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Thesis/Dissertation Collections
6-1-1971
Computer Application of Historical Data
Raymond Wright
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Recommended Citation
COMPUTER APPLICATION OF HISTORICAL DATA
A
Study
Report
Presented
to
the
Faculty
ofthe
Graduate School
Rochester Institute
ofTechnology
In
Partial Fulfillment
of
the
Requirements for
the
Degree
Master
ofBusiness
Administration
by
Raymond
J.
Wright
COMPUTER APPLICATION OF HISTORICAL DATA
by
RAYMOND J, WRIGHT
Submitted
OCTOBER 1970
Approved _ _ _ _ _ _ _ _ _
, Advisor
HOLLISTER SPENCER
ASSOCIATE PROFESSOR
Approved _ _ _ _ _ _ _ _ _
,
Dean
JERRY YOUNG
COLLEGE OF BUSINESS
THIS RESEARCH EFFORT AND THE RESULTANT COMPUTER
PROGRAM
REQUIRED ACCESS TO DATA AND FACILITIES NOT AVAILABLE
TO
ALL COMPANY EMPLOYEES.
I WOULD LIKE
TO
EXPRESS
MY
APPRECIATION
TO MY IMMEDIATE
SUPERVISOR,
MR.
E.
EDWARD
LOWERY,
WHO
ACTED
ON MY BEHALF TO MAKE THIS RESEARCH
A
REALITY.
I
ALSO EXPRESS MY APPRECIATION
TO
DR.
HOLLISTER
SPENCER
WHO PROVIDED THE NECESSARY GUIDANCE DURING
THE
WRITING
OF THE FINAL RESEARCH
REPORT.
CONTENTS
Page
LIST
OF TABLES
viiLIST
OF
FIGURES
viiiChapter
I
INTRODUCTION
1
USE OF ANALYSIS DATA
2
RESEARCH PROPOSITION
4
PRESENT ANALYSIS
4
CRITERIA
6
II
METHODOLOGY
OF DATA COLLECTION AND ANALYSIS
...7
DATA
COLLECTION
7
DATA FLOW
8
METHOD
OF ANALYSIS
12
DATA RETRIEVAL REQUIREMENTS
15
INPUT/OUTPUT DATA FORMAT
19
DATA RETRIEVAL EQUIPMENT
IDENTIFICATION
22
III
ANALYSIS OF RESEARCH
25
DISCUSSION OF DATA
ITEMS
25
SPECIFIC MODEL APPLICATION
29
APPLICATION OF MEASUREMENT CRITERIA
31
IV
LIMITATIONS
35
Page
V
APPRAISAL OF
RESEARCH
STUDY
...38
AREAS
FOR EXPANSION
38
COMPARATIVE
LITERATURE FINDINGS
.39
MANAGEMENT USE
...46
SELECTED
BIBLIOGRAPHY
49
APPENDD.ES
51
A.
SAMPLE
FORMS
OF
HISTORICAL
DATA
...52
B.
COMPUTER PRINTOUT NEWSYSTEM
SIMULATION
59
LIST
OF
TABLES
Table
Page
II-l
EQUIPMENT CLASSIFICATION LIST
24
V-l
SYSTEM AVAILABILITIES
43
Figure
Page
II-l
DATA FLOW
9
II-2
MAINTAINABILITY PREDICTION WORKSHEET
...16
II-3
INPUT DATA FORMAT
21
V-I
EQUIPMENT
AVAILABILITY
45
Chapter
I
INTRODUCTION
There
always existsthe need, somewhere,
andby
someone, to
have
more
information for
analysis,
andto
have
this
at an earlier pointin time.
What may be
suppliedin
sufficientdetail
and within a reasonabletime
period *for
one usemay be
partially
ortotally
inadequate for
meeting the
requirementsof another use.
This
research was not undertakento
attemptto
find
aremedy for
everyone's
time
anddata
problems,
but
ratherto
satisfy
a present and oftenrepeatedneed which
is important
withinthe
researcher'sdepartment,
specifically
the
Product Assurance
department,
and withinthe company,
General
Dynamics,
in
general.This
responseto
animmediate
need wHlhighlight
some useful applicationsto
similarbusiness
requirements.This
research
is
conducted within an electronicsindustry
andis
primarily
orientedtoward
military
communications systems ratherthan
commercialradio,
TV,
etc.
