This book is the first of a series of volumes that cover the topic of aerospace actuators following a systems-based approach. This first volume provides general information on actuators and their reliability, and focuses on hydraulically supplied actuators. Emphasis is put on hydraulic power actuators as a technology that is used extensively for all aircraft, including newer aircraft. Currently, takeovers by major corporations of smaller companies in this field is threatening the expertise of aerospace hydraulics and has inevitably led to a loss of expertise. Further removal of hydraulics teaching in engineering degrees means there is a need to capitalize efforts in this field in order to move it forward as a means of providing safer, greener, cheaper and faster aerospace services. The topics covered in this set of books constitute a significant source of information for individuals and engineers seeking to learn more about aerospace hydraulics.