William Bousman

United States of America

 

1941-2025

William (Bill) G. Bousman was born on March 2nd, 1941. Bousman graduated from Cornell University with a B.S. in Mechanical Engineering in 1964. He enrolled in graduate school at the Massachusetts Institute of Technology (MIT) and examined supersonic gust loading in the Naval Supersonic Wind Tunnel at MIT under thesis advisor Eugene Covert. He received his S.M. in Aeronautics from MIT in 1966.

As a U.S. Army 2nd Lieutenant (Reserve Officer), Bousman was assigned to the Flight Standards Office, U.S. Army Aviation Systems Command (AVSCOM) in St. Louis, Missouri, in October 1966. He completed active duty in 1968 and remained in the Flight Standards Office as a civilian. He worked on qualification programs for the AH‐1G, CH‐47B and C, CH‐54B, and AH‐56A. During this period Bousman performed studies that became codified into the U.S. Army Hot Day Hover Criterion, combining climatology models and hover performance methodology.

In 1970, Bousman transferred to the U.S. Army Aeronautical Laboratory at Moffett Field, California. For the next 15 years, Bousman established himself as the world’s premier rotor dynamics experimentalist. Working closely in collaboration with Dr. Robert Ormiston and Dr. Dewey Hodges as his theoretical analysis counterparts during this period, Bousman established an unmatched record of unique experimental research projects into the dynamics and aerodynamics of hingeless helicopter rotor designs. His work quickly became the benchmark for validation of new blade structural dynamics models (i.e., Hodges and Dowell, CAMRAD, COPTER, and RDYNE). His small‐scale experimental research led to the first documentation of low-frequency dynamic inflow states. The existence of these aerodynamic states had been hypothesized/predicted up to this point but never demonstrated. Bousman was the first to document the existence of the lowest dynamic inflow states (indirectly measured in the rotor dynamics) in his very carefully controlled hover testing of high hinge offset model rotors.

Bousman’s research shifted to focus on rotor airloads in the mid‐1980s. This included analysis of flight airloads measurements on the French Puma helicopter with advanced tip shapes. This research considered not only vibratory airload generation but also the ability to predict specific aerodynamic phenomena with emerging blade and wake analysis models. He spent six months in 1986 at ONERA in Paris, France, looking at ways of estimating airloads from structural measurements. During this period, Bousman also served as co-project manager of the US Army Integrated Technology Rotor Program as new helicopter rotor hub types were being proposed and designed by US industry.

In 1992, Bousman joined the NASA/Army UH‐60A Airloads Program team at NASA Ames Research Center. This decision by Bousman and re‐direction of his research focus became a career‐defining moment for the second half of his technical career. Bousman’s technical leadership inspired and motivated the entire Airloads Program team of many junior, and mostly inexperienced, rotor test and research engineers. His patience, mentoring and teaching were exactly what was needed at that moment within the NASA and Army team. The resulting successful UH‐60A Airloads Program flight testing (1993 and 1994) and the wealth of test data, including the detailed airloads from the pressure‐instrumented blade with 242 dynamic transducers, was arguably the greatest contribution to rotorcraft aeromechanics during that time period.

Bousman’s analysis, understanding and interpretation of the NASA/Army UH‐60A Airloads Program data clearly stands head and shoulders above all other helicopter experimental test programs since the early 1990s. His seminal papers, often with junior coauthors, have described the complex, unsteady, three‐dimensional aerodynamics of edgewise flying rotors at the very limits of the rotor operating capability.

In 2001, following Bousman’s documentation and analysis efforts, the Rotorcraft Technology Center (NRTC) and Rotorcraft Industry Technology Association (RITA) organized the UH-60A Airloads Workshop and took up the challenge of mining the UH‐60A Airloads Program database to resolve the long-standing inability to accurately predict rotor airloads and structural loads. In 2003, that effort led to the breakthrough of successful full coupling of computational fluid dynamics (CFD) and computational structural dynamics (CSD) that became the basis for modern rotary-wing analysis and design.

Bousman retired in January 2003. However, he remained very active in his personal research as a US Army Emeritus Scientist and continued to be an active contributor to the UH‐60A Airloads Workshop. He was invaluable to NASA and the US Army in assisting in the preparation, conduct and initial data analysis of the 2010 UH‐60A Airloads Wind Tunnel Test in the 40‐by-80‐Foot Wind Tunnel of the National Full‐Scale Aerodynamics Complex (NFAC). His technical insight and judgment were critical to the formulation of the detailed wind tunnel test plans. Bousman also provided the government with “real‐time” assessment of data quality and data accuracy in this, the final phase of the UH-60A airloads research.

Bousman also contributed to the goals and initiatives of VFS in many ways. He was an active member of the VFS Dynamics Committee, including Chair. He formerly served as the general chairman of the technical committees, a position since replaced by six deputy directors. Bousman served as associate editor and as editor‐in‐chief of the Journal of the American Helicopter Society. He was also the technical chairman of the 1984 Second Decennial Dynamics Specialists’ Conference.

Bousman delivered the Society’s 2011 Alexander A. Nikolsky Honorary Lectureship, awarded to “an individual who has a highly distinguished career in vertical flight aircraft research and development and is skilled at communicating their technical knowledge and experience.” The Lecture was given at the 67th AHS Annual Forum and Technology Display at the Virginia Beach Convention Center, Virginia Beach, VA on Tuesday, May 3, 2011. His lecture, “Full-Scale Airloads Measurements — Extraordinary Costs,

Extraordinary Benefits,” was later featured in the Journal of the American Helicopter Society. Bousman is shown in the photo on the right, receiving the Nikolsky medallion and certificate from the 2010–2012 chair of the VFS Board of Directors, Phil Dunford, VP/GM of Boeing Vertical Lift.

Bousman dedicated more than 40 years of his career to analyzing and understanding critically important rotary-wing aeromechanics phenomena. He provided a new and clear understanding of hingeless helicopter rotor aeroelastic stability, unsteady 3D rotor aerodynamics, and dynamic stall by authoring more than 70 technical papers, reports and journal articles. He understood and interpreted the lessons learned from model-scale/full-scale wind tunnel testing and flight test. He provided critical personal and technical leadership to the NASA/Army UH-60A Program during the final phase of preparation and flight testing. He transformed it from a struggling enterprise into one of the most important successes in rotorcraft aeromechanics research and development.

Bill Bousman passed away near his home in Menlo Park, California, on April 21, 2025, just a few months after being diagnosed with stomach cancer. He was 84.

Society Updates: In Memoriam, Vertiflite, July/August 2025

 

Milestones associated with William Bousman
January 31, 1981	Test evidence for the existence of a rotor aerodynamic state is discovered
May 31, 1994	The initial report on the UH-60A rotor airloads flight test program is published