Analysis data
is particularly important
for
usein
proposal and specialstudies efforts.
Proposal
and special studiesrequirements,
in general,
require a written
description
ofthe
workto
be done
by
the
oneresponding
to
the
the
proposal orstudy
within eachdepartment,
andthe
method ofaccomplishing
its
overallcomplexity
and magnitude offunctional
operation.The
item is
described
physically
andfunctionally
asbest
aspossible,
because
normally it
exists
only in
the
conceptual or proposal phase.The item is
alsodescribed
quantitatively
asto
the desired
and/or expected performance measurementwhich
it is
to
meet.Even though the item is
only
proposed,
and notyetexistent, the
moredefinitive
eachdescription,
the
more relevantthe
associated
data.
Industry
in general,
andspecifically
those involved
with governmentspace and
defense
contractsfind
it
aninvaluable,
if
notdemanding,
requirement
to
perform such an analysis study.MHitary
contracts arenow,
more sothan
afew
yearsago,
requiring
that
an evaluation and analysisbe
madein
advance of contract placement.
This
evaluation and analysis mustbe for
allsystems,
subsystems,
and equipmentitems
as specifiedby
their
proposalefforts,
specialstudies,
logistics
apportionment,
and economictrade-off
studies.
Considering
that
most ofthis
effortis
relatedto
items
only
in the
conceptual or proposal
phase,
one can realizethe
amount of effortinvolved.
USE
OF
ANALYSIS DATA
The
analysisdata for
proposals and special studies requiredthe
prediction of such
factors
as maintenancetask
times,
frequency
ofoccurrence,
personnel requirements and
obtaining
an overall system quantitative analysisin
an effortto
effectbetter
bids
to
proposals andbetter
data for
studies.The
a.
Provide
abasis for
allocating
orapportioning
quantitativerequirements
(prior to
actualdesign)
given an overall enditem
constraint(e.g.,
availabHity,
mean-time-to-repair,
etc.).End item is the term
usedto
denote
the
final
resultantitem
whetherit
be
a single piece of equipment or aconsole
consisting
of severalitems
allfunctionally
operating
as one unit.b.
Serve
as abasis for measuring
system/equipmentdesign.
Measurement
is
accomplishedthrough
a quantitative prediction of:MTTR
(mean-time-to-repair),
MMM/OH (maintenance time
peroperating
hour),
MTBM (me
an-time -between -maintenance whichincludes
scheduled andunscheduled
events)
, andMTBMA
(mean-time
-between-maintenance-action).c.
Provide
adata
base from
which all support requirements(e.g.,
tools,
test equipment,
spare/repairparts,
maintenancetasks,
andpersonnel)
are
derived.
An
overall analysis requiresmany inputs
and considerabletime.
The
limitation
oftime
andopportunity
for coordinating
these
inputs is
often suchthat the
desired
analysis responseis
untimely.It is untimely in that the
overall
response,
by
the company, has
to
be
completed within a specifictime.
Each
responsehas
adifferent
time
requirement.An
average offifteen days
in
which
to
respondis
not uncommon.Thus
the
limitations
often prevent acomplete closed
loop
system analysis approach.In many
cases somedata
must
be
either prohibitivedue
to
these
restraints,
and use ofan alternativeset of
data
is rarely
possiblethough
oftendesired.
The
analysisis
applicableThis
analysisin
turn
serves as adesign
measurementdevice.
With the
present need and
the
anticipatedfuture demand for
meeting
competition,
industry
mustbe
ableto
respondboth quickly
andaccurately
to
these data
needs.
RESEARCH
PROPOSITION
4
In
an effortto
improve the
method ofsupplying
analysisdata for
responding
to
proposals and specialstudies,
the
following
propositionis
stated:
The
application ofhistorical
maintenance analysisdata,
whensubjectively
appliedto
a proposed systemdata
model,
willprovide analysis
data
capable ofmeeting
proposal and specialstudies requirements.
PRESENT ANALYSIS
Historical
maintenance analysisdata is
a product ofboth
quantitativeand qualitative
data
inputs
from
various organizational groups.These
groupsrepresent,
but
are notlimited
to,
reliability,
maintainability,
human
factors,
technical publications, components,
and systemengineering,
all of which arePresent
analysisdata
requiresthree
days
(8
hr/day)
to
obtainresults which are often
lacking
in
detaU
andincomplete
due
to time
anddata
constraints.
