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Military Standard MIL-STD-781D, Reliability Testing for Engineering Development, Qualification and Production, 1986.

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Military Standard MIL-STD-781D, Reliability Testing for Engineering Development, Qualification and Production, 1986.
MIL-STD-781
17 October
D
1986
SUPERSEDING
MIL-STD-781C
21 October
1977
MIL-STD-1635(EC)
3 February
1978
MIL-STD-2068
(AS)
21 March 1977
MILITARY STANDARD
RELIABILITY TESTING
FOR
ENGINEERING
DEVELOPMENT,
QUALIFICATION,
AND PRODUCTION
I
I
AMSC N3988
DISTRIBUTION
AREA RELI
STATEMENT
A:
Approved
for public
release;
distribution
is unlimited.
Ml L-STD-781
D
DEPARTMENT OF DEFENSE
Washington,
DC 20363-5100
RELIABILITY TESTING
FOR ENGINEERING
1. This Milita~Standard
DEVELOPMENT,
isapproved
foruseby
QUALIFICATION,
ANO PRODUCTION
all Depa~ments
and Agencies
of the Oepaflmentof
Defense.
2. Beneficial comments (recommendations,
additions,
beofuse
inimproving
thisdocurnent
should beaddressedto:
Systems Command, ATTN:
Standardization
Document
by letter.
deletions)
andanypeflinent
datawhich
Commander,
Space and Naval Warfare
may
SPAWAR003-121,
Washington,
DC 20363 -5100, byusing theself-addressed
improvement
Proposal (DDForm
1426) appearing
attheend
ofthisdocumentor
=.
ii
MI L-STD-781”D
FOREWORD
1. MIL-STD-781 Disacomplete
revision of MlL-STD-781C.
task basis and is fully coordi nated with MI L-STD-785.
2. [email protected]~
tasks which can beseleaed
change
tosuitthe
Thisstandard
isorganized
onatailorable
in MlL-STD-781
isthereorganization
ofthisdocumerit
intotailorable
specific needs ofeach program.
Thisstandard
isintentionally
stru~ured
todiscourage
indiscriminate
blanket applications.
seleaed andthatthe
procuring aaiviNwill
provide specified
specified:
(l) Test Planning and Control;
Environmental
Stress Screening.
(2) Development
Tailoring will ensure thatspecific
tasks will be
eswntial information.
Four task areas are
Testing;
(3) ReliaMlity
Accounting
Tests;(4)
3. Thestatistical
testplans andtest environments
have beentransferred
to MlL-HDBK-781,
which will
beissued simultaneously
withthestandard.
Thestandard
testplanswhich
were in MlL-STD-781 Carenow
included in MIL-HDBK-781
without change except that thesufix
letter Cattheend
ofeachtest
plan number
has been
changed
toD.
(Forexample,
Test Plan lVCin
MlL-STD-781
Plan IV-D.)
..
Ill
Cisincluded
in Ml L-H DBK-781
as Test
MIL-STD-781D
CONTENTS
~
Paragraph
1.
1.1
1.2
1.3
2.
2.1
2.1.1
3.
3.1
SCOPE . .
Purpose
. . .
. .
Application.
Equipment
.
.
.
.
.
.
.
categories
.
.
.
.
.
.
.
.
.
.
.
REFERENCECYDOCUMENTS
DEFINITIONS
Terms
.
.
.
.
.
.
.
.
.
.
.
.
.
.
maintenance
.
3.1.3.2
3.1.3.3
Producer’srisk
Discrimination
.
3.1.4
3.1.4.1
Failures
. . ...”.....
Multiple
failures
Pattern failures
3.1.4.2
3.1.4.3
3.1.5
3.1.5.1
3.1.5,2
3.1.5.3
3.1.6.2
.
.
.
.
.
..
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1
1
2
.
2
2
3
3
3
3
3
3
3
3
3
.
3
3
.
.
..
. .
. .. .
. . ..
.
3
3
3
3
3
4
.
failure
.
4
4
4
.
MTBF interval
1
1
.
.
error failure
of reliability
Observed
.
.
.
.
.
.
Demonstrated
.
.
failure
Part manufacturing
3.1.6
3.1.6.1
.
design failure
Software
Measures
.
.
.
:
Equipment
manufacturing
Part design failure
3.1.5.5
.
.
.
.
(a).
ratio (d)
3.1.5.4
.
.
(repair)
Chargeable
failure
Failure categories
Equipment
.
.
.
.
Decision risks
Consumer’s risk @
.
.
.
.
.
Corrective
.
. . .
. .
. .
. ..
3.1.3
3.1.3.1
.
.
.
.
.
.
.
.
.
.
.
.
.
Contractor
.
.
.
.
.
.
.
3.1.1
3.1.2
.
.
.
.
.
.
.
Government
documents
Standards and handbooks
.
.
.
.
.
.
.
(Od )
4
.
MTBF ($)
3.1.6.3
Lower Lest MTBF (6’1 )
4
3.1.6.4
Upper
4
3.1.6.5
Predicted
3.1.6.6
Observed
3.1.6.7
Intensity
test MTBF(80)
4
MTBF(I?P)
cumulative
function
3.1.6.8
Instantaneous
3.1.6.9
Observed
failure
(Pfi))
MTBF function
reliability
4
rate (P(t))
4
. .
4
(M(t))
4
(R(t))
4
3.1.7
Mission
3.1.8
Life-cycle
profile
4
3.1.9
Procuring
activity
5
4..
4.1
profile
6
GENEf7iIL REQUIREMENTS
Reliability test program
4.2
Integrated
4.3
Environmental
reliability
test planning
test conditions
iv
.
.. .
. ..
. .
.
.
.
.
.
.
6
6
6
“’..
- MIL-STD-781D
CONTENTS
Paragraph
4.3.1
4.3.1.1
4.3.1.2
4.3.1.3
4.3.1.4
4.3.1.5
4.4
4.4.1
4.4.2
4.5
4,5.1
- Continued
Combined environmental
Electrical stress.
.
Vibration
stress
Thermal stress
.
Moisture . . . . . . .
.
test conditions
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
Calibration
oftest apparatus
Performance
baselines
.
.
.
.
.
.
.
.
.
.
.
.
7
7
7
.
.
.
7
.
.
.
.
.
.
Failure
4.6.1
4.6.1.1
action system (FRACAS)
Problem and failure action
Problem and failure reporting
4.6.1.2
4.6.1.3
4.6.1.4
Identification
and control of failed
Problem and failure investigations
Failure verification
4.6.1.5
4.6.1.6
4.7
Corrective action
Problem and failure
reporting,
..
.
analysis,
.
.
.
.
.
.
.
Chargeable
failures
Nonchargeable
failures
.,.
4.7.4
4.7.5
4.8
Alternate
failure
GEE..........::::
6.3
6.4
.
.
and closeout
.
.
9
9
9
9
11
11
categories
:
12
Taskdescriptions
.
.
9
II
DETAIL REQUIREMENTS
.
8
8
8
.
.
tracking
7
8
8
8
.
NOTES
7
items
.
6.
6.1
6.1.1
6.2
.
and corrective
Failure categories
Relevant failures
Nonrelevant
failures
5.1
6
6
7
7
.
4.6
5.
.
.
.
.
Pretest performance
Performance
during test
POst-te5t performance
4.7.1
4.7.2
4.7.3
:
6
6
Equipment
cycling
Testinstrumentation
and facilities
Tolerance oftest environments
4,5.2
4.5.3
.
.
12
.
.
.
.
.
.
.
.
.
.
.
.
.
...13
Tailoring of task descriptions
Details to bespecified
Method of reference
13
13
13
Data Item Descriptions
Subject term (keyword)
13
14
(DID).
listing
TASKS
TA5K SECTION
Task
100.
TEST PLANNING
101
INTEGRATED
I 02
RELIABILITY
AND CONTROL
RELIABILITY
TEST PROCEDURE
v
Iol-1
TEST PLAN DOCUMENT
.“
102- I
1,
MI L-STD-781
CONTENTS
D
~ Continued
~a~
Task
103
RELIABILITY
GRQWTH
104
TEST PROGRAM
105
JOINT TEST GROUP
106
RELIABILITY
PUNNING.
.
REVIEWS
.
Task
201
SURVEY TESTING
202
RELIABILITY
OEVELOPMENT/GROWTH
TASK SECTION 300.
RELIABILITY
ACCOUNTING
Task
301
RELIABILITY
QUALIFICATION
302
PRODUCTION
401.
.
.
.
104-1
.
105-1
10G1
DEVELOPMENT
Task
.
.
TEST REPORTS
TASK SECTION 200.
TASK SECTION 400.
103-1
TESTING
...
RELIABILITY
.
.
.
.. .
TEST
201.
..
202-1
TESTS
TEST
ACCEPTANCE
ENVIRONMENTAL
STRESS SCREENING
Environmental
STRESS SCREENING
301- I
TEST
302-1
401-1.
FIGURES
Figure
I
103- I
401.1
Example of failure categories
Reliability growth profile (example).
Random vibration spectrum
.-.
vi
10
103-3
401-3
‘“
‘:
,
MIL-STD-781
D
1. SCOPE
1.1 Pur~ose.
This standard
dud ng the development,
qualification,
1.2 Application.
performed
during
specifies the general
and production
This standard
integrated
establishes
test programs
requirements
and specific
ta$ks for reliability
testing
of systems and equipment.
the tailorable
specified
requirements
in MIL-,STD-785.
for reliability
Task descriptions
testing
for Reliability
DevelopmentiGrowth
Testing (RD/GT), Reliability Qualification
Testing (RQT), Production
Reliability
Acceptance Tests (PRAT), and Environmental
Stress Screening (ESS) are defined.
Tasks specified in this
standard
are to be selectively
applied
of work (SOWS), and Government
equipment.
1.3
Equigment
distinguished
I
categories.
according
procurements,
developments
This standard
which
is applicable
requests
require
1.
Fixed ground. equipment
Category
2.
Mobile
ground
A. Wheeled
to six broad categories
equipment
vehicle
B. Tracked vehicle
C. Shelter configuration
D. Manpack
Category
3.
Shipboard
equipment
A. Naval surface craft
B. Naval submarine
C. Marine craft
D. Underwater
vehicle
Category
4.
Equipment
for jet aircraft
A. Fixed wing
1
Category
5.
