Convair B-36
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The Convair (Consolidated Vultee) B-36 (officially named the "Peacemaker", though the name is rarely used) was a strategic bomber aircraft, operated mainly by the United States Air Force. A huge piston-engined craft, the B-36 is the largest mass-produced bomber aircraft ever flown. The design process began in 1941, the first prototype flew in 1946, and the first production aircraft was delivered in 1947. As the only truly intercontinental bomber in service, the B-36 provided the United States and its newly formed Strategic Air Command with the mainstay of its nuclear deterrent until the mid 1950s, when the B-52 Stratofortress and other long-range jet bombers became operational. The last B-36 was withdrawn from service in 1959, after 384 had been built.
On paper, the B-36 had a great deal of utility as a strategic nuclear deterrent. Some variants could fly up to 50 hours, and with combat ranges of as much as 3,400 miles (5,500 km), the Strategic Air Command was endowed with truly global round-the-clock strategic reach; it was touted by Convair as their "aluminum overcast", a "long rifle" in the hands of the Strategic Air Command. In practice, however, the B-36 was a difficult plane to operate, especially prone to catastrophic engine malfunctions and other costly difficulties. To its critics, these problems made it a "billion-dollar blunder". United States Navy officials saw it as a costly bungle siphoning funding and interest from their pet project, aircraft carrier–based nuclear bombers.
Though giant, lumbering, and somewhat outdated ("a prop bomber in the age of jet fighters"), the B-36's role as the United States' sole practical nuclear deterrent earned it the nickname Peacemaker in the opening years of the Cold War. Though it was never tested in combat, the Strategic Air Command defended its performance. Few fighters of the day could reach the normal operating altitude of the B-36, and at altitude the giant bomber with its lower wing loading was said to be able to out-turn the faster fighters. (Others - including former fighter pilots - challenge this statement.)
While it received all its publicity in connection to its role as a strategic nuclear bomber, the B-36 also performed a number of rarely acknowledged reconnaissance missions. It is believed that variants of the B-36 were involved in numerous penetrations of Chinese (and possibly Soviet) airspace. The cameras carried by the reconnaissance variants (given the designation RB-36) could produce pictures of high resolution: photographs of a golf course taken from 40,000 ft (12,000 m) show recognizable golf balls. Before the development of the Lockheed U-2, the RB-36 was the only plane with the range to fly into Asia from bases in the United States.
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Design
The B-36 concept began with a proposal by Consolidated Aircraft (later Convair) to meet a 1941 United States Army Air Corps intercontinental bomber requirement. (The same design request led to the Northrop YB-35.) If Britain fell, American bombers would need to reach Europe directly in the event of the United States joining the war. Though this need never arose, the B-36 was still considered necessary to take the war to Japan, and development of the project continued.
The B-36 took shape as a six-engined aircraft of immense proportions: at 162 ft (50 m) in length, it was two-thirds longer than the previous superbomber, the B-29 Superfortress. The six engines were embedded in the thick wings, driving immense three-bladed propellers 19 ft (5.8 m) in diameter. The props were arranged in pusher configuration (on the trailing edge of the wing) to avoid interference with wing lift and aerodynamics caused by propeller turbulence. The wing roots were more than 7 ft (2.3 m) thick, so large that flight engineers could perform some maintenance in the air.
As in the B-29, a pressurized flight deck and crew compartment were linked to the rear gunners' compartment by a pressurized tunnel through the bomb bay. In the B-36, this tunnel was equipped with a wheeled trolley to ride upon. A crew of fifteen was needed to fly the plane. The B-36 was equipped with four bunks and a galley in the rear, to provide rest and relief for men on long missions. The galley and other "crew comfort" items were removed from later models to save weight.
The defensive armament consisted of six remote-controlled retractable gun turrets, a tail turret, and a nose mount. All eight were fitted with two 20 mm cannon — the most powerful defensive armament ever carried by any bomber. In its four giant bomb bays, the B-36 could carry as much as 33 tons (30 tonnes) of bombs: eight times the load carried by the famous B-17 Flying Fortress. It was the only aircraft able to carry the massive Mark 17 hydrogen bomb, and was used to carry a conventional 44,000 pound (20,000 kg) bomb, the T-12 Cloudmaker.
