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APPENDIX C

GLOSSARY

A c c e s s i b i l i t y A measure of the relat ive ease of admission to the various areas of an i tem for

the purpose of opera t ion or main tenance .

A c h i e v e d Ob ta ine d a s t he r e su lt o f m e a su r e m e n t .

A l i g n m e n t

Performing the ad jus tments tha t a re necessary to re turn an i tem to spec i f ied

ope r a t i on .

Avai lab i l i ty A me asure of the degre e to wh ich an i tem i s in an operab le and comm it tab le s ta te

a t the s ta r t o f a miss io n w hen the mis s ion i s ca l led for a t an unkno wn ( rando m) t im e . ( I tem s ta te

at the s tar t of mission includes the combined effects of the readiness-related system rel iabi l i ty

a nd ma in t a ina b i l i ty [ R& M] pa r a m e te r s bu t e xc lude s mi s s ion t ime ;s Dependabi l i ty ) .

B u r n - I n ( P r e - C o n d i t i o n i n g )

The operat ion of an i tem under s tress to s tabi l ize i ts character

is t ics; not to be confused wi th

D e b u g g i n g .

C a l i b r a t i o n A

compar i son of a measur ing device wi th a known s tandard ; no t to be confused

wi th A l i g n m e n t{s M I L - C - 4 5 6 6 2 ) .

C h a r g e a b l e Within the respons ib i l i ty of a g iven organiza t iona l en t i ty (appl ied to te rms such

as fa i lures and main tenance t ime) .

C h e c k o u t

Tes ts or observa t ions of an i t em to de te rm ine i t s condi t ion or s ta tus .

Correc t ive Act io n A

doc um ented des ign , process , p rocedure , o r mater ia l s change implem ented

and val idated to correct the cause of fai lure or design deficiency.

Cri t i ca l i ty A

re la t ive measure of the consequence of a fa i lure mode and i t s f requency of

oc c u r r e nc e s .

D e b u g g i n g A process to de tec t and remedy inadequac ies ; no t to be confused wi th te rms such

as

Burn -In , Faul t I so la t ion ,

or

Screen ing .

D e g r a d a t i o n A gradua l impai rment in ab i l i ty to per form.

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D e m o n s t r a t e d

Tha t w hich has been me asured by the use o f ob ject ive ev idence gathered un der

speci f ied cond i t ions .

D e p e n d a b i l i t y A m eas ure of the degree to wh ich an i tem is operable and capable of performing

its required function at any (random) t ime during a specified mission profi le, g iven i tem avail

abil i ty at the start of the mi ssio n. (I tem state during a mis sion inclu des the com bin ed effects

o f the miss ion-re la ted sys tem re l iab i l i ty and main ta inab i l i ty [R&M] parameters bu t excludes

n o n -m iss io n t im e ;

s

Avai labi l i ty . )

D e r a t i n g

(a) Us ing an i tem in such a wa y that applied stresses are below rate d values, or (b) the

lowering of the rat ing of an i tem in one stress f ield .

D i r e c t M a i n t e n a n c e M a n - H o u r s p e r M a i n t e n a n c e A c t i o n ( D M M H / M A ) A measure o f

the main ta ina b i l i ty param eter re la ted to i tem deman d fo r ma in tena nce manpo wer . The sum of

d i rec t main tenance man-hours , d iv ided by the to ta l number o f main tenance ac t ions (p reven t ive

and corrective) during a stated period of t ime.

D i r e c t M a i n t e n a n c e M a n - H o u r s p e r M a i n t e n a n c e E v e n t ( D M M H / M E ) A measure o f

the main ta ina b i l i ty param eter re la ted to i tem dema nd fo r ma in tena nce ma npower . The sum of

d i rec t main tenance man-hours , d iv ided by the to ta l number o f main tenance even ts (p reven t ive

and corrective) during a stated period of

t ime.

D i s a s s e m b l e

Op eni ng an i tem and removin g a num ber o f par ts o r subass emb l ies to ma ke the

i tem that i s to be rep laced access ib le fo r remo val . Th is does no t inc lude the ac tual rem oval o f

the i tem to be rep laced .