The
effort ofthis
researchis
designed
to
develop
acomputer mathematical model whichwill
fulfill the
needfor
supplying
quantitativedata for
proposal
response,
specialstudies,
andprovide quantitative managementdecision data
in
a moretimely
and efficient manner.#
This
model will providefurther depth
ofanalysis,
than
atpresent,
due
to
the
elimination of manual calculations anddecisions.
It
will provide atimely
responseto
the
varioustask
requirements as well asbeing
flexible
enough
to
include
alternativedata for
management consideration.The
modelwill not
only simplify
the
presenttask
effort and reducetime,
but
alsoincorporate
factors
usefulin meeting
future
anticipated requirements.This
referenced analysis wasfor
an enditem
having
nine(9)
majorsubassemblies.
Computational
analysisfor the
quantitativeinput
to
the
study
required a
day
and ahalf.
This
was precededby
anotherday
andahalf
obtaining information
andinputs
from
some ofthe
otherdisciplines
involved in
the
overall proposal.The
analysis was performedby
an experienced analystand
therefore
does
notinclude
alearning
period.Results
of such an analysisare
difficult
to
measureespecially
whenthey
become
part of an overallproposal
by
the
company
to
obtain a contract awardwhichis the
basis
ofThe
research results will provide analysisdata,
similarto
that
mentioned
previously
in the discussion
of present analysisdata
which requiredthree
days
of effort.The
effectiveness ofthe
results wHlbe
measuredusing
the
foUowing
two
criteria:1.
A
computer analysisprintout,
andthe time
expendedto
obtainthe
data
for
developing
the
printout,
will require no morethan
one eighthour
working
day.
2.
A
second computerprintout,
shouldit
be
required,
representing
alternative analysis
data
will not require morethan
onehours
effort,
oncethe
originaldata
requirementshave
been
established.(The
establishment ofdata
requirements willbe discussed
later.
The
requirements referto the
Chapter II
METHODOLOGY
OF
DATA COLLECTION AND ANALYSIS
Accumulation
ofhistorical
quantitativedata
to
be
used as abasis for
the
mathematical modelis
oneprimarily
involving
the location
andthe
transportation
ofthe
actualdata
availableto
the
research.The
analysisdata
was generated under government specification
WRC-30
andGeneral
Dynamics
Specifications
FZM-12-1340, FZM-12-6340A,
andMLA
(Maintenance Level
Analysis)
data resulting
from
seven conferences conductedby
the
government,
at
this
facility.
DATA COLLECTION
The
bulk
ofthe
data
waslocated in
aGeneral Dynamics
storagefacility
here in the
city.
To
obtainthis data for
analysis required writtendescription
as
to
the type
of storageitem requested,
the
identification
numbers assignedto
the
applicable storagecontainers,
as well asthe
name ofthe
personrequesting the
data
containers,
and when and wherethe
containersto
be
delivered.
Having
initiated
this
phase ofdata
collection,
it
wasthen
necessary
to
identify
the
data
containerslocated
withinthe
company.Overall,
the
accumulated
data
records representapproximately
five
(5)
years ofdata.
These
records were written
for
several maintenanceshop
configurations.
Each shop
configuration,
in
turn, has
several systemsfor
whichdetailed data has been
Other data
collectioninvolved the
solicitation ofinputs from
those
organizational
groups, previously
mentioned,
whichcollectively
contributeto
the
proposal/study
qualitative and quantitativeinputs.
As depicted
in the Data
Flow chart,
Figure
II-l,
there is
no one organizationalgroup
whichdoes
notdepend
uponinteraction
from
the
otherdata
sources.This
assures a goodfeed-back
ofdata
flow.
The
data
flow
chart alsohelps
to
point outthe
fact
that
any
systems modelthat
will aidthe
data
generation and collectiontasks
will
certainly be
of valueto
the
overallproposal/stufly
effort.DATA FLOW
The
various organizationalgroups,
depicted
in
Figure
II-l,
whichusethe
analysis andstudy
data
were askedto
expresstheir
recommendationsfor
improving
the
presenttask
requirements.The
one mainconcernexpressed,
as a result of
collecting
recommendations,
wasthe
needfor
a shorterturn
around
time
for
data
accumulation andsummary distribution.
