ROTORCRAFT TRANSMISSION-SYSTEM HUM REQUIREMENTS DERIVED FROM DESIGN SAFETY ANALYSIS

Design safety analysis provides a sound basis for determining the func tional requirements of a rotorcraft health and usage monitoring (HUM) system for flight safety purposes, since it considers the vulnerabilit y to catastrophic failure of every component in each safety critical s ystem. The process thereby identifies the components that may be depen dent upon effective monitoring systems in order to achieve the system safety objectives. From the analysis of a new transmission system desi gn, examples are given of component potential failure modes that eithe r (a) are expected to be preventable by direct design action, or (b) w ill require the additional support of indirect action such as HUM prov isions. Many of these examples are expected to be applicable to new ro torcraft transmission designs in general. A brief review of analysis p rocedures appropriate to rotorcraft transmission systems is included.