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The B-29 Superfortress was a bomber devolped by the Boeing company in 1939. Being equipped with multiple new technologies, such as pressuriezed cabins, it was better in almost every way than its counterparts. The B-29 was used in the Pacific theater and was mostly used to bomb the Japanese Homeland. The B-29 was a very difficult aircraft to shoot down due to its overall design, defensive arsenal, speed of 587km/h, and its ability to fly at heights exceeding 9000m. Most Japanese aircraft could not reach such a height, let alone manage to keep up with its speed. One of the only Japanese aircraft that could intercept it was the Kawasaki Ki-61 Hien. For this reason, many B-29s had most of the guns removed during the later years of the war, leaving only the ones fitted to the tail turret.

Despite these advangtages, the B-29 suffered from a deal of technical problems, with engine trouble and fuel leakage being some of the most common. The most famous mission undertaken by the B-29 was its role in the use of atomic bombs on Hiroshima, dropped by the Enola Gay, and Nagasaki, by the Bockscar. Although it was largely replaced by its B-50 variant, the B-29 was still used in a variety of roles. The B-29 was adapted with multiple new specifications after the war and was used in the Korean War, further nuclear bomb testing, makeshift transport, and multiple other roles. The final B-29 was used was in September, 1960, afterwards being replaced by newer bombers like the B-52 Stratofortress.[1]

History

Development

The Superfortress was first envisaged in the late 1930s, when US military thinking turned to the possibility of an Axis invasion of the Americas, followed by enemy air attack against the industrial centres of the United States of America. This concept, known as 'hemisphere defence', called for the production of a variety of long range bomber types with operational radius of action ranging between 1,500 and 4,000 miles, although the true starting point of the B-29 was the 2,000 mile radius demanded of the bomber specified by the Kilner board in 1938, by which time Boeing's design team had undertaken a series of design studies in this area, such as the XB-15 derived model 316, which included pressurisation as an essential requirement.[2]

In March 1938, Chief of Staff Oscar Westover requested proposals for a new strategic bomber with a pressure cabin,[N 1] to allow it to fly faster and higher than the B-17 Flying Fortress.[3]

Following a series of studies featuring either Alison V-1710s (Model 333/333A), Wright R-1800s (Model 333B) or Pratt & Whitney R-2180s (Model 334) buried in the wing, Boeing proposed the Model 334A, which featured a 135ft span high aspect ratio wing with conventionally mounted Wright R-3350s. The 334A design displayed sufficient promise for Boeing to construct a mock-up of the aircraft in December 1939, at it's own expense.[4]

Boeing also prepared a modified design, which had been initiated in August 1939, known as the Model 341, which used a high aspect ratio wing based on a new high lift aerofoil developed by the Boeing Aerodynamics Unit. The new wing, which spanned 124ft 7in and mounter four 2,000hp Pratt and Whitney R-2800 engines, offered the 341 a speed of at least 405mph at 25,000ft, and the ability to fly 7,000 miles with one ton of bombs, or carry heavier loads over shorter distances. On November 10, 1939 General H. H. Arnold, Chief of the Air Corps, asked for permission from the War Department to issue a specification for a 'Super bomber' to replace the B-17 Flying Fortress and B-24 Liberator, receiving the necessary authority on December 2nd. The specification, known as Data R-40B, was circulated to Boeing, Consolidated, Douglas and Lockheed on January 28 1940, and called for a bomber with a speed of 400mph and the ability to deliver a 2,000lb load over a range of 5,333miles. The specification was almost immediately modified, in light of combat experience in Europe, to incorporate extra armour, enhanced armament and self sealing fuel tanks. Boeing responded by scaling up the 341 and replacing the R-2800s with Wright R-3350s, submitting the Model 345 to Wright Field on May 11 1940. This had a wingspan of 141ft 3in, a maximum bomb load of 16,000lb, defensive armament of 10 0.5in machine guns and a single 20mm cannon, and estimated max speed of 382mph. Evaluation of the primary designs placed Boeing first in order of preference, ahead of the Lockheed, Douglas and Consolidated entries, and led to the issuing of contracts on June 27 1940 for preliminary engineering data for each design, which were designated XB-29 (Boeing), XB-30 {Lockheed), XB-31 (Douglas) and XB-32 (Consolidated). The XB-30 and XB-31 were subsequently withdrawn, but development of the XB-32 continued as a safeguard in case of failure of the XB-29. Funds for the construvtion of two prototypes of both remaining designs was approved on August 24, with a third XB-29 and a static test airframe ordered on December 14.[4] The first unarmed Olive Drab prototype began flying on 21 September 1942.[3]

