RELIABILITY AND MAINTAINABILITY EVALUATION OF ROTOR SYSTEMS

The Army is currently investigating several advanced rotor systems for helicopters which are expected to provide significant structural and aerodynamic improvements and which should also offer similar improvements in reliability and maintainability (RAM). Many of the designs are being subjected to performance evaluations utilizing both analytical assessments and hardware tests and are, indeed, indicating significantly improved flight performance. However, little effort has been expended in developing assessment techniques of the RAM characteristics of these concepts. This is of concern because it is expected that the RAM characteristics and their ultimate effect on operational cost and effectiveness will have a major impact on selecting a rotor concept for application to Army helicopters. The purpose of this work is to develop a standardized RAM evaluation methodology for use by the Army to assess rotor systems. The approach requires performing quantitative and qualitative assessments. The quantitative is concerned with the statistical quantities of mean time between failure (MTBF), mean time between removals (MTBR), maintenance man-hours per flight hour (MMH/FH), and mean time to repair (MTTR) as well as maintenance support costs. The qualitative is concerned with the failure effects, repair complexities, inspection criteria, and helicopter battle damage repair procedures. In the fall of 1981, a report will be published outlining the process in detail with examples of its use.