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Boeing B-29 Superfortress

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The B-29 Superfortress was a bomber developed by the Boeing company in 1939.

DescriptionEdit

Being equipped with multiple new technologies, such as pressurised 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 advantages, 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 in September, 1960, afterwards being replaced by newer bombers like the B-52 Stratofortress.[2]

HistoryEdit

DevelopmentEdit

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.[3]

In March 1938, Chief of Staff Oscar Westover requested proposals for a new strategic bomber with a pressure cabin,[N 2] to allow it to fly faster and higher than the B-17 Flying Fortress.[4]

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 its own expense.[5]

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 construction 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.[5] The first unarmed Olive Drab prototype began flying on 21 September 1942.[4]

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.[6]

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.[6]

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.[7]

As the existing 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 3]

As much of the Superfortress's equipment had not been perfected, or even tested in many cases, it was decided to bring aircraft leaving the production line to modification centres, so that they could be brought up to combat ready standard, without stopping the assembly lines to introduce modifications and equipment by delaying production. This programme was itself delayed by the need to work in the open air in inclement weather, due to the B-29's size, problems in obtaining sufficient tools and support equipment, and the A.A.F's limited experience with the aircraft. This prompted the drafting in of Boeing personnel from the factories at Wichita and Seattle, who assisted with the modifications from March 10th to April 15th 1944, a period which became known as the Battle of Kansas.[8]

By late 1943, production examples were being produced by the Bell-Marietta and Boeing-Renton plants. These were powered by R-3350-23, -23A or -41 engines.[8]

Operational UseEdit

The first USAAF B-29 unit was the 58th Bombardment Wing (VH), which was activated at Marietta, near Bell's Superfortress plant, on June 1st 1943, and transferred to Salina, Kansas on September 15th 1943, This comprised five groups - the 40th, 444th, 462nd, 468th and 472nd Bombardment Groups (VH), with the 472nd remaining at Smoky hill, Selina as an Operational Training Unit.[8]

On 27 November 1943 XX Bomber Command was formed to take overall control of all B-29 units, which now included the 73rd Heavy Bomber Wing, comprising four more groups intended to use the next batch of 150 Superfortress aircraft. However, initial training had to be conducted on B-26s and B-17s because of the limited number of available B-29, due to the delay in AAF approval of the B-29's flight characteristics, which was finally granted on 7 October.[8]

Examples belonging to XX Command were eventually dispatched to bases in China, traveling via India, during early 1944, with one of the first examples to leave the United States being flown to Great Britain for demonstration to the Eighth Air Force, before it proceeded to Calcutta. [N 4]

Following the decision to concentrate all B-29 operations against Japan from the Marianas island group, B-29s were initially dispatched to Saipan, with the first aircraft, named Joltin Josie, arriving there on 12 October 1944.[11] The first attack against the Japanese homeland by Marianas-based B-29s took place on 24 November 1944, with eighty eight aircraft carrying out a high altitude daylight raid against Tokyo,[9] similar to those executed by the 8th Air Force against Germany. The difficulties resulting from this approach led Maj-Gen. Curtiss E LeMay, the new B-29 force commander, to switch the B-29s to night attacks with incendiaries. These increased the available bomb load and decreased the vulnerability of the aircraft, due to the lack of Japanese night defences, with the first such raid being launched against Tokyo on 9 March 1945. Over the following few days, four more major cities were attacked, resulting in the devastation of thirty-two square miles of land. The alomost complete lack of aerial opposition led to the B-29's defensive armament being reduced to a pair of 0.5in machine guns in the tail turret, which allowed the aircraft to carry it's maximum bombload.[N 5]

Three examples made emergency landings in Soviet territory during 1945,[13] including the 'General Arnold Special'[N 6] resulting in the Soviet Union operating several hundred unlicensed copies as the Tu-4. Produced between 1946 and 1949, the Tu-4 mainly differed from the B-29 by using ASh-90 engines and NR-23 cannon.[15]

