A Management Guide To Reliability Predictions

Reasonably accurate reliability predictions can be made using the procedure contained in MIL-HDBK-217 if enough is known about such variables as the operational environment, equipment design, vendor manufacturing capability, and delivery schedule. There are times, however, when management or others need a more rapid, less costly procedure to assess either vendor-claimed reliability levels or estimate the probable reliability level of a piece of equipment. For more than a decade the author has compared operational performance of aircraft electronic equipment with equipment part count, and the results have been consolidated into a simplified prediction chart. This chart, though perhaps not as accurate as MIL-HDBK-217, can be very useful early in a program to assist in deciding whether additional efforts - such as part screening, failure-free burn-in, thermal imaging, reliability growth tests, or other reliability enhancement techniques - are necessary to achieve desired reliability levels. The chart is also useful in assessing the credibility of a prospective vendor's claim for unusually high reliability in equipment not yet proven in the operational environment.