Convair B-36 Peacemaker: Aircraft profile

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The Convair B-36 (nicknamed Peacemaker) was a strategic bomber built by Convair and operated solely by the United States Air Force (USAF).

Convair B-36 Peacemaker: 1950's -- B-36 Peacemaker (U.S. Air Force photo)Convair B-36 Peacemaker: 1950's -- B-36 Peacemaker (U.S. Air Force photo)

The B-36 was the largest mass-produced piston engined aircraft ever made and had the largest wingspan in a combat aircraft ever built (230 ft (70 m)), although there have been larger military transports.

Responding to the U.S. Army Air Forces' requirement for a strategic bomber with intercontinental range, Consolidated Vultee (later Convair) designed the B-36 during World War II. The airplane made its maiden flight in August 1946, and in June 1948 the Strategic Air Command received its first operational B-36. Some B-36s served as photographic reconnaissance aircraft, and others were adapted to launch and retrieve specially modified RF-84F/K reconnaissance planes.

Powered by six Pratt & Whitney R-4360 engines, the B-36J cruised at 230 mph, but for additional bursts of speed its four General Electric J47s increased the maximum speed to 435 mph. It carried 86,000 pounds of nuclear or conventional bombs. When production ended in August 1954, more than 380 B-36s had been built for the U.S. Air Force. In 1958-1959, the USAF replaced the B-36 with the all-jet B-52. Although never used in combat, the B-36 was a major deterrent to enemy aggression. Making the last B-36 flight ever, the aircraft on display flew to the museum from Davis-Monthan Air Force Base, Ariz., on April 30, 1959.

Convair B-36 Peacemaker: Convair B-36B in flight. (U.S. Air Force photo)Convair B-36 Peacemaker: Convair B-36B in flight. (U.S. Air Force photo)

The B-36J was an improved version of the B-36H. Improvements included the addition of fuel cells in the outboard wing area and a strengthened landing gear. The landing gear supported an increase in gross weight to 410,000 pounds -- a 50,000-pound increase over the -H model.

The B-36 remained in service with the Strategic Air Command throughout the 1950s; however, by late 1958 the B-36 was phased out and replaced by the Boeing B-52 as the premier USAF heavy bomber.

Specifications (B-36J):

Span: 230 ft. 0 in.
Length: 162 ft. 1 in.
Height: 46 ft. 9 in.
Weight: 410,000 lbs. (max. gross weight)

Armament: 16 M24 20mm cannons in eight nose, tail and fuselage turrets; plus bombs -- nuclear or 86,000 lbs. of conventional (Featherweight III aircraft had only 20mm cannons)

Engines: Six Pratt & Whitney R-4360-53 radials of 3,800 hp each (takeoff power) and four General Electric J47-GE-19 turbojets of 5,200 lbs. thrust each

Crew: 13 after Featherweight III conversion; 15 otherwise

Performance:

Maximum speed: 411 mph [418 mph for B-36J (III)] at combat weight

Cruising speed: 230 mph

Range: Approx. 10,000 miles

Service ceiling: 43,600 ft. (at combat weight)

Source: US Air Force

Convair B-36 Peacemaker: Convair NB-36H in flight. (U.S. Air Force photo)Convair B-36 Peacemaker: Convair NB-36H in flight. (U.S. Air Force photo)

Detailed background:

Source: wikipedia.org

The B-36 was the first bomber capable of delivering thermonuclear weapons from within a fully-enclosed bomb-bay. With a range of over 6,000 miles (9,700 km) and a maximum payload of at least 72,000 lb (33,000 kg), the B-36 was the first operational bomber with an intercontinental range, setting the standard for subsequent USAF long range bombers, such as the B-52 Stratofortress, B-1 Lancer, and B-2 Spirit.

Development history

The genesis of the B-36 can be traced to early 1941, prior to the entry of the U.S. into World War II. At that time it appeared that there was a very real chance that Britain could fall, making a strategic bombing effort by the U.S. against Germany impossible. A new class of bomber would be needed to fill this role, one offering trans-Atlantic range so it could bomb targets in Europe from bases inside the continental USA. The United States Army Air Corps opened up a design competition for the very long-range bomber on 11 April 1941, asking for a 450 mph (720 km/h) top speed, a 275 mph (443 km/h) cruising speed, a service ceiling of 45,000 ft (14,000 m), and a maximum range of 12,000 miles (19,000 km) at 25,000 ft. These proved too demanding for any short-term design, so on 19 August 1941 they were reduced to a maximum range of 10,000 miles (16,000 km), an effective combat radius of 4,000 miles (6,400 km) with a 10,000 pound bombload, a cruising speed between 240 and 300 mph (480 km/h), and a service ceiling of 40,000 ft.

After the Cold War began in earnest with the 1948 Berlin Airlift and the 1949 atmospheric test of the first Soviet atomic bomb, American military planners sought bombers capable of delivering the very large and heavy first-generation nuclear bombs. The B-36 was the only American aircraft with the range and payload to carry such bombs from airfields on American soil to targets in the USSR (storing nuclear weapons in foreign countries was, and remains, diplomatically sensitive).

