The Douglas DC-6 is a piston-powered airliner and transport aircraft built by the Douglas Aircraft Company from 1946 to 1959. Originally intended as a military transport near the end of World War II, it was reworked after the war to compete with the Lockheed Constellation in the long-range transport market. More than 700 were built, and many still fly today in cargo, military, and wildfire control roles.

The DC-6 was known as the C-118 Liftmaster in United States Air Force service, and as the R6D in United States Navy service.

 History

The United States Army Air Forces commissioned the DC-6 project as the XC-112 in 1944. The Air Force wanted an expanded, pressurized version of the popular C-54 transport with improved engines. By the time the XC-112 flew, the war was over, and the USAAF had rescinded its requirement.

Douglas converted its prototype into a civil transport (redesignated YC-112A, having significant differences from subsequent production DC-6 aircraft) and delivered the first production DC-6 in March of 1947. However, a series of mysterious in-flight fires (including the fatal crash of United Airlines Flight 608) grounded the DC-6 fleet later that year. The cause was found to be a fuel vent located adjacent to the cabin cooling turbine intake. All DC-6's in service were modified to correct the problem, and the fleet was flying again after just four months on the ground.

Pan Am used DC-6 aircraft to inaugurate its first trans-Atlantic tourist class flights, starting in 1952.

On November 1st 1955 a time bomb exploded aboard a DC-6 killing 44 people above Longmont, Colorado.

The USAF Strategic Air Command had C-118 Liftmasters in service from 1957 through 1975.

Douglas designed four basic variants of the DC-6: the "basic DC-6," and higher-gross-weight, longer range versions -- the "DC-6A" had a large cargo door and was designed for cargo work, while the "DC-6B" was designed for passenger work and the "DC-6C" was a "convertible" aircraft that could accommodate both. The military version, essentially similar to the DC-6A, was the C-118. The DC-6B, powered by Pratt & Whitney R-2800-CB-17 engines with Hamilton Standard 43E60 constant speed reversing propellers, was regarded by many to be the ultimate piston-engine airliner from the standpoint of ruggedness, reliability, economical operation, and handling qualities.

The military renewed its interest in the DC-6 during the Korean War, and commissioned a number of aircraft that later found their way into civilian service. Harry Truman's first presidential aircraft was an Air Force VC-118 called The Independence.

Many older DC-6 aircraft were replaced by the Douglas DC-7: those that survived into the Jet Age were replaced by Boeing 707 and Douglas DC-8 aircraft.

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