This book provides readers with a design approach to the automatic flight control systems (AFCS). The AFCS is the primary on-board tool for long flight operations, and is the foundation for the airspace modernization initiatives. In this text, AFCS and autopilot are employed interchangeably. It presents fundamentals of AFCSautopilot, including primary subsystems, dynamic modeling, AFCS categoriesfunctionsmodes, servosactuators, measurement devices, requirements, functional block diagrams, design techniques, and control laws.