The B-36 was arguably obsolete from the outset, being piston-powered in a world of jet interceptors, but its jet rival, the B-47 Stratojet, which did not become fully operational until 1953, lacked the range to attack the Soviet homeland from North America and could not carry the huge first-generation hydrogen bomb. Nor could the other American piston bombers of the day, the B-29 or B-50. Intercontinental ballistic missiles (ICBMs) did not become effective deterrents until the 1960s. Until the B-52 Stratofortress became operational in the late 1950s, the B-36, as the only truly intercontinental bomber, was the mainstay of the Strategic Air Command (SAC).

Convair touted the B-36 as an "aluminum overcast", a "long rifle" to give SAC a global reach. When General Curtis LeMay headed SAC (1949–57) and turned it into an effective nuclear delivery force, the B-36 formed the heart of his command. Its maximum payload was more than four times that of the B-29, even exceeding that of the B-52. The B-36 was slow and could not refuel in the air, but could fly missions to targets 3,400 miles (5,500 km) away and stay aloft as long as 40 hours.Moreover, the B-36 was believed to have an ace up its sleeve: a high cruising altitude, made possible by its huge wing area, that put it out of reach of all piston fighters and early jet interceptors.

Nevertheless, the B-36 was difficult to operate, prone in its early service years to catastrophic engine fires and other costly malfunctions. To its critics, these problems made it a "billion-dollar blunder". In particular, the United States Navy saw it as a costly bungle diverting Congressional funding and interest from naval aviation and aircraft carriers in general, and carrier–based nuclear bombers in particular. In 1947, the Navy attacked Congressional funding for the B-36, alleging it failed to meet Pentagon requirements. The Navy believed the dominance of the aircraft carrier in the Pacific during World War II proved carrier-based air strikes would be decisive in future wars. To this end, the Navy designed the USS United States (CVA-58)Template:WP Ships USS instances, a "supercarrier" capable of launching huge fleets of tactical aircraft or nuclear bombers. It then pushed to have funding transferred from the B-36 to the USS United States. The Air Force successfully defended the B-36 project, and the United States was officially cancelled by Secretary of Defense Louis A. Johnson in a cost-cutting move. Several high-level Navy officials questioned the government's decision, alleging a conflict of interest because Johnson had once served on Convair's Board of Directors. The uproar following the cancellation of United States was nicknamed the "Revolt of the Admirals".

The furor, as well as the significant use of aircraft carriers in the Korean War, resulted in the design and procurement of the subsequent Forrestal class of supercarriers, which were of comparable size to the United States but with a design geared towards greater multirole use with composite air wings of fighter, attack, reconnaissance, electronic warfare, early warning and antisubmarine warfare aircraft. At the same time, heavy manned bombers for the Strategic Air Command were also deemed crucial to national defense and, as a result, the two systems were never again in competition for the same budgetary resources.

Convair B-36 Peacemaker: Front view of Convair B-36A-1-CF (S/N 44-92006). (U.S. Air Force photo)Convair B-36 Peacemaker: Front view of Convair B-36A-1-CF (S/N 44-92006). (U.S. Air Force photo)

Design and development

In 1941, the fall of Britain to a German invasion seemed imminent. This would have left the United States Army Air Corps (AAC) with no bases in Europe from which to bomb Germany. American bombers would have had to reach Europe from bases in North America, necessitating a combat range of at least 5,700 miles (9,200 km), the length of a Gander, Newfoundland–Berlin round trip. The AAC therefore sought a bomber of truly intercontinental range.

On 11 April 1941, the USAAC announced 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 10,000 miles (16,000 km) away. These requirements far exceeded the technology of the day. The B-36 concept began with a proposal by Consolidated Vultee Aircraft Corporation (later Convair) to meet this requirement; the same design request led to the Northrop YB-35. Though the need to bomb Germany from North American bases never arose, the project was not cancelled because the B-36 was seen as playing a possible eventual role in the Pacific war.

The B-36 took shape as an aircraft of immense proportions, two-thirds longer than the previous "superbomber", the B-29. The wingspan and tail height of the B-36 exceeded those of the Antonov An-22, the largest ever mass-produced propeller-driven aircraft. Only with the advent of the Boeing 747 and the Lockheed C-5 Galaxy, both designed two decades later, did aircraft capable of lifting a heavier payload than the B-36 become routine.

The wings of the B-36 were large even when compared with present-day aircraft, exceeding, for example, those of the C-5 Galaxy, and enabled the B-36 to carry enough fuel to fly very long missions without refueling. The wing area permitted cruising altitudes above the operating ceiling of 1940s-era fighters, jet as well as piston. All versions of the B-36 could cruise at over 40,000 ft (12,000 m). B-36 mission logs commonly recorded mock attacks against U.S. cities while flying at 49,000. In 1954, the turrets and other nonessential equipment were removed, resulting in a "featherweight" configuration believed to have resulted in a top speed of 423 mph (700 km/h), and cruise at 50,000 ft (15,000 m) and dash at over 55,000ft (16,800M), perhaps even higher.