B. Vertical
and short takeoff
Turboprop
aircraft
A. Turboprop
B. Helicopter
I
Category
6.
external
A. Air-launched
missiles
B. Assembled external stores
missiles
1
(V]5TOL)
equipment
‘“
Missiles and assembled
C. Ground-launched
and landing
and helicopter
for proposals,
reliability
to their field service applications
Category
I
‘
in DOD contracted
in-house
stores
testing
statements
of systems and
of equipment,
MIL-STD-781
D
2. REFERENCED DOCUMENTS
2.1
Government
2,1.1
Standards
documents.
and handbooks.
Unless otherwise
of the issue listed in that issue of the Department
specified
in the solicitation
specified,
of Defense
form a part of this document
the following
standards
Index of Specifications
to the extent
specified
and handbooks
and Standards
(DODISS)
herein.
STANDARDS
MILITARY
I
MI L-STD-280
Definitions
Of Item Levels, Item Exchangeability,
MIL-STD-721
Definitions
Of Terms For Reliability
MI L-STD-785
Reliability
Program. For Systems And Equipment
Production
MIL-STD.81
o
MI L-STD-45662
Environmental
Calibration
Test Methods
Models,.And
Related Terms.
And Maintainability
And Engineering
Development
And
Guidelines
System Requirements
HANDBOOKS
MILITARY
MIL-HDBK-189
Reliat$lity
MIL-HDBK-781
Reliability Test Methods, Plans, And Environments
Development,
Qualification,
And Production
Gro~h
Management
.,
For Engineering
(Copies of standards and handbooks required by contractors in connection
with specific
functions should reobtained
from theprocuringa
ctivityora sdiretiedb
ythecontractingo
..
procurement
fficer.)
MI L-STD-781D
3. DEFINITIONS
3.1 ~.
Terms used herein areinaccordance
MI L-STD-785, MIL-STD-81O, and MI L-H D8K-189, with
3.1.1 through
Military
3.1.9.
3.1. I Contractor.
Contraaor
systems and equipment.
includes Governmental
3.1.2 Corrective maintenance
item to a specified condition.
3.1.3
I
Decision risks.
3.1.3.1
withatrue
3.1.3.2
MTBFequal
thanthe
i~.
parameter$
ailures (MT8F)equalt
Producer”srisk
(a}.
totheuppertest
MT8F
itistheratioof
3.1.4.1
MTBF
asaresult
in3.1.3.1
through
(a)
lessthan
equipment
less than
equipment
Pattern
of accepting
equipment
with
atrue
witha
true
MTBFgreater
(a).
ratio (d)isone
MTBF (Oo)toth:lower
IJreS. Thesimultaneous
failures.
witha
(fS).
of thestandard
test MTBF
(t?l);
test plan
thatis.
Failure types andclassificati
onsarespecified
in Ml L-STD-72l with
and chargeable
failures which are specified in 3.1.4.1 through 3.1.4.3.
MU1tiDlefail
torestorean
3.l.3.3.
ofrejecting
ofreje~ing
Thediscrimination
theuppertest
of failure,
orproducing
(81 ). Theprobability
istheprobabillty
Theprobability
developing
ofaccepting
(81 )willbe
occurrence
two or more failed parts are found during troubleshooting
multiple failures are presumed to have occurred.
3.1.4.2
per formed,
othelowertestMT8F
.Producer’srisk
(~o).
activities
risk (@ istheprobability
thelowertest
Discrimination ratio(d).
3,1.4 _.
multiple, pattern,
Theatiions
Consumer’s
MTBFlessthan
upper test MT8Fwillbe
3.1.3.3
(rePair~.
orindustrial
Decision risks shall beasspecified
Consumer’srisk
true mean-time-between-f
equipment
with thedefinitions
in MlL-5TD-280,
MlL-STD-72l,
the exception and addition of the terms specified in
Theoccurrence
oftwoor
and failures
oftwoormore
failures
theexceptionof
more independent
cannot
be shown
of thesame
equivalent
applications when the failures are caused by the same basic failure
occur atarate
which isinconsistent
with the pans predicted failure rate.
d=oo/@l.
failures.
When
to be dependent,
patiin
identical
mechanism
or
and the failures
3.1.4.3
Chargeable
failure.
Arelevant,
independent
failure ofequipment
under testand any
dependent
failures caused thereby which are cla,s~ified as one failure and used to determine
contractual
ccsmpliance with acceptance andrejection
criteria.
3.1.5
Failure categories.
Failures shall becategorized
as$pecified
in3.1.5.1
through
3.l.5.5
3.1.5.1
Equi~mentdesiqn
failure.
Any failure which can betraced
directly tothedesign
of the
equipment;
that is, thedesign
of the equipment
caused thepati
inquestion
todegrade
or fail, resulting
an equipment
failure.
3.1.5.2
manufacturing
for example,
3.1.5.3
Equipment
manufacturing
process control
the failure
Partdesiqn
during
failure.
equipment
Afailure
caused bypoorworkmanshi
construction,
testing,
porinadequate
or’repai rpriorto
thestart
obtesting;
of an assembly due to cold solder joints.
failure.
The failure
ofpa~Swhich
3
can betraced
directly
in
toinadequatedetign
I
[
MI L-STD-781D
3.1.5.4
or inadequate
Partmanufacturinq
failure.
Patimanufaduring
failures aretheresult
ofpoorworkmanship
manufacturing
process control during part assembly, inadequate
inspection, or improper
testing.
3.1.5.5
the hardware.
3.1.6
Software
Measures
error failure.
ofreliabilitf.
Afailurecaused
Relia&lity
byanerror
measurement
inthecomputer
shall beasspecifi4
program
in3.1.6.1
associated
through
3.l.6.9.
3.1.6.1
Demonstrated
MTBFinterval
(Od): Demonstrated
MTBFinterval
(6’d) istheprobable
of true MTBF under test conditions; that is, an interval estimate of MTBF at a stated confidence
level.
3.1.6.2
Observed MTBF (jl.
Observed
equipment
divided by the number of relevant
3.1.6.3
standard
Lower test MTBF(6’1).
test plans will reject, with
MTBF (#) isequal
failures.
Lower test MTBF
high probability,
(81)
tothetotal
isthatvalue
equipment
with
operating
which
with
range
timeofthe
isunacceptabie.
The
a true MTBF that approaches
(6? ).
3.1.6.4
UDpertest MTBF (00).
Upper test MTBF (00) isanacceptable
value of MTBFequal
discrimination
ratio times thelowertest
MTBF (81). Thestandard
testplanswill
accept, withhigh
probability,
equipment
withatrue
MTBFthatapproaches
[80).
Thisvalue
(f)o) shall berealistically
attainable,
based on experience and information.
tothe
3.1.6.5
Predicted MTBF (8P).
Predicted MTBF (8P) isthatvalue
of MTBFdeterminedb
yreliabiiity
prediction methods; itisafbnction
of theequipment
design andtheusee~vironment.
(Op) should be
eq”alto
orgreaterthan
(00) invalue, tOensure,with
high probaMbty,
that theequipment
will reaccepted
during
the reliability
qualification
test.
3. I.6.6 Observed cumulative
failure rate( P(t)). Theobsewed.
cumulative
failure
equal to the number of relevan’tsystern
‘failures N(t) accumulated
by t, divided by t.
3.1.6.7
lntensitv function (P(tD. Theintensity
expected value of N(t), thenumber
ofsystem failures
ra.te(p(t))
attim.?tis
function (P(t) )isthechange
perunittimeofthe
bytim et. This is written as:
P(t) = dE(N(t))/dt
where
E represents
the expected
value
3.1.6.8
instantaneous
MTBFfunction
reciprocal of the failure rate function.
3. I.6.9
for a specified
Observed
operating
(M(t)l.
Theinst.antaneous
reliability
(R(t)~. Apointestimate
time, t, given that the equipment
MTBFfunction
attisequal
ofreliab!lity
equal totheprobability
of survival
was operational
at the beginning
of the period.
3.1.7 Mission profile,
Ageneric
definition
isspecified in MI L-STO-721.
Thisamplification
definition
applies to reliability
test programs: A thorough description of all of the major planned
conditions associated with one.specific mission. Amission pro file isonesegment
example, amissile captive-carry
phase oramissile
free-f light phase). Theprofile
event, the expected
anitem
environmental
conditions,
energized
and nonenergized
3.1.8 Life-cvcleorofile.
Athorough
time-l ifedescription
of equipment
from thetime
of final factory acceptance
4
tothe
of that
events and
ofalife-cycle
pro file (for
depicts thetimespanofthe
periods,
and so forth.
of theevents
andconditions
associated with
until itsulti mate disposi tion (for example,
..
MIL-STD-781D
factory-to-target
and checkout,
including
conditions,
sequence).
standby
alternate
Each significant
life-cycle
and ready modes, operational
possibdities.
and the operating
The profile
event,
such astranspotiation,
deployment,
dormant
and mission profiles,
depicts the time span of each event,
storage,
test
are addressed,
the environmental
modes.
3.1.9
Procurinaactivity.
Asusedin
t~sstandard,
procuring
or the prime contractor
in transactions with their SUPPI iers.
$
I
I
5
aaivity
refers tothe
Government
agency
MI L-STD-781D
4. GENERAL REQUIREMENTS
4.}
Reliability
testproqram.
Thereliatility
and production tests in accordance with
bytheprocuring
activity. Thereliability
foreachappropriate
acquisition phase.
4.2
Integrated
reliability
testprogram
shall reintegrated
with
other development
the general requirements
of this standard and the task(s) specified
tests shall. deselected
andtailored
according tothetypeofitem
and
test planning.
lnorder
toavoid
duplication
oftesteffoti
andtoensurethat
deficiencies are not overlooked,
the integrated
reliability test plan document
shall define procedures which
ensure thatreliability
data isderived
from another
tests required bycontract.