Each group,
asexpected,
expressedthe
desire
to
have
moreinformation
upon whichit
couldact and
thus
generatethe
outputfor
usein the proposal/study
effort.The
following
will aidin acquainting the
reader withthe
variousinteractions
involved:
a.
"Human
Factors",
requires suchinputs
asitem
description
andenvironmental operation
data.
Their
outputs consist of recommendations andspecific criteria as related
to
the
man-machineinterface (The
relationship
Reliability
Maintainability
Systems
Engineering
Components
Engineering
Human Factors
Technical
Publications
DATA FLOW
FIGURE
n-1
to the
particular machine or equipment.Thus the
governmenthas
acknowledgedthe term Human
Factors)
.Such
outputincludes the identification
andthe
location
ofthe
controls onthe
equipment whichthe
operator willuse,
informa
tion
relativeto
indicators
andtheir
operationalheight,
and use ofindicator
light
color as well as size andlocation.
The
desire
by
Human
Factors
for
more
data input includes
knowing
more about operationaltimes,
repairtimes
and
specifically
the
type
oftasks
anticipated.This
data
wouldcertainly
help
them
to
provide a moredetailed
outputto ultimately
aidin
determining
equipment
location
and personneltraining
requirements.These items in
turn
are reflective within operator-equipment
safety
precaution warnings and otherrequirements relative
to
controls,
maintenancetools,
operatorfatigue.
b.
"Reliability",
requiresinputs
such as expected equipmentoperating
time
perday,
type
of equipmentused,
andthe
expected equipmentoperating
environment.Their
outputs consistmainly
of prediction reportswhich give
the
expected number of equipmentfailures
per period oftime
usually
per a100
hour
interval.
They
also generate a reporttitled
FMEA
(Failure Mode
andEffects
Analysis)
whichis
usedprimarily
by
Maintainability.
It
canreadily
be
seenthat their desire is for
moredetailed information
concerning
expected equipment operation and components withinthe item
assembly.
This
addedinformation
would resultin
a more specific prediction11
c.
"Systems
Engineering",
requireinputs
relativeto
expectedequipment
operating
life,
anticipated maintenance requirementsboth
preventiveand
corrective,
and expected personnelrequirements.
Their
outputshelp
define
equipmentoperating
parameters which willtentatively
meetthe
proposal/
study
requirements.
Their
needfor
moredetails,
as well asinformation
relating
to
actual analysisdata
whichis
supportedby backup
figures
anddocuments,
wUlcertainly
enhancetheir
efforts of response.Whenever
arespondent
to
aproposal orstudy
can referto
similartask
effortsin
whichhe
has participated,
this
experiencefactor
goes along
way
toward
weighting his
ability
to
performthe
task
proposed.d.
"Components
Engineering",
like
the
other organizationalgroups,
requires
data concerning
equipmenttype,
quantity,
environment,
and usage.Their
outputs referto
recommendations relativeto
equipmentstandardization,
reliability
ofuse,
as well askeeping
up
withthe
state-of-the-artdesign
techniques
and components.Additional data inputs relating
to
componentuse,
quantity,
and overalldesign
complexity
will aidin
identifying
those
items
presently used,
or newto
the
technology field,
whichwillfulfill the
overalldesign
requirementsbeing
imposed.
e.
"Technical
Publications",
requiresinputs
relativeto
maintenancerequirements, both
corrective and preventive.These inputs include
expectedcomponent
quantity
andexpectedfrequency
of repair or replacement.Their
output,
in
turn,
helps
to
define
long
lead
times
for
purchase,
type
of manualswhich are
presently
in the military
federal
stock category.This
knowledge
helps define
the
supply
methods and channelsto
be
recommended.f.
"Maintainability",
requiresthe
prediction reports andFMEA
data
from
the
reliability
group.Other inputs include
expecteddesign
parameters,
equipment use and
environment,
as well as component and personneldata.
Outputs primarily
consist ofthe
quantitative maintenancetask
requirementsand
intervals.