B-29_and_B-36.jpg
The first prototype XB-36 flew on August 8 1946. The speed and range of the prototype failed to meet the standards requested by the Army Air Corps in 1941. Like many aircraft before it that had pushed the size envelope, the XB-36 had a number of difficulties. (Compare the B-29 Superfortress, which was plagued by engine problems, and the Boeing XB-15, which didn't have engines available powerful enough for a useful top speed.) Many of these problems were related to the early "placeholder" engines, weaker engines used until the intended powerplant became available.
The XB-36 also used single-wheel main landing gear, which severely restricted the airfields able to handle the massive plane. These wheels (http://www.wpafb.af.mil/museum/air_power/xb36lg.jpg) stood 9 ft (2.7 m) tall, measured 3 ft (1 m) in thickness, and weighed 1,320 lb (599 kg). They contained enough rubber to make 60 automobile tires. The giant single wheel was soon replaced by a four-wheel bogie (http://www.hill.af.mil/museum/photos/dawnjet/b-36.jpg). A tanklike tracked landing gear (http://www.wpafb.af.mil/museum/research/bombers/xb36-13.jpg) was tested on the XB-36, but proved heavy and noisy.
A second aircraft, the YB-36, flew on December 4 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 YB-36 was actually beaten to the air by the first production model: a single B-36A was built with enough equipment to fly to Wright Field, where its airframe was subjected to a battery of physical tests.)
In 1947, the United States Navy attacked Congressional funding for the B-36, alleging that the aircraft failed to meet its requirements. The Navy had believed that the dominance of the aircraft carrier in the Pacific during World War II provided conclusive proof that carrier-based airstrikes would be the deciding factor in future wars. To this end, they had designed the USS United States (CVA-58), a "supercarrier" capable of launching huge fleets of aircraft — or nuclear bombers. They pushed to have funding transferred from the B-36 to the United States. The Air Force successfully defended their project, and the United States was officially cancelled by Secretary of Defense Louis A. Johnson. Following the cancellation of the United States, several high-level officials of the Navy questioned the government's policy, and asserted that the contract with Convair was corrupt: Johnson was a former member of the Convair Board of Directors. The uproar following the cancellation of the United States has been nicknamed the Revolt of the Admirals.
Production
The first of 21 B-36A planes were delivered in 1948. They were explicitly interim airframes, intended for crew training and conversion to B-36 operations. No defensive armament was fitted, since the system was not ready. Once newer planes were available, all B-36A airframes were converted to RB-36E reconnaissance models.
The first B-36 variant meant for normal operation was the B-36B, delivered beginning in November of 1948. This aircraft met all the 1941 requirements, but had serious engine reliability issues, and difficulties remained with the defensive armament. Parts supply problems kept aircraft availability low.
Even at this stage the B-36 was obsolete, a piston-engined bomber in the age of jet fighters. No jet bomber had the range to reach all strategic targets, however. The B-36 was the only truly intercontinental bomber available. Increasing concern about the Soviet threat kept the B-36 program alive and the aircraft in service.
The limits of piston-engine technology were exemplified during takeoff. The B-36 suffered from long, lumbering takeoff runs and a low top speed. Convair addressed this problem, beginning with the B-36D model, by adding four auxiliary jet engines in pods under the outer wings to provide short-term boosts in power. B-36 crews thus referred to having "six [engines] turning and four [engines] burning". (Given the poor reliability of the engines, this was sometimes changed to, "two turning, two burning, two joking, and two smoking".) Most of the earlier aircraft were converted to B-36D specification. Later models featured increased piston engine power, improved radar, redesigned crew compartments, and (in the final B-36J model) extra fuel tanks to regain the range lost by the jet engines' greater thirst for fuel.
Toward the end of B-36 production, heavy defensive armament was falling out of favor: the range of new air-to-air missiles made hand-aimed guns obsolete. The final fourteen B-36J aircraft were delivered as "featherweights", with all guns but the radar-aimed tail turret removed. The remotely operated power turrets of the original design were heavy, unreliable, and needed significant manpower; removing them allowed the aircraft to reach altitudes above 50,000 ft (15 km) and fly longer and further. Other B-36 aircraft were modified to this configuration, especially the reconnaissance aircraft, for which these attributes were especially advantageous. There were three Featherweight programs. Featherweight I removed most defensive hardware from line aircraft. Featherweight II continued the weight-reduction program by removing crew-comfort items such as the rear-compartment galley. Featherweight III aircraft were delivered from the factory without these items.