Theintegrated
testplanshall
contain a description of the test plans selected for use, the decision risks, and the environmental
test
I
conditions, and shall be keyed to the program
and MIL-HDBK-781.
life-cycle
phases and the appropriate
sections
of this standard
4.3 Envircmmental testconditions.
Theenvironmental
testconditions
to reapplied
duting the test
specified inthisstandard
andthei rvariation
with time shall berepresentati
vedfthe
field service and mission
environment
of theequipment
4.3. I
Combined
undervest.
environmental
Thisrequirement
testconditions.
doesnotapplyto
Unless othen.vise
ESS.
specified
6ythe
procuring
activity,
thestress types defined in4,3.1 .\through
4.3.1.5, shall becomblned
inthesame
chamber atlevelsand
of change appropriate
to the specified stress data. The combined environmental
test conditions profile
be developed in accordance with the guidance provided in MI L-HDBK-781, Section 5.
rates
shall
4.3.1.1
Electrical stre$s. Electrical stressshallincludee
quipmentO N-OFFcyclin
g,'operationin
accordance with thespecified
operating
modes and'duty cycles, andinput
voltage variation
above and
beiowthe
I
nominal
4.3.1.2
value specified
Vibration
stress:
‘
Vi bration
test.levels
orrandom);
andprofiless
themounting
inthedefinition
b) frequency
hall betailoredt
othespecifiedi
range;
c)amplitude;
andd)manner
for
type
(sine sweep, complex,
aPPliCatiOfl.
acharacter,
environment
Theintent
ofthisrequ
irement istoproduce
intheequi
pmenton
test avibration
respo"se with
magnitude,
frequency range, andduration
similar tothatproduced
bythe field service
and mission profile. Themechanical
impedance
effects (the interaction
ofequipment,
fixtures,
4.3.1.3
Thermal stress. Thethermal
stress profile shall bearealistic
simulation
of the actual thermal
environment
thatthe
equipment
experiences inthe service application.
The minimum
factors to be
considered in the definition
of thermal stress shall be; a) statiing temperature
(heat soak, cold soak) and
tum on (warm” P) time; b) operating
temperature
(range, rate of change, and frequency
of change; C)
Moisture,
cycles permission
Moisture
profile;
levels during
andd)cooli
thetemperature
ngairflow
(rate and fluctuation).
cycles shall besufficient
to produce
visible
condensation
and frosting or freezing, when such conditions can beexpeaed
infield
service. The humidity
should decontrolled
during thetest cycle andmaybe
increased toproduce
the desired result by injecting
water vapor at appropriate
times in the test cycle.
4.3. I.5
Equipment
of field operation,
cyclinq.
Equipment
see MI L. HDBK-781,
cycling imposed
Section 5.
6
dutingreliability
:
.,.
: ::.
“.
and axis of
attachment
structures, andshakers
which would influence the laboratory
simulation
of the effects of
vi bration environments)
shall be,accounted
forin. establishing vi bration level sfor all tests. As a minimum,
the weight reduction criteria of MIL-5TO-81O,
Test Method 514.3, shall be applied.
4.3.1.4
-“
..
ntended
location and theclassificati
on category
ofrealistic
vibration) stress shall bea)
ofvibration
oftemperature
~~
in thecontract.
applicatiOn Oftheequipmen:
andshall consider
field use. Theminimum
factors to beconside[ed
number
.
.
tests shall be representative
...
,
MI L-STD-781D
4.4
Test instrumentation
and facilities.
tests aredescribed
in MIL-HDBK-781,
with MIL-STD-45662.
4.4.1
tolerance
Tolerance
of test environments.
of test environments
and facilities
used in conducting
Sinusoidal,
of test apparatus.
stated
the
and tested in accordance
in the equipment
specification,
in a and b:
* 2“Celsius (C) (3.6”Fahrenheit
b. Vibration
amplitude:
MIL-HD8K-781,
Section 5.
Calibration
Unless otherwise
shall be as specified
a. Temperature:
4.4.2
Test instrumentation
Section 6. These items shall be fully calibrated
(F)), after thermal
f 10 percent.
The calibration
Random,
stabilization.
as specified
of instruments,
in MIL-STD-810
test equipment,
and
and chambers
used to control or monitor the test parametem
shall be verified, periodically,
in accordance with the
requirements
of MIL-STD-45662
and to the satisfaction
of the procuring activity.
All instruments and test
equipment used in conducting
the test shall be as specified in a through c:
a. Conform
to laboratory
Standards of the U.S. Department
b. Have a precision
c. Be appropriate
4.5
Performance
standards
whose calibration
of Commerce
of at least one-third
for measuring
baselines.
is traceable
the tolerance
the conditions
Both performance
to the National
for the variable
and reliability
performancemeasurement,
performance
measurements,
to be measured
concerned
shall be assessed in a test program
statistically valid length under combined, cyclic, and time-varying
environmental
conditions expected in service use. This shall be accomplished
by demonstrating
baseline, through detailed
completion of the detailed
Bureau of
of
conditions which simulate
an acceptable
performance
before the start of reliability
testing. After
selected performance
test criteria shall.be used
during the reliability test to ensure acceptable equipment
performance.
Unless otherwise
specified by the
procuring activity, all pretest and post-test measurements
shall be performed
at standard ambient
conditions. Whenever
standard ambient conditions must be controlled to obtain reproducible
results, the
measurements
and tests shall be made using those tolerances
measurement.
Actual
4.5. I
test conditions
Pretest performance.
the specified requirements
be recorded to determine
shall be recorded
Prior to starting
required
during
to obtain
the test period,
tests, the performance
the desired
whether
precision
controlled
of
or not.
level of the test item relative
shall be established under standard ambient conditions.
Performance
compliance
with performance
requirements
and to provide reference
to
data shall
levels or
criteria for checking designed performance
of the item during and at the conclusion of the test. The pretest
performance
check shall be made after installation
of the item in the test facility.
The conditions during the
pretest check will be standard ambient unless otherwise specified.
This test shall also be used to establish
anomalies
in system performance
errors shall not be counted
4.5.2
Performance
caused by malfunctioning
as hardware
durinq
test.
cycle. These data shall be compared
considered
acceptable
during
software.
Identified
and corrected
software
failures.
Performance
with
data shall be recorded
pretest and during-test
the performance
for the test item during
performance
check shall be those specified
data.
each test
The conditions
in the equipment
specifications
and in the test procedure.
4.5.3 Post-test performance.
Performance
data shall be recorded for the test item at the conclusion
of the test. These daja shall be compared with pretest and during-test
performance
data and the specified
requirements.
the procuring
4.6
The conditions
during
the post-test
will be standard
ambient,
unless otherwise
specified
by
activity.
Failure reportinq,
analysis, and corrective
used to collect data on, analyze,
reliab~lity tests. The contractor’s
action system (FRACAS1.
A closed loop system shall be
and record timely corrective action for all failures that occur during
existing FRACAS shall be utilized with the minimum
changes necessary to
7
I
I
MIL-STD-781D
conform to the requirements
of MI L-STD-785 and thisstandard.
The system shall cover all test items,
interfaces between test items, test instrumentation,
test faci Iities, test procedures, test personnel, and the
handling
and operating
instructions.
4.6.1 Problem and failure action.
At the Occurrence of a problem or failure that affects satisfactory
operation of the equipment,
entries shall be made in the appropriate
data logs and the failed equipment
shall be removed
from test with minimum
interruption
to the equipment
continuing
on test.
4.6.1.1 Problem and failure reportinq.
A failure report shall be initiated
at the occurrence of each
problem or failure of contractor hardware and software, and Government-furnished
equipment
(GFE) (see
6.3).
The report shall contain
the information
required
to permit
determination
of the origin
and correction
of failures. The existing failure report forms maybe used with minimum
changes necessary to conform
the requirements
of this standard and shall include the information
specified in a through c:
identification,
a. Descriptions of failure symptoms, conditions
and operating time (or cycles) at time Of failure.
b.
Information
on each independent
of the failure symptoms, the identification
return the item to operational
readiness
c. Information
describing
of failure
surrounding
and dependent
the failure,
failure
and the extent
modes, and a description
the results of the investigation,
analysis of the item design, and the corrective action taken to prevent
action is taken, the rationale for this decision shall be recorded.
failed
to
hardware
of confirmation
of all repairaction
taken to
the analysis of all part failures,
failure
recurrence.
an
If no corrective
4.6.1.2
Identification
and control of failed items. A failure tags hall be affixed to the [email protected] item . ..
immediately
upon the de:ekt~on of any, failure or suspected failure. The failure tag shall provide space for.
the failure report serial number and for other pertinent entries from the item, failure record. All. failed parts
shall be marked conspicuou:l y or tagged, and controlled
to ensure disposal in accordance wi th contract
requirements.
Failed pare, shall not be.bandied
in any manner which may obliterate
facts which might be
pertinent
to the analysis,
Failed par.ts.shall be stored pending
disposition
by theauthorized
approval
.,. .
. . . .,,
.. ..
...
agency:
of the failure analysis.
4.6.1.3
Problem
and. failure
investiqaticms.
An investigation
and analysis of each reported
failure
shall be performed.
Investigation
and analysis shall be conducted to the level of hardware
or software
necessary to identify causes, mechanisms, and potential effects of the failure. Any applicable
method (that
is, test, microscopic analysis, applications
study, dissection, X-ray analysis, spectrographic
analysis. and so
forth) of investigation
and. analysis which may be needed to determine
failure cause shallbe used. When . .
the removed
item is not defective
or the cause of failure
is external
to the item,
the analysis shall be
extended to include the circuit, higher hardware assembly, test procedures, and subsystem if necessary.
Investigation
and analysis of GFE failures shall be limited toverifyingthat
the GFE failure was not the result
of the contractor’s hardware,
notification of the procuring
software,
activity.
or procedures.
This determination
.-.
shall be documented
for
4.6.1.4
Failure verification.
Reported failures shall be verified as actual failures or an acceptable
explanation
provided to the procuring activity for lack of failure verification.
Failure verification
is
determined
either by repeating the failure mode on the reported item or by physical or electrical evidence
failure (leakage residue, damaged hardware,
and so forth). Lack of failure verification,
by itself, is not
sufficient
rationale
to conclude
of
the absence of a failure.
4.6.1.5
Corrective actibn.
When the cause of failure has been determined,
a corrective action shall be
developed to eliminate
or reduce the recurrence of the failure.
Repairs shall be made in accordance with
normal field operating
procedures and manuals. The procuring activity shall review the corrective actions at
the scheduled status review prior to implementation.
In all cases, the failure analysis and the resulting
corrective actions shall be documented.
The effectiveness of the corrective action should be demonstrated
by restarting
the test at the beginning
of the te;t cycle in which the original
8
failure
occurred.
,.
...
