JAMES N. KREBS (1924-2022)

BY JAN C. SCHILLING

JAMES NORTON KREBS, an aerospace visionary who guided General Electric’s leap into the jet age, influencing the course of the jet propulsion industry for nearly 40 years, died on July 20, 2022, at age 98.

Born April 20, 1924, in Sauk Centre, Minnesota, to Leland and Carolyn (née Norton) Krebs, Jim grew up sketching airplanes, rocket ships, and cars. He loved making things and decided a career in engineering made sense. As a high school senior in 1942, he was attracted to Northwestern University’s new Technological Institute where he pursued a B.S. in mechanical engineering.

After graduating from Northwestern in 1945 as part of the Naval ROTC program, he began active duty on the USS Dunlap, stationed off Iwo Jima. After the war, a Northwestern connection led to a job offer at the GE aircraft gas turbine business in Lynn, Massachusetts.

The new jet engine era was unfolding. Jim’s first years at GE were as a test engineer in the combustion research group. This role led to work on advanced compressors and J73 (F-86H fighter jet) component design. New and challenging assignments continued. He was a mechanical design manager for the GOL-1590 demonstrator engine, a game-changing technical effort in GE’s early days in jet propulsion. The engine led to the J79, GE’s workhorse for fighter jets in the 1950s and 1960s. Eventually, a J79 engine with an aft bypass fan powered the Convair 990 passenger jet.

In 1957, Jim became project manager for the J85, one of the most enduring small jet engines in jet propulsion history. The engine powered the U.S. Air Force (USAF) F-5 and was used for air defense in more than 25 countries worldwide. The commercial variant powered the first Learjet business jets. The J85 has powered USAF trainer aircraft since the early 1960s.

In recognition of his knowledge, innovation, and leadership, Jim was chosen in 1962 by Gerhard Neumann (NAE 1970), the division’s top executive, to head GE’s Advanced Product Planning Operation (APPO). It was a special time in GE’s aviation history. APPO identified new engine requirements, opportunities, cycle and architecture, and long-range plans. The group was staffed with senior personnel who had already made lasting marks at GE. The operation played a central role in defining a road map for the large turbofan engines that drove the company’s commercial aviation business in the 1960s and 1970s. Because of APPO’s contributions, GE remains one of the largest jet engine manufacturers in the world today.

Of specific note is the TF39 high-bypass engine configuration. In support of a large military transport, one of Jim’s APPO teams proposed an unprecedented 8:1 bypass ratio engine with a unique arrangement of a 2-stage fan, which became the TF39. A half-scaled demonstrator was tested in 1964, and the full engine was designed and tested in the late 1960s. As aircraft manufacturers leveraged development work on large military airframes at the time, new wide-body commercial jets were introduced, requiring large high-bypass engines. Jim’s team defined TF39 derivatives for these commercial jets (the CF6 family), making large commercial turbofans a reality in the 1970s.

In the late 1960s, Jim directed his APPO team to undertake the preliminary design of the GE13, a high-bypass engine in the 20,000-pound thrust class, utilizing the core of the supersonic B-1 bomber. The anticipated market was mid-sized, single-aisle commercial planes. At that time, NASA-supported engine programs were focused on reducing noise and improving fuel burn, and the GE13 targeted those goals. In addition, SNECMA (today’s Safran Aircraft Engines), a French manufacturer, was focused on the same goals and sought to create a 50/50 partnership. Out of these efforts and much negotiation, a new company arose, CFM International. Its first engine was the CFM56-2, which was based on the two-frame architecture of the GE13 and its military core. Derivative engines evolved, all based on this architecture, and the CFM56 became the best-selling jet engine in the world: More than 33,000 have been delivered to date.

Jim’s team won a NASA contract in the mid-1970s for the Energy Efficient Engine, which was designed, built, and successfully tested in 1984. This engine’s advanced technology became part of GE’s new centerline engine, the GE90, with derivatives and scaled versions entering service from 1995 through today. The GE90 family is the world’s largest and most powerful jet engine and powers the Boeing 777 family.

Jim became vice president of military programs in 1978 until his retirement. He oversaw all of GE’s military products, from small helicopter engines to the large fighter and bomber engines. He managed GE’s underdog victory in what was known at the time as the Great Engine War, obtaining USAF support for GE’s F110 engine on the F-15 and F-16 aircraft.

Jim’s legacy — at GE and in the jet propulsion world — is that of a champion of new and enduring technology. His leadership in a growing propulsion industry is measured by the longevity of the engines he oversaw. For example, the USAF C-5 transport today is powered by a fourth-generation variant of the original TF39. For the CFM program, the military continues to fly KC-135R aircraft with CFM56-2 engines first produced by CFM in the late 1970s. CFM56 engines have powered Airbus A320s and Boeing 737s since the 1980s. And the J85 engine is nearing 85 years in military service!

Jim retired in 1985 after 39 years at GE. He never lost his desire to advance the state-of-the-art in the aviation business. Well into his nineties, he was still sending his signature “Krebs-O-Grams” — lengthy, single-spaced memos — to GE managers.

Jim stayed in touch with Northwestern’s McCormick School of Engineering, serving on the advisory council and funding both the James N. and Margie M. Krebs professorships and a lecture hall in the McCormick Education Center. During his retirement years, he collected Native American contemporary art, some of which is on display at the Museum of Fine Arts Boston and the Peabody Essex Museum in Salem, Massachusetts. Jim was a lifelong photographer who compiled his shots into self-published books. He loved day sailing and spent summer weekends racing.

Jim was elected to the National Academy of Engineering in 1982. He was inducted into the GE Aviation Propulsion Hall of Fame in 1989. In 1992, Jim received the American Institute of Aeronautics and Astronautics Reed Aeronautical Award for his work on high-bypass turbofans.

In December 1945, Jim married Margie “Mitch” Mitcheson, whom he had met in freshman English class at Northwestern. They raised four children and were married for 60 years. In 2006, following Mitch’s death, Jim married Mimi May Nolte McClellan, a childhood friend from Duluth, Minnesota. Mimi died in 2019. Jim is survived by his children, Leslie, David, Stephen, and Mark; and six grandchildren.