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B-29 Superfortress
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B-29 Superfortress

B-29 Superfortress

B-29 Superfortress
Role Heavy bomber
Crew 10
First Flight September 1942
Entered Service 1943
Manufacturer Boeing Corp.
Length 99 ft 30 m
Wingspan 141 ft 3 in 43 m
Height 27 ft 9 in 8.5 m
Wing Area ft²
Empty lb kg
Loaded lb kg
Maximum Takeoff 133,500 lb 60,600 kg
Engines 4 x Wright R-3350
Power 4 x 2,200 hp 4 x 1,640 kW
Maximum Speed 357 mph 575 km/h
Combat Range miles km
Ferry Range 3,700 miles 6,000 km
Service Ceiling 33,600 ft 10,200 m
Rate of Climb ft/min m/min
Wing Loading lb/ft² kg/m²
Power/Mass hp/lb kW/kg
Guns 8 x 0.5 in (12.7 mm) machine guns in remote controlled turrets; 2 x 0.5 in (12.7 mm) machine guns and 1 20 mm cannon in tail
Bombs 20,000 lb (9,000 kg)
The Boeing B-29 Superfortress was an American four-engine heavy bomber, and one of the largest aircraft of World War II to see active service. It was the primary US strike weapon against Japan and continued to serve long after the war was over.

Boeing began planning for a very large, long range bomber in 1938, an aircraft far larger and more ambitious than any yet built. It was a very ambitious project - too ambitious, some felt - but it was not the first time Boeing had tried to build a giant bomber. Their XB-15 project in 1936 resulted in a single prototype that dwarfed anything on active duty at that time. The smaller but no less impressive B-17 had been an equally ambitious design when it was first planned in 1934. However, the avante-garde nature of their proposal (the AAF was actually looking for a 2 engine bomber, Boeing provided them with 4), as well as the unfortunate crash of the prototype 299, resulted in a long road to production for that aircraft. Nevertheless, Boeing offered its design study for a still more advanced pressurised development of the B-17 to the United States Army Air Corps in 1938 and, though there was no immediate interest, they were encouraged to keep working on it.

In January 1940, with the B-17 just entering service and the somewhat larger Consolidated B-24 still more than a year away, the Air Corps issued a request for proposals for a much larger bomber, which was to have the range for operation over the Pacific - it being understood that war with Japan was all but inevitable. Four firms submitted design studies, but Douglas and Lockheed soon withdrew. In September 1940 Boeing and Consolidated were awarded development contracts for the XB-29 and the XB-32.

Boeing's extensive design work paid off: even before the prototype had flown for the first time in September 1942, the USAAC had placed a massive order for 1500 B-29s. Within just 12 months, it was in full-scale production.

By the standards of the day, it was an enormous airplane: 30 m long, a 43 m wingspan, over 32 tonnes empty, and when fully loaded almost 63 tonnes. For range, the mid-set wings had a high aspect ratio, and to keep the landing speed within reason, enormous Fowler flaps were fitted. Three separate pressurised crew compartments were provided: one in the nose, a second one just aft of the wing for gunners, and a third, isolated one for the tail gunner.

Rather than fit traditional bulky manned gun turrets, Boeing used small, remote control units "networked" together with a true digital computer that compensated for things like air temperature and bullet drop. While they gave considerable trouble during development, the turret system ended up working well, with several accounts of "healthy" B-29s peeling out of formation to successfully drive off fighters preying on damaged brethren.

The manufacturing task was immense, involving four main factories at Renton, Wichita (both Boeing plants), Marietta (Bell) and Omaha (Martin), and thousands of sub-contractors. Because of its highly advanced design, challenging requirements, and immense pressure for production, development was deeply troubled. The first prototype crashed during testing, killing the entire crew and several ground personnel. Changes to the production craft came so often and so fast that in early 1944 B-29s would leave the production lines and fly directly to modification depots for extensive rebuilds to incorporate the latest changes. This "battle of Kansas" nearly sank the program, which was only saved by Hap Arnold's direct intervention. It would still be nearly a year before the aircraft was operated with any sort of reliability.

Its advanced gunnery system notwithstanding, the primary culprit for maintenance headaches and catastrophic failures was the engine. The Wright R-3350 would later become a trustworthy workhorse in large piston engined aircraft, early models were beset with dangerous reliability problems. While it had an impressive power-to-weight ratio, this came at a heavy cost in durability. Making matters worse, the cowling Boeing designed for the engine was too close (out of a desire for improved aerodynamics) and the early cowl flaps caused unacceptable flutter and vibration when open in most of the flight envelope.

This all combined to create an engine that ran so hot with combat loads it frequently swallowed its own valves. The resulting engine fires were exacerbated by a crankcase designed mostly of magnesium alloy. The heat was often so intense the main spar burned through in seconds, resulting in catastrophic failure of the wing. This problem would not be fully cured until the aircraft was re-engined with the more powerful Pratt & Whitney Wasp Major; in the B-29D/B-50 program, which arrived too late for WWII.

Pilots, including the present-day pilots of the Commemorative Air Force's 'Fifi', describe flight after takeoff as being (instead of striving for altitude as one generally would) an urgent struggle for airspeed. The engines need that airflow to keep cool, and failure to get up to speed as soon as possible could result in an engine failure and risk of fire.

Perhaps the most recognized B-29 is the "Enola Gay", which dropped the nuclear weapon "Little Boy" on Hiroshima on August 6, 1945. The "Bockscar", also a B-29, dropped "Fat Man" on Nagasaki three days later.

The B-29 was used in World War II only in the Pacific and was later used in the Korean War. 3970 of the aircraft were built before they were retired in 1960. B-29s flew 20,000 sorties in Korea and dropped 200,000 tons of bombs.

The Soviet Air Force's Tupolev Tu-4 was a bolt-for-bolt copy of the B-29, first widely revealed to the world audience in August of 1947.

The B-29 was soon made obsolete by the development of the jet engine. With the arrival of the mammoth B-36, it suffered its first ignominy by being classified a medium bomber with the new Air Force. However, the later B-29D/B-50 variant was good enough to be tasked with a number of auxiliary roles such as air-sea rescue, electronic intelligence gathering, and even air-to-air refueling. It was replaced in its primary role during the early 1950's with the Boeing B-47 "Stratojet, and eventually, the Boeing B-52 "Stratofortress. The final active duty variants were phased out in the mid 1960s.

As of August, 2003, the only B-29 in the world which is still airworthy is the Commemorative Air Force's "Fifi." However, work is actively proceeding at the Boeing plant in Wichita, Kansas on restoring a B-29 named "Doc," and the airplane is expected to fly in 2004. Also, the United States Air Force Museum at the old Wright-Patterson Air Force base is considering restoring "Bock's Car" to airworthy condition; it is presently restored as a static display. In addition, the Smithsonian has not decided whether to restore "Enola Gay" as a static display or to bring the airplane back to flight status.


General Characteristics

Related content
Related Development B-50 Superfortress - Tupolev Tu-4
Similar Aircraft
Designation Series B-26 - XB-27 - XB-28 - B-29 - XB-30 - XB-31 - B-32
Related Lists List of military aircraft of the United States - List of bomber aircraft

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