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The Tupolev Tu-4 (NATO reporting name: Bull) was a piston-engined Soviet strategic bomber that served the Soviet Air Force from the late 1940s to mid-1960s. It was a reverse-engineered copy of the American-made Boeing B-29 Superfortress. ==Design and development== Toward the end of World War II, the Soviet Union saw the need for a strategic bombing capability similar to that of the United States Army Air Forces. The Soviet VVS air arm had the locally designed Petlyakov Pe-8 four-engined "heavy" in service at the start of the war, but only 93 had been built by the end of the war and the type had become obsolete. The U.S. regularly conducted bombing raids on Japan, from distant Pacific forward bases using B-29 Superfortresses. Joseph Stalin ordered the development of a comparable bomber. The U.S. twice refused to supply the Soviet Union with B-29s under Lend Lease.〔Gordon, 2002, p.3〕〔("Aircraft Deliveries." ) ''airforce.ru''. Retrieved: 21 September 2007.〕 However, on four occasions during 1944, individual B-29s made emergency landings in Soviet territory and one crashed after the crew bailed out.〔Gordon, 2002, p.8-10〕 In accordance with the Soviet–Japanese Neutrality Pact, the Soviets were neutral in the Pacific War and the bombers were therefore interned and kept by the Soviets. Despite Soviet neutrality, America demanded the return of the bombers, but the Soviets refused.〔("Soviet Union Impounds and Copies B-29." ) ''National Museum of the USAF''. Retrieved: 21 September 2007.〕 Three repairable B-29s were flown to Moscow and delivered to the Tupolev OKB. One B-29 was dismantled, the second was used for flight tests and training, and the third one was left as a standard for cross-reference.〔Kerber, Leonid. ("Tu-4 bomber epic" ). ''militera.lib.ru'': a compilation of articles published in 1988–1990 (in Russian). Retrieved: 29 December 2009.〕 The aircraft included 1 Boeing-Wichita −5-BW, 2 Boeing-Wichita −15-BWs and the wreckage of 1 Boeing-Renton −1-BN – three different models from two different production lines. Only one of the 4 had de-icing boots as used on the Tu-4.〔Gordon, 2002, p.9-10〕 With the Soviet declaration of war against Japan in accordance with the Yalta agreement to enter the war within 90 days of VE day (to allow it time to move its forces from Europe to Asia) at about 11pm on August 8, 1945—two days after the U.S. atomic bombing of Hiroshima and the subsequent entente with Japan ending, the fourth B-29 was returned to the US along with its crew.〔Gordon, 2002, p.11〕 Stalin told Tupolev to clone the Superfortress in as short a time as possible instead of continuing with his own comparable ANT-64.〔Gordon, 2002, p.14〕 The reverse-engineering effort involved 900 factories and research institutes, who finished the design work during the first year; 105,000 drawings were made. By the end of the second year, the Soviet industry was to produce 20 copies of the aircraft ready for State acceptance trials.〔Gordon, 2002, p.26〕 The Soviet Union used the metric system, thus sheet aluminum in thicknesses matching the B-29's imperial measurements were unavailable. The corresponding metric-gauge metal was of different thicknesses. Alloys and other materials new to the Soviet Union had to be brought into production. Extensive re-engineering had to take place to compensate for the differences, and Soviet official strength margins had to be decreased to avoid further redesign,〔Gordon, 2002, p.20〕 yet despite these challenges the prototype Tu-4 only weighed about more than the B-29, a difference of less than 1%.〔Gordon, 2002, p.24〕 The engineers and suppliers of components were under pressure from Tupolev, Stalin, and the government to create an exact clone of the original B-29 to facilitate production and Tupolev had to overcome substantial resistance in favor of using equipment that was not only already in production but in some cases better than the American version.〔Gordon, 2002, pp.15–25〕 Each component made and each alteration was scrutinized and was subject to a lengthy bureaucratic process. Differences were limited to the engines, the defensive weapons, the radio (a later model used in lend-lease B-25s was used in place of the radio in the interned B-29s) and the identification friend or foe (IFF) system – the American IFF being unsuitable.〔Gordon, 2002, pp.24–25〕 The Soviet engine, the Shvetsov ASh-73 was a development of the Wright R-1820 but was not otherwise related to the B-29's Wright R-3350〔Gordon, 2002, pp.21 & 24〕 — the ASh-73 also powered some of Aeroflot's remaining obsolescent Petlyakov Pe-8 airframes, an earlier Soviet four-engined heavy bomber whose production was curtailed by higher priority programs. The B-29's remote-controlled gun turrets were redesigned to accommodate the harder hitting and longer ranged Soviet Nudelman NS-23 23mm cannon.〔Gordon, 2002, p.25〕 Kerber, Tupolev's deputy at the time, recalled in his memoirs that engineers needed authorization from a high-ranking general to use Soviet-made parachutes.〔 Additional changes were made as a result of problems encountered during testing, related to engine and propeller failures〔Gordon, 2002, p.27〕 and equipment changes were made throughout the aircraft's service life.〔Gordon, 2002, pp.66–68〕 The Tu-4 first flew on 19 May 1947, piloted by test pilot Nikolai Rybko.〔Duffy and Kandalov 1996, p. 98.〕 Serial production started immediately, and the type entered large-scale service in 1949. Entry into service of the Tu-4 threw the USAF into a panic, since the Tu-4 possessed sufficient range to attack Chicago or Los Angeles on a one-way mission, and this may have informed the maneuvers and air combat practice conducted by US and British air forces in 1948 involving fleets of B-29s.〔("Archival RAF film of combat with B-29s." ) ''google.com''. Retrieved: 29 December 2009.〕 Some attempts to develop midair refueling systems were made to extend the bomber's range, but these were fitted to only a few aircraft. 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「Tupolev Tu-4」の詳細全文を読む スポンサード リンク
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