They flew the Seven Seas
Douglas propliners Part 2
The first part of this article is here — I suggest you begin there
The last great rivalry in the age of the prop-liners was between Lockheed’s graceful Constellation series and the Douglas Aircraft Company’s more utilitarian DC-6 and -7.
The Connie captured the world’s heart — of that there is little doubt. With its swooping fuselage, three fins and stalky landing gear, the Lockheed is a beauty. It was expensive to manufacture though, with no two frames of the fuselage being the same diameter.
The Douglas machines were more prosaic, rugged and simple. The fuselage was a simple cylindrical metal tube unkindly called a ‘Long Beach sewer pipe’, after the city where they were manufactured. But Douglas had the last word. Many of that maker’s products are still flying today, having easily outlasted the Connies in commercial service.
The success of the DC-3 and DC-4 had ensured that Douglas secured the majority of the military transport business. With the unprecedented logistical effort required for World War 2, this was a lucrative niche.
The US military commissioned Douglas to build a pressurized successor to the DC-4 (or C-54 Skymaster in military-speak) as a long-range transport in 1944. Dubbed the XC-11, it first flew in 1946, but the war had already ended and the military were no longer interested. Douglas adroitly segued into the civilian market, and while producing DC-4s for the airlines, began planning a pressurized version, dubbed the DC-6. They needed this to compete with the Lockheed Constellation and Boeing 377 Stratocruiser, both of which were pressurized.
Deliveries of DC-6s to American Airlines and United Airlines began in late 1946, but a series of in-flight fires and one fatal crash caused the type to be grounded for four months in 1947.
But after the fault was identified and remedied, the DC-6 proved to be an economical, rugged and reliable machine. Equipped with Pratt & Whitney R-2800 Double Wasp engines and three-bladed Hamilton Standard propellers, they became a fixture in the airline space. By April 1949, United, American, Delta, National, and Braniff were flying DC-6s domestically in the United States.
Internationally, United flew them to Hawaii, Braniff operated ‘Sixes’ to Rio de Janeiro, while Panagra (Pan American Grace Airways) deployed the type on its Miami-Buenos Aires route; KLM, SAS (Scandinavian Airlines System) and Sabena (Belgium’s national carrier) used DC-6s across the Atlantic. Sydney-based British Commonwealth Pacific Airlines (which was later absorbed by Qantas) utilised the Six between Sydney and Vancouver, and DC-6s of Philippine Airlines, based in Manila, carried passengers as far afield as London and San Francisco.
In Australia the DC-6 proved its worth on the domestic networks of Australian National Airways (ANA), then Ansett-ANA (after Ansett Airways bought ANA in 1957), and with the government-backed carrier Trans Australia Airlines (TAA).
Against its main rival, the Lockheed Constellation, the DC-6 held its own. Though not as elegant and slightly slower, the ‘Six’ was cheaper to build and operate. Its Pratt & Whitney engines were also more reliable than the Connie’s Wright Cyclones. More than 700 DC-6s were built; making it a distant in-house third when compared to its siblings the DC-3 and DC-4, but still a successful airplane in its own right.
The US military changed its mind about the DC-6 during the Korean War and bought a total of 167, designated C-117 Liftmaster for the USAF, and R6D for the US Navy. The latter had more powerful engines. Pan American invented ‘tourist class’ service to London using this model, dubbed the DC-6B for civil use, in 1952. Hitherto, most airlines had only one ‘class’ of service. For the first time more affordable flying was available at a lower price — changing air travel forever.
The 29th DC-6 on the Douglas production line was commissioned for use by US President Harry S. Truman. Type-designated VC-118 and named The Independence, the custom-built airplane served the White House for almost the next six years. Subsequently retired from presidential duties, in 1953 The Independence became a VIP transport for several Air Force organizations. Today it is on display at the USAF museum.
More range, more power
American manufacturers and airlines were relentlessly commercially focused. By the late 1940s the writing was on the proverbial wall for piston aircraft, but they chose to ignore it. The de Havilland Comet first flew in 1949 and entered service in 1952. The Avro Canada C102 (a jet-powered medium-range type) also flew for the first time in 1949, but met with so little enthusiasm from North American operators, that the program was cancelled in 1951.
Douglas Aircraft continued to disregard the jet engine, concentrating instead on propeller aircraft with large piston engines. The DC-7 making its first flight in 1953, by which time British European Airways had been flying a turbo-prop airliner, the Vickers Viscount, in airline service for over two years. However, the first fatal Comet 1 crash in passenger service had occurred just a few weeks before the DC-7’s maiden flight, forcing the type’s grounding in 1954 and possibly justifying the Americans’ myopia.
