The Douglas Aircraft Company constructed the Douglas DC-6, a piston-powered airliner and cargo aircraft, between 1946 and 1958.
Originally designed as a military transport towards the end of World War II, Douglas reconfigured the aircraft after the war to compete with the Lockheed Constellation in the long-range commercial transport market.
Over 700 DC-6s were built, with many still in operation today in various capacities, including cargo, military, and wildfire control roles.
During its service in the United States Air Force, the DC-6 was known as the C-118 Liftmaster, while in the United States Navy, it was referred to as the R6D until 1962, after which all U.S. Navy variants were also designated as the C-118.
The prototype Douglas XC-112A, which first took flight on 15 February 1946, was converted to DC-6 standard in 1956 and flown by TASSA of Spain from 1963 until 1965.
The DC-6 project was commissioned by the United States Army Air Forces as the XC-112 in 1944.
The Army Air Forces sought a lengthened, pressurized version of the DC-4-based C-54 Skymaster transport with more powerful engines.
However, by the time the prototype XC-112A took flight on 15 February 1946, the war had ended, and the USAAF had rescinded its requirement.
The aircraft was then converted to YC-112A and sold in 1955.
Douglas Aircraft modified the design into a civil transport that was 80 inches (200 cm) longer than the DC-4.
The civil DC-6 underwent its first flight on 29 June 1946, and it was retained by Douglas for testing.
The first airline deliveries were made to American Airlines and United Airlines on 24 November 1946.
However, a series of inflight fires, including the fatal crash of United Airlines Flight 608, grounded the DC-6 fleet in 1947.
The cause was determined to be a fuel vent located next to the cabin cooling turbine intake.
All DC-6s were modified, and the fleet was flying again after four months on the ground.
Variants XC-112A United States military designation of an improved version of the C-54 (DC-4); became the prototype DC-6. Eventually designated YC-112A, pressurized, P&W R-2800-83AM3 engines DC-6 The initial production variant was produced in two versions. DC-6-1156 is a 53- to 68-seat domestic variant with 2,400 hp (1,800 kW) R-2800-CA15 engines. DC-6-1159 a 48- to 64-seat trans-ocean variant with extra crew, Increased fuel capacity to 4,722 US gallons (17,870 L), Increased takeoff weight to 97,200 lb (44,100 kg) and 2,400 hp (1,800 kW) R-2800-CB16 engines. DC-6A Freighter variant The fuselage was slightly lengthened from DC-6 and fitted with a cargo door; some retained cabin windows, while others had windows Precluded. Originally called “Liftmaster” as USAF models. The rear cargo door came standard with a built-in 4,000 lb (1,800 kg) lift elevator and a Jeep. The Jeep was a public relations stunt and shortly after, was dropped. Slick Airways was the first airline to operate the freighter variant in April 1951. DC-6B All-passenger variant of DC-6A, without cargo door. DC-6B-1198A a 60- to 89-seat domestic variant with 2,400 hp (1,800 kW) R-2800-CB16 engines DC-6B-1225A a 42- to 89-seat trans-ocean variant with an increased fuel capacity to 5,512 US gal (20,870 L), increased take-off weight to 107,000 lb (49,000 kg) and 2,500 hp (1,900 kW) R-2800-CB17 engines. DC-6B-ST Swing tail freighter conversion to the DC-6B done by Sabena. Two converted. DC-6C Convertible cargo/passenger variant. VC-118 The United States military designation for one DC-6 was bought as a presidential transport with a special 25-seat interior and 12 beds. C-118A Designation of DC-6As for the United States Air Force, 101 built. VC-118A C-118As converted as staff transports. C-118B R6D-1s redesignated. VC-118B R6D-1Zs redesignated. R6D-1 United States Navy designation for the DC-6A, 65 built. R6D-1Z Four R6D-1s converted as staff transports. Specifications DC-6 Crew Three to four Capacity 48-68 passengers Length 100 ft 7 in (30.66 m) Wingspan 117 ft 6 in (35.81 m) Height 28 ft 5 in (8.66 m) Wing area 1,463 sq ft (135.9 m2) Empty weight 52,567 lb (23,844 kg) Max take-off weight 97,200 lb (44,100 kg) Powerplant 4 Pratt & Whitney R-2800-CA15 Double Wasp radial engine, 2,400 hp (1,800 kW) with water injection each Propellers Hamilton Standard 43E60 “Hydromatic” constant-speed props with auto feather and reverse thrust. Cruise speed 311 mph (501 km/h) Fuel capacity 4,260 US gal (16,100 L) Range 3,983 nmi (7,377 km) Max payload 4,100 nmi (7,600 km) Max fuel Service ceiling 21,900 ft (6,700 m) Rate of climb 1,070 ft/min (330 m/min). Sources Air Mobility Command Museum. McDonnell Douglas aircraft since 1920: Volume I-René J Francillon. San Diego Air and Space Museum Archive. The National Museum of the U.S. Air Force. Charles Daniels Photo Collection.