The large wing area and the option of starting the jet engines gave the B-36 a wide margin between stall speed (VS) and maximum speed (Vmax) at these altitudes. This made the B-36 more maneuverable at high altitude than the USAF jet interceptors of the day, which either could not fly above 40,000 ft (12,000 m), or if they did, were likely to stall out when trying to maneuver or fire their guns. However, the Navy argued that their F2H Banshee fighter could intercept the B-36, thanks to its ability to operate at more than 50,000 ft. The Air Force declined the Navy's invitation to a fly-off between the Banshee and the B-36. Later, the new Secretary of Defense, Louis A. Johnson, whose personal biases was such that he considered the U.S. Navy and Naval Aviation essentially obsolete in favor of the U.S. Air Force and Strategic Air Command, forbade putting the Navy's claim to the test.

The propulsion system alone made the B-36 a very unusual aircraft. All B-36s featured six Pratt & Whitney R-4360 Wasp Major radial piston engines. Even though the prototype R-4360s delivered a total of 18,000 hp (13.4 MW), early B-36s were slow and required long takeoff runs. The situation improved with later versions delivering 3,800 hp (2.8 MW) apiece. Each engine drove an immense three-bladed propeller, 19 ft (5.8 m) in diameter, mounted in the pusher configuration. This unusual configuration prevented propeller turbulence from interfering with airflow over the wing.

Beginning with the B-36D, Convair suspended a pair of General Electric J47-19 jet engines from each wing; these were also retrofitted to all extant B-36Bs. Thus the B-36 came to have 10 engines, more than any other mass-produced aircraft. The jet pods greatly improved takeoff performance and dash speed over the target. In normal cruising flight, the jet engines were shut down to conserve fuel.

The B-36 had a crew of 15. As in the B-29, the pressurized flight deck and crew compartment were linked to the rear compartment by a pressurized tunnel through the bomb bay. In the B-36, one rode through the tunnel on a wheeled trolley, by pulling oneself on a rope. The rear compartment led to the rear turret, and featured six bunks and a galley. The B-36 also tested the experimental Boston Camera.

The XB-36 featured single-wheel landing gear whose tires were the largest ever manufactured up to that time, 9 ft, 2 in (2.7 m) tall, 3 ft (1 m) thick, and weighing 1,320 lb (600 kg), with enough rubber for 60 automobile tires. These tires placed so much weight per unit area on runways, the XB-36 was restricted to the Fort Worth airfield next to where it was manufactured, and to a mere two USAF bases. At the suggestion of General Henry H. Arnold, the single-wheel gear was soon replaced by a more conventional four-wheel bogie. At one point a tank-like tracked landing gear was also tried on the XB-36, but proved heavy and noisy and was quickly abandoned.

Weaponry

The four bomb bays could carry up to 86,000 pounds of bombs, more than 10 times the load carried by the World War II workhorse, the B-17 Flying Fortress, and substantially more than the B-17's gross weight. The B-36 was not designed with nuclear weaponry in mind, because the mere existence of such weapons was top secret during most of the period when the B-36 was engineered (1941–46), and their mode of delivery had yet to be determined. Nevertheless, the B-36 stepped into a nuclear delivery role immediately upon becoming operational. In all respects but speed, the B-36 could match what was arguably its approximate Soviet counterpart, the Tu-95, which began production in January 1956 and is still in service. Until the B-52 came on line, the B-36 was the only means of delivering the first generation Mark-17 hydrogen bomb, 25 ft (7.5 m) long, 5 ft (1.5 m) in diameter, and weighing 42,000 lb (19,000 kg), the heaviest and bulkiest American nuclear weapon ever. Carrying this massive weapon required merging two adjacent bomb bays.

The defensive armament consisted of six remote-controlled retractable gun turrets, and fixed tail and nose turrets. Each turret was fitted with two 20 mm cannon, for a total of 16 cannons, the greatest defensive firepower ever carried by a bomber. Recoil from gunnery practice could cause the vacuum-tube electronics to malfunction, solid state then being unknown. This contributed to the crash of B-36B 44-92035 on 22 November 1950.

The Convair B-36 was the only plane designed to carry the T12 Cloud Maker, a gravity bomb weighing 43,600 lb (19,800 kg) and designed to produce an Earth quake bomb effect.

Convair B-36 Peacemaker: Convair NB-36H cockpit. (U.S. Air Force photo)Convair B-36 Peacemaker: Convair NB-36H cockpit. (U.S. Air Force photo)

Production

The first prototype XB-36 flew on 8 August 1946. The speed and range of the prototype failed to meet the standards set out by the Army Air Corps in 1941. As is often the case with aircraft pushing the size envelope, the XB-36 experienced a number of problems. (For instance, the B-29 Superfortress was plagued by engine problems, and available engines were too weak to afford the Boeing XB-15 a useful top speed.)

A second aircraft, the YB-36, flew on 4 December 1947. It featured a redesigned high-visibility "bubble" canopy, which was later adopted for production. Altogether, the YB-36 was much closer to the production aircraft. Additionally, the engines used on the YB-36 were a good deal more powerful and more efficient.

The first of 21 B-36As were delivered in 1948. They were admitted interim airframes, intended for crew training and later conversion. No defensive armament was fitted as none was ready. Once later models were available, all B-36As were converted to RB-36E reconnaissance models. The first B-36 variant meant for normal operation was the B-36B, delivered beginning in November 1948. This aircraft met all the 1941 requirements, but had serious problems with engine reliability, and with the availability of armaments and spare parts. Later models featured more powerful variants of the R-4360 engine, improved radar, and redesigned crew compartments.

