MIL-STD-1629-RevA - Barringer and Associates, Inc.

MT T,-STD-I(I?9Ac. Level C - Occasional. An occasional probability ofoccurrence during item operating time interval.Occasional probability may be defined as a singlefailure mode probability of occurrence which is morethan 0.01 but less than 0.10 of the overall probabilityof failure during the item operating time.“d● Level D - Remote. An unlikely probability of occurrenceduring item operating time interval. Remote probabilitymay be defined as a single failure mode probabilityof occurrence which is more than 0.001 but less than0.01 of the overall probability of failure duringthe item operating time.e. Level E - Extremely Unlikely. A failure whoseprobability of occurrence is essentially zero duringitem operating time interval. Extremely unlikelymay be defined as a single failure mode probabilityof occurrence which is less than 0.001 of the overallprobability of failure during the item operatingtime.3.2 Quantitative approach. The failure rate data source usedfor the quantitative approach shall be the same as that used for theother reliability and maintainability analyses required by contract.When other analyses are not required by contract or a failure rate datasource has not been specified by the procuring activity, failure ratesand failure rate adjustment factors (e.g. , enVirO~enta~ and quality r-factors) shall be derived as follows:a. MIL-HDBK-217 shall be the primary source of failurerate data for electronic par~s. Both the basefailure rate and all failure rate adjustment factorsshall be identified.b. When parts are similar to those listed in MIL-Hl)BK-217, base failure rates shall be selected from FfIL-HDBK-217 and shall include other adjustment factors,such as special quality :r-factors,as may be requiredto modify the MIL-HDBK-217 data for applicability tothe particular part.c. Failure rate data for parts not covered bv ?l_II.-l{D13K-217 shall be selected from alternative data sourc(’~.3.2.1 CA worksheet. Items in this section and related subsectionsapply when a quantitative approach has been specified, The calculationof a criticality number or assignment of a probability of occurrencelevel and its documentation are accomplished by completing the columnsof the approved CA worksheet. An example of a CA worksheet format isTASK 10224 November 1980