Published in January 2016 issue
During the heyday of Pan American World Airways’ (PA) prop era, and well into the jet age, one particular airplane figured prominently in the company’s operations around the world: The Douglas DC-6B ‘Super Six Clipper’, nicknamed ‘The Six’ by the pilots Pilots who flew her.
Referred to as ‘The Thoroughbred Airliner’ by R.E.G. (Ron) Davies in Pan Am—An Airline and its Aircraft, the DC-6B played a very significant role in Pan American’s history.
By Jamie Baldwin
The predecessor of the DC-6B, the DC-6, was had been designed by Douglas Aircraft in response to the challenge presented by Lockheed’s Constellation, which out-classed Douglas’s DC-4. Although reliable and route-proven in World War II under its C-54 Skymaster military designationas the C-54 Skymaster, the DC-4 was not pressurized and was an under-performer when compared withto the Constellation. For the DC-6 design, Douglas stretched the DC-4’s fuselage of the DC-4 and pressurized it to maintain a cabin altitude of 5,000ftfeet (1,500m) while flying at 20,000feet (6,100m). It could fly 90mph (145kph) faster than the DC-4, carry 3,000lbpounds (1,350kg) more payload and fly 850 miles (1,400km) further. The wingspan was the same as that of the DC-4.
The DC-6 was a natural evolution of its predecessor.
The first production DC-6 made its inaugural flight on June 29, 1946, and was retained for testing by Douglas Aircraft. Assembly-line manufacturing continued and, in November of that year, American Airlines (AA) and United Air Lines (UA) began receiving their first deliveries. United made the first commercial service flight on April 27, 1947.
The first months of operation in airline service did not go smoothly. In 1947, all DC-6s were grounded for four months due to two inflight fires, one of which fatal, caused by venting fuel entering the cabin heater ram air intake. The problem was fixed and the type was returned to service.
By 1949, domestic carriers United, American, Delta (DL), National (NA) and Braniff (BN) were operating the DC-6 in the United States. United also flew the aircraft to Hawaii and Braniff(BN) flew it to and through South America. Another US carrier, Pan American-Grace Airways (PNG), also operated the DC-6 in South America. International carriers KLM (KL), SAS (SK) and Sabena (SN) operated the DC-6 on their transatlantic routes. Philippine Airlines (PR) operated it between Manila and London, and between Manila and San Francisco.
The US Air Force ordered the 29th DC-6 to come off of the assembly line and adapted it as the United States’ presidential aircraft. Designated the VC- 118, it was delivered on July 1, 1947, and named The Independence after then-President Harry S Truman’s hometown of Independence, Missouri.
With the availability of the more powerful Pratt & Whitney Double Wasp R-2800 engines, and with an order from Slick Airways for a freighter version of the DC-6, the type was further improved in 1948 with the development of the DC-6A, an allcargo aircraft that made its inaugural flight on September 29, 1949. The passenger equivalent, the DC-6B, took to the air for the first time on February 2, 1951. Douglas also developed the DC-6C, a convertible passenger/freighter version of the DC-6A. In all three variants, the fuselage was five feet longer than that of the DC-6 and 12 feet longer than that of the DC-4.
The DC-6B featured a higher-gross weight (107,000lb/49,000kg) and longer range than those of the DC-6. With its four Pratt & Whitney Double Wasp R-2800 engines and Hamilton Standard 43E60 constant-speed reversing propellers, the DC-6B became known as the ultimate piston-engine airliner for its ruggedness, reliability, economical operation, and handling qualities. United Air Lines was the first carrier to operate the DC-6B, inaugurating service on April 11, 1951.
The total production run of the DC-6 series was of 704 aircraft, including military versions. Of these, 175 were commercial DC-6s and 288 were DC-6Bs. Pan American never operated the DC-6. It didn’t take delivery of a model in that series until Douglas developed the DC-6B.
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PAN AMERICAN’S ‘SUPER SIX CLIPPER’
Pan American ordered 45 DC-6Bs in September 1950. They were given the moniker ‘Super Six Clipper’ and all were delivered between February 1952 and June 1954. On May 1, 1952, DC-6B Clipper Liberty Bell inaugurated alltourist ‘Rainbow’ service on the prestigious New York-London route, marking a significant accomplishment in Pan American’s effort to bring air travel to the mass market.
During its deployment for Pan American, the Super Six performed just about every duty conceivable. It could be configured in an all- First Class service with 44 seats, all Tourist Class one fitted with 88 to 109 seats, and in a dual configuration with 82 seats.
By 1956, the Super Sixes were operating extensively on Pan American’s world-wide routes with the aircraft in various configurations, including dual First and Tourist Class service in the Atlantic, Pacific and round-the-world services; all-First Class in the Alaska operation; and all-Tourist (with all-First on some routes) in Latin America.
In 1959, the Super Sixes were the mainstay of Pan American’s Latin America operations, serving Central Americaand, South America and the Caribbean with choices of all-First Class, dualservice, and all-Tourist. On the New York-San Juan route, the aircraft operated with a high-density ‘Clipper Thrift’ 106-seat servicewith106 seats.
With the Jet Age firmly established by 1961, the Sixes were no longer on Pan American’s round-the world and Pacific routes. Most were deployed on the Internal German Service (IGS) out of Berlin, while some remained operating in Latin America and on the Alaska service in an all-First Class configuration.
By 1966, Boeing 727 jets began replacing the DC- 6Bs in West Germany. However, the Sixes returned to the Pacific, having been given a new livesfe as rest-and-recuperation charter aircraft for the US military troops serving in Southeast Asia.
Pan American also purchased several DC-6A freighters for use in its all-cargo operations. These aircraft, which operated worldwide, continued operations through to 1966, when they were replaced by the DC-7C and jet aircraft.
In the mid-1960s, wWhile the DC-6As and DC- 6Bs were being phased out, they were often used in the mid-1960s as training platforms for many of Pan American’s newly hired Ppilots. Assigned to Berlin, where the Sixes were operating on the IGS, these Ppilots got their feet wet as flight engineers on both aircraft, some flying a nightly freighter rotation between Berlin and Frankfurt;, departing at 2300 hours and, returning at 0300.
Rather than taking a nap between flights, the young pilots Pilots spent the layovers in Frankfurt exploring the airplanes and learning everything about itthem under the watchful eyes of their instructors. An interesting facet of this operation was the fact that aircraft from all over West Germany would rendezvous at Frankfurt in a sort of hub-and-spoke operation, exchanging sacks of mail. It was a prelude of to things to come for the entire airline industry.
The aircraft was considered marginally more economical to operate than the Lockheed Constellation, Ron Davies stated. From an engineering standpoint, it was easier to put the its airframe and engines through inspection, maintenance, and overhaul checks.
“[A]lthough later developments of the Douglas line were to outperform the 6B,” Davies said, “this was the aircraft that wise old airline folk would refer to as a thoroughbred.”