The DC-7’s launch customer was American Airlines who had pushed for an aircraft that could operate coast-to-coast across the USA within eight hours, the crew limit at the time. C.R. Smith, still the CEO of American and a close friend of Donald Douglas, ordered 25 aircraft in advance, paying the manufacturer enough to cover development costs.
Pratt & Whitney, whose Double Wasp engine had powered the DC-4, had a larger power plant, the Wasp Major, but it had proved unreliable on the Boeing 377 Stratocruiser. The engine manufacturer was not interested in pushing it further; perhaps realizing that the limits of piston engine propulsion had been reached. Instead, P&W was concentrating its efforts and energies on a turbojet design that would become the famous trend-setting JT3.
In order to meet the need for power and speed, Douglas fitted the DC-7 with Wright R-3350 Duplex Cyclone turbo-compound engines, similar to those on the rival Super Constellation. The Seven also had four-bladed propellers, making this the most obvious distinguishing feature from the essentially similar DC-6.
The 18-cylinder Duplex Cyclone was a complex reciprocating engine at the absolute design limit. Prone to problems, the high power settings required for the fast (by propliner standards) cruise speed and unrealistic eight-hour trans-continental schedule meant. that engine failures and diversions became commonplace.
The early Sevens were designed for US domestic routes. Pan American ordered a version with larger fuel tanks, named the DC-7B. South African Airways used four DC-7Bs to operate the Johannesburg-London route with only one refueling stop, a welcome change from the five (or more) required by rival BOAC’s services.
Of the 217 DC-7s and 7Bs built, domestic US carriers used all but four. American and United had more than 100 between them, with Eastern Airlines and Delta also operating significant fleets.
The final model was the DC-7C, which entered service in 1956. Appropriately named ‘Seven Seas’ it was longer and had a greater wingspan than preceding variants of the ‘Seven’, allowing more fuel to be carried inboard of the engines. This also moved the (noisy) engines further from the passenger cabin, providing a noticeably quieter ride.
Pan Am was the biggest customer for the Seven Seas with 27; Northwest Orient, BOAC, KLM, SAS, Swissair, Sabena and Braniff were also major users. Companies as far afield as Turkey, Persia (Iran), Mexico, Brazil and Japan used the DC-7C too.
The Douglas DC-6 and DC-7 literally flew the ‘seven seas’, seeing service in practically every part of the globe. The operational costs, reliability and relative safety they offered were influential in allowing aircraft to replace passenger liners as the preferred means of long-distance travel.
The DC-7C also finally allowed non-stop trans-Atlantic services in both directions year-round. Strong westerly winds meant that a refueling stop (at either Gander, Newfoundland or Goose Bay — both Canadian outposts) was required by most other types, including the de Havilland Comet 4. By operating nonstop the Seven Seas could save time, despite its relatively slow cruise speed compared to the jets.
The Sud Aviation Caravelle and Boeing’s launch of the (experimental) Model 367–80 in 1955 heralded the end of an era. When Boeing’s first jet airliner the 707 was delivered in 1957, the era of the propliner was finally over. Douglas was forced to follow suit, launching its first jetliner, the DC-8, in 1958.
Both the Douglas ‘Six’ and ‘Seven’ enjoyed a long sunset, with many being converted to freighters and continuing to operate well into this century. With a combined production of over 1000, the Douglas machines outsold their arch-rival Lockheed’s Constellation comfortably.
The simpler and more reliable P&W engine on the DC-6 ensured that this type outlived its ‘big brother’, with several examples remaining in airline service. Red Bull, the world-renowned energy drink company, has a beautifully restored DC-6B based in Salzburg, Austria. The last DC-6 off the production line was also the final one in commercial passenger use, with Namibia Commercial Aviation in Windhoek, but it appears to be no longer airworthy.
This is part of a series on the propliners of the 1950s and the slow transition to the jet age. It all began with the DC-3 of course, and my columns move through the other Douglas propliners, the Boeing 377, Lockheed’s Electras and the elegant Constellation. The Brabazon Committee which sparked such a wave of innovation in the UK with the Vickers Viscount, the Bristol Britannia and the ill-fated de Havilland Comet. Many other significant aircraft, such as Avro Canada’s innovative but aborted C-102 passenger jet and the Sud-Aviation Caravelle, which led us into the start of the Jet Age have columns too.
A few quirky segues I couldn’t resist: the ‘Double Sunrise’ flights between my two homelands Ceylon and Australia; the wonderful Carvairs and that very British habit of taking your car on holiday. I also had to write a paean to my beloved A380 and all my pilot friends in the Gulf as COVID ended that little dream.
Thanks for reading and I hope you enjoyed the series as much as I have relished writing them. My special thanks to my old friend, mentor, editor and repository of knowledge Roger Thiedeman, for all the encouragement and support throughout this project.