This ARP is a system guide for Engine Monitoring System (EMS) definition and implementation. This keystone document addresses EMS benefits, capabilities and requirements. It includes EMS in-flight and ground applications of people and equipment, and recommends EMS requirements that are a balance of selected benefits and available capabilities. This ARP purposely addresses a comprehensive EMS. The intent is to provide an extensive list of possible EMS design options. NOTE: - Section 3 describes an EMS. - Sections 4 and 5 outline benefits and capabilities that should be considered for study purposes to define EMS baselines for how much or how little engine monitoring might be required. - Section 6 provides implementation requirements that should be considered for an EMS after study baseline levels of EMS complexity are selected.