The four jet engines raised fuel consumption, thus reducing range. Meanwhile, new air-to-air missiles made hand-aimed guns mounted in heavy turrets obsolete; they were also unreliable. In February 1954, the USAF awarded Convair a contract to reduce the weight of the entire B-36 fleet by implementing a new "Featherweight" design program in three configurations:

* Featherweight I removed the 6 movable gun turrets and other defensive hardware.

* Featherweight II removed the rear compartment crew comfort features, and all hardware accommodating the XF-85 parasite fighter.

* Featherweight III incorporated both configurations I and II.

The six turrets eliminated by Featherweight I reduced the aircraft's crew from 15 to 9. Featherweight III enabled a longer range and an operating ceiling of at least 47,000 ft (14,000 m), features especially valuable for reconnaissance missions. The B-36J-III configuration (the last 14 made) featured a single radar-aimed tail turret, extra fuel tanks in the outer wings, and landing gear allowing the maximum gross weight to rise to 410,000 pounds (190,000 kg). Production of the B-36 ceased in 1954.

Variants

XB-36

Prototype powered by six 3,000 hp (2,200 kW) R-4360-25 engines and unarmed, one built.

YB-36

Prototype with modified nose and raised cockpit roof, one built later converted to YB-36A.

YB-36A

Former YB-36 with modified four-wheel landing gear, later modified as a RB-36E.

B-36A

Production variant, unarmed used for training, 22 built all but one converted to RB-36E.

B-36B

Armed production variant with six 3,500 hp (2,600 kW) R-4360-41 engines, 73 built later conversions to RB-36D and B-36D.

RB-36B

Designation for 39 B-36Bs temporary fitted with a camera installation.

YB-36C

Projected variant of the B-36B with six 4,300 hp (3,200 kW) R-4360-51 engines driving tractor propellers, not built.

B-36C

Production version of the YB-36 completed as B-36Bs.

B-36D

Same as B-36B but fitted with four J47-GE-19 engines, two each in two underwing pods, 22 built and 64 conversions from B-36B.

RB-36D

Strategic reconnaissance variant with two bomb bays fitted with camera installation, 17 built and seven conversions from B-36B.

RB-36E

The YB-36A and 21 B-36As converted to RB-36D standards.

B-36F

Same as B-36D but fitted with six 3,800 hp (2,800 kW) R-4360-53 engines and four J47-GE-19 engines, 34 built.

RB-36F

Strategic reconnaissance variant of the B-36F with additional fuels capacity, 24 built.

GRB-36F

One RB-36F modified to carry a GRF-84F Thunderstreak on a ventral trapeze as part of the FICON program.

YB-36G

Project for a jet-powered swept wing variant due to the difference between a standard B-36 it was re-designated the YB-60.

B-36H

Same as B-36F with improved cockpit and equipment changes, 83 built.

NB-36H

One B-36H fitted with a nuclear reactor installation for trials, had a revised cockpit and raised nose.

RB-36H

Strategic reconnaissance variant of the B-36H, 73 built.

B-36J

High altitude variant with strengthened landing gear, increased fuel capacity, armament reduced to tail guns only and reduced crew, 33 built.

Reconnaissance capability

More than a third of all B-36 models were reconnaissance models, designated RB-36. Before the development of the Lockheed U-2, the RB-36 was the mainstay of American photo reconnaissance over hostile territory. It was the only American aircraft having range enough to fly into Asia from bases in the USA, and size enough to carry the bulky high-resolution cameras of the day. The RB-36 performed a number of rarely acknowledged reconnaissance missions and is suspected of having carried out numerous penetrations of Chinese (and possibly Soviet) airspace.

Convair B-36 Peacemaker: Convair XB-36 parked beside Boeing B-29-55-BA (S/N 44-84027) for size comparison. (U.S. Air Force photo)Convair B-36 Peacemaker: Convair XB-36 parked beside Boeing B-29-55-BA (S/N 44-84027) for size comparison. (U.S. Air Force photo)

The RB-36 was well-suited for such reconnaissance missions. Its high cruising altitude made it difficult to intercept, and its fuel capacity enabled missions up to 50 hours long. The RB-36 featured a pressurized camera compartment staffed by a crew of seven, in place of a forward bomb bay. The aft bomb bay contained tanks for extra fuel. The RB-36 cameras could produce very high resolution photographs: pictures of a golf course taken from 40,000 ft (12,000 m) show recognizable golf balls. RB-36s were distinguished by the bright aluminium of the camera compartment (contrasting with the dull magnesium of the rest of the fuselage) and by a series of radar domes under the aft fuselage, varying in number and placement.

Operational history

RB-36D.

The B-36, including its RGB-36, RB-36, and XC-99 variants, was in service as part of the USAF Strategic Air Command from 1948 through 1958. Its principal operating units and locations were the 5th Bombardment Wing and 9th Strategic Reconnaissance Wing at Fairfield-Suisun AFB, later renamed Travis AFB, California; 6th Bombardment Wing at Walker AFB, New Mexico, 7th Bombardment Wing and 11th Bombardment Wing at Carswell AFB, Texas; 28th Bombardment Wing at Ellsworth AFB, South Dakota; 42nd Bombardment Wing at Loring AFB, Maine; 72nd Bombardment Wing at Ramey AFB, Puerto Rico; 92nd Bombardment Wing and 99th Bombardment Wing at Fairchild AFB, Washington; and the 95th Bombardment Wing at Biggs AFB, Texas.