Large scale production had actually been authorised on May 17 1941, when the USAAF announced they had placed an order for 250 machines with the Government owned factory at Wichita factory, under the terms of a contract signed in September, which was doubled in January 1942. In February 1942 the USAAF announced that Bell Aircraft, North American Aviation and the Fisher Body Division of General motors would also build the B-29, resulting in tooling for orders for at least 1,664 aircraft was well advanced by the first flight.[5]

The already clean design was further refined, with the nose contours rounded off, and extension of the forward fuselage resulting in the length increasing from 93ft to 98ft 2in. The rear sections of the inner nacelles were extended aft of the trailing edge, and the vertical tail received a dorsal extension to improve asymmetric handling. Internal amendments led to the bomb bay being modified to permit carriage of a large number of smaller bombs, while maximum capacity was increased to 20,000lb. Final armament modifications resulted in the Sperry remotely controlled gun turrets becoming permanently external - despite this, drag was greater than that for the smaller and lighter B-17. Following these modifications, maximum range with one ton of bombs was reduced to 5,333 miles. Despite concern regarding the high wing loading, the finalised aircraft met with complete approval by the USAAF. A suggestion by service engineers to reduce wing loading by increasing the wing area was rejected, as this would reduce performance. Instead, the B-29 was fitted with Flowler flaps which increased wing area by 20% during take off an landing, thus reducing wing loading and increasing lift coefficient.[5]

From April 7 1941, a full scale wooden mock-up was made available for USAAF inspection, with the first engineering drawings for prototype production being released a month later. Production engineering for 14 YB-29s for service evaluation, and 250 B-29s for operational service, began on 16 June 1941, with the first 25 service aircraft required by February 1943.[6]

As the exsisting Boeing plants were occupied with orders for the B-17, a new factory was built for production of the B-29 at Wichita. After the attack against Pearl Harbor, the obvious need for further facilities resulted in production beginning at a new Boeing factory at Renton, a Bell Aircraft factory to be built at Georgia and a Glenn Martin factory at Omaha.[N 2]

References

Notes

  1. At least one source actually describes this proposal as a request for a pressurised version of the B-17 itself. Known as the Model 332, the design would use standard B-17 wing and tail assemblies matched to a new circular section fuselage, fitted with pressurisation equipment and nose wheel undercarriage. Although not taken up officially due to lack of funds, Boeing continued work on the design as a private venture.[2]
  2. This was selected to replace the Fisher body plant at Cleavland.[6]

Sources

  1. Boeing Website History Pages
  2. 2.0 2.1 Green, William. Bombers. 1975. Page 74.
  3. 3.0 3.1 Gunston, Bill.1982. Page 32
  4. 4.0 4.1 Green, William. Bombers. 1975. Page 75.
  5. 5.0 5.1 Green, William. Bombers. 1975. Page 76.
  6. 6.0 6.1 Green, William. Bombers. 1975. Page 77.

Bibliography

  • Green, William. Famous Bombers of the Second World War. Purnell Book Services. 1975.
  • Gunston, Bill. St Michael Aircraft of World Was 2. Octopuss Books. 1982. ISBN 0-86273-014-7

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