The NACA Makes the Jet Engine both More Efficient and More Powerful

I have been working on a general history of the National Advisory Committee for Aeronautics (NACA), the predecessor to NASA, and I have been working on a section of jet research in the 1940s and 1950s. Comments on this draft are welcome.

While the NACA missed the opportunity to pioneer the jet engine, by far the most revolutionary technology applied to aircraft since the Wright brothers, in the period after World War II engineers largely at the Aircraft Engine Research Laboratory in Cleveland transformed aviation with their powerful, efficient, and safe jet engines. The success of jet aircraft in both Germany and Great Britain in World War II spurred American efforts to catch up to this technology. While the NACA had failed to the technology, its leaders were intent on making the technology better and exploiting in every way possible. The Aircraft Engine Research Laboratory, now Glenn Research Center, forwarded a report in December 1945 entitled “Survey of Fundamental Problems Requiring Research” that recommended the expansion of  research on the technologies of turbojets, ramjets, and rockets.

The report concluded: “The simultaneous development of aerodynamic shapes for high-speed flight, and the use of jet-reaction power systems has suddenly placed the aeronautical engineer in position to attain supersonic speeds, but as yet only the outer fringes of research on this mode of transportation have been touched.” The fundamental technology that the NACA pioneered was the axial flow compressor. The first jets were powered by centrifugal compressors; systems that were inefficient and underpowered for anything but the lightest fighter jets. What was needed was axial flow compressors, but the technologies were not well known and most of the baseline knowledge was limited to a few empirical tests over a limited aerodynamic regime that emphasized airfoil research and little else. NACA researchers would change that in the years the followed.

As researchers George E. Smith and David A. Mindell noted, axial flow compression was attained by “stacking a sequence of these airfoil profiles radially on top of one another as if the air flows through the blade row in a modular series of radially stacked two-dimensional blade passages.” The expansion of this approach required a detailed, lengthy, and expensive research agenda only able to be carried out by a government laboratory. Several different efforts emerged at the Lewis Flight Propulsion Laboratory in Cleveland, so named after the passing of the longtime NACA Director of Research in 1948. The contribution was a three-volume “Compressor Bible,” issued in final form in 1956 after a decade of research at Lewis.

The GE J-79 Jet Engine on display at the National Museum of the United States Air Force.

This study was based on a pain-staking empirical research effort that included wind tunnel research and flight research, as well as theoretical studies. This research set the standard for knowledge about axial-flow compression for more than twenty-five years after its publication. According to Smith and Mindell:

The empirical component of the NACA design method was based primarily on a huge number of cascade performance tests of NACA 65-Series airfoils carried out at Langley.…These data allowed designers first to select preferred airfoil shapes along a blade to achieve a given design performance, including thermodynamic loss requirements, and then to predict the performance of the airfoils at specified off-design operating conditions. In large part because of the availability of this data-base, NACA 65-Series airfoils became the most widely used airfoils in axial compressors.

The knowledge gained through the NACA’s research filtered out of the agency through the usual means of technical reports and personal contacts as well as the departure from the NACA of several key researchers who moved to General Electric and developed axial-flow compressor engines, especially turbofans, into the mainstay of American jet technology. Langley’s Jack Erwin and Lewis’s John Klapproth, Karl Kovach, and Lin Wright departed for GE in 1955 and 1956.

John Blanton of GE Aircraft Engines.

These engineers proved instrumental in designing the path-breaking large axial-flow turbofan, the J-79 military jet engine powering the B-58 Hustler, Lockheed F-104 Starfighter, McDonnell Douglas F-4 Phantom II, and North American A-5 Vigilante, oriented toward performance as high as Mach 2. The commercial equivalent, the CJ805, powered the Convair 880 and 990 airliners. Under the leadership of John Blanton at GE, this team successfully developed a powerful engine that found use on both across a broad spectrum. The NACA’s contribution included not only basic research but design expertise. The role of Lin Wright proved especially critical; he was an African American engineer from Wayne State University in Detroit who worked for a decade at Lewis, and then transitioned to GE just as the Civil Rights Crusade was emerging as a force in American politics. Far from an activist, Wright contributed most to that cause through his excellence as an engineer on the cutting edge of aeronautical research and development.