Unlike the B-52, which has seen action in the Vietnam War and the two Gulf Wars, no B-36 ever dropped a bomb or fired a shot at an enemy.

Maintenance

The B-36 was too large to fit in most hangars. Moreover, even an aircraft with the range of the B-36 needed to be stationed as close to the enemy as possible, and this meant the northern continental United States, Alaska, and the Arctic. As a result, most "normal" maintenance, such as changing the 56 spark plugs (always at risk of fouling by the leaded fuel of the day) on each of its six engines, or replacing the dozens of bomb bay light bulbs shattered after a gunnery mission, was performed outdoors, in 100 °F (38 °C) summers or −60 °F (−51.1 °C) winters, depending on the location. Special shelters were built so that the maintenance crews could enjoy a modicum of protection while working on the engines. Often, ground crews were at risk of slipping and falling from icy wings, or being blown off the wings by a propeller running in reverse pitch.

The wing roots were thick enough, 7 ft (2.1 m), to enable a flight engineer to access the engines and landing gear by crawling through the wings. This was possible only at altitudes not requiring pressurization.

The Wasp Major engines also had a prodigious appetite for lubricating oil, each engine requiring its own 100 gallon (380 L) tank. A former ground crewman has written: " an oil change interval as I think the oil consumption factor handled that." It was not unusual for a mission to end simply because one or more engines ran out of oil.

Engine fires

Like all large aircraft powered by piston engines, the B-36 was prone to engine fires. The problem was exacerbated by the pusher configuration, which facilitated carburetor icing. The design of the R-4360 engine tacitly assumed that it would be mounted in the conventional tractor configuration - propeller/air intake/28 cylinders/carburetor - with air flowing in that order. In this configuration, the carburetor is bathed in air warmed by engine cooling and so is unlikely to ice up. However, the R-4360 engines in the B-36 were mounted in the pusher configuration - air intake/carburetor/28 cylinders/propeller. The carburetor was now in front of the engine and so could not benefit from engine heat, and also made more traditional short term carb heat systems unsuitable. Hence when intake air was cold and humid, ice gradually obstructed the carburetor air intake, which in turn gradually increased the richness of the air/fuel mixture until the unburned fuel in the exhaust caught fire. Three engine fires of this nature led to the first loss of an American nuclear weapon, described below (an event known as a broken arrow in military terminology).

Crew experience

Training missions were typically in two parts; first, a 40 hour flight - followed by some time on the ground for refueling and maintenance - then a 24 hour second flight. With a sufficiently light load, the B-36 could fly at least 10,000 miles (16,000 km) nonstop, and the highest cruising speed of any version, the B-36J-III, was only 230 mph (380 km/h). Turning the jet engines on could raise the cruising speed to over 400 mph (650 km/h), but the resulting higher fuel consumption reduced the range. Hence a 40-hour mission, with the jets used only for takeoff and climbing, flew about 9,200 miles (15,000 km).

The B-36 was not a particularly enjoyable aircraft to fly. Its overall performance, in terms of speed and manuverability, was never considered sprightly. Lieutenant General James Edmundson likened it to "...sitting on your front porch and flying your house around." Despite its immense exterior size, the pressurized crew compartments were relatively cramped, especially when occupied for 24 hours by a crew of 15 in full flight kit.

War missions would have been essentially one-way, taking off from forward bases in Alaska or Greenland, overflying the USSR, and landing in Europe or the Middle East. Ironically, recollections of crew veterans reveal that while crews were confident of their ability to complete a mission if called upon to do so, they were less confident of surviving the weapon delivery itself. Their concerns were a function of the relatively low speed of the aircraft coupled with the extreme destructive power of the bombs they were carrying, resulting in the plane still being in harm's way once the bombs detonated on target. These concerns were borne out by the 1954 Operation Castle tests, in which B-36s flew near detonations in the 15-megaton range, at distances believed typical of wartime delivery, and experienced blast damage.

Experiments

The B-36 was employed in a variety of aeronautical experiments throughout its service life. Its immense size, range and payload capacity lent itself to use in research and development programs. These included nuclear propulsion studies, and "parasite" programs in which the B-36 carried smaller interceptors or reconnaissance aircraft.

In May 1946, the Air Force began the Nuclear Energy for the Propulsion of Aircraft (NEPA) project which was followed in May 1951 by the Aircraft Nuclear Propulsion (ANP) program. The ANP program required that Convair modify two B-36s under the MX-1589 project. One of the modified B-36s studied shielding requirements for an airborne reactor to determine whether a nuclear aircraft was feasible. The Nuclear Test Aircraft (NTA) was a B-36H-20-CF (Serial Number 51-5712) that had been damaged in a tornado at Carswell AFB on 1 September 1952. This plane, designated the NB-36H, was modified to carry a 1 MW, air-cooled nuclear reactor in the aft bomb bay, with a four ton lead shield between the reactor and the cockpit. The cockpit was encased in lead and rubber, with a 6-inch (15 cm)–thick acrylic glass windshield. The reactor was operational but did not power the plane; its sole purpose was to investigate the effect of radiation on aircraft systems. Between 1955 and 1957, the NB-36H completed 47 test flights and 215 hours of flight time, during 89 of which the reactor was critical.

