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The Yakovlev Yak-24 (NATO reporting name ''Horse'') was a twin engine, tandem rotor transport helicopter developed in the USSR. ==Design and development== In late summer 1952, the Soviet Union issued two design specifications for helicopters, with the intent of catching up to the United States in post-World War II helicopter development. The design for the a medium-size helicopter which could transport 12 people was issued to the Mil Design Bureau, whereas the design for a larger version capable transporting 24 people was given to the Yakovlev Design Bureau, which had not had any previous design experience on helicopters prior to this project. Yakovlev made two prototypes for flight testing, and two more for static and dynamic ground tests. The first prototype was flown on 3 July 1952. It was powered with two 1,268 kW (1,700 hp) Shvetsov ASh-82V radial engines and was built in a tandem rotor layout, which was not typical for Soviet helicopters, which soon brought it nickname ''Letayushchiy Vagon'' (Летающий вагон) – 'the Flying Railroad Car'. The engines and transmission system were identical to the already-proven single-engine Mil Mi-4, but the Yak-24 proved to be less successful. Its engines were linked together so each could drive one or both rotors, but such arrangement caused strong vibrations in the airframe. After problems were partially solved, the new helicopter was order for production, which began in 1955. In July 1955, the Yak-24 was first presented to the public, and on 17 December 1955 it set two new world payload records, lifting a 2,000 kg (4,409 lb) load to 5,082 m (16,673 ft) and 4,000 kg (8,818 lb) to 2,902 m (9,521 ft). The initial variant was the Yak-24 – Army transport helicopter, that could carry up to 30 airborne troops, 18 stretchers or 3,000 kg (6,614 lb) of cargo. From 1958, the improved model Yak-24U was produced, with all-metal rotors of bigger diameter (21 m/69 ft) and all-metal fuselage. It could carry 40 soldiers or 3,500 kg (7,716 lb) of cargo, including 2 GAZ-69 jeeps or anti-tank guns. A civilian variant for 30 passengers was the Yak-24A, produced from 1960 in small numbers. It was also used as a flying crane, lifting an external load of 5,000 kg (11,023 lb). There were two proposed models: the Yak-24K 9-seat VIP salon with shorter fuselage and civilian Yak-24P for 39 passengers with stronger 2,013 kW (2,700 hp) turboshaft engines, but neither reached production. The exact number of Yak-24 helicopters produced is unknown with estimates ranging from 40 to 100 units, depending on the source of the data. All sources agree that production was curtailed due to technical problems, and the need for a heavy transport helicopter was fulfilled by the successful Mil Mi-6. According to some sources, the passenger Yak-24A was not actually produced. A surviving Yak-24 is preserved at the Central Air Force Museum at Monino, outside of Moscow. 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「Yakovlev Yak-24」の詳細全文を読む スポンサード リンク
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