-32 tail radar was standard, and a chaff dispenser system was later added. Initial flight was on 28 November 1950, with 34 built. 24 "RB-36F" reconnaissance machines with increased fuel load were also produced.
The "B-36H" was another stepwise refinement of the breed, with an improved flight deck, AN/APG-41A tailgun radar -- featuring twin side-by-side radomes, which likely invited comparisons to a brassiere -- and other small changes. Initial flight was on 5 April 1952, and a total of 83 were built, as well as 73 "RB-36H" reconnaissance machines.
The final production version of the B-36 was the "B-36J" -- there was no "B-36I", the Air Force didn't use "I" as a suffix since it could be confused with a "1". It featured additional wing tanks and reinforced landing gear to handle higher gross weights. Initial flight was on 3 September 1953, with 33 built; all ended up in Featherweight configuration. The last of the batch, the last of 383 B-36s to be built, was delivered to the Strategic Air Command on 14 August 1954. SAC was effectively the B-36's only user; it was never operated by any other nation.

CONVAIR B-36J:

wingspan 70.1 meters 230 feet
length 49.4 meters 162 feet 1 inch
height 14.22 meters 46 feet 8 inches

empty weight 77,580 kilograms 171,035 pounds
loaded weight 181,975 kilograms 410,000 pounds

max speed at altitude 660 KPH 410 MPH / 355 KT
service ceiling 12,160 meters 39,000 feet
range 10,950 kilometers 6,800 MI / 5,915 NMI

The B-36 did not remain in service long, being phased out in the late 1950s. The type was officially retired on 12 February 1959. The last flight of a B-36 was on 30 April 1959, when a B-36J was flown to Wright-Patterson AFB in Ohio, to take up residence in the Air Force Museum, where it still lives today.
* Some crews had fond memories of the B-36, but there were those who hated the thing, and even those who liked it had their horror stories about it. One pilot who called it a "big, wonderful old bird" but said piloting it was "like sitting on your front porch and flying your house around." A less enthusiastic pilot called it a "horrible, lazy beast to fly".
When it crashed, its magnesium construction made for a spectacular and thorough fire. At least nine were lost in accidents. There was also a disastrous incident at Carswell on 1 September 1952, when a tornado ripped across the flightline and damaged 71 B-36s, disabling half of SAC's heavy bomber fleet. 51 of the aircraft were put back into service by early October, but the rest had to be rebuilt, with one completely written off.
The B-36's major virtue was its long range, though in practice not as long as had been desired, and in its Featherweight manifestations it could operate well above the reach of enemy defenses of its era. B-36s didn't fly combat missions during the Korean War -- heavy bombing could be performed by Boeing B-29s, with the B-36 reserved for the strategic bombing mission -- but RB-36s performed overflights of Red China and possibly the USSR. The details of these missions were kept secret and remain unclear; there were no losses, and no doubt the defenders were frustrated at watching the Magnesium Clouds fly far overhead.
As far as the B-36's usefulness as a nuclear deterrent went, that could be argued -- but since the B-36 never dropped a bomb in anger, the argument cuts both ways, and it seems that uncertainty afflicted the Soviets as well. Even an ineffective deterrent is a deterrent if an adversary doesn't want to push his luck

UNUSUAL VARIANTS
* From 1942, even as Consolidated was (slowly) working on getting the XB-36 out the door during World War II, the company was considering a transport version of the bomber, the "Model 37". The plan was to use the same wings, engine, tail, and many subsystems of the XB-36 mated to a double-decker fuselage, with seating for 400 troops, rivaling a modern jumbo jet.
As with the XB-36 itself, development of the Model 37 was a low priority, and the sole prototype, designated the "XC-99", didn't fly until 23 November 1947. By that time, the military had decided they didn't need such a big cargolifter after all, and the airlines had lost interest in the concept. However, the single prototype did go into service with the Air Force, acquiring a nose radome, and remained in operation until 1957.

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Given the concerns over the low performance of the B-36, not too surprisingly Convair engineers investigated a variant with all-jet propulsion and swept wings originally designated the "B-36G". This dovetailed with USAF plans to obtain a jet-powered strategic bomber, and the service was interested enough to award a contract for two prototypes, designated "YB-60", on 15 March 1951.
The first YB-60 prototype flew on 18 April 1952. It was a very distinctive aircraft -- some claim extremely ugly -- mating the B-36 fuselage to swept wings and tail. It was powered by eight P&W J57 turbojets, each providing 38.7 kN (3,945 kgp / 8,700 lbf) thrust, mounted on a total of four pylons under the wings in twin-engine pods. After some fiddling, the decision was made to reduce defensive armament to the tail turret. Crew was accordingly reduced to five.
The Air Force was actually much more interested in the new-design Boeing B-52, and was only interested in the YB-60 as a cheap-and-dirty backup solution in case the B-52 program went off track. It didn't, the YB-60 was inferior to the B-52 in most respects, and that was the end of it. Both YB-60 prototypes were scrapped.

