The Douglas C-118 Liftmaster/ Douglas R6D was the military version of the DC-6, and most were based on the improved DC-6A model.
The DC-6 had originally been developed with military funding, as the XC-112A. It was a pressurized and otherwise improved version of the wartime DC-4/ C-54, with full cabin pressurization, an 81in longer fuselage, and powered by four 2,100hp Pratt & Whitney R-2800-34 radial engines. Flight tests of the XC-112A began on 15 February 1946, but although the new aircraft was a significant improvement over the DC-4, the US military had no need for new transport aircraft in 1946. However the type did enter production as the commercial DC-6, which after initial problems became a successful aircraft.
The first DC-6 to enter USAF service was the twenty ninth DC-6, which was purchased for use as a Presidential aircraft, and given the designation C-118-DO. This aircraft was named The Independence, after President Truman's home town, and was donated to the National Air & Space Museum after twenty years with the Presidential flight. It had special communications equipment and VIP accommodation installed.
In 1948 Douglas introduced the DC-6A. This was intended for use as a cargo aircraft. It used more powerful Double Wasp engines, was 5ft longer than the DC-6, had a reinforced cabin floor, no fuselage windows and two upward opening freight doors - one just behind the cockpit and one behind the wings. The first DC-6A made its maiden flight on 29 September 1949.
The first military version of the DC-6A was the US Navy's R6D-1. The Navy ordered 65 DC-6As in 1950. 61 R6D-1s were delivered by 1952 and four R6D-1Zs in 1954. They were used as logistic transports (as the R6D-1) or as VIP/ staff transports (as the R6D-1Z). The R6D was used by Fleet Tactical Support Squadrons VR-1 and VR-21. Forty were later transferred to the USAF to join the C-118As, operating as part of the Military Air Transport Service, with Navy crews. In 1962 the aircraft still in use with the Navy became the C-118B (R6D-1) or the VC-118B (R6D-1Z).
The USAF ordered 101 aircraft, giving them the designation C-118A-DO. They were powered by four 2,500hp R-2800-52W engines, had military equipment and could carry 74 troops or 27,000lb of cargo. The USAF also gained the 40 aircraft transferred from the US Navy. The C-118A was used as a personnel and logistic transport by the Military Air Transport Service, which later became the Military Airlift Command. When it began to be replaced by jet transports in the logistics role, the remaining C-118As were used as medical and staff transports.
Engines: Two Wright R-1820-44s
Power: 1,000hp each
Wing span: 117ft 6in
Length: 105ft 7in
Height: 28ft 8in
Empty weight: 49,767lb
Max take-off weight: 107,000lb
Cruising speed: 315mph
Rate of climb: 1,010ft/ min
Maximum range: 2,925 miles with 28,188lb cargo or 4,720 miles empty