Mil-HDBK-470A Appendix B Section 3.1

716 Pages·1997·4.83 MB·English

by  Reliability Analysis Center

NOT MEASUREMENT
SENSITIVE
MIL-HDBK-470A
4 AUGUST 1997
SUPERSEDING
MIL-HDBK-470
12 JUNE 1995
MIL-HDBK-471
12 JUNE 1995
DEPARTMENT OF DEFENSE
HANDBOOK
DESIGNING AND DEVELOPING MAINTAINABLE
PRODUCTS AND SYSTEMS
VOLUME I
This handbook is for guidance only. Do not cite this document as a
requirement
AMSC N/A AREA MNTY
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
MIL-HDBK-470A
FOREWORD
1. This handbook is approved for use by all Departments and Agencies of the Department of
Defense (DoD). It was developed by the DoD with the assistance of the military departments,
federal agencies, and industry and replaces in their entirety Military Handbooks 470 and 471
(both formerly military standards). The handbook provides guidance to maintainability managers
and engineers in developing and implementing a sound maintainability program for all types of
products.
2. This handbook is for guidance only. This handbook cannot be cited as a requirement. If it is,
the contractor does not have to comply.
3. Maintainability is a discipline that has become more importance over the past 30 years as
military systems became more complex, support costs increased, and defense budgets decreased.
It is also important in the commercial sector, where high levels of maintainability are increasingly
becoming an important factor in gaining customer loyalty. In fact, American products that once
were shunned in favor of foreign alternatives recently have made or are making a comeback. This
shift in consumer preferences has been directly attributed to significant improvements in the
quality of the American products, a quality that includes good maintainability.
4. Despite the fact that maintainability has been a recognized discipline for much longer than 30
years, achieving the high levels of maintainability needed in military and complex industrial
systems is too often an elusive goal. System complexity, competing performance requirements,
the rush to incorporate promising but immature technologies, and the pressures of acquisition
budget and schedule contribute to this elusiveness.
5. Noting the significant improvement in the quality of commercial products and the rapidity
with which new technology is incorporated in commercial products, and facing a shrinking
defense budget, the Department of Defense changed its acquisition policies to foster the
evolution of a unified military and commercial industrial base. The objective is to capitalize on
the "best practices" that American business has developed or adopted, primarily in response to
foreign competitive pressures. When combined with the knowledge and expertise of military
contractors in building complex, effective military systems (soundly demonstrated during Desert
Storm), these commercial practices will help the Department of Defense to acquire world-class
systems on time and within budget.
6. The information in this handbook reflects both the move to incorporate commercial practices
and the lessons learned over many years of acquiring weapon systems "by the book." When
appropriate, commercial standards are cited herein for reference. Military standards and
specifications, which cannot be used as requirements in solicitations without obtaining a waiver,
are also cited for guidance. These documents are familiar to both military and commercial
companies, contain a wealth of valuable information, and often have no commercial counterpart.
Whereas many of these documents emphasize what to do and how to do it, this handbook, in the
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MIL-HDBK-470A
spirit of the new policies regarding acquisition, focuses on the objectives of a sound
maintainability program and the tools available to meet these objectives.
7. Beneficial comments (recommendations, additions, deletions) and any pertinent data which
may be useful in improving this document should be addressed to: Rome Laboratory/ERSR, 525
Brooks Road, Rome, NY 13441-4505. Comments should be submitted using the self-addressed
Standardization Document Improvement Proposal (DD Form 1426) appearing at the end of this
document or by letter.