D o r m a n t

The state wherein an i tem is able to function but is not required to function; not to

be confused wi th downt ime operab le , which i s the s ta te o f being ab le to perfo rm the in tended

funct ion ; the same as

N o t O p e r a t i n g .

D o w n i n g E v e n t The even t tha t causes an i tem to become unavai lab le to in i t ia te i t s miss ion

( the t rans i t ion f rom up t ime to downt ime) .

D u r a b i l i t y

A measure of useful l ife (a special case of rel iabil i ty) .

E n v i r o n m e n t Th e a ggregate o f a l l ex ternal and in ternal cond i t ions (e .g . , temp eratu re , hum id

i ty , rad ia t ion , magnet ic and e lec t r ic f ie lds , shock v ib ra t ion) , whether natu ra l o r man-made, o r

self- induced, that influences the form, performance, rel iabil i ty , or survival of an i tem.

E n v i r o n m e n t a l S t r e s s S c r e e n i n g ( E S S ) A ser ies o f tes ts conducted under env i ronmenta l

s t resses to d isc lose weak par ts and workmansh ip defects fo r co rrect ion .

F a i l u r e The event, or inoperable state, in which any i tem or part of an i tem does not or would

not perform as previously specified.

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GLOSSARY

Fai lure Ana lys i s Subsequent to a fai lure, the logical systematic examination of an i tem, i ts

construction, application, and documentation to identify the fai lure mode and to determine the

fa i lu re mechan ism and i t s bas ic course .

F a i l u re C a t a s t r o p h i c

A failure that can cause i tem loss.

Fai lure Cr i t i ca l

A failure, or combination of fai lures, that prevents an i tem from performing

a specified mission.

F a i l u re D e p e n d e n t Failure that is caused by the fai lure of an associated i tem(s); not Fai lure

I n d e p e n d e n t .

Fa i lure Ef fec t The consequence(s) a fai lure mode has on the operation, function, or status of

an ite m. Fa ilur e effects ar e classifie d as loca l effect, next hig he r level, and end effect.

F a i l u re , I n d e p e n d e n t Failure that occurs without being caused by the fai lure of any other

i tem; no t Fai lure Dependent .

Fa i lure , In termi t t ent Failure for a l imited period of

t ime ,

followed by the i tem's recovery of

i ts abil i ty to perform within specified l imits without any remedial action.

F a i l u r e M e c h a n i s m Th e physica l , chemica l , e lec t r ica l , thermal , o r o ther p rocess that resu l ts

in failure.

F a i lu r e M o d e

The consequence of the mechanism through which the fai lure occurs ( i .e. , short ,

open , f rac tu re , excess ive wear) .

F a i l u r e M o d e a n d E f f e c t s A n a l y s i s ( F M E A )

A procedure by which each po ten t ia l fa i lu re

mode in a system is analyzed to determine the results or effects thereof on the system, and to

classify each potential fai lure mode according to i ts severi ty .

F a i l u r e , N o n - C h a r g e a b l e

(a) A non-relevant fai lure, or (b) a relevant fai lure caused by a

condit ion previously specified as not within the responsibil i ty of a given organizational enti ty .

(All relevant fai lures are chargeable to one organizational enti ty or another.)

F a i l u re , N o n - R e l e v a n t

(a) A failure verif ied as having been caused by a condit ion not present

in the operational environment, or (b) a fai lure verif ied as peculiar to an i tem design that wil l

not enter the operational inventory.

F a i l u r e , R a n d o m Fai lu re wh ose o ccurre nce i s p red ic tab le on ly in a p robab i l i s t ic o r s ta ti s t ica l

sense. This applies to al l d istr ibutions.

Fai lure Rate The total number of fai lures within an i tem population, d ivided by the to tal

num ber o f li fe un i ts expen ded by that popu la t ion , dur ing a par t icu lar me asurem ent in terval

under s ta ted cond i t ions .

F a u l t Immediate cause o f fa i lu re (e .g . , malad jus tment , misa l ignment , defect ) .

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Faul t I so la t ion The process of determining the location of a fault to the extent necessary to

effect repair.

