Douglas DC-6 and DC-7

Built for the US Air Force as a C-118A, N747CE was transferred to the Navy in 1964 and sold to Hawkins & Powers in 1983, flown to Greybull WY and parked. It was acquired by Everts Air Cargo in 2005 and underwent a 12-month overhaul at Paine Field WA before entering service (Steve Davis; Fairbanks AK, 06Aug26).

DC-6. Demand for wartime quantity over comfort ensured the Army Air Force remained focused on the unpressurised C-54 Skymaster. With competitors Boeing and Lockheed offering the pressurized Stratoliner and Constellation, Douglas persuaded the Government to fund construction of an improved version of the C-54, designated XC-112A. Government funding for the project was switched off at the end of the war, but Douglas had already been able to secure an order from American Airlines for 50 of the commercial version, the DC-6. An order from United Air Lines followed shortly after, and the two airlines received the first deliveries simultaneously.

The DC-6 continues to enjoy a commercial career, with a small number still in operation with the Everts Group in Alaska.

First flight: 15 Feb 46 (c/n 36326, 45-873)

Production: 704, at Santa Monica, CA

First delivery: 20 Nov 46, to American Airlines (c/n 42855, N90702) and United Airlines (c/n 42865, N37501)

Last delivery: 17 Nov 58, to Jugoslovenski Aero Transport (c/n 45564, YU-AFB)

Variants: XC-112A - prototype, derived from the C-54G but powered by 4 Pratt & Whitney R-2800-34 Double Wasp radials, featuring stretched fuselage, pressurised cabin, increased accommodation and payload, and performance improvements (1 built);

   DC-6 - initial production version powered by R-2800-CA15s, with seating for up to 86 passengers, (175 built, including one for the USAF as a Presidential transport under the designation C-118; first flight 29 Jun 46);

   DC-6A - stretched version powered by R-2800-CB16 or -CB17 radials, optimised for all-cargo use with strengthened floor, two large cargo doors, increased fuel capacity and payload of 28,000 lbs (74 built, including some as DC-6C with provision for rapid conversion between passenger and all-cargo configurations);

   DC-6B - DC-6A with cargo modifications deleted and accommodation for up to 102 passengers (288 built);

   C-118A Liftmaster - military version of the DC-6A, powered by R-2800-52W radials (101 built);

   R6D-1 - US Navy version of C-118A (65 built, of which 40 transferred to the USAF as C-118A and surviving US Navy examples re-designated C-118B in 1962).

Conversions: Pacific Airmotive was licensed to convert DC-6Bs to DC-6As and there were many other conversions to all-cargo configuration under unofficial designations that included DC-6AB, DC-6AC and DC-6BF. In addition, Sabena converted 2 DC-6Bs into swing-tail cargo aircraft in 1968.

The DC-7 was developed by Douglas in response to a 1951 American Airlines request for an airliner to compete with the Lockheed Super Constellation ordered by Trans World Airlines. Powered by a turbo-compound version of the Wright R-3350 engine producing 30% more power than the 18-cyclinder radial R-3350s powering American's DC-6s, the Super Constellation was capable of non-stop transcontinental operations, even into headwinds. Douglas was unenthusiastic about the project, believing it would undermine its DC-6B programme, then in the latter stages of development. However, Douglas was persuaded following American's offer to pay $40m for 25 of the new aircraft, thus covering most of the development costs.

Despite the company's misgivings, the DC-7 sold well, with over 170 delivered to American, Eastern Air Lines, Pan American and United Air Lines. A higher gross weight version was developed, followed by a version capable of non-stop transatlantic operations. Service with major operators was brief with phase-out of the DC-7s beginning less than five years after service entry, as a result of the switch to jetliners. Plans for a version powered by Rolls-Royce Tyne turboprops were abandoned for the same reason.

Many DC-7s went to on enjoy successful careers as freighters, but the complexity and unreliability of the turbo-compound engines has meant survivor numbers have been low for some time. Flying operations came to a close following the retirement of Erickson Aero Tanker's aerial firefighting fleet in 2020, although two of Erickson’s DC-7 have been acquired by a group with ambitious plans to bring them back into service flying passengers between Long Beach and Las Vegas.

First flight: 18 May 53 (c/n 44122, N301AA)

Production: 338, at Santa Monica, CA

First delivery: 10 Oct 53, to American Airlines (c/n 44125, N304AA)

Last delivery: 10 Nov 58, to KLM (c/n 45549, PH-DSR)

Variants: DC-7 - initial production version based on the DC-6B but powered by 4 Wright R-3350-18DA-2 turbo-compound radials, with stretched fuselage and strengthened undercarriage, and seating for up to 99 passengers (105 built);

DC-7B - higher gross weight version with increased fuel capacity, powered by R-3350-18DA-4s (112 built, first flight Oct 54);

DC-7C Seven Seas - long-range version with stretched fuselage, increased wing span, heightened tail fin and further increases to fuel capacity (121 built, first flight 20 Dec 55).

Conversions were made to all-cargo configuration under unofficial designations DC-7F, DC-7BF and DC-7CF. An additional 3 DC-7Cs were converted in 1966 by UTA Industries to AMOR (avions de mesures et d'observations au réceptacle) for satellite launch and re-entry tracking by the Centre d'Essais en Vol.

Douglas DC-6 and DC-7 survivors Sep26.pdf

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