Douglas DC-6 Historical Background

DC-6 Liftmaster

The fact that the competion was introducing cabin pressurisation (Boeing Stratoliner and Lockheed Constellation) made Douglas decide that the improved version of the C-54 (DC-4) needed that too. It would enable to maintain higher altitudes and fly 'over the weather'. Of course, as a result other improvements had to be faced too: improved de-icing system, more power from the engines, better radio- and navigational equipment, etc
Ground work was laid during W.W.2 and the first testflight was made in february 1946. This was the military XC-112A prototype.
Douglas used the same wing as with the DC-4 and the fuselage was lengthened by 2.06 metres (6 ft. 9 in.).
Initially Douglas had a military order in mind, but the end of the war brought a change of direction towards commercial use.
One of the things they had to keep in mind, was of course the distribution of weights. There were high loads of cargo of sorts, but with fashionable ladies on board, they had to keep in mind the weight of a woman concentrated in the pressure of her high-heel, without damage. The difference in use with the military and civilian operators, if there ever was one at that time !

Both American Airlines and United Airlines received their first deliveries in 1947. Companies like National Airlines, Braniff and Delta followed quickly. The competition was Eastern and TWA with their Constellations.
Unfortunately, only months after the first initial deliveries, all DC-6s were grounded as a result of the crash of a DC-6, operated by United Airlines, at Bryce Canyon and an inflight fire onboard an American A/l DC-6.. After investigation into these mishaps, all aircraft were subsequently modified and were back in service during march 1948.
The US Air Force took delivery of one (no.26th of the production line), designated it C-118, and this one became the presidential aircraft ('Independence')
After confidence was restored in the DC-6, Delta and European customers (Sabena, KLM, SAS) put in orders in 1948. So did Philippine Air Lines, which started using the DC-6 in 1948 on routes from of Manilla to London and San Francisco .
Many companies followed and when the last order was counted in 1950, it totalled 175.
Then Douglas came with the improved DC-6A and -B models.

Schiphol (Amsterdam Int'l Airport) by night... in the 1950s ! This postcard was made available to me by Arie Groen, who happened to have this postcard (made by KLM Aerocarto NV) among some old stuff in his loft. KLM's DC-6B "Fox-Mike'' (PH-DFM, cn43554/247) is seen here preparing for a night departure.In 1960 this aircraft went to Overseas National Airways a N7919C and in 1962 to Reeve Aleutian (as N7919C), operating routes in Alaska. Anno 2002 it's still in Alaska, operating for Northern Air Cargo since 1978 ! (Anno 2006 it had gone over to Everts Air Cargo and used as an engine teststand - only a matter of time before the scrapman comes along...)

Many operators used their Sixes on long-haul routes. In most cases they were replaced in the late 1950s or early 1960s. Some had airframe hours totalling around 50.000 - 55.000 and were scrapped. Others moved down the line, selling (in the 1960s) for aprox. usd 500,000.
In 2000 there is but one DC-6 still operational, serving as an airtanker, fighting forest fires. This is N90739 (cn43044/84) and it operates for TBM in the USA.

The DC-6A is a freighter-version with improved Pratt & Whitney R2800-CB17 radial engines, with water-methanol injection. With all this extra power, the DC-6 fuselage was lengthened by 5 ft. It was nicknamed "the Liftmaster" and was meant to transport cargo. The DC-6A kept its cabin pressurisation, had a reinforced cabinfloor to take the weight of the cargo, it had no windows in the fuselage and it featured cargodoors both forward of the wing, as well as aft. Fuel capacity was increased, too. The electrical system was improved over the DC-6, which had been comparitively poor. The DC-6A was meant to suit both military- as well as civil operators.
Slick Airways in the USA was the first civil operator (april 1954). American Airlines, Japan A/l, Flying Tigers, Sabena, KLM followed quickly as customers.
A total of 74 DC-6As were produced.

Some DC-6As were later converted to passenger use, by removing the metal plugs fitted over the cabin windows. Others were built with normal cabin windows to enable rapid change from cargo- to passenger configuration and vice versa. These were designated DC-6C.
The US Navy took delivery of 65 examples, designating them R6D-1. The US Navy redesignated them C-118B in 1962.
The US Air Force accepted 101 C-118As.

The DC-6B is the passenger version, with many of the specifications of the DC-6A in terms of performance and dimensions, but without the reinforced floor and maindeck cargo doors. At first, it seated 54 passengers but later it was configured, in high density, to as much as 102 passengers. The first production model of the DC-6B went to United Airlines in 1951 and served United until 1968. The 288th and last DC-6B to be produced was delivered to JAT Jugoslovenski Aerotransport in 1958 (YU-AFB; anno 2010 survives as the last passenger-configured DC-6B V5-NCG see
Production of the DC-6B ended in 1958, by which time 288 had been built.

Many DC-6As and -Bs were later reconfigured for non-scheduled operators to convertable passenger-cargo configurations. Later in aviation history we see many types, like the DC-9-33 and B737, produced by the factory to 'Rapid Change' or 'Quick Change' versions, borrowing on the idea of transporting passengers during the day and cargo during the night. A small number of DC-6As were reconfigured thus by Douglas prior to delivery and they received the designation DC-6C; others, the ones reconfigured later, were referred to as DC-6A/B.

Two DC-6Bs were converted to 'swingtails' (DC-6B-ST). This was done by the engineering shop of SABENA (see my Swingtail page). A photo of cn44434 is shown on the DC-6 photopage.

The Douglas DC-6B was the surpreme piston-engined airliner. Its success was brought on by its low operating costs. When the first orders were placed, in 1949, it cost usd 900,000.
A grand total of 704 Sixes have been produced.
Technical data DC-6B:
Engines: 4 Pratt & Whitney R2800 Double Wasp Radials
Max.speed 645 km/h
Cruising speed: 507 km/h
Ceiling: 7.620 m.
Range: 4.836 km with max payload
Weight empty: 25.110 kgs
Weight loaded: 48.534 kgs
Dimensions: span 35,81m - length 32,18m - height 8,74m

Douglas DC-6

Credits: Douglas Propliners DC-1 - DC-7 by Arthur Pearcy, by Airlife (1995). Recommended reading for all aviation historians.
AirlinerTECH Douglas DC6 and DC-7 by Harry Gann, Douglas' own...
DC6 Production List and Pictorial History by P.R. Smith (ISBN 0 9509910 0 7)

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