Acknowledgments

This book is the product of an opportunity afforded to me by the University of Maryland. The research and writing of the first edition of this book was unique experience and has lea to many lessons. It was gratifying to see how well the first edition was received, with feedback being received from the four comers of the world. The first edition took the best part of 2,500 desk hours, mainly during evenings and weekends and spread over three years. In this regard, I am forever grateful to my wife, Alice Marie Leishman, for her love and understanding, and for providing me continuous support where writing, proofreading, drawing figures, and plotting graphs meant many long nights and all too short weekends. Preparing this second edition required about 1,300 desk hours, spread over about eighteen months, but ultimately even with the benefit of experience and hindsight, it proved to be no lesser a task than the first edition.

Special acknowledgment is due to a great many people, both on and off the University of Maryland campus. I am most grateful for the council of my colleagues at the University of Maryland, Professors Alfred Gessow (now deceased), Inderjit Chopra, Roberto Celi, James Baeder, Christopher Cadou, and Dr. Vengalattore Nagaraj. Professor Gessow had read substantial parts of the first edition and offered many useful suggestions for improve­ment. Before he passed away in May of 2002, Alfred Gessow and I had many significant discussions about the autogiro and the role it played in the fundamental development of the helicopter, from the point of view of both engineering theory and practice. Chapter 12 in this second edition reflects the spirit of our discussions, and I dedicate this chapter to his memory. A1 Gessow’s knowledge and first-hand experience working at NACA Langley during the 1940s and 1950s in the technical development of early helicopters was also invaluable to me. Professors Inderjit Chopra and Roberto Celi provided good suggestions for Chapter 4 and kindly allowed me to use some of their own course material on blade motion and rotor trim. Professor James Baeder read Chapter 8 on unsteady aerodynamics and Chapter 14 on computational methods for helicopter applications, and I am grateful to him and his students for their willingness to help me with figure preparation. Dr. Chris Cadou read the revised parts of Chapter 1, and I enjoyed our engaging conversations on early engine development and the history of aircraft technology in general. Dr. Nagaraj read the revised Chapters 5 and 6 and offered more good suggestions on helicopter design issues.

I am particularly grateful to Dr. Richard Brown of Imperial College at the University of London who is responsible for a substantial part of the writing in Chapter 14 of the second edition. This chapter on computational methods proved to be one of the most satisfying to write, although it took the longest amount of time out of the four new chapters with numerous iterations required to finally define the appropriate content. Dr. Brown also provided useful feedback for improvement on the other three new chapters.

I am indebted to my graduate students at the University of Maryland, both past and current, who have both directly and indirectly contributed to the content of both the first and second editions of this book. The current members of my research group, namely Shreyas Ananthan, Sandeep Gupta, Arun Jose, Robin Preator, and Manikandan Ramasamy,

enthusiastically read many parts of the second edition and offered useful advice and con­structive criticism from a student’s perspective. Many of the students in my classes proof­read drafts of revised chapters, and I am particularly grateful to the group of Moble Benedict, Brandon Bush, Mamta Jangid, Nitin Gupta, Vinit Gupta, Vinod Lakshminarayan, and Eric Schroeder for their careful reading and checking of equations. Sandeep Gupta did much to help me refine the material in Chapter 13 on wind turbines. Yik-Loon Lee and Karthikeyan Duraisamy spent time with me explaining the intricacies of ad vanced computational meth­ods and grid generation techniques, and I appreciate them lending me some of the results from their own research for Chapter 14 in the second edition of this book. I am grateful to Dr. Mahendra Bhagwat (now at US Army/NASA Ames) for running the prescribed – and free-vortex wake solutions and for allowing me to adapt his analysis of the tip vortex aging problem in Chapter 10. Dr. Preston Martin (also now at US Army/NASA Ames) took several of the rotor wake visualization images for Chapter 10 and did much to help me find references and other material on airfoils and airfoil design for Chapter 7. Jacob Park (now at Bell Helicopter Textron) ran several of the rotor wake calculations, sifted through lots of experimental results on rotor wakes, and organized the data for a good number of the figures in Chapter 10. Gregory Pugliese read many of the draft chapters for the first edition, made endless trips to the library to hunt down reports, cross checked more than several hundred references, and helped me turn more than a few of my many crude sketches into professional looking figures. Other former students who have directly or indirectly contributed material used in this book include Dr. Ashish Bagai (Sikorsky), Dr. Peter Bi (US Navy NSWC), Dr. Gilbert Crouse (Da Vinci Technologies), Dr. Berend van der Wall (DLR), Mark Daghir (Boeing), Erwin Moederesheim, Joe Tyler, Alan Coyne (Sikorsky), Col. Keith Robinson (US Army), Greg Pugliese, and Dan Griffiths (Sikorsky). A special thanks to Dr. Ashish Bagai and Dr. Mahendra Bhagwat for their generosity in allowing me to adapt some of their results and graphics for Chapter 10. Dr. Peter Bi provided me with good feedback on the new content included in Chapter 11.

