|The Douglas DC-6 is a piston-powered airliner and transport aircraft built by the Douglas Aircraft Company from 1946 to 1958. 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.
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 Skymaster 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 By the time the XC-112 flew, the war was over, and the USAAF had rescinded its requirement.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 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-6s in service were modified to correct the problem, and the fleet was flying again after just four months on the ground.
Douglas designed four basic variants of the DC-6: the "basic DC-6," and the longer fuselage, higher-gross-weight, longer range versions—the "DC-6A" with large cargo doors forward and aft of the wing on the port (left hand side) with a cargo floor, the "DC-6B" designed for passenger work,had passengers doors only and a lighter floor and the "DC-6C" a "convertible" aircraft built with the 2 cargo doors, but fitted with removable passenger seats. The military version, essentially similar to the DC-6A, was the USAF C-118 Liftmaster, and the USN R6D. The DC-6B, powered by Pratt & Whitney R-2800-CB-17 engines with Hamilton Standard 43E60 constant speed reversing propellers, was regarded as the ultimate piston-engine airliner from the standpoint of ruggedness, reliability, economical operation and handling qualities.
The USAF and USN renewed their interest in the DC-6 during the Korean War, and ordered a total of 167 C-118/R6D aircraft, some of which later found their way into civilian service. Harry Truman's first presidential aircraft was an Air Force VC-118 called The Independence.
Total production of the DC-6 Series was 702 including military versions.
In the 1960s, two DC-6s were used as transmitter platforms for educational television, based at Purdue University, in a program called MPATI (Midwest Program for Airborne Television Instruction).
Many older DC-6 aircraft were replaced in airline passenger service by the Douglas DC-7, but the simpler, more economic engines in the DC-6 has meant that this type has out-lived the more sophisticated DC-7. DC-6/7s surviving into the Jet Age were replaced in front line service by Boeing 707 and Douglas DC-8 aircraft.
2006 marked the 60th anniversary since the introduction of the DC-6.