The
outputs aidin
defining
design
criteriato
be incorporated in
the
specifications as well assupporting
data
relativeto
componentuse,
quantity,
and expected mode of
failure
.The
needfor
moredetailed inputs
relativeto
equipment
complexity,
type
andquantity
ofcomponents,
aidthe
expected modeof operation and
failure
will resultin
a moredetailed
prediction,
the
morerealistic and
informative
willbe
the
data
in the resulting
system analysis.METHOD
OF ANALYSIS
The
abovedescription
ofthe
variousinput
and output needsforms
the
basis
of analysis.It is
impossible,
or moreaptly,
impractical,
to
supply
allthe
data
requiredby
each organizationalgroup
andto
supply
it for
eachproposal or study.
And
notwo
proposals or studies are alike sothat
a uniformmethod of
supplying data is
acceptable.Therefore,
it
wasnecessary
to
consider
the
outputs of eachgroup
andto
seeif
there
was a common need.Also
it
wasnecessary to
determine
if
there
was a consistent pattern asto
the
type
ofdata
to
be
supplied.As
expected,
there
was a consistent pattern and13
The
recommendations receivedfrom
the
various organizational groupsas well as
the
data
which wasphysically
collected werethoroughly
reviewed.One
ofthe
first
questions,
which requireddata
analysisbefore
answering,
waswhether
the
volumes ofhistorical
quantitativedata
containeddata
relatedto
present
data
requirements.The
analysis showedthat the data
was quiteplentiful as weU as adaptable
for
proposal andstudy
orientation.The data
contained
information
whichdescribed
variousdesign
considerations whichhad
been investigated
as well as adescription
ofthe item's functional
use,
maintenance requirements
both
recommended andrequired,
personnel requirements,
and also gavethe
reasonexplaining the
choice ofthe
variousmaintenance concept requirements or recommendations.
Another
question or pointneeding
analysis wasthe
consistency
ofthe
data
as relatedto
a common reference point.The
data
wasfound
to
be in
terms
ofhours
whenrelating to
MTBF, MTBMA,
andthe
various otheroperating
measurement rationale.Component
failure
rates werein terms
offailures
per100 hours
of operationandin
other cases were expressedin terms
of
failures
perhour
ofoperation.
The
conversion ofthis
data
to
a uniformreference
base
was a simpletask
anddid
not change analysis results.One
other areawhich contained a
different
referencebase
was when some ofthe
more recent
data
wasquantitatively based
upon aneighty
(80)
hour
work week.This 80
hour
data
base
was a result of customer requirements.In
any
event,
this
difference
ofbaseline
requiredthat the data be
convertedto
aforty
(40)
feasible
however,
practically
all requirements use a40
hour
base.
The
40
hour base
willthen
be
the baseline
for
the
research.Some
ofthe
moredetailed data
forms
enablefurther
understanding
ofthe
reasons and methods ofdetermining
the
various maintenancetasks
andoverall
item
concept.The
olderdata
containedindividual itemization
ofcomponents and
the
task
time
associated with each component such asfault
isolation time
and repairtime.
The
newer or more recentdata
depicts,
in
logical flow
chartform,
the
variousisolation tasks
requiredto
locate
a malfunction item.
The
flow
chart alsoindicates the
type
of corrective actionto
be
taken
following
localization.
This
data
in
itself is the type
ofdata
requiredby
proposals and studies.However,
it is
only
possibleto
supply
this
data
for
an overall
item,
whichmany
people referto
as a chassisassembly,
anddoes
not
include
details
on subassemblies and piece parts.The detailed
analysiswhich
includes the
piece parts and subassemblies within an enditem
is
prohibitive when
the study is only in
the
conceptual or proposal stage.The
application of
historical
data
willhelp
fulfill this
data
requirement.(Some
ofthe
different
forms,
upon whichthe
data
wasrecorded,
areto
be found in
Appendix
A
.)The
comparison ofthe detailed
data
form
withthe
logic flow
chartresolved
the
question ofconsistency
ofdata
and maintenance measurements.Tasks
depicting
simHar events such asrepairing
subassemblies orremoving
and
replacing
piece partshad
a smallvariatiorin time
andfailure
ratefactors
15
nine
(9)
minutesto
do
atask
whichthe
newerdata may
represent asrequiring
eight
(8)
minutes.
The
same analysis could alsobe
reversed.SDme
ofthe
task time
determining
factors
wouldbe
the
overallitem
complexity
andthe
method of
item installation
as relatedto the
location
withinthe
overall circuitry.The
majorsignificance
here
wasthat the
data
showedconsistency
in
depicting
task
requirements andtime
intervals
whenreferring
to
similaritems.
