This is an in-depth yet easy to read book; technical yet understandable. It is an excellent supplement to the primary helicopter textbook or a primer for those first considering earning a helicopter pilot's rating.

From Principles of Helicopter Flight Back Cover: Principles of Helicopter Flight explains the complexities of helicopter flight in clear easy-to-understand terms. Helicopter pilots need to thorouly understand the consequences of their actions and base them on sound technical knowledge. This textbook provides the background knowledge explaining why a helicopter flies and, more importantly, why sometimes it doesn't. It examines aerodynamic factors associated with rotor stalls, mast bumping, wind effect, and many other important aspects which pilots must know. Principles of Helicopter Flight is an excellent textbook on helicopter flight covering how and why helicopters fly, operational techniques in a variety of normal and special situations, helicopter aerodynamics and performance, and a bit on design and maintenance.