Field Data as a Correction of Mil-Handbook Estimates

The MIL-HDBK-217 represents the most serious attempt of giving an exhaustive answer to the problem of calculating the failure-rates of electronic equipments. It plays a central role in designing reliable electronic systems, in deciding whether or not a given reliability goal is achievable, in comparing alternative design-solutions and so forth. The degree of up-dating of the handbook has been kept at satisfactory levels by subsequent releases, the latest version (217 D) [1] has been issued in1982. Some criticism has been raised against the MIL-HDBK in that its estimates are felt to be too pessimistic by reliability analysts, operational experience is invoked to support such a statement. Anyway, no matter how close the MIL-HDBK is to the reality, it still remains the only available standard for measuring the reliability of electronic devices, the other proposed models [2], [3] being not world-wide-accepted. The premise above does not lead to rejecting operational experience as a corrective of MIL-HDBK, field data do contain information we are not allowed to ignore, this information can be profitably used in the frame of MIL-HDBK itself as we show in the sequel.