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MIL-HDBK-470A
CONTENTS
PARAGRAPH
PAGE
FOREWORD....................................................................................................................... ii
1.0 SCOPE AND PURPOSE OF HANDBOOK............................................................. 1-1
1.1 Scope.................................................................................................................. 1-1
1.1.1 Purpose of the Handbook...................................................................... 1-1
1.1.2 Using the Handbook............................................................................... 1-2
1.2 Applicable Documents....................................................................................... 1-2
1.3 Definitions, Acronyms and Abbreviations........................................................ 1-8
2.0 THE CONCEPT OF MAINTAINABILITY.............................................................. 2-1
2.1 What is Maintainability?.................................................................................... 2-1
2.2 Effect of Maintainability on Operations and Cost............................................ 2-2
2.2.1 Operations.............................................................................................. 2-2
2.2.1.1 Relationship of Reliability and Maintainability...................... 2-3
2.2.1.2 Availability and Operational Readiness.................................. 2-4
2.2.2 Life Cycle Costs..................................................................................... 2-5
2.2.2.1 Research and Development (R&D) Costs (DoD
Phases 0, I, and II)................................................................... 2-5
2.2.2.2 Production and Construction (P&C) Costs (Part of
DoD Phase III)........................................................................ 2-6
2.2.2.3 Operation and Maintenance (O&M) Costs (Part of
DoD Phase III)........................................................................ 2-6
2.2.2.4 Product Retirement and Phase-out (PR&P) Costs................. 2-7
2.2.2.5 Opportunity and Equivalent Costs......................................... 2-7
2.2.3 Affordability.......................................................................................... 2-7
2.3 Other Relationships........................................................................................... 2-8
2.3.1 Manufacturing........................................................................................ 2-8
2.3.2 Human Engineering................................................................................. 2-9
2.3.3 Safety..................................................................................................... 2-9
2.3.4 Diagnostics and Maintenance................................................................. 2-9
2.3.5 Logistics Support................................................................................... 2-10
2.4 Maintainability and the Acquisition Process..................................................... 2-10
3.0 OBJECTIVE OF A MAINTAINABILITY PROGRAM......................................... 3-1
3.1 Understand the Customer’s Maintainability Needs........................................... 3-2
3.2 Integrate Maintainability with the Systems Engineering Process...................... 3-5
3.3 Thoroughly Understand the Design................................................................... 3-5
3.4 Design for Desired Level of Maintainability...................................................... 3-5
3.5 Validate the Maintainability Through Analysis and Development Test........... 3-6
3.6 Monitor and Analyze Operational Performance................................................ 3-6
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MIL-HDBK-470A
PARAGRAPH
PAGE
4.0 ELEMENTS OF A MAINTAINABILITY PROGRAM........................................... 4-1
4.1 Overview.............................................................................................................. 4-1
4.2 Management Approach........................................................................................ 4-1
4.2.1 Clear Responsibility................................................................................. 4-2
4.2.2 Adequate Resources (Quantity and Quality)........................................... 4-2
4.2.3 Lines of Communication.......................................................................... 4-2
4.2.4 Integration with Related Functions.......................................................... 4-2
4.2.5 Subcontractor and Vendor Control........................................................... 4-2
4.2.6 Reviews.................................................................................................... 4-3
4.3 Design for Maintainability................................................................................... 4-3
4.3.1 Specific Considerations............................................................................ 4-3
4.3.1.1 Support Concept....................................................................... 4-4
4.3.1.2 Operational and Support Environment..................................... 4-6
4.3.1.3 Preventive Versus Corrective Maintenance Requirements....... 4-6
4.3.1.4 Human Engineering (HE)........................................................... 4-9
4.3.1.4.1 Presentation of Information.................................... 4-10
4.3.1.4.2 Controls................................................................... 4-11
4.3.1.4.3 Anthropometrics..................................................... 4-11
4.3.1.5 Maintenance Tools and Support Equipment............................ 4-12
4.3.1.6 Maintenance Training................................................................ 4-12
4.3.1.7 Testability and Diagnostics....................................................... 4-12
4.3.1.7.1 Testability Design................................................... 4-13
4.3.1.7.2 Diagnostic Capability.............................................. 4-16
4.3.1.8 Interfaces and Connections....................................................... 4-17
4.3.1.9 Safety and Induced Failures...................................................... 4-18
4.3.1.10 Standardization and Interchangeability..................................... 4-18
4.3.1.10.1 Standardization Design Goals and Principles.......... 4-18
4.3.1.10.2 Interchangeability Design Goals and Principles...... 4-19
4.3.2 Design Tools............................................................................................ 4-21
4.3.2.1 Analytical.................................................................................. 4-21
4.3.2.2 Mockups................................................................................... 4-23
4.3.2.3 Simulation and Virtual Reality.................................................. 4-23
