17 June 2010

The L-1000: Lockheed's Own Jet Engine

Probably one of the most obscure yet fascinating episodes in the history of jet engine development stemmed from Lockheed's innovative jet-powered L-133 fighter design that was submitted to the USAAF in March 1942. While the fighter design boasted advanced features like a canard and a blended wing-body, the Army Air Forces were more interested in the proposed engines of the L-133 which were to be two axial-flow jet engines designed by Lockheed itself designated L-1000. The engine had a multi-stage turbine to increase compression which translated into a greater thrust output. At a meeting at Wright Field in Dayton (where the USAAF's Power Plant Laboratory was located) in August 1942, military researchers and Lockheed engineers reviewed the L-1000's design- it was only 24 inches in diameter, 139 inches long, and weighed 1,235 lbs. Lockheed estimated that at full takeoff thrust, the L-1000 could develop 6,700 lbs of thrust. Despite the reservations of the Power Plant Laboratory, they felt there were enough features in Lockheed's jet engine that had potential that made it worth funding further development.

By comparison, that same year General Electric was working on their version of Frank Whittle's British W.1X centrifugal flow engine. GE first ran their I-A (which would later be designated the J31) on 18 April 1942, making it the first jet engine to operate in the US. It was 41.5 inches in diameter, 72 inches long, and weighed 865 lbs. At full thrust it developed only 1,250 lbs of thrust. At the time, Allied jet development had been focused primarily on centrifugal flow jets as that was the what was furthest along in terms of engineering and development compared to axial flow jets. The only other axial flow jet in development in 1942 was the Junkers Jumo 004 in Germany. It was already at the flight hardware stage that year and it was 152 inches long, 32 inches in diameter, weighed approximately 1,600 lbs and the early versions then being tested developed just under 2,000 lbs of thrust.

By comparison to the working jet engines of the day, the Lockheed L-1000 engine would have been quite a leap in performance in an axial flow engine that was smaller than the Jumo 004. Despite the potential, some officials in the USAAF were less than pleased with the idea of an airframe manufacturer developing its own jet engine, even though Northrop at the time was working on its own Turbodyne turboprop engine for its flying wing bomber designs. It was felt that airframe manufacturers lacked the expertise and facilities for the development, testing and production of jet engines.

Regardless of the objections of some officials in the USAAF, a contract was finally signed with Lockheed for good (there had been some dispute over intellectual property rights) on 31 July 1944 for approximately $1.2 million. A year later, Lockheed requested a one year extension as the pressures of wartime production had left it without sufficient engineering resources to devote to the L-1000, just as some in the military had predicted a few years earlier. As a result, Lockheed subcontracted 60% of the project to the Menasco Manufacturing Company. The Army acquiesced to this arrangement as long as Lockheed remained ultimately responsible for the engine. Menasco was allowed to manufacture the engine but under Lockheed's own engine patents. In the summer of 1946, the USAAF appropriated an additional $1.9 million to the L-1000 project by which time it would receive the designation J37. Lockheed assured the USAAF that production could begin as early as 1947.

Initial delays were due to manufacturing pressures at Menasco which was providing high-precision parts to the aircraft manufacturers of Southern California including Douglas, Convair, as well as Lockheed for the war effort. But with the cancellation of a good number of military production contracts with the Japanese surrender, Menasco was able to devote additional resources to the J37 project. Despite this, however, progress remained slow with the USAAF steadily losing patience with Lockheed. In late 1946, the J37 project was handed off to Wright Aeronautical Corporation, but by that time, Wright was more interested in its own developments and the GE/Allison J33 engine that was developed from Whittle's designs was a proven and mature powerplant already powering the Lockheed P-80 (later redesignated F-80) Shooting Star fighter.

The GE/Allison J35 engine would be the first axial-flow jet engine for the USAF and it had already made its first flight powering the Republic P-84/F-84 Thunderjet in February 1946 and would eclipse the centrifugal flow J33 engine in its performance. And even more powerful and successful development of the J35 was already being tested that year, the J47 engine. Lockheed quietly abandoned its efforts in developing a powerplant and all that exists of the L-1000 today is a mockup at the Planes of Fame Museum in Chino, California.

Source: Experimental & Prototype U.S. Air Force Jet Fighters by Dennis R. Jenkins and Tony R. Landis. Specialty Press, 2008, pXI, 21-23.

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