Tins book originally was intended to be a modest revision of my earlier work, Dynamics 0/ Flight—Stability and Control, published in 1959. As the task progressed, however, I found that the developments of the intervening decade, and the shift in my own approach to the subject, made a "modest revision" impossible. Thus this volume is virtually a new book, with organization and content substantially different from its predecessor. Two principal factors caused this change: (1) the proliferation of vehicle types and flight regimes, particularly hypersonic and space flight, and (2) the explosive growth of machine computation.

The first factor compelled me to abandon the long-standing simplifying assumption that the Earth's surface could be represented by a plane fixed in inertia] space, and to include in the mathematical model all the complications that arise from the curvature and rotation of the Earth.

The second factor had two profound effects. One was that since we are no longer confined to primitive computation methods, it is commonplace nowadays in industry to construct highly sophisticated mathematical "simulations" of systems for the purpose of carrying out research and design studies. The emphasis on simple approximations is thereby reduced, and the need to set up accurate (even though complicated) mathematical models increased. The other effect of the computing revolution (on me at any rate) has been to produce a shift to modern algebra (vector/matrix analysis) as the basic tool for analysis. This is ideally suited to digital computation. A tertiary effect lias derived, from the ready availability to me of sophisticated computing machinery, which I have used for the computation of many numerical examples, to illustrate both typical results and how to apply the theory.

B.Etkin Dynamics of Atmospheric Flight 1972