4.3.2.4 Handbooks and Other Reference Documents........................... 4-25
4.3.2.5 Artificial Intelligence................................................................. 4-25
4.3.2.5.1 Expert Systems....................................................... 4-26
4.3.2.5.1.1 Rule-Based Expert Systems............... 4-26
4.3.2.5.1.2 Model-Based Expert Systems............ 4-28
4.3.2.5.2 Fuzzy Logic............................................................ 4-28
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PARAGRAPH
PAGE
4.3.2.5.3 Neural Networks..................................................... 4-29
4.4 Maintainability Analyses and Test...................................................................... 4-31
4.4.1 Analyses................................................................................................... 4-31
4.4.1.1 Objectives of Maintainability Analyses................................... 4-31
4.4.1.2 Typical Products of Maintainability Analyses........................ 4-32
4.4.1.3 Commonly Used Maintainability Analyses............................. 4-32
4.4.1.3.1 Equipment Downtime Analysis.............................. 4-32
4.4.1.3.2 Maintainability Design Evaluation.......................... 4-33
4.4.1.3.3 Failure Modes and Effects Analysis (FMEA)........ 4-34
4.4.1.3.4 Testability Analysis................................................ 4-37
4.4.1.3.4.1 Dependency Analysis........................ 4-38
4.4.1.3.4.2 Dependency Analysis Tools.............. 4-40
4.4.1.3.4.3 Other Types of Testability
Analyses............................................. 4-40
4.4.1.3.5 Human Factors Analysis......................................... 4-40
4.4.1.4 Quantitative Measures of Maintainability................................ 4-42
4.4.1.4.1 Maintainability Models and Maintenance
Activities Block Diagrams....................................... 4-43
4.4.1.5 Qualitative Maintainability Factors.......................................... 4-44
4.4.1.6 Predictions, Allocations, and Assessments............................... 4-45
4.4.1.6.1 Maintainability Prediction...................................... 4-45
4.4.1.6.1.1 Maintainability Prediction in
Accordance with MIL-HDBK-472.... 4-46
4.4.1.6.2 Maintainability Allocation...................................... 4-47
4.4.1.6.2.1 Failure Rate Complexity Method...... 4-48
4.4.1.6.2.2 Variation of the Failure Rate
Complexity Method........................... 4-50
4.4.1.6.2.3 Statistically-Based Allocation
Method............................................... 4-50
4.4.1.6.2.4 Equal Distribution Method................ 4-51
4.4.1.6.3 Maintainability Assessment................................... 4-51
4.4.2 Test.......................................................................................................... 4-51
4.4.2.1 Objectives.................................................................................. 4-52
4.4.2.2 Types of Testing....................................................................... 4-52
4.4.3 Statistical Distributions Used in Maintainability Models....................... 4-53
4.4.3.1 Lognormal Distribution............................................................. 4-54
4.4.3.2 Normal Distribution.................................................................. 4-55
4.4.3.3 Exponential Distribution........................................................... 4-56
4.5 Data Collection and Analysis............................................................................... 4-58
4.5.1 Types of Data.......................................................................................... 4-58
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MIL-HDBK-470A
PARAGRAPH PAGE
4.5.1.1 Development Data.................................................................... 4-58
4.5.1.2 Field Data................................................................................. 4-60
4.5.2 Sources of Data....................................................................................... 4-60
4.5.3 Data Analysis Techniques....................................................................... 4-62
4.5.3.1 Data Used Explicitly for Compliance Verification.................. 4-63
4.5.4 Uses of Data............................................................................................ 4-64
APPENDIXES
Appendix A. Acquisition Guidance, Templates for Preparing Maintainability Section of
Solicitation, and Guidance for Selecting Sources......................................... A-1
Appendix B. Maintainability Test and Demonstration Methods........................................ B-1
Appendix C. Design Guidelines (Volume II of Handbook)............................................... C-1
Appendix D. Maintainability Predictions........................................................................... D-1
Appendix E. Phasing of Maintainability Elements............................................................ E-1
Appendix F. Maintainability References............................................................................ F-1
Appendix G. Maintainability Glossary of Terms, Definitions, Acronyms and
Abbreviations................................................................................................ G-1
FIGURES
Figure 1: Different Combinations of MTBF and MTTR Yield the Same
Inherent Availability...................................................................................... 2-3
Figure 2: Some Key Disciplines to Which Maintainability is Related......................... 2-8
Figure 3: QFD House of Quality.................................................................................. 3-3
Figure 4: Example Excerpt of House of Quality.......................................................... 3-4
Figure 5: Major Categories of Maintenance................................................................. 4-7
Figure 6: The Steps in an RCM Approach to Identifying Preventive Maintenance..... 4-8
Figure 7: The Human Information Processing System................................................. 4-10
Figure 8: Interactions Between Human and Product.................................................... 4-11
Figure 9: Steps in a General Approach for the Physical Development of a
Maintainability Expert System...................................................................... 4-28
Figure 10: Fuzzy Logic Set Membership........................................................................ 4-29
Figure 11: Typical Neural Network Configuration......................................................... 4-30
Figure 12: Steps in an FMEA......................................................................................... 4-36
Figure 13: Typical FMEA Worksheet............................................................................ 4-36