Faul t Loca l i z a t ion

The process of determining the approximate location of a fault .

Inherent R M V alue

A measure of rel iabil i ty or maintainabil i ty (R&M) that includes only

the effects of an i tem design and i ts application, and assumes an ideal operation and support

env ironment .

I n t e r c h a n g e Removing the i tem that is to be replaced, and instal l ing the replacement i tem.

Inventory , Act ive The group of i tems assigned to an operational status.

Inventory , Inac t ive

The group of i tems being held in reserve for possible future assignments

to an operational status.

I t e m

A non-specific term used to denote any product, including systems, materials parts,

subassem bl ies , se ts , and accessor ies . (Source: MI L-ST D-2 80. )

Life Prof i le A t ime-phased descr ip t ion o f the even ts and env ironments an i tem exper iences

from manufacture to f inal expenditures of removal from the operational inventory, to include

one or more mission profi les.

Li fe U ni t s

A m eas ure of use duratio n app licable to the i tem (e.g . , oper ating hou rs, cycle s,

distance, rounds fired, at tempts to operate) .

M a i n t a i n a b i l i t y

The measure of the abil i ty of an i tem to be retained in or restored to speci

fied condit ion when maintenance is performed by personnel having specified skil l levels, using

prescribed procedures and resources, at each prescribed level of maintenance and repair .

M ainta inabi l i ty , M iss ion The measure of the abil i ty of an i tem to be retained in or restored

to specified condit ion when maintenance is performed during the course of a specified mission

prof i le ( the miss ion-re la ted sys tem main ta inab i l i ty parameter) .

M a i n t e n a n c e

All actions necessary for retaining an i tem in or restoring i t to a specified

cond i t ion .

M a i n t e n a n c e A c t i o n

A n elem ent of a m ain ten anc e event. On e or mo re task s ( i .e. , fault

localization, fault isolat ion, servicing, inspection) necessary to retain an i tem in or restore i t to

a specified condit ion.

M a i n t e n a n c e , C o r r e c t i v e All actions performed as a result of fai lure, to restore an i tem to

a specified condit ion. Corre ctive mai nte nan ce can include any or al l of the followin g steps:

local iza t ion , i so la t ion , d isassembly , in terchange, reassembly , a l ignment , and checkou t .

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GLOSSARY

M a i n t e n a n c e E v e n t One or more main tenance ac t ions requi red to e f fec t cor rec t ive and

prevent ive maintenance due to any type of fai lure or malfunct ion, false alarm, or scheduled

maintenance p lan .

M a i n t e n a n c e M a n n i n g L e v e l

The total authorized or assigned personnel per system at speci

f ied levels of maintenance organizat ion.

M a i n t e n a n c e , P r e v e n t i v e

All act ions performed in an at tempt to retain an i tem in specif ied

condi t ion by providing systemat ic inspect ion, detect ion, and prevent ion of incipient fai lures .

M a i n t e n a n c e R a t i o

A measure of the total maintenance manpower burden required to maintain

an i t em. I t i s expresse d as the cum ula t ive num ber of man -hours of main tena nce expe nded in

direct labor during a given per iod of the l i fe uni ts divided by the cumulat ive number of end-i tem

life uni ts dur ing the same per iod.

M a i n t e n a n c e , S c h e d u l e d

Prevent ive main tenance per formed a t prescr ibed poin t s dur ing the

life of an item.

M a i n t e n a n c e T i m e

An e lement of downt ime tha t exc ludes modi f i ca t ion and de lay t ime .

M a i n t e n a n c e , U n s c h e d u l e d Correc t ive main tenance requi red by i t em condi t ions .

M a l f u n c t i o n

The event , or inoperable s tate , in which any i tem or par t of an i tem does not , or

would not , perform as previously specif ied; the same as Failure .

M e a n M a i n t e n a n c e T i m e The measure of i t em mainta inabi l i ty , t ak ing in to account main te

nance pol icy . Th e sum of prevent ive and cor rec t ive main tenance t im es , d iv ided by the sum of

scheduled and unscheduled main tenance event s , dur ing a s t a ted per iod of

t ime .

