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Ministry of Defence

Defence Standard

00-49/Issue 1 26 JANUARY 1996

RELIABILITY AND MAINTAINABILITY

MOD GUIDE TO TERMINOLOGY

DEFINITIONS

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AMENDMENTS ISSUED SINCE PUBLICATION

AND NO DATE OF TEXT AFFECTED SIGNATURE &

ISSUE DATE

Revision Note

Historical Record

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RELIABILITY AND MAINTAINABILITY

MOD GUIDE TO TERMINOLOGY

DEFINITIONS

PREFACE

i The principle of this Standard is to state explicitly the exact meaning

of the Reliability and Maintainability (R&M) terminology used by the

Ministry of Defence (MOD) in R&M Defence Standards.

ii The MOD accepts the British Standards concepts of R&M(A) and by

inference accepts BS 4778: Part 3 Availability, Reliability and

Maintainability Terms but excluding the terms listed in the Defence

Standard.

iii The MODs hierarchical order of preference of sources of referenceddefinitions for R&M terminology is stated at 2.4.

iv Users of this Standard shall note that some material may be claimed to

be subject to copyright in this or other countries. Copyright, where

known, is acknowledged.

v This Standard was prepared by the Committee for Defence Equipment

Reliability and Maintainability (CODERM).

vi This Standard has been agreed by the authorities concerned with its useand is intended to be used whenever relevant in all future designs,

contracts, orders etc and whenever practicable by amendment to those

already in existence. If any difficulty arises which prevents applicationof the Defence Standard, the Directorate of Standardization shall be

informed so that a remedy may be sought.

vii Any enquiries regarding this Standard in relation to an invitation totender or a contract in which it is incorporated are to be addressed to the

responsible technical or supervising authority named in the invitation to

tender or contract.

viii This Standard has been devised for the use of the Crown and itscontractors in the execution of contracts for the Crown. The Crown hereby

excludes all liability (other than liability for death or personal injury)

whatsoever and howsoever arising (including, but without limitation,

negligence on the part of the Crown its servants or agents) for any loss or

damage however caused where the Standard is used for any other purpose.

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CONTENTS

Preface

0 Introduction

1 Scope

2 Related Documents3 Definitions

Annex A Lines, Depths/Levels of Service Maintenance

Annex B Matrix of RN Lines and Depths of Maintenance

Annex C Matrix of Army Lines of Equipment Support and Levels

of Maintenance

Annex D Matrix of RAF Lines and Depths of Maintenance

PAGE

1

3

3

3

5

A-1

B-1

C-1

D-1

2

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RELIABILITY AND MAINTAINABILITY (R&M)

MOD GUIDE TO TERMINOLOGY

DEFINITIONS

0 Introduction

The MOD considers the term 'Reliability and Maintainability' (R&M) to be

generic and interprets it to encompass related specific concepts such as

availability, supportability, testability etc.

Whereas the MOD accepts the concepts of R&M described in BS 4778: Part 3

Section 3.1, and by inference generally accepts the derived definitions,

but by reasons of: uniqueness of some MOD R&M terms; extant NATO

definitions; exceptions; etc, this Defence Standard is considered necessary

towards a rationalization of MOD R&M terms that will facilitate exact and

taut specifications/contracts.

1 Scope

This Defence Standard addresses only those R&M terms that are unique to the

MOD, are extant NATO definitions, attract particular meaning in an

individual Service, are exceptions to MODs acceptance of BS 4778; or are

accredited quotations, selected from the related documents and included for

completeness.

All other R&M terms that are adequate and acceptable to the MOD are defined

in the Def Stan 00-40 through 00-49 Series or in the documents noted at

2.1.