Off the university campus there are a great many people and colleagues who provided advice during the writing of both the first and second editions. I remain indebted to the reviewers of my original book proposal, who were able to make good suggestions on what should be included and what should be left out, particularly Prof. Edward Smith and Dr. Andrew Lemnios. The draft second edition saw many more critical eyes, and I was humbled by the care and thoroughness that each reviewer took over their respective chapters. All of their comments were duly taken into account and they led to a better book as a result. Many other people made suggestions on the originally published text or recommended topics for the second edition. Some colleagues read draft copies of the new chapters, while still others sent me hard-to-find reports, computer files of experimental data, figures, photographs, or other information that was used or adapted for the book. In particular, I appreciate the contributions of Douglas Baldwin, Tom Beddoes, Dr. John Berry, Dr. Bill Bousman, Dr. Richard Brown, Marshall Buhl, Tim Candsdale, Dr. Mark Chaffin, Prof. Muguru Chandrasekhara, Dr. Bruce Chamov, Dr. Colin Coleman, Roger Connor, Shawn Coyle, Prof. George Done, Lee-Jay Fingersh, Prof. Peretz Friedmann, Susan Gorton, Dr. Richard Green, David Groen, Jay Groen, Robert Hansford, Franklin Harris, Jennifer Henderson, Michael Hirschberg, Dr. Stuart Houston, Dr. Wayne Johnson, Markus Krekel, Andrew Line, James Mayfield, Dr. Kenneth McAlister, Dr. Patrick Moriarty, Dr. Khanh Nguyen, James Mayfield, Dr. Reinert Muller, Prof. Gareth Padfield, John Perry, Prof. Ganesh Rajagopalan, Dr. Rex Rivolo, Dr. Scott Schreck, Prof. Michael Sellig, Sergei Sikorsky, Dr. Roger Strawn, Prof. Edward Smith, Dr. James Tangier, Dr. Chee Tung, Dr. Hal Youngren, Dr. Daniel Wachspress, and Dr. David Wood. A great number of people, too numerous to mention, sent me letters or e-mail about the first edition giving me comments for improvement, pointing out remaining typographical errors, or suggesting areas for further clarification. Instructors who have used the book and the solutions manual for their classes gave me excellent feedback, which was duly taken into consideration. As they will see in this second edition of the book, most of their suggestions were enthusiastically incorporated and their critiques are most gratefully acknowledged.

Thanks are due to the helicopter companies, who were kind enough to send me pho­tographs of their various helicopters or give me permission to publish those that I found in publicity materials and on their web sites. In particular, I acknowledge Madelyn Bush and Jack Satterfield of Boeing Helicopters, Kevin Hale of Bell Helicopter Textron, David Long of Kaman Aircraft Corporation, Eurocopter, and the Public Affairs Department at GKN Westland (now Agusta-Westland). Other photographs were obtained from NASA, the National Renewable Energy Laboratory, Sandia National Laboratories, and the photo archive at Patuxent Naval Air Station. I am also grateful to the staff of the National Air and Space Museum for giving permission to publish some of the historical photographs included in Chapter 1 and to Brian Riddle of the Royal Aeronautical Society in London for finding some early published papers and reports on autogiros and helicopters.

I want to express my sincere gratitude to the staff at Cambridge University Press for their help and support during the writing and publication process of both the first and second editions of this book. Florence Padgett was the editor for the first edition, and my thanks extend also to Ellen Carlin for her help with the various editing and production issues. Peter Gordon was the editor for the second edition, and I am grateful for his enthusiastic support and encouragement throughout. Finally, my thanks again to the staff at TechBooks for their help in the production of the second edition of this book.