Aircraft manufacturers have long been adept at leveraging designs to gain as much utility — and production — as possible.
The dual tracks of commercial transport and military airlift had more in common in the 1940s than today. It was an era before low-sitting, end-loading, and air-dropping cargo behemoths defined military transport procurement. The need for moving large numbers of troops and large numbers of airline passengers over long distances had some commonality back then.
World War II blunted the development of pure civilian transports for the duration, but big players in the airline business, including Pan American Airways, had important wartime transport duties. Pan American also had enough clout to influence the development of a super transport for the Navy that might one day also be an ocean-spanning airliner.
In 1942, several iterations of designing led to the Lockheed XR6O-1.
The use of the capital letter O in the designation reflects that era’s use by the Navy of the letter O to represent airplanes built by Lockheed at its Plant B as opposed to Lockheed’s Vega division, Plant A, which carried the identifying letter V.
The XR6O was a large airplane for any era. Its wing spanned just over 189’. Length was 156’, 1”. The top of its tail stood a towering 50’, 4-1/2” above the tarmac.
Top speed was listed as 300 mph; economy cruise would be about 40 mph less.
The double-lobed pressurized fuselage of the XR6O could carry a maximum of 204 military passengers. This was the first pressurized transport aircraft in U.S. Navy service.
Airline variants were planned to carry 58 passengers in sleeper berths and an additional 51 passengers in seats. Alternately, civilian versions could carry passengers on the upper deck and freight below. However, the civilian versions never materialized.
The XR6O was given the name Constitution, no doubt in part a phonetic decision, given Lockheed’s other four-engine transport of the day, the Constellation.
Although developed as a project for the Navy, the XR6O did not enjoy a priority as high as some combat aircraft during the war. Additionally, a huge new hangar had to be built to house the giants. Originally contracted for a 50-aircraft production run, this was dramatically scaled back to two prototypes when World War II ended in the Pacific.
It wasn’t until Nov. 9, 1946, that the first XR6O tested its wings on a flight from Lockheed’s Burbank facility to Muroc Army Air Base, with the test crew taking more than two hours to evaluate the aircraft en route.
The second Constitution was not airborne until June 1948. The two Constitutions flew with variations of the huge R-4360 Wasp Major 28-cylinder engine.
The Constitution used an unusual 120-volt DC system for electrical power. The dual tandem mainwheel sets used electric motors to spin the wheels before contacting the runway. Only the inboard engines had reversible propellers.
Although never produced beyond the two prototypes, both Constitutions entered regular Navy service with the U.S. Navy’s VR-44 transport squadron at Naval Air Station Alameda in California in 1949.
Issues of range deficiency and power plagued the Constitutions. The problems were at least in part due to engine cooling demands that were only resolved by flying with cowl flaps partly open, to the detriment of fuel economy.
When the Navy decided to list all Lockheed products under the letter V, the Constitutions became XR6V-1s in 1950. The following year, the two transports returned to Lockheed for major overhaul. By 1953, the Navy decided to store the Constitutions at Litchfield Park in Arizona, when the supply of spare parts became an issue.
A proposed antisubmarine warfare variant of the XR6V never materialized. And Pan American Airways, which had been instrumental in the original Constitution concept, decided that so much bulk did not suit its post-war needs.
But the airline had an answer. Pan American had earlier helped influence Boeing’s decision to develop the Model 377, which became the successful Air Force C-97, and saw posh airline service as the Stratocruiser.
Lockheed researched civilian derivatives in an effort to secure an airline market for all the effort that went into the design of the Constitution, but no buyers were to be found.
Possibly the most promising of these outgrowths on paper was a turboprop version to be powered by four 5,500 shaft horsepower Wright Typhoon propjet engines. But the Typhoon powerplant did not enter production and the window of opportunity for the Constitution airframe passed from the scene.
The two forlorn Lockheed Constitutions were sold to civilian buyers in the mid-1950s. One was ferried to Las Vegas, Nevada, and the other to Opa-Locka, Florida. Neither Constitution obtained a civil Approved Type Certificate, and both were ultimately scrapped.