Rotorcraft Transmission System HUM Requirements Derived from Design Safety Analysis

Abstract

Design safety analysis provides a sound basis for determining the functional requirements of a rotorcraft health and usage monitoring (HUM) system for flight safety purposes, since it considers the vulnerability to catastrophic failure of every component in each safety-critical system. The process thereby identifies the components that may be dependent upon effective monitoring systems in order to achieve the system safety objectives. From the analysis of a new transmission system design, examples are given of component potential failure modes that either (a) are expected to be preventable by direct design action, or (b) will require the additional support of indirect action such as HUM provisions. Many of these examples are expected to be applicable to new rotorcraft transmission designs in general. A brief review of analysis procedures appropriate to rotorcraft transmission systems is included.