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

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M1l.-STD-l629A50.4 FFfECA-maintainability information (task 103). The FMECAmaintainabilityinformation analysis is ut~l~zed to provide early designcriteria for test methods, accessibility, and repairability for the itembeing analyzed. This analysis is an extension of the FMEA and is dependentupon FMEA generated information; therefore, the FMECA-maintainabilityinformation analyses should not be imposed without imposition of theFMEA . The identification of how each failure will be detected andlocalized by the operational level maintenance technician will provideinformation for evaluating the effectiveness of built-in-test. Descriptionsof the basic organizational level maintenance actions required forfailure localization and correction will identify Potential accessibilityproblems permitting early design correction. Th; failure mode listingwhich is included on the completed worksheets should be utilized to.provide this required data for both the maintenance plan and logisticssupport analyses.50.5 DMEA (task 104). The DMEA provides essential inputs forthe vulnerability assessment of a weapon system to aid in the identificationof deficiencies and the evaluation of designs for enhancing survivability.Since the DMEA utilizes the failure mode information from the FMEA, itshould not be imposed without imposition of the FMEA. The DMEA, likethe initial FMEA, should be done early in the conceptual phase to providedata related to the capability of the conceptual weapon system design LOsurvive the effects of the specified hostile Lllreats. Development ofthis data before weapon system design configuration is finalized willprovide significant survivability benefits with minimal impact on costand schedule.50.6 Criticality number (C=) calculation example. Calculationof meaningful criticality numbers requires the use of specific failurerate and part configuration data. When part configurations are known,failure rate data can be obtained from the appropriate reliabilityprediction, field data from past systems of similar design and environment,?luse, or failure rate data sources such as MIL-HDBK-217. With knownfailure rates, the criticality number for an item is the number offailures of a specific type expected per million hours due to the item’sfailure modes under a particular severity classification as discussed jnTask 101. A failure mode criticality number, ~, for a particularseverity classification is given by the expression:(1)The item criticality number, CrJ under n particular sever~~y cl,lssifjcation,is then calculated by summing the Cm for each failure mode under thatseverity classification. This summation is given by the expressions:jcr=~ (Cm)n orn=]cr=z-jn= 16fl~lpt X i(l )n R = 1,2,3, ...j (2).-. .
MIL-STD-1629AWhere:C= “ Criticality number for the item.Cm = Criticality number for a failure mode under a particularseverity classification (see 4.4.3).fi= Conditional probability of mission loss given that thefailure mode has occurred.“(3= Failure mode ratio. The probability, expressed as a decimalfraction, that the part or item will fail in the identifiedmode.A = Part failure rate.PIt should be noted that failure rates are usually defined in terms offailures per million hours (fx10‘6) a[ld, for simplification purposes,equation (1) may be multiplied by a factor of 106 to eliminate anunnecessary degree of arithmetic precision in worksheet entries. Thatis, ic is easier to enter criticality number on the worksheets as 1.08than to enter 1.08 x 1o-6 or 0.00000108. Tl)e importance of the criticalitynumber is in providing a relative ranking of the failures or failuremodes and not in the absolute value of the riurner’ic.For example, the calculations for C,nand ~r for a given mission ph
Page 1 and 2: MIL-STD-1629A24 NOVEMBER 1980SUPERS
Page 3 and 4: MT7,-STW 1629AFOREWORDIThe~failure
Page 5 and 6: ----MIL-STD-16Z9ACONTENTS(Continued
Page 7 and 8: MI1.-STD-1629A1. SCOPEThis standard
Page 9 and 10: MTL-STD-1 629A3. DEFINITIONS3.1 Ter
Page 11 and 12: !’11 L-!;’J’l)- 1629A3. 1.17.
Page 13 and 14: .MT1.-ST~-l629A4.3.5 Failure defini
Page 15 and 16: MTT,-sTn-1629Afor each mission, mis
Page 17 and 18: ?f?l.-STD-l629Ab. Des~ripGlon of de
Page 19 and 20: MT1,-STD-1629A3.2 Functional approa
Page 21 and 22: MI J,-STD-16?9Afunctional block dia
Page 23 and 24: MI L-STD-1629A5.6.2 Next higher lev
Page 25 and 26: Ml 1,-STD-1079Afurther amplified in
Page 27 and 28: MIL-STD-1629A. --1III[IIIIIIIIIIIii
Page 29 and 30: MIL-STD- 1629ATASK 102CRITICALITYAN
Page 31 and 32: IMII.-ST1)-162(]Ashown in Figure 10
Page 33 and 34: MIL-STD-1629Awhere:C* = Criticality
Page 35 and 36: MI I.-sTI)-I629AINCREASINGCRITICALI
Page 37 and 38: MIL-STD-1629A3*1 Failure predictabi
Page 39 and 40: .--— .-—--— , --—— ——
Page 41 and 42: MTL-STD- 1629A4\l Damage modes. All
Page 43 and 44: NI 1.-[; 1’1)- 1(); ?!)Au0.-.mr-r
Page 45 and 46: MI I,-ST1)-1629A3. Content. The FME
Page 47 and 48: —..-A 1MIL-STD-1629AAPPENDIXA10.
Page 49: MIL-STD-1629A50.1.3 Intended use. T
Page 53 and 54: INSIRUCII ONS: In ● continuing ef
Page 55 and 56: MIL3TD-1629ANotice 17 June 1983MILI
Page 57 and 58: MIL-STD-1629ACONTENTS (Continued)Fi
Page 59 and 60: MIL-STD-1629ASPECIFICATIONSMilitary
Page 61 and 62: MIL-STD-1629Ad. Functional Failure
Page 63 and 64: MIL-STD-1629A..2’Ilm.o.,id1-< xQ
Page 65 and 66: —MIL-STD-1629A50.5 DMEA (Task 104
Page 67 and 68: MIL-STD-1629ACONTENTS (Continued)Pa
Page 69 and 70: .-MIL-STD-1629AAPPENDIX AAPPLICATIO
Page 71 and 72: 20-30Stop LCNMIL-STD-1629AEnter the
Page 73: NOTICE OFCANCELLATIONNOT MEASUREMEN

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