,,, .,
,,
MI L-STD-781D
include
4.6.1.6
Problem and failure trackina and closeout.
The closed loop failure reporting system shall
provisions for tracking problems, failures, analyses, and corrective actions. Status of corrective
actions for all problems
closeout
4.7
shall be reviewed
at scheduled
test status reviews.
Problem
and failure
to assure their adequacy.
Failure categories..
acceptance
chargeable
Failure
and failures
shall be reviewed
All failures
occurring
during
reliability
qualification
and production
reliability
tests shal I be classified as relevant or nonrelevant.
Relevant failures shall be further classi fied as
or nonchargeable.
Rules for classification of failures shall be in agreement
with the approved
Definition
classifications
4.7.1
and Scoring Criteria.
Relevant
failures.
a. Intermittent
b. Unverified
or for which
Relevant
failures
activity
of failure
shall be as specified
Nonrelevant
excluded
which
d:
are still under investigation,
under 4.7
failures.
Nonrelevant
failures
shall be as specified
in a through
g:
damage
b. Accident or mishandling
c. Failures of the test facility or test-peculiar
d. Equipment
test requirements
e. Normal
in a through
fai Iures
a. Installation
approved
will make the final determination
failures
failures (failures which cannot be duplicated,
no cause could be determined)
c. Verified failures not otherwise
d. Pattern
4.7.2
The procuring
(see FIGURE 1).
failures
operating
instrumentation
caused by an externally
adjustments
applied
(nonfailures)
overstress
specified
condition,
in the approved
in excess of the
equipment
operating
instructions
f. Secondary
relevant
failures within
the equipment,
primary failures. The secondary failures
g. Failures caused by human errors
4.7.3
Chargeable
failures.
a. Intermittent
Chargeable
failures
caused by nonrelevant
to be dependent
shall be as specified
on the prima~
in a through
or
failure
d:
failures
b. Unverified
or verified
c. Independent
failures
1. Equipment design
failures
2. Equipment
manufacturing
3. Part design
4. Part manufacturing
verification,
which are directly
must be proved
..
5. Software errors identified,
corrected, and verified during
and the test, shall not be chargeable
as equipment
failures
6. CFE (operating,
d. Relevant failures
maintenance,
or repair procedures
9
the pretest,
the system
that cause equipment
failures)
I
MI L-STD-781D
INCIDENT
FAILURE WHICH
CAN
EXPECTED
TO OCCUR
CLASSIFIED
NONRELEVANT
8E
IN
FAILURE
OF CFE (SEE NOTE)
PLUS ANY DEPENDENT
FAILURES
‘o..
YES
=,
+
CLASSIFIED
CHARGEABLE
NOTE:
Contractor-furnished
equipment
FIGURE
1. Exam~leof
failure
10
cataqories.
?-
,,.,
MI L-STD-781D
4.7.4
Nonchargeable
failures.
a. Ncmrelevant
failures
Nonchargeable
failures shall be as specified in a through c:
b. Failures induced by GFE operating, maintenance, or repair procedures
c. Failures of items having.a specified life expectancy and operated beyond the specified
replacement time of the item
4.7.5
Alternate
used to categorize
by embedded
failure
categories.
both hardware
The alternate
and software
failure
failures
categories
specified
for systems the operations
in a through
c can be
of which are controlled
software.
a. Critical failure is a failure which prevents the system from performing
its mission
b. Major failures areas specified in 1 through 6:
.1. Any failure which reduces performance
of on-line hardware or software so that the
system mission capability
is degraded but not eliminated
2. Any failure which prevents”built-in
test equipment
on-line
hardware
or software
software
hardware
or software
3. Any failure
which causes BITE to continuously
major failures to the lowest group
5. Any failure which causes BITE to continuously
c. Minor failures
1. Any failure
4,8
to isolate and localize
~.
Equipment,
contract.
Reliability
be tested.
to the required
facilities,
and localizing
furnished
or software
(creates
on-line
performance,
false alarms),
false alarm
major failures
in on-line
hardware
or.
in on-line
level
but permits’the
but permits
BITE, when
rate exceeds specified
will be specified
for any GFE included
in
hardware
a major failure
the specified
by the Government
by the Government
11
failure
isolate and localize
level, except when
and material
test data will be provided
a major
rate to exceed
are as specified in 1 and 2:
which impairs on-line hardware
system to fully perform mission
2. Any failure which impairs BITE performance
recycled,
indicate
when such a failure does not exist
4. Any failure which prevents BITE from isolating
or software when such failure does not exist
6. Any failuie which causes BITE false alarm
(BITE) from detecting
level
in the
in the equipment
to
I
I
MI L-STD-781
D
5. DETAIL REQUIREMENTS
5.1
Task descriptions.
Task descriptions
Planning and Control; Section 200, Development
Section 400, Environmental
Stress Screening.
are divided
Testing;
into four general
.-.
12
tasks: Section
Section 300, Reliability
Accounting
100, Test
Tests; and
MI L-STD-781D
6. NOTES
6.1
Tailoring
of task descriptions.
as required by governing
regulations,
type, magnitude,
and funding.
6.1.1
Details to be spe~ified.
The task descriptions
and as appropriate,
specified
herein
to the particular
The Details to be specified
by the procuring
each task description specifies the details, additions, modifications,
deletions,
of the task that should be considered by the procuring activity when tailoring
program needs. Detai Is annotated
by an asterisk (*) are essential
proper implementation
of the task.
6.2
Method
of reference.
When
specifying
are intended
activity
program
paragraph
under
or options to the requirements
the task description to fit
and shall be provided
the task descriptions
to be tailored
system or equipment,
to the contractor
of this standard
as requirements,
both the standard and the specific task description number(s) shall be cited. Applicable
information
required for the Details to be specified by the procuring activity paragraph
of each task shall be included
the SOW.
6.3
Data Item Descrirstions
(DID1.
When
this standard
is used in an acquisition
for
which
in
incorporates
a
DD Form t 423, Contract Data Requirements
List (CDRL), the data requirements
speci fied for Task 101
through Task 401 shall be developed
as specified by an approved
DID (DD Form 1664) and delivered in
accordance’with
the approved CDRL incorporated
into the contract,
When the provisions of DOD FARSUP
52.227-7031
are invoked and the DD Form 1423 is not used, the data specified for Task 101 through Task 401
and 4.6 shall be delivered
by the contractor in accordance with the contract or purchase order requirements.
Deliverable
data required by this specification
are:
DATA REQUIREMENT
~
APPLICABLE
101
DI-RELI-80250
Reliability
Test Plan
102
DI-RELI-80251
Reliability
Test Procedures
103
DI-RELI-80250
Reliability
Test Plan
106
DI-RELI-80252
Reliability
Test Report
201
DI-RELI-80247
DI-RELI-80248
Thermal Suwey Report
Vibration
Survey Report
202
DI-RELI-80250
DI-RELI-80251
DI-RELI-80252
DI-RELI-80253
DI-RELI-80254
DI-RELI-80255
301
DI-RELI-80250
DI-RELI-80251
DI-RELI-80252
DI-RELI-80253
DI-RELI-80254
DI-RELI-80255
DID
‘
Reliability
Test Plan
Reliability
Test Procedures
Reliability Test Report
Failed Item Analysis Report
Corrective Action Plan
Failure Summary and Analysis
Report
Reliability Test Plan
.
Reliabi Iit y Test Procedu res
Reliability Test Report
Failed Item Analysis Report
Corrective Action Plan
Failure Summary and Analysis
13
Report
.
r
MI L-STD-781
302
DI-RELI-80250
DI-RELI-80251
DI-RELI-80252
DI-RELI-80253
DI-RELI-80254
DI-RELI-80255
I
I
401
DI-RELI-80249
DI-RELI-80250
DI-RELI-80251
DI-RELI-80253
DI-RELI-80255
Paraaraph
4.6
6.4
I
I
I
I
D;-RELI-80253
DI-RELI-80254.
Subiect term (kev word)
D
Reliability Test Plan
Reliability Test Procedures
Reliability Test Report
Failed Item Analysis Report
Corrective Action Plan
Failure Summary and Analysis
Environmental
Stress Screening
Reliability Test Plan
Report
Reliability Test Procedures
Failed Item Analysis Report
Failure Summary
and Analysis
Failed Item Analysis
Corrective
Action
Report
Plan
Iistinq.
Built-in test (BIT)
Built-in test equipment
(BITE)
Development
Testing Tasks
Environmental
Stress Screening (ESS) Tasks
Failure reporting, analysis, and.correctiv.e
action (FF&CAS)
Production Reliability Acceptance Tests (PRAT)
Reliability Accounting Tests Tasks
~.
,
Reliability Development/Growth
Testing (RD/GT)
Reliability Qualification
?esting(RQT).
Test Planning and Control Tasks .:
,,
Custodians:
Army - CR
Navy. EC
Air Force- 11
Report
Preparing activity:
Navy - EC
(Project No. RELI-0025)
Review activities.
Army - CR, Ml, AR, AV
Navy -AS, SH, OS
Air Force-01,
10, 13, 16, 17, 18, 19
User activities:
Army - AR, ME
I
14
Report
TASK
SECTION
TEST PLANNiNG
,,.
,
...
AND
.
-.
100-1
100
CONTROL:
MI L-STD-781
D
TASK 101
INTEGRATED
101.1
PurDose.
The purpose
which identifies the reliability.
reliability test program.
101.2
integrates
Task description.
all tests that provide
101.3
●
*
*
equipment
.
Reliability
Corrective
*
An integrated
by the contract
reliability
data for evaluating
the information
TEST PIAN
of TASK 101 is to develop
tests required
Details to be specified
SOW shall include
RELIABILITY
an integrated
and integrates
activitv
in a through
reliability
them
(see 6.1.11.
The details
and
(see 6.3).
to be specified
in the
f, as applicable:
of the reliability
b. Identification
c. Identification
of the contra~ual
status of the integrated
reliability
of the life-cycle, mission, and environmental
profiles
of MI L-STD-785
which identifies
of systems and equipment
a. Identification
usage in service
d. Identification
test plan document
into a comprehensive
test plan shall be prepared
the reliability
bv the wocurinq
specified
DOCUMENT
test tasks
tasks for use i.n support
test plan document
which represent
of the reliability
test program
(that is,
Predictions, Failure Mode Effects, and Criticality Analysis (FM ECA), Failure Repofling, Analysis, and
Action System (FRACAS), and so forth)
e. Specification
of alternate
failure categories
f. DI-RELI-80250,
Reliability Test Plan, applies to this task and shall be specified when required
as a deliverable
data item
“Essential
-.
