|Articles by Peter M. Bowers
The Lockheed Constitution
Peter M. Bowers
The first of two Lockheed Model 89 Constitutions made its first flight on Nov. 9, 1946. An experimental U.S. Navy transport, it was designated XR6O-1 for the sixth R-model (transport) developed for the Navy by Lockheed, code-lettered O. At the time of its first flight, the XR6O-1 was the largest airplane built by the Lockheed Aircraft Corp. of Burbank, California.
Design work began in June 1942 under somewhat strange circumstances. The aircraft was not the Navy’s idea. Pan American Airways, using state-of-the-art prewar equipment, was operating a worldwide airline network for the government under wartime conditions. Bigger and faster transports were needed. Pan Am had built its reputation with flying boats, but wisely noted that the type had no postwar future. To serve its immediate wartime needs, and to provide a source of new postwar airliners, the airline prevailed upon the military to have industry develop new and larger land-plane transports.
As a result, Lockheed received a contract for the two XR6O-1s. With the 1942 Douglas DC-4 serving the Army and Navy as the C-54 and R5D, and combat airplanes getting top priority in the factory, the XR6O-1s got low priority from both Lockheed and the Navy. The first one was not completed until 15 months after V-J Day.
The XR6O-1 was the biggest land-plane transport of its day. Powered by four 3,000-horsepower Pratt & Whitney R-4360 engines, the double-deck, double-lobe fuselage was pressurized, and the wing was basically an enlargement of the type Lockheed used on the prewar Model 12 transport and the P-38 fighter. The aircraft accommodated 204 armed troops in high-density seating or 160 in airline-type seating. Passengers or cargo could be carried on either deck, and stairways at each end of the cabins connected them.
The postwar airline version was to carry 51 seated passengers plus 58 in sleeper berths. The airliner crew was to be 11.
The first takeoff was made from the factory in Burbank, and the landing was made at Muroc Army Air Base (now Edwards AFB), where flight testing was conducted. Despite its 3,000-horsepower engines, the XR6O-1 was underpowered, so the R-4360-18 engines were replaced with 3,500-horsepower R-4360-22W engines with water injection.
The second XR6O-1 flew in June 1948, and both were delivered to Navy Transport Squadron VR-44 at Alameda, California, in 1949. They were used on the California-Hawaii run, but were still underpowered. Cooling problems with the engines made it necessary to fly with the cowl flaps partly open. That increased drag, reduced speed and required more fuel for the distance. As a consequence, payload had to be reduced.
In 1950 the Navy changed the letter designation for Lockheed from O to V, so the XR6O-1s became XR6V-1s. They were retired from the Hawaii run in 1952 and sent back to Lockheed for overhaul. Without adequate spare parts, the Navy could not afford to make new ones, so it sold both XR6V-1s as surplus in 1955.
Both found new civil owners and got on the civil register, but as experimental military models they had not been designed to postwar civil requirements. They did not qualify for approved type certificates as built, and the cost of rework and testing would have been prohibitive. Both were eventually scrapped.
Meanwhile, Lockheed, after recognizing the problems with insufficient power, offered a revised Model 289 with 5,500-horsepower Wright Typhoon turboprop engines, but Pan Am turned it down. The airline had bought the civil version of the smaller Boeing C-97 Army transport, the Model 377 Stratocruiser, and had it in service only two months after the first XR6O-1 flew. The airline also rejected the Douglas and Convair proposals for civil versions of their C-74 and XC-99 military cargo planes.
Wingspan 189 ft 1-1/4 in
Length 156 ft 1 in
Wing area 3,610 sq ft
Gross weight 184,000 lbs
High speed 303 mph @ 20,000 ft
Cruise speed 269 mph
Initial climb 1,010 fpm
Service ceiling 27,600 ft
Range (no payload) 6,300 mi
1. Rollout of the first Lockheed XR6O-1 Constitution, Navy Serial No. 85163. This view emphasizes the double-lobe fuselage. It was unusual for a military prototype to carry company logos, but the XR6O-1 had five: one on each side of the nose, a smaller one near the lower lobe entry door, and large ones on each side of the fin. The nose logos stayed on both planes throughout their service.
2. There seems to be an unwritten rule in the airplane business: When you build a big airplane, put a smaller one alongside it for a comparison photo. In this case, the little plane is a twin-engine Lockheed 12A prewar transport.
3. First takeoff of the first XR6O-1 from Lockheed Air Terminal, Nov. 9, 1946. Note the size of the partially extended Fowler flap on the wing.
4. Flight view of the first XR6O-1. Note the partially open cowling flaps; engine cooling was a major problem throughout the XR6O-1s’ careers. With the entry doors on the left side, only two Lockheed logos were painted on the right sides of the planes.
5. The second XR6O-1, in front of a dirigible hangar at Moffett Field in Sunnyvale, California. The three-digit number on the fuselage is the last three digits of the plane’s Navy serial number, 85164. The first XR6O-1 was similarly marked while in service.
6. The second Constitution, now designated XR6V-1, was flown to Opa Locka, Florida, under its new civil registration, N7673C. The Lockheed logo was still on the nose. The price for the two of them was only $98,000.