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} |} The Boeing B-50 Superfortress strategic bomber is a post–World War II revision of the Boeing B-29 Superfortress, fitted with more powerful Pratt & Whitney R-4360 radial engines, stronger structure, a taller fin, and other improvements. It was the last piston-engined bomber designed by Boeing for the United States Air Force. Not as well known as its direct predecessor, the B-50 was in USAF service for nearly 20 years. After its primary service with SAC ended, B-50 airframes were modified into aerial tankers for Tactical Air Command (KB-50) and as weather reconnaissance aircraft (WB-50) for the Air Weather Service. Both the tanker and hurricane hunter versions were retired in March 1965 due to metal fatigue and corrosion found in the wreckage of KB-50J, ''48-065'', which crashed on 14 October 1964.〔("Serial Number Search, B-50 48-065." ) ''rcn.com.'' Retrieved: 8 August 2010.〕 ==Design and development== Development of an improved B-29 started in 1944, with the desire to replace the unreliable Wright R-3350 engines with the more powerful four-row, 28-cylinder Pratt & Whitney R-4360 Wasp-Major radial engine.〔Knaack 1988, p. 163.〕 A B-29A-5-BN (serial number ''42-93845'') was modified by Pratt & Whitney as a testbed for the installation of the R-4360 in the B-29, with four R-4360-33s replacing the R-3350s. The modified aircraft, designated XB-44 Superfortress, first flew in May 1945.〔("Boeing/Pratt & Whitney XB-44 factsheet." ) ''National Museum of the United States Air Force''. Retrieved: 27 June 2010.〕 The planned Wasp-Major powered bomber, the B-29D, was to incorporate considerable changes in addition to the engine installation tested in the B-44. The use of a new alloy of aluminum, 75-S rather than the existing 24ST, gave a wing that was both stronger and lighter, while the undercarriage was strengthened to allow the aircraft to operate at weights of up to greater than the B-29. A larger vertical fin and rudder (which could fold to allow the aircraft to fit into existing hangars) and enlarged flaps were provided to deal with the increased weight.〔〔Peacock 1990, p. 204.〕 Armament was similar to that of the B-29, with two bomb bays carrying of bombs, and a further externally. Defensive armament was 13 × .50 in (12.7 mm) machine guns (or 12 machine guns and one 20 mm cannon) in five turrets.〔〔 First flying in May 1945, the sole XB-44 proved faster than the standard B-29. (Available sources do not indicate how much of this increased speed was due to differing aircraft weight or to deleted armament.)〔("XB-44 Superfortress Factsheet." ) ''National Museum of the United States Air Force.'' Retrieved: 28 December 2012.〕 An order for 200 B-29Ds was placed in July 1945, but the ending of World War II in August 1945 prompted mass cancellations of outstanding orders for military equipment, with over 5,000 B-29s canceled in September 1945.〔 In December that year, B-29D orders were cut from 200 to 60, while at the same time the designation of the aircraft was changed to B-50.〔 Officially, the aircraft's new designation was justified by the changes incorporated into the revised aircraft, but according to Peter M. Bowers, a long-time Boeing employee and aircraft designer, and a well-known authority on Boeing aircraft, "the re-designation was an outright military ruse to win appropriations for the procurement of an airplane that by its B-29D designation appeared to be merely a later version of an existing model that was being canceled wholesale, with many existing examples being put into dead storage."〔 The first production B-50A (there were no prototypes, as the aircraft's engines and new tail had already been tested) made its maiden flight on 25 June 1947, with a further 78 B-50As following.〔 The last airframe of the initial order was held back for modification to the prototype YB-50C, a planned version to be powered by R-4360-43 turbo-compound engines. It was to have a longer fuselage, allowing the two small bomb bays of the B-29 and the B-50A to be replaced by a single large bomb bay, more suited to carrying large nuclear weapons. It would also have longer span wings, which required additional outrigger wheels to stabilize the aircraft on the ground. Orders for 43 B-54s, the planned production version of the YB-50C, were placed in 1948, but the program was unpopular with Curtis LeMay, commander of Strategic Air Command (SAC), as being inferior to the Convair B-36 and having little capacity for further improvement, while requiring an expensive redevelopment of air bases owing to the type's undercarriage. The B-54 program was therefore canceled in April 1949, work on the YB-50C being stopped prior to it being completed.〔Knaack 1988, pp. 181–182.〕〔Willis 2007, pp. 162–163.〕 While the B-54 was canceled, production of less elaborate developments continued as a stopgap until jet bombers like the Boeing B-47 and B-52 could enter service. Forty-five B-50Bs, fitted with lightweight fuel tanks and capable of operating at higher weights, were built, followed by 222 B-50Ds, capable of carrying underwing fuel tanks and distinguished by a one-piece plastic nose dome.〔Willis 2007, p. 162.〕〔Peacock 1990, pp. 205–206.〕 To give the Superfortress the range to reach the Soviet Union, B-50s were fitted to be refueled in flight. Most (but not all) of the B-50As were fitted with the early "looped hose" refueling system, developed by the British company Flight Refuelling Limited, in which the receiving aircraft would use a grapple to catch a line trailed by the tanker aircraft (normally a Boeing KB-29) before hauling over the fuel line to allow transfer of fuel to begin. While this system worked, it was clumsy, and Boeing designed the alternative Flying Boom method to refuel SAC's bombers, with most B-50Ds being fitted with receptacles for Flying Boom refueling.〔〔Willis 2007, pp. 156–158.〕〔Knaack 1988, pp. 186–187.〕 Revisions to the B-50 (from its predecessor B-29) would boost top speed to just under 400 mph (644 km/h). Changes included: *More powerful engines *Redesigned engine nacelles and engine mounts *Enlarged vertical tail and rudder (to maintain adequate yaw control during engine-out conditions) *Reinforced wing structure (required due to increased engine mass, larger gyroscopic forces from larger propellers, greater fuel load, and revised landing gear loading) *Revised routing for engine gases (cooling, intake, exhaust and intercooler ducts; also oil lines) *Upgraded remote turret fire-control equipment *Landing gear strengthened and takeoff weight increased from 133,500 lb / 60,555 kg to 173,000 lb / 78,471 kg *Increased fuel capacity with underwing fuel tanks being added.〔("On Permanent Alert." ) ''Popular Mechanics'', November 1950, pp. 91-94, see bottom page 92.〕 *Improvements to flight control systems (the B-29 was difficult to fly; with increased weights the B-50 would have been more so). *Nose wheel steering rather than a castering nose wheel as on the B-29 Redesigned with a large upper fuselage grafted on, the B-50 design would form the basis for the Boeing 377 series of airliners and C-97/KC-97 military transports, with 816 of the KC-97 built. The B-29 and B-50 were phased out with introduction of the jet-powered B-47 Stratojet. The B-50 was nicknamed "Andy Gump" because the redesigned engine nacelles reminded aircrew of the chinless newspaper comic character popular at the time. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Boeing B-50 Superfortress」の詳細全文を読む スポンサード リンク
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