18 May 2016

CHECK SIX: The Douglas DC-7


Douglas launched the DC-7 program at the prodding of C.R. Smith of American Airlines who wanted a competitor to TWA's Lockheed Super Constellations for the first transcontinental nonstop services. American's requirement even called for the same engines as the Super Constellation, the Wright R-3350 Turbo Compound (the DC-6 used the Pratt & Whitney R-2800 Double Wasp) radial. Douglas didn't think there was a market for such an aircraft, but Smith ordered 25 of what would become the DC-7 for $40 million which pretty much covered Douglas' development costs. To save time and make the most of the $40 million, the DC-7 was a stretched DC-6 with Wright R-3350 engines. The DC-7 was slightly faster than the Super Consellation and could under *ideal* conditions (which was rare) do a nonstop transcon in under 8 hours. 

The first variant of the DC-7 was good for transcon runs but was no better than the DC-6 for oceanic routes. That first variant went exclusively to US operators- American (34), United (57), Delta (10), and National (4). American Airlines inaugurated its own nonstop "Mercury Service" DC-7 flights between Los Angeles and New York Idlewild on 29 November 1953. As the DC-7 had a higher cruising speed than the Super Constellation, the eastbound LA-New York run was made easily in 7 hours, 15 minutes (a fact not lost upon American's marketing department, hence the name "Mercury Service"), but the westbound run from New York to LA couldn't be made within 8 hours. Despite over a dozen modifications to the DC-7s made by American's engineers which included tweaks of the Wright R-3350 radial engines to squeeze every bit of horsepower out of the engines, the DC-7s still couldn't beat the prevailing winds. American's pilot union repeatedly pointed this fact out, but C.R. Smith's influence in Washington left the issue unaddressed by federal regulators. In the following year, federal regulators adjusted the time limit to allow the flight to be made legally and American's DC-7s blocked in at 8 hours, 15 minutes on a westbound nonstop.

The next DC-7 variant was the DC-7B which had uprated engines and more fuel tanks in the engine nacelles which made oceanic crossings possible. Pan American launched its own transatlantic services in the summer of 1955 and South African Airways was finally able to fly Johannesburg-London nonstop.

The final DC-7 variant had longer wings and a stretched fuselage, the DC-7C "Seven Seas". The fuel capacity of the Seven Seas allowed full westbound nonstop transatlantic capability, something that the DC-7B couldn't routinely perform. 

There was a DC-7D which would have Rolls-Royce Tyne turboprops (same engine as the Vickers Vanguard) and a swept back vertical fin, but it never made it off the drawing board as Donald Douglas decided jets were the way to go and development of the DC-8 was given priority. 

Further reading: 

(Photos: Vintage Ad Browser, California Classic Forums)

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