Figure 14: Abbreviated Results from FMEA of a Solid Propellant Rocket Motor........ 4-37
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MIL-HDBK-470A
FIGURES (Continued)
Figure 15: Simple System Showing Test Dependencies................................................. 4-38
Figure 16: Maintenance Activities Block Diagram.......................................................... 4-43
Figure 17: Example of Maintainability Allocation.......................................................... 4-50
Figure 18: Example FRACAS Form................................................................................ 4-59
Figure A-1: Sections of a Government Solicitation or Contract........................................ A-8
Figure A-2 Example Wording for a Statement of Objectives............................................ A-10
Figure A-3: Checklist for Evaluating Maintainability Portion of a Proposal.................... A-22
Figure B-1: Time Phasing of Maintainability Testing....................................................... B-2
Figure B-2: Procedure for Maintainability-Index Selection............................................... B-9
Figure B-3: OC Curve for Test A..................................................................................... B-29
Figure B-4: OC Curve for Test B...................................................................................... B-30
Figure B-5: OC Curve for Test Method 2........................................................................ B-32
Figure B-6: OC Curve for Test Method 3........................................................................ B-36
Figure B-7: Distribution of Means.................................................................................... B-43
Figure B-8A: Acceptable Combinations of Dual Requirements.......................................... B-49
Figure B-8B: Values Acceptable to Dual Requirement of Maximum Values of
Two Percentiles.............................................................................................. B-49
Figure B-8C: Superimposition of Figure B-8A on B-8B..................................................... B-50
Figure B-8D: OC Curve for Test Method 8........................................................................ B-54
Figure B-8E: Probability of Passing Test A........................................................................ B-55
Figure B-8F: Probability of Passing Test B ....................................................................... B-56
1
Figure B-8G: Probability of Passing Test B ....................................................................... B-56
2
Figure B-9: OC Map Relative to a Given Dual Requirement........................................... B-57
Figure B-10: Node Consisting of Fan-In Branches, a Fan-Out Origin, and Fan-
Out Branches.................................................................................................. B-79
Figure C-1: Redundancy BIT............................................................................................ C-5
Figure C-2: Wrap-Around BIT......................................................................................... C-6
Figure D-1: RI Data Analysis Sheet - A............................................................................ D-12
Figure D-2: RI Data Analysis Sheet - B............................................................................ D-12
Figure D-3: MTTR Submodels......................................................................................... D-14
Figure D-4: Definitions of MTTR Submodel Terms........................................................ D-15
Figure D-5: Matrix For Correlating FD&I Features With RIs.......................................... D-23
Figure D-6: Fault Isolation Output and RI Correlation Tree............................................ D-24
Figure D-7: Manual Fault Isolation Output And RI Correlation Tree (Partial)................ D-24
Figure D-8: Sample Maintenance Flow Diagram............................................................... D-26
Figure D-9: Example Time Synthesis Analysis................................................................. D-28
Figure D-10: Maintenance Correlation Matrix Format....................................................... D-29
Figure D-11: Standard Screws............................................................................................. D-32
Figure D-12: Hex or Allen Set Screws................................................................................. D-32
Figure D-13: Captive Screws............................................................................................... D-32
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MIL-HDBK-470A
FIGURES (Continued)
Figure D-14: Dzus Fasteners............................................................................................... D-33
Figure D-15: Tridair Fastener.............................................................................................. D-33
Figure D-16: Thumbscrews................................................................................................. D-33
Figure D-17: Machine Screws............................................................................................. D-34
Figure D-18: Nuts or Bolts.................................................................................................. D-34
Figure D-19: Retaining Rings............................................................................................... D-35
Figure D-20: Drawhook Latch............................................................................................. D-35
Figure D-21: Spring Clip Latch-Catch................................................................................. D-35
Figure D-22: Butterfly Latch............................................................................................... D-36
Figure D-23: ATR Latch..................................................................................................... D-36
Figure D-24: Lift and Turn Latch........................................................................................ D-36
Figure D-25: Slide Lock Latch............................................................................................. D-37
Figure D-26: Terminal Post Connections............................................................................ D-37
Figure D-27: Screw Terminal Connections.......................................................................... D-37
Figure D-28: Termipoint Connection.................................................................................. D-38
Figure D-29: Wirewrap Connection.................................................................................... D-38
Figure D-30: Taperpin Connection..................................................................................... D-38