Other experiments involved providing the B-36 with its own fighter defense in the form of parasite aircraft carried partially or wholly in a bomb bay. One parasite aircraft was the tiny McDonnell XF-85 Goblin, which docked using a trapeze system. The concept was tested successfully using a B-29 carrier, but docking proved difficult even for experienced test pilots. Moreover, the XF-85 was seen as no match for Soviet aircraft, and the project was cancelled.

More successful was the FICON project, involving a modified B-36 - called a GRB-36D "mothership" - and the RF-84K, a fighter modified for reconnaissance, in a bomb bay. The GRB-36D would ferry the RF-84K to the vicinity of the objective, whereupon the RF-84K would disconnect and begin its mission. Ten GRB-36Ds and 25 RF-84ks were built and saw active service until 1959.

Projects TIP TOW and Tom-Tom involved docking F-84s to the wingtips of B-29s and B-36s. The hope was that the increased aspect ratio of the combined aircraft would result in a greater range. Project TIP TOW was canceled when the combination of two EF-84Ds and a specially modified test EB-29A crashed, killing everyone on all three aircraft. This accident was attributed to one of the EF-84Ds flipping over onto the wing of the EB-29A. Project Tom-Tom, involving RF-84Fs and a GRB-36D from the FICON project (redesignated JRB-36F), continued for a few months after this crash, but was also canceled due to the violent turbulence induced by the wingtip vortices of the B-36.

Obsolescence

The operational life of the B-36 ended because:

* Long range jet-powered bombers became feasible, resulting in such aircraft as the B-47 and B-52, with cruising speeds more than double that of the B-36.

* The speed and operating ceiling of jet fighter interceptors steadily rose.

* Radar-guided surface-to air missiles, such as the Soviet SA-2 Guideline, capable of reaching 20,000 meters (65,616 ft), emerged.

* The airframe, especially the wings, proved vulnerable to metal fatigue.

* Wing flexing led to fuel leakage, a common problem.

The B-36 was progressively removed from service as the B-52 became operational in 1955. The last B-36s left active USAF service in 1959.

Survivors

Only four (and a half) B-36 type aircraft survive today, from the 384 produced.

* YB-36/RB-36E AF Serial No. 42-13571. This was the first prototype to be converted to the bubble canopy used on production B-36s. It was on display in the 1950s at the former site of the Air Force Museum, now the National Museum of the United States Air Force, at Wright-Patterson Air Force Base near Dayton, Ohio. When the museum moved to its current location at Wright-Patterson, the cost of moving the bomber was more than simply flying a different B-36 to the new location and the aircraft was slated to be scrapped. Instead, private collector Walter Soplata bought it and transported the pieces by truck to his farm in Newbury, Ohio, where it sits today in several large pieces. The bomb bay currently contains a complete P-47N still packed in its original shipping crate.

* RB-36H AF Serial No. 51-13730, is on display at the Castle Air Museum at the former Castle Air Force Base in Atwater, California.

* B-36J AF Serial No. 52-2217, is on display at the Strategic Air and Space Museum, (formerly located at Offutt Air Force Base) and now just off base near Ashland, Nebraska.

* B-36J AF Serial No. 52-2220, is on display at the National Museum of the United States Air Force (formerly The U.S. Air Force Museum) at Wright-Patterson Air Force Base near Dayton, Ohio. Its flight to the museum from Davis-Monthan Air Force Base in Arizona on 30 April 1959 was the last flight of a B-36. This B-36J replaced the former Air Force Museum's original YB-36 AF Serial Number 42-13571 (see above). This was also the first aircraft to be placed in the Museum's new display hangar, and was not moved again until relocated to the Museum's latest addition in 2003. It is displayed alongside the only surviving example of the massive 9 ft (2.7 m) XB-36 wheel and tire.

* B-36J, AF Serial No. 52-2827, the final B-36 built, named "The City of Fort Worth", was loaned to the city of Fort Worth, Texas on 12 February 1959. It sat on the field at the Greater Southwest International Airport until that property was redeveloped as a business park. It then moved to the short-lived Southwest Aero Museum, which was located between the former Carswell Air Force Base (now NAS Fort Worth) and the former General Dynamics (now Lockheed Martin) assembly plant. From there it went to the Lockheed Martin plant, where some restoration took place. As Lockheed Martin had no place to display the finished plane, and local community efforts in Fort Worth to build a facility to house and maintain the massive aircraft fell short, the USAF Museum retook possession of the plane and it was transported to Tucson, Arizona for loan to the Pima Air & Space Museum. It is now undergoing restoration and reassembly at the Pima Air & Space Museum, just south of Davis-Monthan AFB, Arizona and will ultimately be displayed at that location.

* XC-99, AF Serial No. 43-52436, the sole example of the cargo version of the B-36, was stored for years at the former Kelly AFB, now the Kelly Field Annex of Lackland AFB, in San Antonio, Texas. It has since been relocated and is currently undergoing restoration and reassembly at the National Museum of the United States Air Force at Wright-Patterson AFB in Dayton, Ohio.

