A Giant Ahead of its Time: The Lockheed R6V Constitution
Before the start of the Second World War, Pan American Airways was the world’s biggest operator of large ocean-going flying boats with a fleet consisting of the Boeing 314, Martin M-130, and Sikorsky S-42 aircraft. However, the airline recognized that the pace of development in aviation technology meant that land planes would be the dominant airline aircraft of the future.
Defining the Need
Pan Am worked with Boeing to bring the Boeing 307 Stratoliner (the world’s first pressurized airliner) to fruition, but with the start of the war for the United States in 1941, Pan American’s operations were shifted to support the war effort. As a result, the airline solicited the US Navy for the construction of a true heavy-lift land-plane transport. This was finalized with the US Navy, Lockheed and Pan American in November 1942 with what became the Lockheed Model 89 Constitution.
A year later, on 1st November 1943, the contract was formally issued to Lockheed. The requirements, issued by the Navy as suggested by Pan American, were for aircraft with a range of 5,000 miles, a 17,500lb payload at 255 mph, and a 25,000-foot cruising altitude.
Pan American’s engineers, led by their head engineer Andre Priester, worked alongside Lockheed’s engineers including their head engineer Willis Hawkins (who also designed the Constellation and would later work on the F-80 Shooting Star, F-104 Starfighter, and the C-130 Hercules).
The fuselage of the Constitution was a double-deck, double-lobed, cross-section design with the large wing passing through the mid-fuselage between decks. With a fully-pressurized double-deck, the Constitution could carry up to 204 military passengers, but the normal complement would be 168 passengers. Pan American’s plans were for 51 passengers on the lower deck and 58 passengers on the top deck.
Cargo doors were installed on the lower deck and the wings were deep enough to allow mechanics to access the four radial engines in flight for maintenance. The Constitution was also the first large transport aircraft to have multi-wheel main landing gear bogies (four wheels to each main landing gear).
The wing itself was based on the layout and structure of the wings used on the Constellation and the P-38 Lightning. Four 3,000 horsepower Pratt & Whitney R-4360 28-cylinder Wasp Major engines drove four bladed props. Unusually, the upper surface trailing edge root of the wings could hold rocket-assisted take-off (RATO) units to shorten take-off runs. There were three units in each wing and they were fired when the landing gear retraction sequence started. As the landing gear took 14 seconds to retract, the RATO units burned for 15 seconds.
Though standard for today’s design work on modern airliners, Lockheed used a full-scale hydraulic and electrical systems test rig that today would be known as an ‘iron bird.’ The system was loaded so the hydraulics and flight control systems would ‘experience’ loads similar to what would be found inflight and was invaluable in letting the Constitution’s test pilots get familiar with the large aircraft.
Since the Constitution was a low-priority project during the war, it wasn’t until well after the war ended, in August 1945, that the aircraft was completed. The first flight came on 9 November 1946 but after the first 44 hours of flight testing, the Constitution was found to be significantly underpowered.
More powerful versions of the R-4360 Wasp Major were installed that theoretically produced 3,500 horsepower, but in practice, even these engines could only garner 2,900 to 3,300 horsepower and that was with water injection and bypassing the superchargers on take-off. As a result, use of the integral RATO units was commonplace.
To keep Pan American interested in the project, Lockheed proposed the civilian version of the Constitution. It was to be powered by a Wright 5,500 horsepower Typhoon turboprop, but by this point Pan American had fully committed to the Boeing Stratocruiser and so bowed out of the Constitution program.
Designated XR6O-1 by the US Navy, the first Constitution underwent a full year of flight testing at NAS Patuxent River, Maryland. The second XR6O-1 made its first flight on 9 June 1948 and unlike the first aircraft, the upper deck was fitted out for VIP passenger service with 92 seats while the lower deck was fitted out to carry as much as 40,000lbs of cargo. Dual spiral staircases at each end of the cabin provided access to the upper deck from the lower deck and passenger entry was via the nose gear-well which was large enough to allow air-stairs to be pulled up just in front of the nose-gear.
In February 1949 the second R6O (the X prefix was dropped) was commissioned into service at NAS Moffett Field, California, with the fleet logistics support squadron VR-44. Soon joined by the first R6O, the Navy embarked on a series of publicity flights across the country, using the Constitution to not only transport personnel and material, but also to stimulate interest in naval aviation. The R6O carried one and a half times more cargo than the next biggest Navy transport, the Douglas R5D (C-54 Skymaster/DC-4).
In 1950, the two R6Os were redesigned as R6V. Prior to 1962, the Navy’s aircraft designation system used ‘V’ which stood for the Vega Division of Lockheed that had built the PV-1 Ventura and PV-2 Harpoon. And during the Second World War, the ‘O’ of Lockheed was dropped as it could be confused with the number zero and ‘V’took its place as the Lockheed designator code.
The R60 Constitutions were reassigned to VR-5 for expanded operational duties that included flights to Hawaii and Alaska. But in 1953, with a total of 3,760 flying hours between them, they were retired and placed in storage at NAF Litchfield Park, Arizona. The aircraft were offered to the airlines on a proposed five-year lease, but they showed no interest.
A Sad End
The first Constitution ended up in Las Vegas as a promotional billboard for Alamo Airways at McCarran Airport and plans were floated to move the aircraft to the Strip to be part of a casino. However, the plans never materialized and when Howard Hughes acquired the property that the aircraft sat on, he also gained ownership of the aircraft and had it scrapped in 1970.
The second Constitution ended up in Opa Locka, Florida, where it was to be sold to a German businessman who wanted to use it for a restaurant in Barcelona, Spain. The deal fell through and the aircraft mysteriously caught fire which gutted the interior but spared the exterior. After several years of legal wrangling, the aircraft was also scrapped in 1979.
To learn more about the Lockheed R60/R6V Constitution, download Steve Ginter’s book here. (Verification required)