101-1
MI L-STD-781D
TASK 102
RELIABILITY
102.1
Purpose.
The purpose of TASK 102 is to develop reliability test procedures for each tesl
included in the integrated
reliability test plan document
102.2 Task description.
A separate reliability
integrated
reliability
test plan document (see 6.3).
102.3
Details to be specified
SOW shall include
●
●
TEST PROCEDURE
the information
bv the grocurina
specified
after its approval by the procuring activity.
test procedure
activity
in a through
shall be prepared
for each test in the
(see 6.1.1 ~. The details to be speci fied in the
f, as applicable:
a: Identi;cation
b. Identification
of contractual
of equipment
status of reliability
test procedures
to be used forreliabilityqualification
testing
c. Identification
of equipment
and quantity
development
to be used for reliability
and growth
testing
●
*
required
d. Details of hardware configuration
and system operation under test
e. Performance
parameters to be monitored
during the test
f. DI-RELI-80251,
Reliability Test Procedures, applies to this task and shall be specified
as a deliverable
data item
‘Essential
,,
. ..
..
102-1
when
MI L-STD-781D
TASK 103
RELIABILITY
103.1
Purpose.
The purpose
GROWTH
PIANNING
of TASK 103 is to develop
a reliability
specifies the plan for achieving. specified reliability
values and which
growth and monitoring
progress as the test proceeds.
103.2 Task description.
to indicate what the reliability
the reliability
requirement
growth
provides
planning
curve whkh
a means for tracking
reliability
A graphically
portrayed reliability growth planning curve shall be prepared
value should be at various points in full-scale development
if conformance
to
is to be achieved.
103.2.1
Reliability a rowth Dlannina curve development.
development
shall be based on data from previous development
The reliability growth planning curve
programs for items of the same type being
developed. These data shall be analyzed to determine the length of the reliability growth test period and to
provide project management with a meansof monitoring progress during test (see 6.3). Detailed guidelines
are provided in MIL-HDBK-189.
103.2.2
rowth
Reliabilitva
curve preparation.
The reliability
growth
curves shall be prepared
as point
estimates of each reliability
parameter
specified (that is, system MTBF, mission MTBF, probability
of success,
and so forth) for the entire system and each major subsystem, as specified by the procuring activity. The
vertical axis of the graph shall portray cumulative
values of the reliability
parameter
of the system or major
subsystem and the horizontal
axis shall be in units of both calendar time and test time.
shall be clearly indicated.
A growth curve is shown in FIGURE 103-1.
Each test planned
rowth curve startinq point.
103.2.3
Reliabilitva
Planned growth curves shall depict planned levels of
reliability achievement
at specific points in calendar time and test time and shall be coordinated
with the
scheduled reliability program reviews. Values along the planned growth curve shall represent the planned
reliability
improvement
as measured by a point estimate.
The MTBF value indicated by the planned gro~h
curve at the end of any test program (for example, RD/GT in FIGURE 103-1) should be achieved or exceeded
at or before the end of that test program.
The starting point for the planned growth curve shall be
determined:
1) from information
of previous programs on similar systems; 2) by specifying a minimum
level
of reliability
engineering
which must be achieved to conform to the specified requirements;
assessment of the design and any previous development
test data.
or 3) by conducting an
If historical data are
unavailable,
the starting point maybe estimated by applying a constant factor (K) (that is, 10 percent, 15
percent, and so forth) to the reliability
predicted for the mature system. Every effort should be made,
however, to obtain information
relevent to a realistic starting point prior to applying a K. A second curve,
called the Adjusted Growth curve, which reflects the level at which the achieved
corrected failures were discounted,
may also be provided.
=.
103.2.4
growth
Predicted
reliability
rate that is predicted
rowth
between
rate,
been derived from historical data from similar
with the present program shall be specified.
103.3
contract
.
●
Details to be specified
shall includq the information
a. Identification
b. Identification
c. Imposition
Engineering
the scheduled
programs,
bv the procuring
specified
review
rationale
activitv
in a through
shall he provided
points. When
these programs
[see 6.1 .1).
the predicted
the requirement
curves
103-1
would
The details
be if the
for the reliability
growth
and the similarities
curves have
and differences
to be specified
in the
e, as applicable:
of contractual
status of the reliability growth
of majOr subsystems which require reliability
of TASK 101 with
reliability
to incorporate
planning curve
growth planning
the reliability
curves
growth
planning
MIL-STD-781D
.
d. Termination
e. DI-RELI-80250,
as a deliverable
data item
criteria
for test
Reliability
Test Plan, applies to this task and shall be specified
●Essential
103-2
when
required
w
o
w
25
50
75
100
125
I
SVSTEtA/lTEM:
NUMBER:
OATE:
,ED,CTCD so
,~UAL
M
ICNAL.
“MULATIVE 30
~
EDT
ROIGT
D1 II
01 II
07111
01 Ill
‘ESTPROGRAM
VEAR(CY)
I)TR
MTBF
(HRS)
150
175
200
225
250
,70
I00
Es
I
300
IOQ
I10
3
OXVZACORADAR
gooooo
15 JULY1985
so
10
2
so
70
1
ADJUSTEDGROWT~
PREDICTEDVALUE
450
‘on
tso
13
2
86
I
A
son
A
FIGu REI03-1.
REMARK’:
700
300
150
1
A’”
~
4
“0
Reliablityq
‘m
.3
1
rowth
1‘m
2
87
profile
lW
J.
I
b
(exam
,Cm
1
88
Dle~
,Sm
2
—
1000
0
0
1SW
I500 I500
89
0
MI LJSTD-781D
TASK 104
TEST PROGRAM
104.1
Purpose.
reviews at specifed
milestones.
104.2
The purpose
of TASK 104 is to establish
ti mes to erwtcre that reliability
Task description.
REVIEWS
The reliability
a requirement
tests are proceeding
test program
to conduct
i n accordance
shall be planned
test program
with contractual
and scheduled
to permit
the
review of test status. Formal review and assessment of contract test requirements
shall be conducted at
major program points as specified by the contract.
Progress of individual tests shall be assessed by test status
reviews. Test reviews shall be scheduled with subcontractors
aa”vity shall be informed in advance of each review.
and vendors
as appropriate.
The procuring
104.2.1
Test readiness reviews.
To assure that the test item and all supporting elements are ready at
the start of the test, a test readiness review shall be planned and scheduled at least 7 days prior to the start
of any test.
104.2.2
Pretest readiness
review.
(This review
shall be conducted
when
specified
for U.S. Army
procurements).
After the procuring activity approves the reliability
test procedure and before start of the
shajl be convened at the contractor’s test facilitY to ‘eview
reliability test, a reliability test readiness review
the test prerequisites
and to ensure that all test requirements
specified in the apprOved test Plan and test
procedures are compatible
and understood by all parties. The contractor shall notify the procuring activity a
minimum
of 10 days before conduct of the review.
documented
by the contractor and made available
of the test.
The results of the pretest readiness review shall be
to the procuring activity at least 2 days prior to the start
104.2.3
Status reviews.
Formal reviews shall be scheduled as preplanned
milestones during the
reliability tests to permit the review of testing status and the results achieved to date. The status reviews
shall be scheduled in accordance with the contract and shall consider, but not necessarily be limited to, the
information specified in a through g:
a. Current reliability
assessments and projections based on test results
b. Results of current problem and failure investigations
and engineering
c. Preventive and corrective action recommendations
d. Potential
design problems
based on the preventive
and corrective
analysis
action
recommendations
e. Status of subcontractor
and supplier, or both, reliability development
tests
f. Status of previously assigned acQ.on items
g. Assignment of action items resulting from the review including scheduled completion
dates
104,2.4
Test completion
review.
test. This review shall be conducted
specified
in a through
A test completion
to evaluate
review
shall be conducted
at the completion
the results of the test and shall consider the informati
of the
on
f:
a. Current reliability
growth assessments and achievements
b. Status of open problems and failures
c. Status of preventive
and corrective actions
d. Status of previousl y assigned action items
e. Assignment of action items resulting from the review,
dates
f. Conclusions
of the review
104-1
based on test results
.:
including
scheduled
completion
MI L-STD-781
104.2.5
As specified
by the procuring
activity,
D
the contractor
shall document
each review.
104.3
Details to be specified bv the procurinq activitv (see 6.1.l\.
Details to be specified
contract shall include the information
specified in a through e, as applicable:
.
●
~
a.
b.
A record of the results of each review
The speci fic number of days advance notice
c.
Identification
of advance
d.
Identification
of procuring
e.
Delivery
for test readiness
and pretest
in the
readiness
reviews
notification
for other scheduled
a’ctivity and contractor
items
identification
of any data item required
●Essential
104-2
follow-up
reviews
methods
on review
of open
MI L-STD-781
D
TASK 105
JOINT TEST GROUP
105.1
provide
Purgose.
coordination
105.2
The purpose
throughout
Task description.
of TASK 105 is to require. the establishment
the reliability
test program
The JTG shall periodically
and to periodically
review
of a joint test group (JTG) to
review
test data including
all test data.
subcontractor
qualification,
and acceptance test data (see 6.3). The JTG also shall approve on the spot changes
previously approved preventive
maintenance
schedules and detailed test procedures.
105.2.1
JTG membership.
The membership
of the JTG shall be comprised
of Government
reliability,
to
and
contraflor
personnel and shall be chai red by a Government
representative.
Contractor JTG members shall
include appropriate
representatives
from design, reliability,
system safety, test, parts, and quality assurance
activities.
Additional
contractor or Government
personnel may 15eassigned as temporary
members for
special tasks, as required.
105.2.2
Specific JTG tasks.
to, the tasks specified
a.
b.
schedules
malfunction
nonrelevant
in a through
Conduct
Approve
Specific tasks to be performed
by the JTG shall include,
but not be limited
e:
periodic review of all test data
on the spot changes t~ all previously
approved
preventive
maintenance
and detailed test procedures
c.