VariantsEdit

  • XB-29: Initial prototypes. 3 built.[16]
  • YB-29: Service test aircraft.
  • B-29A: Standard bomber. [N 7]
  • B-29B: Development of B-29 with reduced armament, consisting of standard tail armament, together with a pair of 0.5in machine guns fitted in waist positions in the pressurised gunner's cabin.[12]
  • B-29D: Initial designation of post-war B-50.[18]
  • B-29F: Designation of six B-29s modified for cold weather testing in Alaska.
  • F-13: B-29 aircraft modified for photo reconnaissance.[12]
  • KB-29M: Designation for B-29s fitted with in flight refueling hose system - ninety two modified.
  • KB-29P: Post war designation for B-29s fitted with Flying Boom refueling system - one hundred and sixteen modified.[19]
  • SB-29: B-29 aircraft modified for air sea rescue duties, including provision for an air drop-able lifeboat.[20]
  • XB-29G: Designation of Bell built B-29 44-84043, following modification for testing of General Electric turbojets.[19]
  • XB-39: Development of YB-29 powered by Allison V-3420 inline engines - Fourteen built.[16]
  • YKB-29T: Single KB-29M fitted with additional hose refueling pods under the wingtips.[19]

ReferencesEdit

NotesEdit

  1. Other Details - Origin: Boeing Airplane Company, Seattle. Renton and Wichita; also built by Bell Aircraft, Marietta, and Glenn L. Martin Company, Omaha. Height: 27ft 9in (8.46m). Climb to 25,000ft (7620m): 43min. Service ceiling: 36,000ft (10,973m). History: First flight 21 September 1942; (pre-production YB-29 26 June 1943); squadron delivery July 1943; first combat mission 5 June 1944; last delivery May 1946.[1]
  2. 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.[3]
  3. This was selected to replace the Fisher body plant at Cleavland.[7]
  4. The use of this route was apparently part of a ploy, intended to trick the Axis into believing that B-29s were to be used against Germany,[9] which may have happened if the Luftwaffe had been able to deploy significantly increased numbers of jet fighters, especially if the war had continued into 1946.[10]
  5. These field modified aircraft were supplemented by 311 B-29B aircraft built at the Bell-Atlanta plant. These aircraft had the twin tail machine guns supplemented by a pair of 0.5in machine guns mounted on special hand held mounts, located in the waist positions of the pressurised gunner's cabin.[12]
  6. This was the first aircraft over the target during the first B-29 mission of the war.[14]
  7. Eighty seven were loaned post war to the RAF, becoming Washington Mk 1s.[17]

SourcesEdit

  1. Gunston, Bill. Illustrated Directory Page 344
  2. Boeing Website History Pages
  3. 3.0 3.1 Green, William. Famous Bombers of the Second World War. Purnell Book Services. 1975. Page 74.
  4. 4.0 4.1 Gunston, Bill. St Michael Aircraft of World War 2. Octopus Books. 1982. ISBN 0-86273-014-7 Page 32
  5. 5.0 5.1 Green, William. Bombers. 1975. Page 75.
  6. 6.0 6.1 Green, William. Bombers. 1975. Page 76.
  7. 7.0 7.1 Green, William. Bombers. 1975. Page 77.
  8. 8.0 8.1 8.2 8.3 Green, William. Bombers. 1975. Page 78.
  9. 9.0 9.1 Green, William. Bombers. 1975. Page 82.
  10. Schick, Walter and Ingolf Meyer. Luftwaffe Secret Projects - Fighters 1939-1945. Midland Publishing Limited. 1994/1997. ISBN 1 85780 052 4 Page 176.
  11. Kaplan, Phillip. Big Wings - The Largest Aeroplanes Ever Built.Pen and Sword Aviation. 2005. ISBN 1 84415 178 6. Page 39
  12. 12.0 12.1 12.2 Green, William. Bombers. 1975. Page 83.
  13. Gunston, Bill. Illustrated Directory of Fighting Aircraft of World War II. Salamander Books. 1988. ISBN 0-86101-390-5 Page 345
  14. Green, William. Bombers. 1975. Page 85.
  15. Gunston, Bill - M&S WW2 Aircraft Page 30
  16. 16.0 16.1 World Aircraft Information Files Aviation Partwork. Midsummer Books Ltd. File 34 Sheet 1 (World Military Aircraft: Boeing B-29/B-50 Superfortress - B-29: The first A Bomber)
  17. WAIF File 34 Sheet 3 (World Military Aircraft: Boeing B-29/B-50 Superfortress - B-29 Briefing)
  18. WAIF File 34 Sheet 4 (World Military Aircraft: Boeing B-29/B-50 Superfortress - B-50: B-29 superlative)
  19. 19.0 19.1 19.2 WAIF File 34 Sheet 5 (World Military Aircraft: Boeing B-29/B-50 Superfortress - Special variants)
  20. Green, William. Bombers. 1975. Page 84.


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