In 1950, a young engineer named Walter R. Evans introduced a revolutionary graphical method for analyzing feedback control systems. His paper, “Control System Synthesis by Root Locus Method,” transformed the practice of control engineering and became one of the most influential contributions in the history of the field.
In Into Stability, Walter’s son, Gregory Walter Evans-himself an engineer-tells the untold story behind that breakthrough. Drawing on family archives, correspondence, and rare photos from aerospace history, Evans reconstructs the inventive process that led from wartime analog computers to the elegant logic of Root Locus. He reveals how his father’s inventive spirit was shaped by mentors at Washington University, by the entrepeneurial environment at North American Aviation, and by a lifetime devoted to clarity, precision, and education.