Operational history
Reconnaissance
The B-36 was especially suited for reconnaissance missions. Its immense size allowed it to carry large amounts of equipment, including huge high-resolution cameras; its high cruising altitude made it difficult to intercept; and its long range and great endurance enabled missions of extreme distance. In the reconnaissance variants (designation RB-36), the first of the four bomb bays was permanently converted to a pressurized camera compartment. The aft bomb bay was usually loaded with extra fuel tanks. Later RB-36 models are said to have been able to reach 60,000 ft (18,000 m) and remain aloft for 50 hours. RB-36s were distinguishable by the bright aluminum 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. The number and placement of these varied.
More than a third of all B-36 models were reconnaissance models, and before the advent of the Lockheed U-2 in the late 1950s, the RB-36 was the mainstay of American photo reconnaissance over hostile territory. It is known that missions were made into China; it is also believed that missions approaching or even overflying the Soviet Union were also undertaken.
Crew experience
The B-36 was not a sprightly aircraft: it was one of the largest planes ever built when it was first introduced. Lieutenant General James Edmundson likened it to "...sitting on your front porch and flying your house around." However, [1] (http://www.pbs.org/wgbh/amex/bomb/filmmore/reference/interview/edmund10.html) its relatively low wing loading made it more maneuverable at high altitude than jet interceptors, which would stall in a tight turn at high altitude. (It should be noted that reports of the B-36 outmaneuvering jet fighters at altitude have tended to come from bomber crews. Perhaps not surprisingly, some fighter pilots have disputed these reports.)
Despite its immense exterior size, the pressurized crew compartments were relatively cramped when occupied for 24 hours by a crew of fifteen in full flight kit. Although bunks were provided for off-duty flight crewmen in the aft compartment, most preferred to sleep in their seats. Convair rigged a couple of bunks at the top of the 12-foot-diameter radio compartment behind the flight deck.
Even an aircraft with the range of the B-36 needed to be stationed as close to the enemy as possible, and this meant far north. B-36 bases were scattered throughout the northern United States, with regular deployments to bases in Alaska. The B-36 was too large to fit in most hangars, so most "normal" maintenance (for example, changing 56 spark plugs on each of six engines, replacing dozens of bomb-bay light bulbs shattered after a gunnery mission) was performed outside in 100-degree summers and 60-below winters. Special shelters were built so that the maintenance crews could have a modicum of protection while working on the engines. Often, groundcrew risked slipping and falling from ice-covered wings, or being blown off by a propeller running in reverse pitch. Some procedures required the mechanic to sit astride the running engine, a 19-foot diameter propeller at his feet, his hand near the 34-inch diameter cooling fan.
The B-36 needed a great deal of maintenance between flights; although in an emergency an aircraft could be "turned around" in a few days for a ferry flight, it took much longer to get the airplane ready for an operational mission. In January 1951 a B-36 amassed 200 hours of flight time (8.3 standard 24-hour missions); this is apparently a record.
Large piston-engined aircraft were notoriously fire-prone, but the B-36 was worse than most, especially in extreme cold. In typical aircraft, the carburetors are behind the engine and stay warm with the air flowing back from it. With the pusher configuration of the B-36, the carburetors had no warm air flow, and iced up when the intake air was very cold and humid. With the carburetors iced up, the air/fuel mixture would get richer and richer until the unburned fuel being expelled in the exhaust caught fire. These problems were exacerbated even further by the climate; during maintenance, special heaters had to be used. Engine fires also led to the crash of B-36B 44-92075 on February 13 1950, the first plane carrying a nuclear weapon to be lost. A crash on takeoff or landing was disastrous: because of its high magnesium content, the B-36 airframe burned readily.
The engines also had a prodigious appetite for lubricating oil. Each had a 100 U.S. gallon (380 L) tank. One ground crewman wrote, "[I don't recall] an oil change interval as I think the oil consumption factor handled that." Though it could continue flying with as many as three engines inoperative, the extra stress often caused additional failures.
Surviving crewmembers' recollections (http://forums.delphiforums.com/n/main.asp?webtag=B36forum) show that while crews were confident in their ability to perform their mission if called upon to do so, they were less confident that they would survive it. 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 assuming that the crew survived the weapon delivery itself. The Operation Castle tests in which B-36 aircraft flew near nuclear bomb detonations at ranges simulating a wartime delivery resulted in heavy damage to the aircraft from blast and heat effects.
