Flügge-Lotz conducted pioneering studies of aircraft wing lift distribution and made significant contributions to modern aeronautic design. She served as an advisor to the National Aeronautics and Space Administration (NASA) as well as to German and French research institutes. During an era when there were few women engineers, Flügge-Lotz was named the first female professor in Stanford University's College of Engineering. Describing her 20-year career at Stanford, John R. Spreiter, and Wilhelm Flügge wrote in Women of Mathematics, "her work in fluid mechanics was directed toward developing numerical methods for the accurate solution of problems in compressible boundary-layer theory. She pioneered the use of finite-difference methods for such purposes and was quick to employ the emerging capability of computers to deal with the large computations inherent in the use of these methods . . . She applied these methods to solve a series of important and previously unsolved problems in compressible boundary-layer theory."
Flügge-Lotz was born on July 16, 1903, in Hameln, Germany. Her father, Oskar Lotz, was a journalist and amateur mathematician. Her mother, Dora (Grupe) Lotz, came from a family that had been in the construction business for generations. Visiting the firm's building sites, in addition to watching Count von Zeppelin conduct airship tests, fueled her interest in engineering. When she was a teenager, Flügge-Lotz's father was drafted into the German army during World War I. To help support her mother and younger sister, she began tutoring fellow students in mathematics and Latin. She continued this work after her father returned from the war in ill health. After graduating from high school in 1923, she studied applied mathematics and engineering at the Technical University of Hanover. In 1929, she earned a doctorate in engineering. Her dissertation explored the mathematical theory of circular cylinders and heat conduction.
Wins Supervisory Position
Opportunities for women in engineering were limited in the 1930s, and Flügge-Lotz had difficulty finding a level of employment that was commensurate with her education. When she began working at the Aerodynamische Veruchsanstalt (AVA) research institute in Göttingen, she spent half of her time as a cataloguer. Perceptions of Flügge-Lotz's abilities changed dramatically after she solved a problem that had stymied Ludwig Prandlt and Albert Betz, two leading aerodynamicists at the AVA (Betz was the director of the institute). A decade earlier, Prandlt had developed a differential equation for his theory about the lift distribution of an airplane wing. However, he had made little progress in solving the equation. Flügge-Lotz tackled the problem and solved the equation for the general case. Continuing to work with the equation, she developed it so that it had widespread practical applications. Her cataloguing days ended, and she was named supervisor of a group of engineers who researched theoretical aerodynamics within the AVA.
In 1931, Flügge-Lotz published a technique she had developed for calculating the lift distribution on aircraft wings. Later dubbed the "Lotz method,"it is still used today. Continuing to delve into wing theory, she added to the knowledge base of the effects of control surfaces, propeller slipstream, and wind-tunnel wall interference.
The course of Flügge-Lotz's career changed in 1938 when she married Wilhelm Flügge, a civil engineer from Göttingen. The husband and wife team went to work at Berlin's Deutsche Versuchsansalt für Luftfahrt (DVL), a German agency similar to NASA. Beginning work as a consultant in flight and aerodynamics, Flügge-Lotz conducted groundbreaking research in automatic control theory, especially pertaining to on-off controls. Subsequently, these controls came into widespread use because they were reliable and inexpensive to build.
In 1944 Flügge-Lotz and her husband moved to the small town of Saulgau, where they continued to work for the DVL. After Germany's defeat in World War II, the town and its surrounding area became part of France. The Flügges joined the staff of the French National Office for Aeronautical Research (ONERA) in Paris. Flügge-Lotz headed a research group in theoretical aerodynamics and continued her work in automatic control theory. In 1948 the couple accepted positions at Stanford University in California.
Flügge was hired as a professor at Stanford. Nepotism regulations prohibited his wife from holding a similar position, so she was hired as a lecturer. Flügge-Lotz developed graduate and undergraduate courses in mathematical hydro- and aerodynamics and automatic control theory. She also designed a weekly seminar in fluid mechanics that was attended not only by Stanford students but also by young engineers from the National Advisory Committee for Aeronautics--NASA's predecessor. The seminar has continued to serve as an important forum for faculty and students of varying specializations to share their findings. The Flügges had no children, but they frequently invited their students to their home for dinner parties with other faculty members and visitors.
Advances Automatic Control Theory
In addition to teaching, Flügge-Lotz also continued her research while at Stanford. She applied numerical methods and analog computer simulations to boundary layer problems in fluid dynamics and continued studying automatic control theory. Her 1953 book, Discontinuous Automatic Control, presented the theoretical foundation for using discontinuous controls for flight paths of missiles. Specifically, the problem concerns a missile in flight encountering some force (such as a wind gust) that causes it to begin oscillating. An automatic control mechanism could be used to counteract the vibration. Flügge-Lotz was particularly interested in discontinuous controls, which could be activated only when needed. A simple analogy is a furnace thermostat; rather than continuously adjusting the amount of heat generated by a furnace, the thermostat simply turns the furnace on when needed and off when the proper temperature is achieved. The fact that discontinuous automatic controls were simpler and cheaper to make than continuous-control mechanisms made them particularly desirable for one-time use in missiles that would crash after flight.
Flügge-Lotz's second book, published in 1968, presented techniques for optimizing discontinuous automatic controls for objects such as airplanes, rockets, and satellites. In the preface to Discontinuous and Optimal Control, she noted that optimal control theory literature was difficult for practicing engineers to read because it was so mathematically rigorous. "The purpose of this book," she wrote, "is to acquaint the reader with the problem of discontinuous control by presenting the essential phenomena in simple examples before guiding him to an understanding of systems of higher order."
Flügge-Lotz attended the First Congress of the International Federation of Automatic Control in Moscow as the only female delegate from the United States. Upon her return from that congress, Stanford University finally offered her a professorship in 1961. In fact, she was granted that rank in two departments--aeronautics and astronautics, and engineering mechanics. She retired from teaching seven years later. Flügge-Lotz continued her research activities, however, studying heat transfer and the control of satellites. Her retirement years were physically difficult, due to progressive arthritis.
The Society of Women Engineers gave Flügge-Lotz its Achievement Award in 1970. The American Institute of Aeronautics and Astronautics (AIAA) chose her to deliver the prestigious annual von Kármán Lecture in 1971 and elected her as its first woman fellow. The University of Maryland awarded her an honorary degree, citing "contributions [that] have spanned a lifetime during which she demonstrated, in a field dominated by men, the value and quality of a woman's intuitive approach in searching for and discovering solutions to complex engineering problems." Flügge-Lotz died a year later, on May 22, 1974.
This is the complete article, containing 1,200 words
(approx. 4 pages at 300 words per page).