More photos:

Convair B-36 Peacemaker: Personnel and equipment required to get and keep a B-36 Peacemaker airplane in the air. (U.S. Air Force photo)Convair B-36 Peacemaker: Personnel and equipment required to get and keep a B-36 Peacemaker airplane in the air. (U.S. Air Force photo)

Convair B-36 Peacemaker: Convair B-36A-10-CF (S/N 44-92013). This aircraft completed a simulated attack on Hawaii by flying a non-stop round-trip from Fort Worth, Texas, on May 13-15, 1948. (U.S. Air Force photo)Convair B-36 Peacemaker: Convair B-36A-10-CF (S/N 44-92013). This aircraft completed a simulated attack on Hawaii by flying a non-stop round-trip from Fort Worth, Texas, on May 13-15, 1948. (U.S. Air Force photo)

Convair B-36 Peacemaker: Convair B-36A-1-CF (S/N 44-92004, the first -A model built) in flight. (U.S. Air Force photo)Convair B-36 Peacemaker: Convair B-36A-1-CF (S/N 44-92004, the first -A model built) in flight. (U.S. Air Force photo)

Convair B-36 Peacemaker: DAYTON, Ohio -- Convair B-36J Peacemaker in the Cold War Gallery at the National Museum of the United States Air Force. (U.S. Air Force photo)Convair B-36 Peacemaker: DAYTON, Ohio -- Convair B-36J Peacemaker in the Cold War Gallery at the National Museum of the United States Air Force. (U.S. Air Force photo)

Convair B-36 Peacemaker: This original drawing from the early 1950s shows how the camera was installed in the RB-36. The camera could be used in this position to take vertical photographs, or rotated on its mount to point out of the lower left side of the fuselage to take oblique photographs. (U.S. Air Force photo)Convair B-36 Peacemaker: This original drawing from the early 1950s shows how the camera was installed in the RB-36. The camera could be used in this position to take vertical photographs, or rotated on its mount to point out of the lower left side of the fuselage to take oblique photographs. (U.S. Air Force photo)

Convair B-36 Peacemaker: DAYTON, Ohio -- A B-36J is placed in the original museum building on Dec. 28, 1970. (U.S. Air Force photo)Convair B-36 Peacemaker: DAYTON, Ohio -- A B-36J is placed in the original museum building on Dec. 28, 1970. (U.S. Air Force photo)

Convair B-36 Peacemaker: 1940's -- The Convair RB-36D, the jet-augumented version of the U.S. Air Force's intercontinental strategic bomber. Bomb bay was fitted with 14 cameras. The number 2 bay was used to carry up to eighty 100 lb. photo flash bombs for nighttime aerial photography. Four General Electric J-47 jet engines, mounted in pairs under outer wing edges, supplement six Pratt & Whitney piston engines. (U.S. Air Force photo)Convair B-36 Peacemaker: 1940's -- The Convair RB-36D, the jet-augumented version of the U.S. Air Force's intercontinental strategic bomber. Bomb bay was fitted with 14 cameras. The number 2 bay was used to carry up to eighty 100 lb. photo flash bombs for nighttime aerial photography. Four General Electric J-47 jet engines, mounted in pairs under outer wing edges, supplement six Pratt & Whitney piston engines. (U.S. Air Force photo)

Convair B-36 Peacemaker: 1950's -- B-36 Peacemaker (U.S. Air Force photo)Convair B-36 Peacemaker: 1950's -- B-36 Peacemaker (U.S. Air Force photo)

Convair B-36 Peacemaker: 1950's -- B-36 Peacemaker (U.S. Air Force photo)Convair B-36 Peacemaker: 1950's -- B-36 Peacemaker (U.S. Air Force photo)

Convair B-36 Peacemaker: Convair GRB-36F in flight with Republic YRF-84F (S/N 49-2430). (U.S. Air Force photo)Convair B-36 Peacemaker: Convair GRB-36F in flight with Republic YRF-84F (S/N 49-2430). (U.S. Air Force photo)

Convair B-36 Peacemaker: Convair B-36A-10-CF (S/N 44-92015) in foreground and B-36A-15-CF (S/N 44-92023) in flight. (U.S. Air Force photo)Convair B-36 Peacemaker: Convair B-36A-10-CF (S/N 44-92015) in foreground and B-36A-15-CF (S/N 44-92023) in flight. (U.S. Air Force photo)

Convair B-36 Peacemaker: Front view of Convair B-36A-1-CF (S/N 44-92006). (U.S. Air Force photo)Convair B-36 Peacemaker: Front view of Convair B-36A-1-CF (S/N 44-92006). (U.S. Air Force photo)

Convair B-36 Peacemaker: Side view of Convair B-36A-1-CF (S/N 44-92006). (U.S. Air Force photo)Convair B-36 Peacemaker: Side view of Convair B-36A-1-CF (S/N 44-92006). (U.S. Air Force photo)

Convair B-36 Peacemaker: Convair RB-36E, originally B-36A-15-CF (S/N 44-92020), of the 5th Strategic Reconnaissance Wing (Circle X), 72nd Strategic Reconnaissance Squadron, Travis Air Force Base, Calif. (U.S. Air Force photo)Convair B-36 Peacemaker: Convair RB-36E, originally B-36A-15-CF (S/N 44-92020), of the 5th Strategic Reconnaissance Wing (Circle X), 72nd Strategic Reconnaissance Squadron, Travis Air Force Base, Calif. (U.S. Air Force photo)