Experiments
B-36s were used for a variety of aeronautical experiments. The most bizarre was the NB-36H flying nuclear reactor testbed, a fore-runner to the Convair X-6 project. An operational nuclear reactor was fitted in the aft bomb-bay of the aircraft, a four ton lead shield inserted in front of the bomb bay, and the crew was encased in a lead and rubber capsule with a tiny, 1 foot (30 cm)–thick leaded glass windshield. The reactor, though operational, did no useful work. Rather, its inclusion was in preparation for planned nuclear aircraft, to see if radiation would damage aircraft systems. The NB-36H first flew in 1955. Following the abandonment of the nuclear aircraft program, it was scrapped in 1957, the radioactive parts being buried.
Other experiments were concerned with providing the B-36 with its own fighter defence in the form of parasite aircraft carried in or with it. One plan used the tiny McDonnell XF-85 Goblin, which was to be carried in a B-36 bomb bay. The concept was tested successfully using a B-29 carrier, but docking proved difficult even for experienced test pilots. Budgets were short, and it was expected that the XF-85 would be no match for Soviet aircraft in any case. The project was cancelled.
A similar project, FICON, involved modifying F-84 Thunderjet fighters so that they could be carried by specially modified B-36 aircraft, and dropped to perform independent reconnaissance missions. This project was more successful, with ten B-36D bombers being modified into GRB-36D "motherships" to carry the 25 modified RF-84K reconnaissance Thunderjets ordered. They saw active service until 1959, when they were quietly withdrawn as newer reconnaissance planes were introduced.
A third project, Tom-Tom, had F-84s dock to the wingtips of the B-36. The idea was that the increased aspect ratio of the combined aircraft would help stretch the range of the combined aircraft. The Peacemaker's powerful wingtip vortices made the concept problematic, and it was cancelled when an F-84 flipped over onto the wing of the B-36, resulting in the loss of both aircraft and the death of both crews.
Obsolescence
As the B-52 Stratofortress entered service, the B-36 fleet was scaled back. However, defense cutbacks in the 1950s slowed delivery of B-52s, keeping some B-36s in service through 1958. The last aircraft in service was withdrawn on February 12, 1959 and donated to the city of Fort Worth, Texas, where it had been produced.
Four B-36 aircraft survive, one a B-36H and the other three B-36J models. The B-36H is on display at the Castle Air Force Base museum in Atwater, California. The other three are on display at the National Museum of the United States Air Force at Wright-Patterson Air Force Base near Dayton, Ohio, the Strategic Air Command Museum (formerly Offut Air Force Base) near Ashland, Nebraska, and the final one built has been restored and is in storage in its home town of Fort Worth. Officials and volunteers at the B-36 Peacemaker Museum are currently (March 2005) planning exhibit space at Meacham Field (http://www.meacham.org) in Fort Worth to once again display the aircraft.
It is highly unlikely any will ever fly again; the B-36 was a challenge to keep aloft even when it was new [2] (http://forums.delphiforums.com/B36forum/messages/?msg=308.1).
Variants and design stages
| 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 |
- Main article: Convair B-36 variants
The development of the B-36 design followed a steady progression from prototype to production aircraft. Several changes occurred over the course of its operational history, including the trend toward "featherweights", planes in which all extraneous weight was minimized. The B-36 also included several RB-36 variants converted for reconnaissance duty. Being a roomy testbed, it naturally served this purpose in several experiments as well (see the experiments section above), including studies on the use of parasite fighters and nuclear aircraft.
The B-36 was replaced in service by the Boeing B-52 Stratofortress; Convair's challenger, a jet-powered, swept-wing development of the B-36, earned a contract for two prototype Convair YB-60 airplanes, one of which flew. It was an inferior aircraft to the B-52 and the second prototype was not completed.
A transport version of the B-36, the Convair XC-99, was derived from the giant bomber. One prototype flew, but the aircraft never went into production. It was used for transcontinental cargo shipments during the Korean war. A commercial airliner derived from the XC-99, the Convair Model 37 was on the drawing board, but it was never produced. After it was retired, the XC-99 was stored outside in San Antonio for decades. As of March 2005 plans are underway to move the giant transport to the National Museum of the United States Air Force at Wright-Patterson Air Force Base near Dayton, Ohio.
