By the time the United States entered World War II at the end of 1941, the Navy had recognized the need for long-range transport aircraft for both passengers and cargo. This situation led to Pan American Airways teaming with Lockheed Aircraft Corp. and the Navy to develop a new, massive transport plane. PanAm was operating a large fleet of flying boats on long-distance flights, but there would be advantages to using long-range landplanes. The result of this joint effort was the R6O Constellation, the largest aircraft ever flown by the U.S. Navy.
PanAm’s interest in large landplanes led the Douglas and Boeing firms to initiate the Army-sponsored C-74 and C-97 transports, respectively. The Navy sponsored the Lockheed Model 89, with two prototypes being ordered with the designation XR6O-1.1 The plan was for PanAm to operate surplus Navy planes after the war and for the Model 89 to serve as the basic design for a postwar passenger fleet.
Led by Willis Hawkins and project engineer William A. “Dick” Pulver, the Lockheed team studied more than two dozen layouts before selecting a conventional, four-engine, mid-wing design. The fuselage, however, would have a figure-eight cross section, using the advantages of a cylinder for structural strength and cabin pressurization without the wasted space of one huge cylinder. This arrangement was to provide two decks—connected by a pair of spiral staircases—for cargo and up to 200 military passengers in high-density seating, or 17,500 pounds of cargo, with a range of 5,000 miles. In a civilian configuration, the design was to provide for 129 seated passengers or 109 passengers in sleeper berths with a crew of 15. The R6O was to be powered by four Pratt & Whitney Wasp Major radial engines, each generating 3,000 horsepower and turning four-blade propellers.
The aircraft, with a planned gross weight of more than 85 to 90 tons, required an unusual landing gear configuration. Each of the main landing-gear had two struts in tandem with two wheels per strut. To reduce stress upon landing, these eight main wheels were spun by electric motors before touchdown.
Construction of the giant transports was given low priority during the war, as was the need for giant six-story hangars to house them. Thus, the first of two planned prototypes was not completed until 15 months after the end of the war in the Pacific. The first flight of an XR6O-1 took place on 9 November 1946 and lasted 2 hours, 17 minutes. Improved engines—producing 3,500 horsepower with water injection—soon were provided to the first prototype, and the second XR6O-1 flew in June 1948 with the new engines.
Eventually the aircraft were fitted for JATO (jet assisted takeoff) rocket boosters. Six JATO “bottles” mounted in three racks in each wing root could shorten the takeoff run by about 25 percent.
Both aircraft—with the name “Constitution” given by Lockheed and accepted by the Navy—were flown nonstop from Moffett Field near San Francisco to Washington, D.C. On its second transcontinental flight, on 3 February 1949, the aircraft carried 74 members of the press in addition to its flight crew. That was the largest number of passengers flown to that date across the United States on a single, nonstop flight. The Navy used the aircraft on transcontinental flights for six months.
The two planes were placed in service with Navy Transport Squadron (VR) 44 at Naval Air Station Alameda, California, in 1949. The aircraft were underpowered and lacked sufficient range for many Pacific routes. On the California-to-Hawaii run, a 2,300-mile route, the payload had to be reduced “substantially,” according to aviation historian René J. Francillon.2 Intended to power production R6O aircraft, the Wright Typhoon turboprop engine, rated at more than 4,000 horsepower, was abandoned.
The aircraft did fly on Pacific routes with VR-44 until 1953 (having been redesignated XR6V-1 in 1950). The lack of spare parts and operational limitations led to both planes being stored at Naval Air Station Litchfield Park, Arizona, while their ultimate fates were decided. PanAm had no interest in the aircraft because more efficient landplanes were available, especially the Lockheed Constellation. Finally, the two planes and 13 spare engines were sold to civilian owners in 1955 for $97,785.
The first prototype was flown to Las Vegas, Nevada, and the second to Opa-Locka, Florida. The first aircraft encountered engine problems during the delivery flight. On his first flight in a Constitution, pilot L. M. Hammer lost an engine. Still, with just three engines, he recalled, “I flew the aircraft for awhile and found the 189-foot wing and engines very docile to control.”3
At Las Vegas, the first prototype became a stationary billboard for Alamo Airways; subsequently it was scrapped by Howard Hughes when he acquired the property. The second aircraft was stored at the Opa-Locka Airport before being towed to a scrap yard where it was set on fire by vandals in 1979.
Significantly, the competitive Boeing C-97 Stratofreighter, also with a figure-eight fuselage, was highly successful, with 888 aircraft being built for the U.S. Air Force and foreign air forces for the VIP, airborne command post, transport, cargo, electronic test, search-and-rescue, tanker, and spyplane roles. The design had great success in the commercial airliner role; 56 were produced as the Boeing 377 Stratocruiser.
The R6O/R6V Constitution was a failure by any criteria, although in several respects the design was highly innovative. Lockheed’s proposal for modifications of the design for commercial service—Models 389 and 489—failed to find customers, as did a proposed long-range maritime patrol variant of the aircraft.
2. Francillon, 287.
3. L. M. Hammer, “Lockheed XR6O-1 Constitution,” American Aviation Historical Society Journal (Summer 1998), 112.