TABLE OF CONTENTS [1]Essential to the analytical processes of flight control system design is a mathematical model of the subject aircraft configured in an appropriate way. Since a significant part of the design process is concerned with control law development, in which the mathematical tools of control engineering play a leading role, then the most appropriate aircraft model is that described by the classical small-perturbation equations of motion. By definition, the aircraft model described in this way is mathematically linear, hence it is easily manipulated algebraically, longitudinal and lateral-directional motion is decoupled and the six degree-of-freedom equations split into two groups, each describing three degrees of freedom. The most important advantage associated with the linearised equations of motion is the relative ease with which they may be analysed to reveal a complete description of the basic flight dynamics of the aeroplane.
It is a straightforward matter to arrange the linearised equations of motion in a state-space formulation which greatly facilitates the use of matrix methods for their solution and subsequent analysis. Indeed, the steps in this process are set out briefly in the following paragraphs. The critical importance of this flight-dynamics analysis as a precursor to control law design cannot be stressed enough. It essential for every flight control system designer to build a system on the secure foundation which comes from a sound appreciation of the basic flying qualities of the aeroplane. It is just not good enough to describe the aircraft state equation as the...