M e a n T i m e B e t w e e n D e m a n d s ( M T B D ) A measure of the sys tem re l i ab i l i ty parameter

related to de m an d for logis t ic supp ort . Th e total num ber of system l i fe uni ts divided by the

total number of i tem demands on the supply system during a s tated per iod of t ime, such as shop

replaceab le unit (SRU ) , wea pon replacea ble uni t (WR U) , line rep lacemen t uni t (LR U) , and shop

r e p l a c e a b l e a s s e mbl y ( SRA) .

M e a n T im e B e t w e e n D o w n i n g E v e n ts ( M T B D E )

A measure of the system rel iabi l i ty param

eter related to avai labi l ity and read ines s . Th e total num ber of system l i fe uni ts , divided by the

total number of events in which the system becomes unavai lable to ini t ia te i t s mission(s) , dur ing

a s tated per iod of t ime.

M e a n T i m e B e t w e e n F a i l u r e s ( M T B F ) A basic measure of rel iabi l i ty for repairable i tems.

The mean number of l i fe uni ts dur ing which al l par ts of the i tem perform within their specif ied

l imi t s , dur ing a par t i cu la r measurement in te rva l under s t a ted condi t ions .

M e a n T i m e B e t w e e n M a i n t e n a n c e ( M T B M )

A measure of rel iabi l i ty, taking into account

m aint ena nc e pol icy. Th e total nu m be r of l ife uni ts expen ded by a given t ime , divided by the

to ta l number of main tenance event s ( scheduled and unscheduled) due to tha t i t em.

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M e a n T i m e B e t w e e n M a i n t e n a n c e A c t i o n s ( M T B M A ) A measure o f the sys tem re l iab i l i ty

para me ter re la ted to dem and fo r ma in tena nce m anpow er . The to ta l num ber o f sys tem l ife un i ts ,

d iv ided by the to ta l number o f main tenance ac t ions (p reven t ive and correct ive) dur ing a s ta ted

per iod o f t ime.

M e a n T im e B e t w e en R e m o v a l s ( M T B R ) A measure of the system reliabil i ty parameter related

to demand for logist ic support . The total number of system life units d ivided by the to tal number

of i tems rem oved f rom that sys tem dur ing a s ta ted per iod o f

t im e .

This term is defined to exclude

removals perfo rmed to fac i l i ta te o ther main tenance and removals fo r p roduct improvement .

M e a n T i m e t o F a i lu r e ( M T T F ) A basic measure o f re l iab i l i ty fo r non-repai rab le i tems. The

total number of l ife units of an i tem divided by the to tal number of fai lures within that popula

t ion , dur ing a par t icu lar measurement in terval under s ta ted cond i t ions .

M e a n T i m e t o R e p a i r ( M T T R ) A basic meas ure o f main ta ina b i l i ty . Th e sum of co rrect ive

maintenance t imes at any specific level of repair , d ivided by the to tal number of fai lures within

an i tem repai red a t tha t level , dur ing a par t icu lar in terval under s ta ted cond i t ions .

M e a n T i m e t o R e s t or e S y st e m ( M T T R S )

A measure o f the sys tem main ta inab i l i ty parameter

re la ted to avai lab i li ty and read in ess . Th e to ta l co rrect ive main tena nce t ime , associa ted wi th

downing even ts , d iv ided by the to ta l number o f downing even ts , dur ing a s ta ted per iod o f t ime.

Excludes t ime fo r o f f -sys tem main tenance and repai r o f detached componen ts .

M e a n T i m e t o S e r v i c e ( M T T S )

A measure o f an on-sys tem main ta inab i l i ty character is t ic

related to servicing that is calculated by dividing the to tal scheduled crew, operator, and driver

serv ic ing t ime by the number o f t imes the i tem was serv iced .

Miss ion Profi le A t im e-phase d descr ip t ion o f the even ts and env ironments an i tem e xper iences

from in i t ia t ion to complet ion o f a speci f ied miss ion , to include the cr i ter ia o f miss ion success

or cri t ical fai lures.