Review and approve
all corrective action recommendations
generated
as a result of
.
report5
d. Approve recommended
classifications of malfunctions
and failures as relevant or
during the reliability qualification
or production
reliability
acceptance tests
e. Approve acceptance recommendations
audit of all documentation
at the end of the test to affirm
at the completion
of the test and conduct
compliance
with contractual
requirements
105.3 Detail$ to be soecified bv the mocurinq activitv
contract shall include the information
specified in a through
of Government
(see 6.1. 1). Details
d, as applicable:
a.
Identification
b..
c.
d.
Identification
of additional
tasks
Recording of the results of the tasks
Delivery identification
of any data items required
representatives
105-1
to be specified
in the
an
MI L-STD-781D
TASK 106
RELIABILITY
TEST REPORTS
106.1 Purpose.
The purpose of TASK 106 is to establish a requirement
for the preparation
of
reli abtlity test reports whjch summarize
reliability
test results obtained to date and other pertinent
information.
106.2 Task description.
Periodic summary and final test reports shall be prepared to summarize test
results obtained.
The test reports shall include summaries of failures, failure analyses, and recommended
or
implemented
corrective actions.
106.2.1.
Final reliability
equipment
reliability.
charts or graphs with
against test time.
106.3
contract
●
required
test reDort.
Details to be specified
shall include
The final reliability
test report
shall include
a general
analysis of
A summary of pertinent data and information
shall be presented including applicable
test data plotted thereon, failures plotted against time, and observed MTBF plotted
the information
a. Identification
bv the procurina
specified
of tests which
b. Delivery schedule
c. DI-RELI-802S2,
Reliability
as a deliverable
data item
activitv
in a through
require
Test Report,
(see 6.1. 1).
Details
to be’specified
in the
c, as applicable:
final test reports
applies
●Essential
106-1
to this task and shall be specified
when
MI L-STD-781
D
...
!
TASK SECTION
200
DEVELOPMENTTESTING
200-1
MIL-STD-781D
TASK 201
SURVEY TESTING
201.1
that thermal
Purpose.
The purpose of TASK 201 is to establish and implement
survey testing
stabilization
and resonant conditions of the equipment
can be determined.
201.2 Task description.
Thermal and vibration survey testing
equipment
to determine
the level of equipment
thermal stabilization
procedures
so
shal( be conducted on a sample of the
and to search for resonant conditions
and design weaknesses.
Thermal andwibration
suweys shall be performed
prior to the start of reliability
growth testing and, when specified, prior to reliability
qualification
testing and environmental
stress
screening (ESS). Equipment
selected for reliability
specifically authorized
by the procuring activity.
testing
shall not be used for survey testing
unless
201.2. I Thermal survey.
A thermal survey shall be performed
on one sample of the equipment
to,be
tested, under the temperature
and duty cycle specified in the reliability test procedures.
The thermal survey
shall be used to identify hot spots and the component
of greatest thermal inertia, andto establish the timetemperature
relationship
between
the equipment
and the chamber air. These relationships
shall be used to
determine
the Ievet of equipment
thermal stabilization.
The 10wer test level [email protected] $ta~lizatiOn.
occurs when the temperature
of the point of the maximum
thermal inertia is within 2°C of the lower test
level temperature
or the rate of change is less than 2-C per hour. Upper test level temperature
stabilization
occurs when the temperature
of the maximum thermal inertia point is within 2°C of the upper temperature
level or the rate of change is less than 2-C per hour. Temperatures
of equipment
cooling air and chamber air
shall be recorded continuously .during both. the.survey and the tests. Should the results of the thermal survey
indicate local temperatures
significantly
higher than those predicted by the final thermal design analysis or
greater than those used for derating in the reliability
prediction,
corrective action shall be accomplished,
verified,
and approved
prior to the start of reliability
testing.
201.2.2
Vibration
survey. A vibration survey shall be per forrned,on one sample of the equipment
to
be tested to search for resonant conditions and design weaknesses.
Unless otherwise specified by the
procuring activity, the vibration conditions shall be those specified in the reliability
test procedures.
Any
failures
which occur during
vibration
survey testing
shall be reported,
investigated,
and analyzed
and corrective action shall be accomplished,
verified, and approved prior to the start of reliability
Equipment
mounting
for the vibration survey shall simulate mounting in actual use.
201.3
Details to be mecified
bv the mocurina
activitv (see 6.1. 1~, Details
contract shall include the information
specified in a and b, as applicable:
reliability
a. Identification
test procedures
b. DI-RELI-80247,
this task and shall be specified
of vibration
and temperature
conditions
if other than specified
Thermal Survey Rep6rc, and DI-RELI-80248,
when required as deliverable
data items
201-1
to be specified
Vibration
for cause;
testing.
in the
in the
Survey Report, apply to
MIL-STD-781D
TASK 202
RELIABILITY
202.1
=.
DEVELOPMENT/GROWTH
The purpose of TASK 202 is to conduct
also known as test, analyze, and fix (TAAF), which
incorporating
corrective actions into the design.
202.2
identification,
a reliability
developmentfgrowth
a basis for resolving
reliability
performance
of design corrections
minimize
202.2.1
(see 4.3) applied
202.2.1.1
which
Combined
during
failure
the recurrence
environmental
test conditions.
failure
The combination
The equipment
of a typical
analysis,
and
through the
effectiveness.
The
and the verification
(see MIL-HDBK-189).
by the procuring
of test item in test facility.
which is representative
detection,
of failures
RD/GT tests shall be as specified
Installation
in a manner
monitoring,
test (RD/GT),
problems
Task description.
An RD/GT shall be conducted
to enhance system reliability
analysis and correction of failures, and the verification
of corrective action
RD/GT test will incorporate
test facility
provides
TEST
of environmental
test condi tians
activity.
to be tested
field installation,
shall be installed
and the flow of external
in the
air
around the equipment
shall simulate corresponding
anticipated
operational
conditions.
All instrumentation
required to monitor the test, including the operation
of the test facility, shall be provided.
Calibration
and
adjustment
of the test items during the test shall be limited to that which is specified in the approved test
procedure.
202.2.1.2
Testinq sequence.
The testing sequence shall be performed
as specified in the test
procedure and shall be repeated until a failure occurs. When a failure occurs, investigation
and analysis shall
be initiated
to determine
failure
cause (see 4.6).
202.2.2
Reliability test records. Reliability
in the approved test procedures and shall account
test records shall be maintained
continuously
for all calendar and operating
time.
as specified
202.2.2.1
Performance
Parameter measurements.
The equipment
performance
parameters
measured and the frequency of measurement
shall be as specified by the procuring activity. When
of required performance
parameters
time of failure cannot be determined,
recorded
measurement
is not within specified limits, a failure shall be recorded.
If the exact
the failure shall be presumed to have occurred at the time of the last
of the same parameter.
The results of all measurements
during the test cycle. Atleastonesetof
measurements
after any specified equipment
startup period.
202.2.2.2
Failure
actions.
to be
the value
When
a failure
shall be made when
i:observed,
shall be made and recorded
the equipment
is first energized
entries shall be made on the data Iogsand
the
failed equipment
shall be removed from test with-minimum
interruption
to the equipment
continuing
on
test. Failure actions shall be specified in the test procedure.
The absence of one or more items of equipment
from test shall not interfere with the continued entry of log data.
failed
202.2.2.3
Replacement
parts may be authorized
of failed items. Temporary
replacement
of plug-in items or replacement
of
by the procuring activity to permit the test to continue while failures are
being investigated.
Modules and wbassemblies
shall not be permanently
designated as dispo~able-at-fail
ure items. Failure of disposable-at-failure
determine
failure cause (see 4.6. 1.3).
202.2.2.4
Failure
recordinq,
analysis, and corrective
action.
replaced unless previously
items shall be investigated
All failures
occurring
during
to
RD/GT tests
shall be recorded, investigated,
and analyzed to determine
the cause of failure.
Corrective actions shall be
developed to preclude recurrence of the failure (we 4.6. I ). The effectiveness
of each corrective action shall
redemonstrated
prior to incorporating
it in the equipment
design.
202-1
I
MI L-STD-781
202.2.3
Reliabilitva
rowth
monitoring.
Reliability
D
growth
shall be monitored
during
RD/GT tests by
comparing test results to the reliability growth profile. The achieved reliability,
expressed as a point
estimate, shall be plotted on the same chart as the predicted growth curve (see FIGURE 103-1). Data from
the RD/GT test and other applicable
tests shall be used to plot this curve. The achieved reliability curve shall
not be adjusted by excluding past failures after the design changes which purport to eliminate
these failures
have been implemented.
202.2.4
Reliability
estimates
and projections.
shall be prepared for each specified system reliability
statistical methods and techniques in MI L-H DBK-189
Details to be specified
202.3
contract shall include the information
.
.
“
●
.
.
a. Specification
b. Identification
c.
d.
e.
f,
g.
bv the procurinq
specified
parameter
activitv
in a through
estimates
and future
(see 6.1. Il.
proje’aions
using the
Details to be included
in the
i, as applicable:
of the required value for each reliability
of eauioment
to be used
. .
parameter
to be measured
Specification of the combination
of environmental
test conditions and levels
Specification,o f.performance
parameters to be measured and frequency of measurement
Imposition of TASK 102 as a prerequisite
task
Imposition of TASK 103 as a prerequisite
task
Imposition of MIL-STD-785,
TASK 104, Failure Reporting, Analysis, and Corrective Action
System (FRACAS), as a requisite task
h. Authorization
of temporaw
failure investigation
required
Reliability
parameter.
Projections shall be made
and MI L-H DBK-781, Section 4.
use of plug-in’ modules
i. The following data item descriptions
as deliverable data items:
(DIDs) apply. to thistask
DI-RELI-80252
DI-RELI-80253
DI-RELI-80254
DI-RELI-80255
continued
and”shallbe
.,
Reliability
Reliability
Test Plan
Test Procedures
Reliability Test Repo~
Failed Item Analysis Repoti
Corrective Action Plan
Failure Summary and Analysis Report
g Essential
202-2
,,,:
.’.
“. .
.testing during
specified
when
T~
plQ
DI-RELI-802S0
DI-RELI-802S1
to permit
:
..
.
~.
.’
MIL-STD-781
TASK SECTION
RELIABILITY
D
300
ACCOUNTING
300-1
TESTS
MI L-STD-781D
TASK
ENVIRONMENTAL
SECTION
400
STRESS SCREENING
400-1
MI L-STD-781’D
●
d.
