The Douglas DC-7 is an American transport aircraft built by the Douglas Aircraft Company from 1953 to 1958. A derivative of the DC-6, 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. Unlike other aircraft in Douglas's line of propeller-driven aircraft, no examples remain in service in the present day, as compared to the far more successful DC-3 and DC-6. 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 proposed DC-7 was unrelated to the later DC-6-derived airliner. American Airlines revived the designation when they requested an aircraft that could fly the USA coast-to-coast non-stop 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 that of the DC-4 and DC-6, with the same span; the fuselage was 40 inches (100 cm) longer than the DC-6B. Four eighteen-cylinder Wright R-3350 Duplex-Cyclone Turbo-Compound engines provided power.[6] The prototype flew in May 1953 and American received their first DC-7 in November, inaugurating the first non-stop 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 notional schedules, causing overheating and failure of the engines' power recovery turbines. 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 over the wing in the rear of the engine nacelles, each carrying 220 US gallons (183 imp gal; 833 l). 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. Variants DC-7 Production variant, 105 built. DC-7B First long-range variant with higher gross weight and fuel capacity, with most of the added fuel in saddle tanks in enlarged engine nacelles. (Only Pan Am and South African DC-7Bs had the saddle tanks.) 112 built. DC-7C Seven Seas Longer-range variant with non-stop transatlantic capability, improved 3,400 hp (2,500 kW) R-3350 engines and increased fuel capacity mainly in longer wings, 121 built. DC-7D Unbuilt variant with Rolls-Royce Tyne turboprops. DC-7F Freight conversion of all three variants with two large freight doors.
