Helicopter Flight Dynamics, 3rd Edition

Preface to Third Edition

Long ago, in the late 1960s, the author was introduced to a clever mathematical method for explaining and predicting the loss of stability that can occur when pilots increase their control gain to reduce the excursions in aircraft flight path, attitude, or speed. The clever part of the approximation came from a recognition that, although both pilot and aircraft dynamics might be complex – multidimensional and nonlinear – in combination, a new dynamic emerged that could be represented by a relatively simple, linear, model of low order. Effectively, the pilot action separated the combined system dynamics into two or more subsystems. In the extreme case of very high pilot gain, the controlled states become fully constrained while the uncontrolled states form into new modes with the potential risk of instability. The author's understanding of flight dynamics was in its infancy in 1968, but this technique enabled physical interpretations that became one of the foundations on which his continued learning would be based − a foundation of analytic approximations that provide insight into why and how things happen the way they do.

The publication on this research (Ref. 4A.6), titled The Strongly Controlled Aircraft, applied Ronald Milne's theory of weakly‐coupled systems; Ronald was the author's supervisor for his final‐year undergraduate project. Many engineers have influenced the author's thinking and career journey but none so significantly as Ronald Milne, ...