Specification
of performance
parameters
to be measured
of measurement
●
e. Imposition of TASK 102 as a prerequisite
task
●
f.
Imposition of MIL-STD-785,
TASK 104, Failure
SYstem (FRACAS), as a prerequisite task,
g.
h.
required
Identification
of refurbishment
The following
data item descriptions
as deliverable
Reporting,
during
Analysis,
the test and the frequency
and Corrective
requirements
(DIDs) apply to this task and shall be specified
data items:
DI-RELI-80250
DI-RELI-80251
DI-RELI:80252
DI-RELI-80253
DI-RELI-80254
DI-RELI-80255
Action
Reliability
Reliability
Test Plan
Test Procedures
Reliability Test RepoR
Failed Item Analysis Report
Corrective Action Plan
Failure Summary and Analysis
●Essential
302-3
Report
when
MI L-STD-781D
TASK 302
PRODUCTION
RELIABILITY
ACCEPTANCE
TEST
302.1 Pumose.
The purpose of TASK 302 is to determine
if the production
equipment
conform to specified performance
and reliability
requirements
under specified environmental
302.2 Task description.
Production
selected equipments from each production
selected
by the procuring
acceptance
tests specified
activity
Reliability Acceptance
Tests (PRAT) shall be conducted on
lot as specified by the procuring activity.
PRAT shall be as
from the sequential,
in MIL-HDBK-7B1,
continues to
conditions.
fixed duration,
or all-equipments
Section 4 and shall be executed
environmental
test conditions used in the reliability
qualification
equipments
tested shall statistical y represent the lot from which
and the rules for sample selection shall be as specified
PRAT shall be subjected to acceptance
preconditioning
under
production
the same combined
tests. For a sampling-type
test, the
they are sel ected. Lot size shall be defined
by the procuring activity.
All equipment
selected for
and shall pass the tests specified in the production
test specification.
302.2.1
Combined environmental
test conditions.
4.3) to be applied during reliability
production
acceptance
procuring activity.
The combined environmental
test conditions (see
tests shall be as specified or approved by the
302.2.1.1
Installation
of test item in test facility.
The equipment
to be tested shall be installed in the
test facility in a manner which is representative
of a typical field installation,
and the flow of external air
around the equipment
shall simulate corresponding
anticipated
operational
conditions.
All instrumentation
required to monitor the test, including the operation
of the test facility, shall be provided.
Calibration
and
adjustment
procedure.
of the test items during
the test shall be limited
to that which
is specified
302.2.1.2
Te$tinq sequence.
The testing sequence shall be performed
procedure.
This sequence shall be repeated until an acceptor
reject decision
is completed.
302.2.2
Reliability
approved test procedure.
test records.
Reliability
in the approved
test
as specified in the test
is reached or the total test time
test records shall be maintained
as specified
in the
302.2.2.1
Performance
parameter
measurements.
The equipment
performance
parameters
to be
measured and the frequency of measurement
shall be as specified by the procuring activity. When the value
of any required performance
parameter
is not within specified limits, a failure shall be recorded.
If the exact
time of failure cannot be determined,
the failure shall be presumed to have occurred at the time of the last
recorded observation or successful measurement-6f
that parameter.
Observations
and measurements
$hall
be periodically
made and recorded during the test cycle. At least one set of measurements
shall be recorded
when the equipment
is first energized
after any specified equipment
shutdown
period.
302.2.2.2
Failure actions.
At the time of failure, entries shall be made on the data logs and the failed
equipment
shall be removed from test and repaired with minimum
interruption
to the equipment
continuing
on test. Failure actions shall be as specified in the test procedure.
All failed item$ shall be
replaced.
Any item-which
has deteriorated
but does not exceed specified tolerance limits shall not be
replaced unless that part is known to have been stressed beyond its rated capability
due to the failure of
another part. After a failed and repaired equipment
has been returned to operable condition,
and the
effectiveness
of the repair verified, the equipment
shall be returned to test with minimum
interruption
to
the other equipment
on test. The absence of one or more items of equipment
undergoing
repair shall not
interfere with the continued entry of log data. Unless determined
to be nonrelevant,
failures discovered in
equipment
or subelements
during
troubleshooting
which are not dependent
302-1
on the basic failure,
shall be
MI L-STD-781
categorized,
recorded and considered as relevant multiple failures occurring at the same time as the basic
failure.
Failed modules and subassemblies shall not be permanently
replaced unless previously designated
1
disposable-at-failure
rnaybea.
thorized
I
permit the test to continue.
Piece parts removed
the equipment
could be impaired.
I
I
I
I
as
items or approved by the procuring activity.
Temporary
replacement
of plug-in items
by the procuring activity during troubleshooting
and repair periods, when necessary, to
during
repair shall not be reinstalled
when
the reliability
of
302.2.3
Failure classification.
Ali failures shall be classified as relevant or nonrelevant.
Relevant
failures shall be further classified as chargeable
or nonchargeable.
Classification
of failures shall be
proposed by the contractor and forwarded
to the procuring activity’for
approval.
Failure categories are
specified
in 4.7.
302.2.4
Lot acceptance.
If an accept decision is reached on a lot sampling basis by conforming
requirements
of the specified test plan and procedures, all equipment
in that production lot shall be
accepted.
The reliability test units shall be resubmitted
refurbishment
of test units is required, see 302.2.10.
for the performance
acceptance
to the
tests. When
302.2.5
All-equipment
test acceptance.
During all-equipment
production reliability
acceptance
testing, all equipment
that complete the specified test satisfactorily
shall be accepted until the reject line of
the test is crossed.
302.2.6
Lot reiection.
If a reject decision is reached on a lot sampling basis, all equipment
in that lot
are noncompliant,
and further acceptance and shipment of units shall be discontinued..
Corrective action
shall be taken as specified
(see 302..2,8).
,.
302,2.7
All-equipment
test reiection.
If all-equipment
production
reliability acceptance testing
results in a reject decision by crossing the reject line of the test plan, further acceptance shall be
discontinued,
Corrective
action shall b.etaken
as specified
(see 302.2.8).
302.2.8
Corrective action.
When a reject decision is reached or.the occurrence of pattern failures is
determined,
the procuring activity shall be immediately
notified and a corrective action plan developed.
The corrective action plan shall specify the proposed corrective action and its impact on the program and the
reliability
rendered
of the equipment.
Requirements
obsolete because of any redesign
for the disposition of all defective material and material
shall be included to ensure their exclusion from the production
equipment.
Prior to implementation,
the corrective action
for its approval in accordance with contract requirements.
302.2.9
Preventive
maintenance.
Only preventive
plan shall be submitted
maintenance
to the procuring
procedures
specified
activity
for the
equipment
during service use and specified in the approved test procedures shall be performed
dwing
PRAT. No additional
preventive
maintenance
is permitted during PRAT or during repair unless specifically
..
authorized
by the procuring activity.
302.2.10
Refurbishment.
Unless otherwise specified by the procuring activity, the equipment
shall
be refurbished
and returned to satisfactory operation at the completion
of PRAT. Failed parts and parts
which have deteriorated
b“t have “ot exceeded specified tolerance limits shall be replaced, unless the
procuring activity directs otherwise.
test procedures prior to shipment.
All refurbished
equipment
302.3 Details to be specified by the procurinq activity
contract shall include the information
specified in a through
.
.
.
a.
b.
Specification
Specification
of test plan to be used
of rules for sample selection
c.
Specification
of the comb!ned
302-2
shall successfully
complete
the acceptance
(see 6.1, Il. Details to be specified
h, as applicable:
and definition
environmental
I
I
D
of a lot
test conditions
and levels
in the
MI L-STD-781.D
●
*
●
*
a.
Specification
of test plan to be used
b.
c.
d.
Identification
Specification
Specification
of equipment
to be used
of the combined environmental
test conditions
and levels
of performance
parameters
to be measured during the test and the frequency
of measurement
●
e.
●
f.
required
Imposition
Imposition
of TASK 102 as a prerequisite
task
of MI L-STD-785, TASK 104, as a prerequisite
g.
Identification
of refurbishment
h.
The following
data item descriptions
as deliverable
requirements
task
after completion
of test
(DIDs) apply to this task and shall be specified
data items:
QIQ
D1-RELl~80250
DI-RELI-80251
DI-RELI-80252
DI-RELI-80253
DI-RELI-80254
DI-RELI-80255
Reliability
Test Plan
Reliability y Test Procedu res
Reliability Test Report
Failed Item Analysis Report
Corrective Action Plan
Failure Summary and Analysis
‘Essential
301-3
Report
when
MI L-STD-781D
TASK 301
RELIABILITY
301.1
specified
Purpose.
performance
QUALIFICATION
The purpose of TASK 301 is to demonstrate
and reliability
301.2 Task description.
representative
of the approved
requirements
TEST
that the equipment
under the specified
combined
design conforms
environmental
to
conditions.
Reliability qualification
tests shall be conducted
on equipments
which are
production configuration.
Unless otherwise
speci fied, two equipments
shall
be used for reliability qualification
testing. Test plans utilized
those from MIL-HDBK-781,
Section 4, as specified or approved
a, fl, and d values shall be
and the appropriate
by the procuring activity.
301.2.1 .Reliabilitv qualification
test requirements.
Reliability qualification
tests shall be conducted
in accordance with reliability
test procedures which have been approved by the procuring activity.
Testing
shall be continued
been completed,
301.2.1.1
(see 4.3) applied
until an acceptor
unless otherwise
reject decision
directed
has been reached
by the procuring
or the total
required
test time has
activity.
Combined environmental
test conditions.
The combined environmental
test conditions
during reliability qualification
tests shall be as specified or approved
by the procuring
activity.
301.2.1.2
Installation
of test items in test facility.
The equipment
to be tested shall be installed in the
test facility in a manner which is representative
of a typical field installation,
and the flow of external air
around the equipment
shall simulate corresponding
anticipated
operational
conditions.
All instrumentation
required to monitor the test, including the operation
of the test facility, shall be provided.
Calibration
and
adjustment
procedure.
of the test items during the test shall be limited
301,2.2
approved
Reliability
test records.
Reliability
to that which
is specified
test records shall be maintained
in the approved
as specified
test
in the
test procedure.
301.2.2.1
Performance
Parameter
measurements.
The equipment
performance
parameters
measured and the frequency of measurement
shall be as specified by the procuring activity.
