Howard "Pat" C. Curtiss, Jr. dies
Professor Howard C. (“Pat”) Curtiss. Jr.
Robert Stengel, September 20, 2012
Howard C. "Pat" Curtiss, Jr. was the Mechanical and Aerospace Engineering Department's central figure in helicopter flight dynamics and control for over forty years. During that time, his accomplishments within and outside the university were both broad and deep.
Professor Curtiss was responsible for the design and construction of Princeton's 750-ft-long Dynamic Model Track, and he directed all experimental activities at the track for several decades. The "Long Track" was essentially an inverse wind tunnel -- aircraft models moved through still air, allowing an accurate portrayal of the boundary layer in ground effect. Numerous models of helicopters and V/STOL aircraft were tested over the years, the XC-142 and Sikorsky's ABC helicopter among them. The track operated in two modes: the model could be driven along a programmed path in and out of ground effect, or the model could fly freely, with the mount servoed to follow the model's motion without disturbance. Thus, this facility was uniquely able to collect aerodynamic data that could not be obtained in a conventional wind tunnel.
Over the years, Pat, whose nickname derived from his birth on St. Patrick’s Day, did not merely collect data, he reported on it and made insightful analyses of its consequences. Pat advised over three dozen graduate students in the pursuit of his research, many of whom advanced to the top of their professional fields. These include James Adamson (astronaut, later group vice president and general manager, Lockheed Martin), Andrew Kerr (director, US Army Aeroflightdynamics Laboratory), Alain Cassier (director, Eurocopter France), J. Victor Lebacqz, John Burks, and Charles Morris (senior NASA administrators), and Sun Mao (professor, Beijing University). His research accomplishments include
• Fundamental aerodynamic and dynamic studies of the Vertol VZ-2, LTV XC-142, Bell X-22, Sikorsky Tilt-Wing Design, Sikorsky ABC helicopter, Grumman 698 VTOL Design, and several compound helicopter designs
• Introduction of the reduced Locke number concept currently used by industry in mathematical modeling of rotor aerodynamics
• Detailed experimental studies of the flow under a lifting rotor in ground effect, showing significant departures from prior theory and correlating with flight testing results
• First paper showing the importance of including the lag or in-phase degrees of freedom in the rotor blades for the design of stability augmentation systems
• First paper to show the importance of wake curvature on rotor blade motion and off-axis coupling
• First paper using flight test data to show that overly strong lag damping can decrease overall blade damping through aeroelastic effects
Professor Curtiss was co-author of the highly regarded book, A Modern Course in Aeroelasticity, currently in its third edition.
Professor Curtiss was in great demand as a lecturer throughout his career. For many years, he co-taught the widely acclaimed summer course, Helicopter and VSTOL Technology, with Barnes McCormick at the Pennsylvania State University. He gave numerous lecture series at the Nanjing Aeronautical Institute and was named an honorary professor of the institute in 1985. He presented short- and full-length courses on rotorcraft at all of the major U.S. helicopter manufacturing companies. He was a visiting research fellow at Glasgow University and the Technical University of Braunschweig. In 2000, Curtiss was selected to deliver the American Helicopter Society's Nikolsky Honorary Lecture, named for his Princeton Ph.D. thesis adviser, Alexander Nikolsky.
While Pat became a professor emeritus in 1998, he remained an active force in helicopter research and development. The titles of the two most recent Ph.D theses advised by Professor Curtiss are "High frequency directional axis dynamics of helicopters with ducted tail rotors" (Kothmann, 2000) and "The effect of rotor motion on the induced velocity in predicting the response of rotorcraft" (Keller, 1998). He played a central role in the development of composite main-rotor and tail-rotor blades for the Carson Helicopters retrofit to Sikorsky S-61 helicopters. With no modification to the powerplant, the main rotor provides a startling 2,000-lb increase in load-carrying ability, and it allows a significant increase in both cruising speed and range, challenging the performance of state-of-the-art helicopters. He consulted for many aerospace companies, including Sikorsky Aircraft, Agusta Helicopters, Kaman Aerospace, Piasecki Aircraft, Kellett Aircraft, Hamilton Standard, and Reflectone.
Pat attended conferences regularly here and abroad, presenting technical papers on his recent work. He was the Editor of the Journal of the American Helicopter Society from 1972 to 1974. Professor Curtiss wsa a graduate of Rensselaer Polytechnic Institute (B.S.) and Princeton University (M.A., Ph.D.). He was a Fellow of the American Helicopter Society and the American Institute of Aeronautics and Astronautics.
Some insight into the nature of the man is offered by the quotation from Anton Chekov with which Pat opened his Ph.D. thesis: "I believe in individuals. I see salvation in a few people living their own private lives -- Whether they be intellectuals or peasants, the power is in them. A man is never a true prophet in his own country; and the individuals of whom I speak play an obscure part in society. They are not domineering, but their work is apparent." It was not Pat's style to trumpet his accomplishments, yet he had a remarkable impact on helicopter science and technology during his career.