History of the Douglas DC-7

Project of a civil C-74

HP-379 HP-379, ex 42-65409, N3181G C-74 Heracles
at Turin, Italy, May 1967, Zoggavia Collection

The original project of the Douglas DC-7 was a civil version of the military transport C-74 'Globemaster 1' but never reached the market introduction despite a first order of 26 aircraft from Pan American World Airlines. As the limited military production run increased the cost per civilian aircraft Pan American canceled its order. Douglas then dropped the DC-7 project. The DC-7 designation was later used for a completely different civilian airliner project in the early 1950s, having no relationship to the C-74.

DC-7

N6301C DC-7 United on a test flight, 
early 1954,  Clinton H. Groves Collection

After much persuasion of the President of American Airlines, C.R. Smith, Douglas decided to modify the DC-6B around the new Curtiss-Wright R-3350 turbo-compound engine available for civil use late in 1951. This new powerplant developed 3'250 hp for take-off and the increased power brought the speed up to 360 mph (560km/h), which also gave an improved range allowing transcontinental operations the first time. The DC-7 differed further from the DC-6B in having a 40inch  (1,02m) stretch in fuselage length, and four bladed propellers. The first flight was on 18 May 1953, and American Airlines introduced the first of totally 25 ordered new airliner on the daily non-stop New York - Los Angeles service on 29 November 1953, reducing the coast to coast flying time to 8hrs 45min westbound and 8hrs eastbound. The DC-7 was not as economical per seat mile as the DC-6B and the market was limited to four major U.S. airlines; American (24), National (4), Delta (10) and United (57 in total), resulting in a total production of 105 aircraft.

DC-7B

N345AA DC-7B of American Airlines,
1963, Clinton H Groves Collection

The DC-7B was basically designed as a long range version of the DC-7, which included greater fuel capacity the nacelles to from saddle tanks and an increased all-up weight. Many of the aircraft delivered did not incorporate these arrangements.

N777PA DC-7B of Pan American World Airways on a test flight over California,
April 1955, Clinton H Groves Collection

As an interim measure to compete with the Super Constellations Pan American World Airways introduced DC-7B's on its transatlantic service from New York to London 13 June 1955, though they were later transferred to more suitable routes owing to the inadequacy of their range on these transatlantic routes.

DC-7C



The last DC-7 built and delivered 4 November 1958, HB-IBP DC-7C in Swissair colors,
seen arriving at New York Idlewild 1959, Clinton H. Groves Collection

When the development of the DC-7B was under way, Douglas realized the potential of the  new 3 '400 hp version of the Wright R-3350 engine in manufacturing an even longer version of the DC-7 capable of flying the most important transatlantic routes non-stop in both directions and in all but the most adverse weather conditions. This ability was later used under the synonym 'Seven Seas', meaning all seas could be crossed non-stop.

N294 DC-7C leaving the Tokyo ramp
1960, Clinton H. Groves Collection

The fuel capacity was increased by an additional 5 foot (1,5 ) wing section inserted between the inboard engine and the wing root, thus giving the DC-7C an extra 10 foot (3m) wing span. This gave an additional capacity of 1'000 gallons (4'450 l) resulting in a range of 5'600 miles (9'000 km). A further 42 inch (1,06 m) fuselage ahead of the wings, and a taller fin and rudder to cope with the greater power and weight. The DC-7C's managed the a considerable share of the passenger traffic across the North Atlantic until the Boeing 707 and DC-8 jetliners were introduced in 1959 and 1960. Plans for a turboprop version, designated DC-7D, with Rolls Royce Tyne engines never materialized. All DC-7 built; 338 of all series.

DC-7C/F

PH-DSF DC-7C/F KLM,  arriving at Zurich Kloten on a all freight schedule
from Amsterdam, September 1967, Zoggavia  Collection

Military
French Air Force

DC-7 photo gallery - click the photo to enlarge