Specifications (B-36J)
General characteristics
- Crew: 15 — (Pilot, co-pilot, radar/bombardier, navigator, flight engineer, two radiomen, three forward gunners, five rear gunners; reconnaissance versions added seven technicians in the photo reconnaissance compartment)
- Length: 162 ft 1 in (49.40 m)
- Wingspan: 230 ft 0 in (70.10 m)
- Height: 46 ft 8 in (14.22 m)
- Wing area: 4772 ft² (443.3 m²)
- Empty: 171,035 lb (77,580 kg)
- Loaded: 266,100 lb (120,700 kg)
- Maximum takeoff: 410,000 lb (190,000 kg)
- Powerplant (jet): 4× General Electric J47 turbojets; 5,200 lbf (23 kN) thrust each
- Powerplant (prop): 6× Pratt & Whitney R-4360-53 Wasp Major radials; 3,800 hp (2,500 kW) each
Performance
- Maximum speed: 439 mph (707 km/h)
- Range: 8,000 miles (13,000 km)
- Service ceiling: 48,000 ft (15,000 m)
- Rate of climb: 1,920 ft/min (585 m/min)
- Wing loading: 55.76 lb/ft² (272.3 kg/m²)
- Thrust/weight (jet): 0.078:1 (0.078 lbf/lb, 0.76 N/kg)
- Power/mass (prop): 0.086 hp/lb (120 W/kg)
Armament
- 16× 20 mm M24A1 cannon
- 86,000 lb (39,000 kg) of bombs
Media
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References
- Jacobsen, Meyers K. (1997). Convair B-36: A Comprehensive History of America's "Big Stick". Atglen: Schiffer Military History. ISBN 0764309749
- Jacobsen, Meyers K. (1999). Convair B-36: A Photo Chronicle. Atglen: Schiffer Military History. ISBN 0764309749
- Jenkins, Dennis R. (2003). B-36 Photo Scrapbook. Minnesota: Specialty Press Publishers and Wholesalers. ISBN 1580070752
- Jenkins, Dennis R. (1999). Convair B-36 Peacemaker. Specialty Press Publishers and Wholsalers. ISBN 1580070191
- Jenkins, Dennis R. (2001). Magnesium Overcast. Minnesota: Voyageur Press. ISBN 1580070426
- Wagner, Ray (1982). American Combat Planes. New York: Doubleday. ISBN 0930083172
- "Lt. General James Edmundson interview transcript (http://www.pbs.org/wgbh/amex/bomb/filmmore/reference/interview/edmund10.html): Flying B-36 and B-47 planes.". Race For the Superbomb. PBS Online.
- "B-36: Bomber at the Crossroads (http://www.airspacemag.com/ASM/Mag/Index/1996/AM/bacr.html)". Smithsonian Air and Space. 1996.
- Original B-36 main landing gear (http://www.wpafb.af.mil/museum/air_power/xb36lg.jpg)
- Tom-Tom project (http://www.air-and-space.com/tomtom.htm)
- XB-36 caterpillar gear (http://www.wpafb.af.mil/museum/research/bombers/b3-69.htm)
- B-36 maintenance discussion (http://forums.delphiforums.com/B36forum/messages/?msg=308.1)
External links
- B-36 plane veterans group (http://www.cowtown.net/proweb/B36_Home.htm)
- B-36/Cold War vet's forum (http://forums.delphiforums.com/n/main.asp?webtag=B36forum)
- Cowtown.net: portal to B-36 resources (http://www.cowtown.net/proweb/b36net/)
- Encyclopedia of American aircraft (http://home.att.net/~jbaugher2/b36.html)
- Goleta Air Museum (http://www.air-and-space.com/peacemkr.htm)
- USAF Museum (http://www.wpafb.af.mil/museum/research/bombers/b3-72.htm)
Related content
Related development: B-32 Dominator - Convair XC-99 - Convair YB-60 - Convair Model 37
Comparable aircraft: Boeing B-52 - Convair YB-60 - Tupolev Tu-95
Designation sequence: XB-33 - B-34 - YB-35 - B-36 - B-37 - XB-38 - XB-39
Related lists: List of military aircraft of the United States - List of bomber aircraft
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