Figure D-31: PCB Connection............................................................................................. D-39
Figure D-32: BNC Connectors............................................................................................ D-39
Figure D-33: Quick Release Coax Connectors..................................................................... D-39
Figure D-34: Friction Locking Connector............................................................................ D-40
Figure D-35 Friction Locking Connector with Jackscrew.................................................. D-40
Figure D-36: Threadlocking Connector............................................................................... D-40
Figure D-37: Slide Locking Connector................................................................................. D-41
Figure D-38: Dip ICs........................................................................................................... D-41
Figure D-39: Guided CCAs................................................................................................. D-41
Figure D-40: Guided CCAs with a Tool............................................................................. D-42
Figure D-41: Non-guided CCAs.......................................................................................... D-42
Figure D-42: Modules......................................................................................................... D-42
Figure D-43: Crimp Lugs..................................................................................................... D-43
Figure D-44: Form Leads..................................................................................................... D-43
Figure D-45: Soldering Terminal Posts................................................................................ D-43
Figure D-46: Soldering PCB Connections........................................................................... D-43
Figure D-47: Desoldering with a Braided Wick................................................................... D-44
Figure D-48: Desoldering Using a Vacuum.......................................................................... D-44
Figure D-49: Form Flat Pack Leads..................................................................................... D-44
Figure D-50: Panels, Doors and Covers.............................................................................. D-45
Figure D-51: Drawers.......................................................................................................... D-45
Figure D-52: Display Lamps............................................................................................... D-45
Figure E-1: Life Cycle Phases of a Product...................................................................... E-2
Figure E-2: Application of Activities by Phase................................................................ E-4
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MIL-HDBK-470A
TABLES
Table I: Scope of Key Topics.................................................................................... 1-1
Table II: Maintainability and Related Tasks............................................................... 1-3
Table III: Program Activity Characteristics and Guidelines for Supplier-Product
Classifications............................................................................................... 1-5
Table IV: Task Cross Reference: Old MIL-HDBK-470 to new MIL-HDBK-470A.. 1-8
Table V: Operational and Design Maintainability Contrasted.................................... 2-2
Table VI: Types and Purposes of Design Reviews...................................................... 4-3
Table VII: Risks and Consequences of Not Making BIT Part of Product Design........ 4-17
Table VIII: Comparison of AI Techniques..................................................................... 4-25
Table IX: First Order Dependency Model for Simple System.................................... 4-39
Table X: Typical Types of "In-Place" Repair and Maintenance................................ 4-48
Table XI: Allocation Using Failure Rate Complexity Method..................................... 4-49
Table XII: Example of Equal Distribution Method....................................................... 4-51
Table XIII: Risks and Consequences of a Testing Approach That is Not Integrated..... 4-52
Table XIV: Values of z(t’ 1-a ) Most Commonly Used in Maintainability Analysis... 4-55
Table XV: Values of k for Specified a ...................................................................... 4-57
e
Table XVI: Example Data Fields From an Existing R&M Data Base............................... 4-61
Table B-I: Test Method Matrix..................................................................................... B-7
Table B-II: Factors Affecting the Suitability of a Specified Maintainability Index
for Maintainability Demonstration.............................................................. B-11
Table B-III: Causes of Discrepancies Between Test and Field Results........................... B-11
Table B-IV: Example of Step-by-Step Stratification........................................................ B-14
Table B-V: Calculations of Relative Frequency of Occurrence and Sample Size
for Example Radar Equipment...................................................................... B-15
Table B-VI: Stratification Procedure................................................................................ B-17
Table B-VII: Failure Mode Selection................................................................................. B-19
Table B-VIII: Standardized Normal Deviates..................................................................... B-25
Table B-IX: Sampling Plans for Specified p , p , a , and b When p is Small (e.g.,
0 1 0
p <0.20)........................................................................................................ B-35
0
Table B-X: Plan A . Observations Exceeding the Value of the Mean............................ B-51
1
Table B-XI: Plan B . Observations Exceeding M = 90 Percentile............................... B-52
1 max
Table B-XII: Plan B . Observations Exceeding M = 95 Percentile............................... B-53
2 max
Table B-XIII: f vs. b................................................................................ B-59
~ ~
Table B-XIV: Acceptance Table for M or M ; Sample Size = 50................................ B-61
ct pm
Table B-XV: Acceptance Table for M or M ; Sample Size = 50.......................... B-62
max max
c pm
Table B-XVI: Penalty Values, P, for LFSR Signature Analyzers Implementing
Primitive Polynomial of Degree, k................................................................ B-80
Table B-XVII: Representative Faults for the Fault Equivalence Classes............................. B-82
x