This book presents general problems of Automatic Control Theory as a base of aircraft control systems research and design. It consists of two parts: Continuous Control Systems and Digital Control Systems. Problems of mathematical modeling, stability, accuracy, synthesis, etc. both for continuous and digital control systems are included. For this purpose the time- and frequency-domain approaches are utilized. Some design and compensation methods of the dynamic systems are presented. In spite of the wide known issues related to these problems there are few complete works concerned with computer application for analyses and design of the control systems.