Why Design for Maintainability?

The relationships among down time (a system-maintainability measure), time between failures (a system-reliability measure), equipment availability, number of equipments, number of on-call technicians, and system-readiness reliability are developed under the assumption of constant failure and repair rates. Design trade-off between reliability and maintainability is shown to be feasible with resulting reduction in both design and operating costs. A technique for specifying combined reliability, maintainability, and availability constraints to manufacturers is reported which allows the latter a great deal of design flexibility in meeting operational requirements at least cost. Finally, the need for research to establish the quantitative effects of maintainability-design practice upon down time is explored.