2 Related Documents

2.1 The followingof this Standard:

ARMP-7

BS 4778: Part 3

JSP 110

MIL-STD-721

MIL-STD-1309

MIL-STD-2165

ANSI/IEEE: 610.12

documents and publications are referred to in the text

NATO R&M Terminology Applicable to ARMPs

Availability, Reliability and Maintainability Terms

Joint Service Glossary

Definitions of Effectiveness Terms of Reliability

Maintainability, Human Factors and Safety

Definitions of Terms for Test, Measurement and

Diagnostic Equipment

Testability Program for Systems Equipment

Glossary of Software Engineering Terminology

2.2 Reference in this Standard to any related documents means in anyinvitation to tender or contract the edition and all amendments current at

the date of such tender or contract unless a specific edition is indicated.

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2.3 The documents listed may be obtained from the sources shown below:

DOCUMENT SOURCE

Allied Reliability and Directorate of Standardization

Maintainability Publication (ARMP) Stan 2

Kentigern House

65 Brown Street

GLASGOW G2 8EX

British Standard (BS) BSI

Sales Department

389 Chiswick High Road

LONDON W4 4AL

Defence Standard (Def Stan) Directorate of Standardization

Stan 1

Kentigern House

65 Brown Street

GLASGOW G2 8EX

Joint Service Glossary (JSP 110) MOD Forms and Publications Branch

CSEMwrawg Road

Llangenennech

Llanelli

DYFED SA14 8YP

Military Standard (MIL-STD) Technical Indexes

Willoughby Road

American National Standards Bracknell

Institute (ANSI)/ BERKS RG12 4DW

Institute of Electrical &

Electronics Engineers (IEEE):

610.12 Glossary of Software

Engineering Terminology

2.4 The above documents are listed in order of preference and hierarchy

for the selection of Standards for MOD procurement and hence infer the

hierarchal order of preference of sources of MOD R&M terminology.

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availability - operational (Ao)

The proportion of the defined operational period during which the equipment

is available for use without any performance limitations.

ie Ao = uptime measured over an operational period

uptime + downtime

Operational availability may be expressed by the formula:

Ao = OT + ST

OT + ST + TPM + TCM + ALDT

where: OT = operating time

ST = standby time

TPM = total preventative maintenance time

TCM = total corrective maintenance time

ALDT = administration and logistics delay time spent waiting for

parts, maintenance personnel or transportation

NB: Units will be defined in accordance with Service practice.

battle damage repair

Is essential repair, which may be improvised, carried out in a battle

environment in order to return damaged or disabled equipment to temporary

service.

battle damage repair - aircraft (RAF use)

Is the maintenance action taken in wartime to maximize the availability of

damaged mission capable aircraft.

battlefield day

The battlefield day specifies how the equipment is likely to be used during

a typical 24 - hour period in war.

battlefield mission

The battlefield mission specifies how the equipment is likely to be used

during a typical war-time mission. This may specify the usage profile for

the equipment for a battlefield mission, or it may be comprised of a series

of consecutive battlefield days or equipment operating cycles.

build standard

Is the approved specifications, design and contemporary support thatcomprise the performance and engineering definition.

built-in-test (BIT) (see ARMP-7)

built-in-test equipment (BITE) (see ARMP-7)

cannibalize (cf robbing)

To remove, without subsequent replacement, useful serviceable items from

one equipment/system for use on other equipment/systems.

NOTE: These definitions for cannibalize and robbing are a clarification of

the Joint Service Glossary (JSP 110) definition.

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configurationIs the functional and physical characteristics of materiel as described in

technical documents and achieved in a product.

configuration control (see ARMP-7)

data classificationIs the process by which incident data are sorted into different categories,

(eg cause, significance, maintenance requirement) applicable to the R&M

parameters being assessed.

defect (see ARMP-7)

degradation

Is a gradual impairment of the ability to perform.(MIL-STD 721)

degradation fault

Is a fault which reduces performance below a specified level, but which

does not necessarily terminate the function.

degradation - graceful/gradual. (synonymous terms)

Is the sufficiently long interval between the occurrence of a potential

failure, which produces degraded capability, and its dec