TABLE OF CONTENTS In the preceding chapters, we have studied the airplane stability, dynamics, and control with the assumption that the longitudinal and lateral-directional motions of the airplane could be decoupled and studied separately. With these assumptions, the problem of airplane dynamics and control was linearized so that the analyses methods of linear systems could be used. For example, the response of the airplane to a 2-deg elevator input would be exactly double that for a 1-deg elevator input. Also, there was no cross coupling between the longitudinal and lateral-directional degrees of freedom. In other words, operating the rudder or the ailerons would not generate any pitching motion or a change in the forward speed or a change in the angle of attack. Similarly, moving the elevator would not generate any sideslip, rolling, or yawing motion. As a consequence, one had to solve the problem for only one set of control inputs and, using those solutions, the response to any other combination of control inputs could be quickly deduced. Furthermore, the response to combined control inputs was the sum of the responses to individual control inputs. In other words, the flight dynamicist had to solve the problem only once. Then, he had it solved for all other cases. What could be simpler?
However, this type of simple approach cannot be used for problems in which the longitudinal and lateral motions are coupled. Such coupling occurs because of either inertial cross coupling or aerodynamic nonlinearities. The examples of the first category are...
