Initially the DC-7 designation was applied to a commercial development of the C-74 Globemaster I that PanAm ordered in 1945. This contract was quickly cancelled, and the DC-7 nomenclature was subsequently applied to a completely unrelated derivative of the DC-6. As it emerged in the 1950s, the DC-7 arose from an American Airlines requirement for a stretched longer range development of the DC-6. The resulting aircraft was based on the same wing of the DC-6 (also the same basic wing designed for the DC-4), with a stretched DC-6 fuselage, more powerful Wright Turbo Compound engines and extra fuel allowing Douglas to guarantee it could offer nonstop transcontinental US range in both directions. The prototype DC-7 flew for the first time on May 18 1953,
On premier routes across the United States and over the North Atlantic, airlines vigorously competed for leadership. By the late 1950s, American Airlines and Pan Am both wanted bigger, faster transports to exceed the performance of late-model Lockheed Constellations. Reports of a new Boeing jet airliner had already surfaced. The Douglas executive leadership temporized, torn over the decision of whether to build a new piston-engine airliner or take a leap into the future with a new turbojet. An informal group at Douglas, led by Art Raymond,"kicked around a number of airframe-engine combinations, but all the while in the back of minds was the big question . . . could the engine people stifle the turbojet's fuel-guzzling appetite?"
The DC-4 was followed by the DC-6, DC-6B, DC-7, DC-7B and DC-7C. The Douglas aircraft grew from 44 seats (DC-4) to 105 seats (DC-7C). The DC-7 can be distinguished from the DC-4 and DC-6 models by square windows, with three being forward of the wing (DC-4 has round windows), and four-blade propellers (DC-4 & DC-6 have three-blade propellers). The DC-6 is similar to the DC-7 as it has the same wingspan and square windows but is about 1 foot shorter in length and has smaller engines. The DC-6 has three-blade propellers (DC-7 has four-blade propellers) and may or may not have windows (1 or 2) ahead of the wing. The DC-4 has the same wingspan as the DC-6 and DC-7 models but is considerably shorter in length. It can be identified by the round windows and three-blade propellers. The "Super" DC-4 is a stock model that has been converted to operate with larger engines.
Continued interest from American Airlines led to development of the DC-7, followed by the DC-7B and -7C models. The Douglas DC-7 was an advanced development of the DC-6B piston-engine airliner. It was introduced by American Airlines on its New York-Los Angeles route in November 1953 and was the first airliner to provide nonstop transcontinental service in both directions. The fastest transport aircraft in service, the DC-7 cruised at 580 kilometers (360 miles) per hour. Influenced by major customers like American and United, who questioned the economics of fuel-hungry jets, Donald Douglas committed his company to a new piston-engine transport. A key factor involved the extremely promising performance of a new Wright turbo-compound engine, which used exhaust-driven turbochargers that yielded 20 percent more power from each engine.
The DC-7 began service with American in November 1953. The new DC-7 (1953) and DC-7B were soon followed by the DC-7C, the ultimate evolution of the piston-engine airliner designed for nonstop transcontinental service in the United States or to thunder across the Atlantic without having to land in Newfoundland or Iceland to refuel.
The Douglas DC-7C "Seven Seas" first flew on December 20, 1955. On May 15, 1956, CAA type-certificated the four engine, propeller-driven aircraft. The transport was able to fly nonstop between the United States and many European cities and had a maximum capacity of 99 passengers. The plane entered scheduled airline service with Pan American World Airways on Jun 1, 1956. The elegant transport with matchless service became internationally renowned as the "Seven Seas," with a speed of 355-400 mph and a range of over 4,000 miles. For Pan Am, British Overseas Airways Corporation, and other international carriers, it handled the North Atlantic with aplomb and also equipped new, long distance routes across the Pacific. The Scandinavian airline, SAS, launched a sensational Europe-to-the-Far-East route that crossed over the North Pole.
Because Douglas Aircraft Company continued to field various advertising campaigns, the launch of new service by customer airlines clearly multiplied the awareness of Douglas as a leading brand name in the airliner business. During the years that the postwar DC-4/-6/-7 series won such a wide customer base, the Douglas name constantly cropped up in regional as well as national venues. For example, when Braniff took delivery of its first DC-7C, its own publicity department trumpeted the virtues of the new equipment and disbursed a flurry of press releases that featured Texas native Ginger Rogers posed with the new plane. Although Douglas Aircraft delivered 127 models of the big plane, production ended in 1958, the inaugural year of jet service offered by the Boeing 707.
By late 1958, Douglas had produced more than 700 DC-6 and 300 DC-7 aircraft, including military transport versions of both. A total of 338 DC-7s of all types were purchased by 18 different airlines. The DC-7's proved to be less reliable than the fabled DC-6B, and less economical as well. Thus, the DC-7's had a short stay in service with the major airlines, and were sold soon after the arrival of the jets. Like other piston-engine airliners, it was made obsolete by the introduction of turbine-engine Boeing 707s and Douglas DC-8s. Some DC-7s later served as cargo and charter planes.
On 24 April 1964 the deliberate wrecking of a Douglas DC-7 near Phoenix, Ariz., began a testing program in which FAA and the Flight Safety Foundation attacked the problem of preventing postcrash fatalities. FAA crashed a Lockheed 1649 Constellation at the same site in Sep 1964. These experiments reflected a growing realization that fatalities in takeoff or landing accidents could be reduced if passengers were prevented from colliding with the aircraft's interior structure or furnishings and protected from postcrash fire and smoke. The test aircraft crashed through manmade barriers and then into a rocky slope, carrying dummy passengers, cameras, and instruments for recording impact forces, G-forces, hydrostatic pressures, and other stresses. The tests provided valuable data on such matters as fuel spillage, safety characteristics of rear-, forward-, and side-facing passenger seats, and the efficacy of passenger-restraining devices.
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