Development of a Realistic, Automated, & Efficient Reliability Development Growth Test for a Large, Distributed, Environmental Control System 1999-01-2165

The intent of a Reliability Development Growth Test (RDGT) is to maximize the initial reliability of newly designed equipment so that fewer failures occur in the field, and design changes to fielded equipment are averted. This improvement in initial fielded reliability is accomplished by revealing and eliminating core design flaws which result in failures normally distributed over the entire system life. To accelerate the exposure of faults, equipment is exposed to rapid cycling through severe conditions and environments, customized for the anticipated equipment application. Once revealed, rigorous pursuit and follow through in correcting a fault is applied to ensure that future failures due to the same design flaw do not occur.

A perfect RDGT is impossible to implement when real world constraints such as space, funding, and time are included in the mix. This is especially true for large, distributed systems operating under extreme conditions. However, the intent of RDGT can be met and necessary trade-offs made so that a successful RDGT can be completed. This paper presents the efforts involved with developing an effective RDGT design for a Helicopter Environmental Control System (ECS) while addressing real world issues, and is intended as a reference guide for other test development efforts. This test is unique in that it is being performed on 88 components assembled into an integrated system approximating a large aircraft ECS. Difficulties encountered, decisions and compromises made while establishing the Reliability Development Growth Test design for helicopter ECS are presented. Selection of environmental test equipment, the environment each component is subjected to, system operational modes, layouts and automated versus manual test control are described. The evolution of the design is discussed, which includes an overview of the lessons learned during the establishment of the RDGT.

The end result of the RDGT development is a design with automated control of test equipment and the system under test, that incorporates power cycling, testing at supply voltage extremes, temperature cycling, vibration and operation in various system modes, as well as a number of lessons learned. Testing has been initiated, failures have occurred, reliability improvements have been initiated, and testing is scheduled for completion in December of 1999.