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One of the more unusual branches of the B-36's history was its use in "parasite fighter" experiments, in which the bomber was supposed to carry its own escort fighter into hostile territory. Once again, the exercise was provoked by concerns over the B-36's vulnerability. The initial idea was to develop a very small fighter, the McDonnell "XF-85 Goblin", that would fit into a B-36 bombbay. One Goblin would be carried along with the B-36's bombload, though there schemes to fit some B-36s as "flying aircraft carriers" with three Goblins. The Goblin development program went poorly, and the little fighter was quickly seen to be inadequate in any case.
However, the Air Force remained interested in the concept under the name of "Fighter Conveyor (FICON)". At least 12 RB-36Fs were modified to "GRB-36F" standard, with a trapeze system in the bombbay to carry, drop, and pick up an GRF-84F Thunderflash reconnaissance jet with a snag hook on the nose. Flight experiments with the GRB-36F and GRF-84F began in May 1953. FICON actually worked fairly well, and the scheme went into formal service in the mid-1950s for about a year. FICONs are suspected to have flown some long-range penetration missions over the Eastern Bloc, though no public records confirm it.
Another scheme, known as "TOM-TOM" for some obscure reason, involved fitting a connector to each wingtip of an RB-36F that would allow an RF-84F Thunderflash reconnaissance aircraft to link its wingtip to the RB-36F for a "tow". Experiments were conducted in 1953, but the scheme was dodgy, particularly because wingtip turbulence from the RB-36F made life very troublesome for the Thunderflash pilots, and the scheme was abandoned.
* There were a number of other special mods of the B-36:

• One B-36H was fitted out as an inflight refueling tanker, with a single-point hose-and-drogue refueling system. The aircraft could be easily converted back to bomber configuration. However, there was no real need for a B-36 tanker and that was the end of the idea.
  
• Three B-36Hs were modified to carry and control the Rascal air-to-ground missile and redesignated "DB-36H", but the Boeing B-47 Stratojet was assigned the role of Rascal carrier instead, and the DB-36Hs saw little or no service in their intended role. The Rascal program was cancelled anyway.
  
• One B-36 was modified to haul the airframe of the Convair B-58 Hustler bomber. The wings of the B-58 prevented the B-36 from retracting its main landing gear, and so it had to be flow with gear down all the way through its flight, with the jet engines left on to maintain airspeed.
  

One of the most unusual modifications was the "atomic" B-36. The US was completely atom-crazy in the 1950s, and accordingly the Air Forced began a program to develop an atomic-powered aircraft. As a first step, a B-36H was converted into a test bed, the "NB-36H", which carried a nuclear reactor. The reactor didn't power anything, with the whole purpose of the exercise being to determine how well a reactor could be flown around in an aircraft. This particular B-36H had been one of the victims of the tornado attack on Carswell in September 1952 and needed to be rebuilt in any case.
The NB-36H was fitted with a new crew compartment with a distinctive nose and cockpit and radiation shielding to protect the crew. The cockpit glazing was leaded glass up to 30 centimeters (a foot) thick; the crew was so isolated that they couldn't hear the outside world. Close-circuit TV links allowed them to keep an eye on the reactor and the engines. The NB-36H was given a spiffy paint job -- detailing over bare metal -- and named "Crusader".

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First flight of the NB-36H was on 17 September 1955. On flights, it was shadowed by a transport carrying a load of Marine paratroopers who were to jump and secure the area if the NB-36H had to perform an unscheduled landing at a remote location, or crashed; they were called the "glow in the dark" crew. A fully nuclear-powered version, the "X-6", was to follow, but (in hindsight unsurprisingly) the Air Force realized that flying nuclear reactors around was a bad idea and gave up on the concept, with the final flights in March 1957.


* The following table summarizes B-36 variants and production: variant built mod notes
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XB-36 1 Initial prototype with stepped cockpit.
YB-36 1 Second prototype with bugeye cockpit.
B-36A 22 Unarmed evaluation machines.
B-36B 62 Fully armed initial operational version.
B-36C - Uprated engines, tractor configuration, not built.
B-36D 26 59 Added jet pods, snap-open bombbay doors.
RB-36D 24 Reconnaissance version of B-36D.
RB-36E - 22 Upgrades of YB-36 & B-36As to RB-36D configuration.
B-36F 34 Uprated Wasp Major engines.
RB-36F 24 Reconnaissance B-36F.
GRB-36F - 12 RB-36F parasite conversions.
B-36H 83 New tail gun radar, other minor changes.
RB-36H 73 Reconnaissance B-36H.
NB-36H - 1 Trials B-36H with nuclear reactor.
B-36J 33 B-36H with more fuel.
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SUM 383 Total B-36 production.
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