Douglas DC-7B

DC-7
Butler Aircraft Services' DC-7, Tanker 66
Role	Airliner and transport aircraft
National origin	United States
Manufacturer	Douglas Aircraft Company
First flight	18 May 1953
Introduction	29 November 1953
Primary users	American Airlines (historical) United Airlines (historical) Eastern Air Lines (historical) Pan Am (historical)
Produced	1953–1958
Number built	338
Developed from	Douglas DC-6

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.

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. That DC-7 was 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.) 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. Four eighteen-cylinder Wright R-3350 Turbo-Compound engines provided power. 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.

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