STABILITY PROBLEMS—AUTOMATIC CONTROLS

When the airplane is under the control of an AFCS the controls are neither fixed nor free. The control vector c, which fixes the control inputs of Fig. 4.4, are then deter­mined by the feedback loop that activates the control systems in response to the val­ues of the 12 dependent variables and inputs from other sources such as navigation, guidance, or fire control systems, and so on. Problems of this class are studied in Chap. 8.

RESPONSE TO CONTROLS

The effectiveness of an airplane’s controls is conventionally studied by specifying the variation of (Se, Sr, 8a, 8p) with time arbitrarily, e. g., a step-function input of aileron angle. The airplane equations of motion then become inhomogeneous equations for (u, v, w), (p, q, r), (в, ф, ф) with the control angles as forcing functions. Problems of this type are treated in Chap. 7.