When
to be
the value
of any required performance
parameter
is not within specified limits, a failure shall be recorded.
If the exact
time of failure cannot be determined,
the failure shall be presumed to hive occurred at the time of the last
recorded observation or successful measurement
of that same parameter.
Observations
and measurements
shall be made at the specified interval
shall be recorded when the equipment
and recorded during the test cycle. At least one set of measurements
is first energized
after any specified equipment
shutdown period.
301.2.2.2
Failure actions. At the time of tilu,re, entries shall be made on the data logs and the failed
equipment
shall be removed from test and repaired with minimum
interruption
to the equipment
continuing on test. Failure actions shall be as specified in the test procedure.
All failed items shall be
replaced. Any item which has deteriorated
but does not exceed specified tolerance
limits shall not be
replaced unless that part is known to have been stressed beyond its rated capability
another part. After a failed and repaired equipment
has been returned to operable
due to the failure of
condition,
and the
effectiveness of the repair verified, the equipment
shall be returned to test with minimum
interruption
to
the other equipme?t
on test. The absence of one or more items of equipment
undergoing
repair shall not
interfere with the continued entry of log data. Unless determined
to be nonrelevant,
failures discovered in
equipment
or subelements
during troubleshooting
which are not dependent
categorized,
recorded, and considered as relevant multiple failures occurring
failure. Failed modules and subassemblies shall not be permanently
replaced
disposable-at-failure
may be authorized
on the basic failure, shall be
at the same time as the basic
unless previously designated
as
items or approved by the procuring activity.
Temporary
replacement
of plug-in items
by the procuring activity during troubleshooting
and repair periods, when necessary, to
301-1
I
I
MI L-STD-781D
permit the test to continue.
Piece parts removed
the equipment
could be impaired.
during
repair
shall not be reinstalled
when
the reliability
of
301.2.3
Failure classification.
All failures shall be classified as relevant or nonrelevant.
Relevant
failures shall be further classified as chargeable
o! nonchargeable.
Classification
of failures shall be
proposed by the contractor and forwarded
to the procuring activity for approval.
Failure categories are
specified
in 4.7.
I
I
301.2.4
Reliability q ualification
comtiiance.
by the procuring activity after each equipment
failure
Compliance shall be based on the total accumulated
the time of the review.
Reliability qualification
compliance
shall be reviewed
is categorized
or at any other appropriate
time.
test time and the total
number
of chargeable
failures
at
301.2.4.1
Compliance determination.
Compliance
shall be determined
by comparing
the test
results with the accept or reject criteria of the specified test plan. The accumulated
test time is the total
equipment
equipment
operating time or exposure time, whichever
is appropriate,
and shall be recorded asaccumulated
test hours. Failures classified as chargeable
shall not be reclassified as nonchargeable
on the
basis of a recommended
reliability
corrective
301.2.4.2
Accept decision.
when an accept decision
and the procedure
of the reliability
any single equipment
equipments on test.
action.
The equipment
design shall be qualified
for production
with
is reached by conforming
to the requirements
of the specified
qualification
has accumulated
test.
An accept decision
Iess,than one-half
of the average
respect to
test plan
shall not be made at a point where
creditable
test time for all
301.2.4.3
Reie<t decision.
If the relia~lity
qualification
test results in a reject decision, the
equipment design has not been qualified
for production with respect to reliability.
In the event of a reiect
.,.
decision, a corrective action plan shall be developed
in accordance with 301.2,5 which shall address all
failures that have occurred during the test. After the corrective actions have been-approved
and
incorporated
in the equipment,
a retest shall be conducted using the same or other sample size as approved
by the procuring activity.
surveys shall be repeated
reliability
rendered
action.
activity
When a reject decision is reached or the occurrence of pattern failures
shall be immediately
notified and a corrective action plan developed.
action plan shall specify the proposed
of the equipment.
Requirements
obsolete because of any redesign
.,
,.
. . .. .>
corrective
action and its impact. on.the
is
program. and the.
for the disposition of all defective material and material
shall be included to ensuret heir exclusion from the production
equipment.
Prior to implementation,
the corrective action
for its approval in accordance with contract requirements.
plan shall be submitted
to the procuring
activity
=.
301.2.6
Preventive maintenance.
Only the preventive” maintenance
procedures specified for the
equipment
during service use and listed in the approved test procedures shall be performed
during the
reliability qualification
test. No additional
preventive
maintenance
shall be permitted
during the reliability
qualification
,
.
.
Unless otherwise specified by the procuring activity, the thermal and vibration
if those aspects of the design are affected by the corrective action.
301.2.5
Corrective
determined,
the procuring
The corrective
..,,
test or during
repair unless specifically
authorized
by the procuring
activity.
301.2.7
Refurbishment.
Unless otherwise specified by the procuring activity, the equipment
shall
be refurbished and returned to satisfactory operation at the completion
of the reliability
qualification
test.
Failed items shall be replaced>nd
items which have deteriorated
but do not exceed specified tolerance limits
shall be replaced, unless the procuring activity directs otherwise.
All refurbished
successfully complete the acceptance test procedures prior to shipment.
301.3 Details to be specified bv the procurinq activitv
contract shall include the information
specified in a through
301-2
equipment
shall
(see 6.1. 1). Details to be included
h, as applicable:
in the
..
:
.
.
MI L-STD-781D
0.04g2/Hz
+ 3 d8 /OCTAVE
-3 d8 IOCTAVE
./
\
.-.
20
2000
350
80
FREQUENCY-Hz
FIGURE
401-1.
Random
401-3
vibration
spectrum.
*,9
MI L-STD-781D
TASK 401
ENVIRONMENTAL
401.1
Purvose.
environmental
defective
reliability
procuring
The purpose
stress screening
STRESS SCREENING
of TASK 401 is to require
(ESS) to detect
and correct
the formulation
latent
and implementation
manufacturing
defects
(marginal
of
and
parts, workmanship p defects, and other nonconforming
anamolies)
before the initiation
of
accounting
tests. (ESS also may be applied to each production item before acceptance by the
activity.)
401.2
Task description.
ESS shall be conducted
at selected
levels of assembly.
During
full-scale
development,
ESS procedures shall be developed
for the system and for all lower levels of equipment
which
may be procured separately as spare or repair parts: The application
and implementation
of these
procedures during full-scale development
and production
shall be included in the overall reliability test
planning.
401.2.1
ESS desiqn.
ESS shall be deigned
to stimulate
failures
due to latent
manufacturing
defects. The applied environmental
stresses need not simulate the item’s specified life-cycle, mission and
environmental
profile. Ouring ESS. the item shall be cycled through operational
modes while simultaneously
being subjected
MIL-HDBK-781.
to the required
environmental
stresses. A discussion of ESS techniques
is specified
in
401.2.2
Environmental
stresses. Unless otherwise specified by the procuring activity, the
environmental
stresses applied during ESS shall be random vibration and temperature
cycling. The random
vibration
power spectral density curve and the thermal profile definition
for temperature
cycling shall be as
specified by the procuring activity.
These environmental
stresses maybe applied either in combination
or in
sequence. “Unless otherwise specified by the procuring activity, the random vibration spectrum specified in
FIGURE 401-1 shall be utilized.
401.2.2,
the equipment
number
I
Equipment
installation.
shall be hard-mounted
Unless otherwise
on the vibration
specified
platform
or approved
by the procuring
401.2.2.2
Random vibration.
Random vibration shall be applied fora minimum
of axes along which vibration shall be applied shall be based on the packaging
equipment.
of 5 minutes
When vibration
on each axis.
on more than one axis is required,
activity,
or fixture.
the vibration
of 10 minutes.
design of the
shall be applied
The
for a minimum
401.2.2.3
Temperature
cyclinq.
Temperature
cycling shall be performed
continuously
in accordance
with the specified thermal profile and for the specified number of cycles. Unless otherwise specified by the
procuring activity, the rate of temperature
change may be the maximum attainable
by the chamber but in
no case shall it cause the equipment
to experience a rite of change less than 5-C per minute
the equipment
to experience
thermal shock. More detail is provided in MI L-H DBK-781.
401.2.2.4
ESS sequence.
sequence shall be continuously
failure free cycles is completed.
until the specified
failure
nor shall it cause
The ESS sequence shall be performed
as specified in the ESS procedure.
This
repeated until a failure occurs or the specified failure free time or number of
When a failure occurs, the equipment
shall be repaired and ESS resumed
free time or cycles are completed.
401.2.3
ESSapplicability.
ESS$hall be applied to all equipments
submitted for reliability testing.
Failures occurring during ESS are not chargeable
for acceptor reject decisions but shall be recorded and
analyzed, and appropriate
repair action shall be taken. Repair shall be limited to that which is necessary to
restore the equipment
to its prefai lure condition,
in accordance with contract requirements.
Unless
401-1
MI L-STD-781D
otherwise
operating
specified in the ESS procedures, the last repair during the ESS shall be ve~fied
period of at least two consecutive temperature
cycles.
401.3 Details to be specified bv the procurinq activitv (see 6.1. Il.
contract include the information
specified in a th,rough k, as applicable:
a.
Reliability
*
●
●
Imposition
of TASK 10J,
Test Procedure
b. Environmental
Integrated
Test Plan Document,
stress types
h.
Vibration
axes requirements
The following
as deliverable
in the
and TASK 102,
Specification
of random vibration power spectral density curve
Specification
of thermal profile for temperature
cycling
Specification
of number of hours (cycles) for the ESS
Specification
of number of consecutive failure-free
operating
hours (cycles)
Equipment
mounting
requirements
for vibration
k.
L
Details to be specified
c.
d.
e.
f.
g.
i.
Performance
measurement
●
j.
Imposition of MI L-STD-78S,
System (FRACAS), as a prerequisite
task
required
Reliability
by a failure-free
and minimum
vibration
time per axis
requirements
before, during, and after ESS
TASK 1.04, Failure Reporting, Analysis, and Corrective
data item descriptions
Action
[DIDs) apply to this task and shall be specified
data items:
DI-RELI.80249
DI-RELI-80250
DI-RELI-80251
DI-RELI-80253
DI-RELI-80255
Environmental
Stress Screeqi.ng
Reliability Test Plan
Repo~.
.,
Reliability Test Procedures
Failed Item Analysis Report
Failure Summary
*Essential
401-2
and Analysis
Report
when
,“
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