The Convair B-36 (nicknamed Peacemaker) was a strategic bomber built by Convair and operated solely by the United States Air Force (USAF). The B-36 was the largest mass-produced piston engined aircraft ever made and the biggest wingspan combat aircraft ever built, although there have been larger military transports. The B-36 was the first bomber capable of delivering thermonuclear weapons from within a fully-enclosed bomb-bay. With a range of over and a maximum payload of at least , 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.
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 , 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 multi-role use.
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 , 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 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 , 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 Secretary of Defense, Louis A. Johnson, whose personal bias 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. .
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 and designed to produce an Earth quake bomb effect.
| Variant | Built |
|---|---|
| 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 |
| Total | 384 |
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:
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.
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.
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.
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 summers or 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: "[I don't recall] 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.
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.
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.
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.
B-36s were also involved in two "Broken Arrow" incidents. On 13 February 1950, a B-36, serial number 44-92075, crashed in an unpopulated region of British Columbia, resulting in the first loss of an American nuclear weapon (see 1950 British Columbia B-36 crash). It was never confirmed whether the crew ditched the nuclear payload into the north Pacific. Locating the crash site took some effort, and what the USAF recovery team found there was classified.
On 22 May 1957, a B-36 accidentally dropped a Mark-17 hydrogen bomb on a deserted area while landing at Kirtland AFB in Albuquerque, New Mexico. Only the conventional trigger detonated, the bomb being unarmed. These incidents were classified for decades. See list of military nuclear accidents.
In 1951, the USAF asked Convair to build a prototype of an all-jet variant of the B-36. Convair complied by replacing the wings on a B-36F with swept wings, from which were suspended eight Pratt & Whitney XJ57-P-3 jet engines. The result was the B-36G, later renamed the Convair YB-60. The YB-60 was deemed inferior to Boeing's YB-52, and the project was terminated.
Just as the C-97 was the transport variant of the B-50, the B-36 was the basis for the Convair XC-99, a double-decked military cargo plane that was the largest piston engined, land-based aircraft ever built, and the longest practical aircraft (185 ft, 56 m) of its era. The sole example ever built was extensively employed for nearly a decade, especially for cross-country cargo flights during the Korean War. In 2005, this XC-99 was dismantled in anticipation of its being moved from the former Kelly Air Force Base, now the Kely Field Annex of Lackland AFB in San Antonio, Texas, where it had been retired since 1957. The XC-99 was relocated to the National Museum of the United States Air Force at Wright-Patterson Air Force Base near Dayton, Ohio, with C-5 Galaxy transports carrying pieces of the XC-99 to Wright-Patterson as space and schedule permitted.
A commercial airliner derived from the XC-99, the Convair Model 37, never left the drawing board. It would have been the first "jumbo" airliner.
The B-36 featured prominently in Paramount's Strategic Air Command (1955), starring Jimmy Stewart and June Allyson. In the film Jimmy Stewart's character is forced to crash land his B-36 in the Arctic. Strategic Air Command features many good aerial shots of B-36s and B-47s.
In Top of the World (1955), a formation of early B-36s (without the four jet engines) is shown just before the end title.
The 1957 John Wayne film Jet Pilot also shows a B-36 on a test mission being intercepted by an F-94 Starfire.
Retrieved: 4 September 2006.
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