Mis s io n T ime Be twe e n Cr i t i c a l Fa i lur e s (MTBCF)

A me asur e o f miss ion re l iab i li ty . Th e

to ta l amount o f miss ion t ime, d iv ided by the to ta l number o f cr i t ica l fa i lu res dur ing a s ta ted

ser ies o f miss ions .

M i s s i o n T i m e to R e st o r e F u n c t i o n s ( M T T R F )

A mea sure o f miss ion main ta inab i l i ty . Th e

to ta l co rrect ive cr i t ica l fa i lu re m ain te nan ce t im e, d iv ided by the to ta l numb er o f cr i tica l fa i lu res ,

during the course of a specified mission profi le.

N o t O p e r a t i n g ( D o r m a n t )

The state wherein an i tem is able to function but is not required

to function; not to be confused with T i m e , D o w n ( D o w n t i m e ) .

O p e r a b l e

Th e s ta te o f being ab le to perfo rm the in tended funct ion .

O p e r a t i o n a l R e a d i n e s s The abil i ty of a mili tary unit to respond to i ts operation plan(s) upon

receipt of an operations order (function of assigned strength, i tem availabil i ty , status, supply,

training, etc.) .

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GLOSSARY

O p e r a t i o n a l R M V a l u e A measure o f re l iab i l i ty o r main ta inab i l i ty (R M) that includes

the com bine d ef fec ts o f i tem des ign , ins ta l la t ion , qual i ty, env i ronmen t , opera t ion , ma in tena nce,

and repair .

P r e d i c t e d That which i s expected a t some fu tu re t ime, pos tu la ted on analys is o f pas t exper i

ence and tes ts .

R e a s s e m b l y Assembl ing the i tems that were removed dur ing d isassembly and c los ing the

reassem b led i t em s .

R e d u n d a n c y Th e ex is tenc e of m ore than one means fo r accompl ish ing a g iven funct ion . Each

means o f accompl ish ing the funct ion need no t necessar i ly be iden t ica l .

R e d u n d a n c y , A c t i v e

T h a t r ed u n d an cy w h ere in a l l r ed u n d an t i t em s a re o p e ra t in g s im u l t a

neously .

R e d u n d a n c y , S t a n d b y

That redundancy wherein the a l ternat ive means o f perfo rming the

function is not operating unti l i t is activated upon fai lure of the primary means of performing

the function.

Re l ia b i l i ty

(a) The duration or probabil i ty of fai lure-free performance under stated condit ions,

or (b) the probabil i ty that an i tem can perform its in tended function for a specified in terval under

s ta ted cond i t ions . (For non-re dund an t i tem s, th is i s equ ivalen t to def ini t ion (a) . For redu ndan t

i tems, th is is equivalent to the definit ion of mission rel iabil i ty .)

Re l ia b i l i ty Gr o wth

Th e imp rove me nt in a re l iab i l ity param eter caused by the successfu l co r

rec t ion o f def ic iencies in i tem des ign o r manufactu re .

Re l ia b i l i ty Mis s io n

The abil i ty of an i tem to perform its required functions for the duration

of a specified mission profi le.

R e p a i r a b l e I t e m An i tem that can be res to red by correct ive main tenan ce to perfo rm al l o f i ts

requ ired funct ions .

R M A c c o u n t i n g Th at se t o f mathem at ica l tasks that es tab l ish and a l locate quan t i ta t ive re l i

ab i l i ty and main ta inab i l i ty ( R M ) requ irements , and p red ic t and measure quan t i ta t ive R M

r eq u i r em en t s .

R M E n g i n e e ri n g That se t o f des ign , development , and manufactu r ing tasks by which re l i

ab i l i ty and main ta inab i l i ty

(R M)

are ach ieved .

S c r e e n i n g A pro cess for inspec ting i tems to rem ove thos e that are unsatisfactory or those l ikely

to exhibit early fai lure. Inspection includes visual examination, physical d imension measurement,

and funct ional perfo rmance measurement under speci f ied env ironmenta l cond i t ions .

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Se r v ic ing The perform ance of any act neede d to keep an i tem in operat ing c ondi t ion ( i .e . , lubr i

cat ing, fuel ing, oi l ing, c leaning) , but not including prevent ive maintenance of par ts or correct ive

maintenance t asks .

