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The Douglas C-54 Skymaster was a four-engined transport aircraft used by the United States Army Air Forces in World War II and the Korean War. Like the Douglas C-47 Skytrain, the C-54 Skymaster was derived from a civilian airliner (the Douglas DC-4). Besides transport of cargo, the C-54 also carried presidents, prime ministers, and military staff. Dozens of variants of the C-54 were employed in a wide variety of non-combat roles such as air-sea rescue, scientific and military research, and missile tracking and recovery. During the Berlin Airlift it hauled coal and food supplies to West Berlin. After the Korean War it continued to be used for military and civilian uses by more than 30 countries. This was one of the first aircraft to carry the President of the United States. ==Design and development== The first DC-4 design (later redesignated DC-4E) originated in 1935 from a requirement by United Air Lines.〔Pearcy 1995, p. 17.〕 The goal was to develop a much larger and more sophisticated replacement for the DC-3 even before the first DC-3 had even flown.〔Yenne 1985, p. 122.〕 There was enough interest from other airlines that American Airlines, Eastern Air Lines, Pan American Airways, and Transcontinental and Western Air (TWA) joined United, providing $100,000 each toward the cost of developing the new aircraft. As cost and complexity rose, Pan American and TWA withdrew their funds in favor of the Boeing 307 which was anticipated to be less costly.〔Francillon 1979, p. 267.〕 With a planned day capacity of 42 passengers (13 rows of two or more seats and a central aisle) or 30 as a sleeper transport (like the DST), the DC-4 (as it was then known) would seat twice as many people as the DC-3 and would be the first large aircraft with a nosewheel. Other innovations included auxiliary power units, power-boosted flight controls, alternating current electrical system, and air conditioning. Cabin pressurization was also planned for production aircraft. The novel tail with three low vertical stabilizers enabled use of existing hangars and provided sufficient vertical fin area to allow the aircraft to continue flight with only two engines on one side operating. The wing planform was similar to the DC-3, with a swept leading edge and almost straight trailing edge. The four Pratt & Whitney Twin Hornet 14-cylinder radials were all mounted with noticeable toe-out, particularly the outer pair.〔Francillon 1988, pp. 266–268.〕 The prototype (''NX18100'', s/n 1601) first flew, without incident, on 7 June 1938 from Clover Field in Santa Monica, California, piloted by Carl Cover. Testing issues, however, delayed the Approved Type Certificate until 5 May 1939. It was used by United Air Lines for in-service evaluation during 1939. On 9 June 1939 when the DC-4 was in Dayton, Ohio, along with Carl Cover, Orville Wright was a passenger on a flight over the city. Although the aircraft was relatively trouble-free, the complex systems proved to be expensive to maintain and performance was below expectations, especially with an increase in seating to 52 and gross weight to . The design was abandoned in favor of a smaller, less-complex four-engined design. This newer design was also designated DC-4, leading the earlier design to be re-designated DC-4E (E for "experimental"). Before the definitive DC-4 could enter service the outbreak of World War II meant production was channeled to the United States Army Air Forces and the type was given the military designation C-54 Skymaster, with US Navy aircraft designated Douglas R5D. The first aircraft, a C-54, flew from Clover Field in Santa Monica, California on 14 February 1942. With the introduction of the Tri-Service aircraft designation system in 1962, all R5Ds were re-designated C-54. In the end, only 80 DC-4s were built, the remaining aircraft being C-54s. 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「Douglas C-54 Skymaster」の詳細全文を読む スポンサード リンク
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