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Appendix H
Maintainability Prediction Modeling 631
Appendix H
Maintainability Prediction
Modeling
This appendix presents theoretical development for five maintainability modeling
techniques:
• Maintenance Corrective Time (Mct)
• Mean time to repair (MTTR)
• Ambiguity factor
• Maximum Corrective Maintenance Time
• Mean Maintenance Man-hours per Maintenance Action (MMH/MA)
Maintenance Corrective Time
The formula for computing Mct is
Mctj = TPREPj + TISOj + TDISj + TR / Rj + TREASj + TCALj + TVERj + TSTj
where:
Mctj
average maintenance corrective or repair time for the jth
replaceable item
TPREPj
average preparation time for the jth replaceable item
TISOj
average fault isolation time for the jth replaceable item
TDISj
average disassembly time for the jth replaceable item
TR/Rj
average time to remove/replace (interchange) the jth
replaceable item