Sing le -Po in t Fa i lur e

The fai lure of an i tem that would resul t in fai lure of the system and is

not compensa ted for by redundancy or a l t e rna t ive opera t iona l procedure .

Sne a k Cir c u i t An a ly s i s A procedure conducted to ident i fy la tent paths that cause occurrence

of unwanted funct ions or inhibi t desi red funct ions, assuming al l components are funct ioning

properly.

Storage Life (She lf Life ) The length of t ime an i tem can be s tored under specif ied condi t ions

and s t i l l meet specif ied requirements .

S u b s y s t e m A combina t ion of se ts , groups, and so for th that performs an operat ional funct ion

within a system and is a major subdivis ion of the system (e.g. , data processing subsystem, guid

a nc e s ubs ys t e m) . ( Sour c e : M I L - STD - 28 0 . )

S y s t e m , G e n e r a l A co mp os i te of equipm ent and sk i ll s , and techniques c apable of per forming

or support ing an operat ional role , or both. A complete system includes al l equipment , re lated

faci l it ies , ma ter ial , sof tware, serv ices , and person nel required for i ts operat ion a nd sup port to the

degree that i t can be considered sel f -suff icient in i ts intended operat ional environment .

Sy s te m R M P a r a m e t e r A measure of re l i ab i l i ty and main ta inabi l i ty (R&M) in which the

uni t s of me asurem ent a re d i rec tly re la ted to opera t iona l readiness , miss ion su ccess , main tenance

manpower cost , or logis t ic support cost .

Te s t, Ac c e pta n c e

A test conducted under specif ied condi t ions by, or on behalf of , the govern

me nt , using del ivered or del iverab le

i t em s ,

to determ ine the com plianc e of the i tem with specif ied

requirements ( including acceptance of f i rs t product ion uni ts) .

Te st M e a s ur e me n t a nd Dia g no s t i c Equ ipm e nt (TM DE )

A ny system or device used to evalu

ate the condi t ion of an i tem to ident i fy or isolate any actual or potent ial fai lures .

Test , Qual i f icat ion (Des ign Approval) A test conducted under specif ied condi t ions, by or on

behalf of the government , using i tems representat ive of the product ion configurat ion, in order

to de te rmine co mp l iance w i th i t em des ign requi rem ents as a bas i s for produc t ion approva l ; a l so

known as demons t ra t ion .

T e s t i n g D e v e l o p m e n t ( G r o w t h ) A ser ies of tes ts conducted to disclose def iciencies and to

ver ify that correct ive act ions wil l preve nt recu rren ce in the operat iona l inventory. N ote that

repair of tes t i tems does not const i tute correct ion of def iciencies; a lso known as tes t -analyze-

and-f ix (TAAF) test ing.

T i m e Th e universa l me asure of dura t ion . Th e genera l word t im e wi l l be modi f i ed by an

addi t ional term when used in reference to operat ing t ime, mission t ime, tes t t ime, and so for th.

In general expres sions such as m ean t ime betw een fai lure (M TB F), t ime s tands for l i fe uni ts ,

which must be more specif ical ly def ined whenever the general term refers to a par t icular i tem.

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GLOSSARY

See Figure C.l for time relationships.

Not

Operating

Time

Up

Time

lert

Time

Reaction

Time

Time to Restore

Functions During

Mission

Time

ctive

Time

Mission

Time

Inactive

Time

Corrective

Maintenance

Time

Preventive

Maintenance

Time

Figure Cl

Time relationships

Down

Time

Maintenance

Time

Modification

Time

Delay

Time

Supply

Delay

Time

dministrative

Time

Time, ActiveThat time during which an item is in an operational inventory.

Time, AdministrativeThat element of delay time, not included in the supply.

Time, Alert

That element of uptime during which an item is assumed to be in specified operat-

ing condition and is awaiting a command to perform its intended mission.

Time, CheckoutThat element of maintenance time during which performance of an item is

verified to be a specified condit ion.

Time, Delay

^That element of downtime during which no maintenance is being accomplished

on the item because of either supply or administrative delay.