Convair B-36 Peacemaker: Convair RB-36D on the assembly line at the Convair plant in Fort Worth, Texas. (U.S. Air Force photo)Convair B-36 Peacemaker: Convair RB-36D on the assembly line at the Convair plant in Fort Worth, Texas. (U.S. Air Force photo)

Convair B-36 Peacemaker: Convair RB-36D in flight. (U.S. Air Force photo)Convair B-36 Peacemaker: Convair RB-36D in flight. (U.S. Air Force photo)

Convair B-36 Peacemaker flight: Convair B-36D, converted B-36B (S/N 44-92074), in flight. (U.S. Air Force photo)Convair B-36 Peacemaker flight: Convair B-36D, converted B-36B (S/N 44-92074), in flight. (U.S. Air Force photo)

Convair B-36 Peacemaker: Convair B-36D in flight. (U.S. Air Force photo)Convair B-36 Peacemaker: Convair B-36D in flight. (U.S. Air Force photo)

Convair B-36 Peacemaker: Side view of Convair B-36D-5-CF (S/N 49-2652) of the 7th Bomb Group (Heavy), Carswell Air Force Base, Texas. (U.S. Air Force photo)Convair B-36 Peacemaker: Side view of Convair B-36D-5-CF (S/N 49-2652) of the 7th Bomb Group (Heavy), Carswell Air Force Base, Texas. (U.S. Air Force photo)

Convair B-36 Peacemaker: Convair B-36B in flight. (U.S. Air Force photo)Convair B-36 Peacemaker: Convair B-36B in flight. (U.S. Air Force photo)

Convair B-36 Peacemaker: Convair B-36H-1-CF (S/N 50-1087, the fifth H model built). Note the aft upper weapons bay is open showing the turrets. (U.S. Air Force photo)Convair B-36 Peacemaker: Convair B-36H-1-CF (S/N 50-1087, the fifth H model built). Note the aft upper weapons bay is open showing the turrets. (U.S. Air Force photo)

Convair B-36 Peacemaker: Convair B-36F with XB-58 structure mounted in a specially modified bomb bay. (U.S. Air Force photo)Convair B-36 Peacemaker: Convair B-36F with XB-58 structure mounted in a specially modified bomb bay. (U.S. Air Force photo)

Convair B-36 Peacemaker: Convair NB-36H in flight. Note the radiation warning symbol on the tail. (U.S. Air Force photo)Convair B-36 Peacemaker: Convair NB-36H in flight. Note the radiation warning symbol on the tail. (U.S. Air Force photo)

Convair B-36 Peacemaker: Convair RB-36H in flight. Note the dual radomes on the tail turret, a characteristic of the H and J model's improved AN/APG-41A fire control radar system. (U.S. Air Force photo)Convair B-36 Peacemaker: Convair RB-36H in flight. Note the dual radomes on the tail turret, a characteristic of the H and J model's improved AN/APG-41A fire control radar system. (U.S. Air Force photo)

Convair B-36 Peacemaker: DAYTON, Ohio - Convair B-36J Peacemaker instrument components at the National Museum of the U.S. Air Force. (U.S. Air Force photo)Convair B-36 Peacemaker: DAYTON, Ohio - Convair B-36J Peacemaker instrument components at the National Museum of the U.S. Air Force. (U.S. Air Force photo)

Convair B-36 Peacemaker: DAYTON, Ohio - Convair B-36J Peacemaker cockpit at the National Museum of the U.S. Air Force. (U.S. Air Force photo)Convair B-36 Peacemaker: DAYTON, Ohio - Convair B-36J Peacemaker cockpit at the National Museum of the U.S. Air Force. (U.S. Air Force photo)

Convair B-36 Peacemaker: DAYTON, Ohio - Convair B-36J Peacemaker instrument components at the National Museum of the U.S. Air Force. (U.S. Air Force photo)Convair B-36 Peacemaker: DAYTON, Ohio - Convair B-36J Peacemaker instrument components at the National Museum of the U.S. Air Force. (U.S. Air Force photo)

Convair B-36 Peacemaker: Convair XB-36 in flight. (U.S. Air Force photo)Convair B-36 Peacemaker: Convair XB-36 in flight. (U.S. Air Force photo)

Convair B-36 Peacemaker: The only Convair XB-36 built (S/N 42-13570). (U.S. Air Force photo)Convair B-36 Peacemaker: The only Convair XB-36 built (S/N 42-13570). (U.S. Air Force photo)

Convair B-36 Peacemaker: Convair XB-36 in flight just after takeoff or just before landing. (U.S. Air Force photo)Convair B-36 Peacemaker: Convair XB-36 in flight just after takeoff or just before landing. (U.S. Air Force photo)

Convair B-36 Peacemaker: F-84E in extended position under B-36. (U.S. Air Force photo)Convair B-36 Peacemaker: F-84E in extended position under B-36. (U.S. Air Force photo)

More photos: Convair B-36 Peacemaker photo gallery

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