|
The Douglas DC-7 is a transport aircraft built by the Douglas Aircraft Company from 1953 to 1958. It was the last major piston engine-powered transport made by Douglas, being developed shortly after the earliest jet airliner - the de Havilland Comet - entered service and only a few years before the jet-powered Douglas DC-8 first flew. ==Design and development== In 1945 Pan American World Airways requested a DC-7, a civil version of the Douglas C-74 Globemaster military transport. Pan Am soon canceled their order, and that DC-7 is unrelated to the later airliner. American Airlines revived the designation when they requested an aircraft that could fly the USA coast-to-coast nonstop in about eight hours. (Civil Air Regulations then limited domestic flight crews to 8 hours flight time in any 24-hour period.〔''Aviation Week'', February 1, 1954, p. 16.〕〔''Aviation Week'', June 21, 1954 p. 16.〕) Douglas was reluctant to build the aircraft until American Airlines president C. R. Smith ordered 25 at a price of $40 million, thus covering Douglas' development costs. The DC-7 wing was based on the DC-4 wing with the same span; the fuselage was 40 inches longer than the DC-6B. The engine was the eighteen-cylinder Wright R-3350 Turbo-Compound.〔"Douglas Airlines". ''Sport Aviation'', April 2012, p. 19.〕 The prototype flew in May 1953 and American received their first DC-7 in November, inaugurating the first nonstop east-coast-to-west-coast service in the country (unrealistically scheduled just under the eight-hour limit for one crew) and forcing rival TWA to offer a similar service with its Super Constellations. Both aircraft frequently experienced inflight engine failures, causing many flights to be diverted. Some blamed this on the need for high power settings to meet the schedules, causing overheating and failure of the engines' power recovery turbines. These recovered power from the exhaust stream and delivered it to the crankshaft; they boosted the R-3350's power by 600 HP.〔''Aviation Week,'' April 21, 1958, p. 38: "In one three-month period, CAA records indicate that operators of the Douglas DC-7B ... reported 334 feathered propellors, or one feathered propellor for every 1,472 engine hours."〕 The DC-7 was followed by the DC-7B with slightly more power, and on some DC-7Bs (Pan Am and South African Airways), fuel tanks on top behind the engine nacelles, each carrying 220 US gallons. South African Airways used this variant to fly Johannesburg to London with one stop. Pan Am's DC-7Bs started flying transatlantic in summer 1955, scheduled 1 hr 45 min faster than the Super Stratocruiser from New York to London or Paris. 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 DC-7」の詳細全文を読む スポンサード リンク
|