Time, Down Downtime)

That element of active time during which an item is not in condi tion

to perform its required function reduces

Availability

and

Dependability).

Time, InactiveThat time during which an item is in reserve.

Time, MissionThat element of uptime required to perform a stated mission profile.

Time, Modification

The time necessary to introduce any specific change s) to an item to

improve its characteristics or to add new ones.

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ACCELERATED TESTING

Time, Not OperatingThat element of uptime during which an item is not required to operate.

Time, ReactionThat element of uptime needed to initiate a mission, measured from the time

that the command is received.

Time, Supply Delay

That element of delay time during which a needed replacement item is

being obtained.

Time, TurnaroundThat element of maintenance time needed to replenish consumables and

check out an item for recommitment.

Time, Up Uptime)

That element of active time during which an item is in condition to per-

form its required functions.

Uptime Ratio

A composite measure of operational availability and dependability that includes

the combined effects of item design, installation, quality, environment, operation, maintenance,

repair, and logistic support; the quotient of uptime divided by uptime plus downtime.

Useful LifeThe number of life units from manufacture to when the item has an unrepairable

failure or unacceptable failure rate.

Utilization Rate

The planned or actual number of life units expended, or missions attempted,

during a stated interval of calendar time.

Wearout

The process that results in an increase of the failure rate or probability of failure

with increasing number of life units.

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APPENDIX D

LISTOFACRONYMS

The fo l lowing acronyms a re used throughout th i s book:

A M SA A Ar m y M a t e r i a l Sys t e ms Ana l ys i s Ac t i v it y

D M M H / M A Di r e c t ma i n t e na n c e ma n- ho ur s pe r ma i n t e na nc e a c t ion

D M M H / M E Di r e c t ma i n t e na n c e ma n- ho ur s pe r ma i n t e na nc e e ve n t

EM I Elec t rom agne t ic in te r fe rence

E SD Elec t ros ta t i c d i scharge

ES S Env i ronm enta l s t ress sc reening

E S S E H

nvironmental Stress Screening of lectronic Hardware

F M E A Fai lure m ode s and e f fec ts ana lys i s

FR AC A S Fai lure ra te ana lys i s and cor rec t ive ac t ion sys tem

GPA Gra de poin t average

G R M S g- force root m ean square

HA LT High ly acce le ra ted l if e t es t ing

H A SS High ly acce le ra ted s t ress sc reen

HP He wl e t t - Pa c ka r d

IC Integ rated ci rcui t

IES Ins t i tu te of Env i ronm enta l Sc iences

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ACCELERATED TESTING

I /O Input and outpu t

LR U Line rep lac em ent un i t

M TB C F Miss ion t ime betw een cr i t ica l fa i lu res

M T B D M e a n t i m e b e t w e e n d e m a n d s

M T B D E M ean t im e b e tw een d o w n in g ev en t s

M T B F M ean t im e b e tw een f a ilu res

M T B M M e a n t i m e b e t w e e n m a i n t e n a nc e

M T B M A M ean t im e b e tw een m a in ten an ce ac t io n s

M T B R M ean t im e b e tw een r em o v a l s

M T T F M ean t im e to f a ilu re

M T T R M ean t im e to r ep a i r

M TT R F Mis s ion t ime to res to re funct ions

M T T R S Me an t im e to r e s to re sy s t em

M TT S M ean t ime to serv ice

OC Ope rat ing character is t ic (cu rve)

PS D Pow er spect ra l densi ty

R A D C R o m e A i r D ev e lo p m en t C en te r

RI W Rel iab i l i ty impr ovem ent warran ty (con trac t )

R & M Rel iab i l i ty and main ta inab i l i ty

RO I Retu r n on inves tment

SPC S ta t i s tica l p rocess con t ro l (p rogram )

S R A S h o p r ep laceab le a s sem b ly

SRU Shop rep lacea b le un i t

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LIS T

OF ACRONYMS

TA AF Tes t -ana lyze-and- f ix ( t est ing)

TM D E Te s t me a s u r e me n t a nd d i a gnos ti c e qu i pme n t

W RU W e a pon r e p l a c e a b l e un i t