Flight dynamics create important research problems in the process of helicopter design. They involve advanced design ideas and engineering technology theories. This book concerns flight theory and research methods for helicopter flight science and technology. The contents include the fundamentals of rotor aerodynamics, helicopter trim, helicopter stability and control, and helicopter performance analyses. The book also lokks at the kinematics, dynamics, control, and aerodynamics of the helicopter during maneuvering flight. With an emphasis on the physical concepts, the characteristics of rotor flapping, theoretical analyses and numerical simulation methods for helicopter flight mechanics are detail described in detail. The book is primarily intended for senior undergraduates and postgraduates who major in aerospace engineering. It is also a good reference book for helicopter engineers interested design and operational engineering. It lays a foundation for the study of helicopter aeromechanics.