This
factor
is very
important.
DATA RETRIEVAL
REQUntEMENTS
In
aneffortto
fulfill
tie
needfor
data
for
proposals andstudies,
it
wasnecessary
to
reviewthe
requirementspresently
used.Figure II-2 is
aMaintainability
Prediction
Worksheet.
This
worksheet andits
continuationsheets,
represents one ofthe
maintypes
of quantitativedata inputs
to
proposalsand
studies.
The
inputs,
aspreviously
defined,
represent an accumulation ofdata
from
various organizational groups.A
brief description
of atypical
sequence of eventsin preparing
aproposal submittal will
help
the
readerto
understandthe
method ofdata
retrieval
determination.
For
example,
the
proposal or specialstudy
is
requestedby
the
Contracts
Department.
(A
special studies requirementmay
alsobe
initiated
withinthe
company.)
In
any
event,
the responsibility is
assignedto
a project engineer who will coordinate
the necessary technical task
efforts.The task
requirements aredefined in terms
of responsible project areas andu u. o s r-UJ UJ I H h-9 O X (A CO u UJ " O c/> z u 2 < u. 1-_ o UJ 2
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z 3 1-< CC o Ll. z wo _1 CC UJ ><
z UJ
Q.
O 5
s 1- z
Q UJ o z UJ 2 o < QC a.
1- o0)
>-UJ
z (T>
K <CC
o
5
_j UJ > N -1 m < << z
9
. < UJ
H t-< Z q: _
< wxc: _i UI l-o < Ll. < z tr < Q. UJ CC t-< _l O z UJ c 35 Ul O
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17
required proposal response
time
requirements as aguideline.
(Usually
the
requested response
time
is
so shortthat task
definition
is
notfully
defined.
In
this
casethe
incoming
requestis
studiedto
determine
whatproject areas areinvolved
andthen
each project area willbe
given a completecopy
ofthe
request.)
Depending
uponthe time response,
ameeting is
held,
with allconcerned project areas
represented,
to
discuss
the
requirements andto
clarify any
anticipatedproblem areas.The
responsible areasthen
pursuetheir
tasks.
As
expressedearlier, there is
considerableinteraction among
the
various areas.One
ofthe
majortime
elementsinvolved
in responding to
a proposal
is the time
requiredto
define
the
types
of equipment needs andthe
parameters
to
satisfy
the
request.Mixed
withthis
is the
composite of electricaloperating constraints,
the
overall mechanicalconfiguration, the total
weightlimits,
andtime
and costfactors.
The
success of a responseis
dependent
uponmany
factors
which are allinterrelated.
This
interrelationship
of quantitativefactors
was evidentin Figure
II-l.
The
recognition ofthis
needfor
timely
anddetailed data
helped
to
determine
the
data
recall program requirements.Each
organizationgroup
neededto
know
the type
of equipmentinvolved,
the complexity
ofoperation,
andthis
needin turn is
reflectedin the
overall systembreakdown into subsystems,
assemblies,
and piece parts.Each breakdown
ofthe
systemis then
concernedwiththe
operating
requirements whichin
turn
is
reflectedin the
equipmentreliability.
The
equipmentreliability is
affectedby
the
design,
operationalthe
abovedependent
items forms
abuilding
block
in the
generation offinal
analysis
data.
The
data
flow depicted
in
Figure
II-l
may
require severalcycles
before arriving
at an acceptable analysis.However,
this
cycling
event
is
time
consuming
andthus
in many
instances
cannotbe
continuedto
anoptimum
because
ofthe time
responsefactor.
The data
recall requirementstherefore
put emphasis ondefining
those
quantitative
factors
which serve as abasis for
defining
otherdata items
.These
factors included
MTBF (also
calledfailure
rate)
,MTBMA, MTTR,
andcorrective maintenance
time.
The historical
data records,
upon whichthe
data
research was
based,
werein
variousformats
asdepicted
by
the
sampleforms
in Appendix
A.
Each
ofthese
forms
was studiedin
an effortto
determine
the
depth
of analysis which was requiredto
completethe
form.
Such
an analysisaided
in
determining
if the
data
content representedthe
efforts ofbasically
oneorganizational
group
orif there
wastotal
group
interaction requiring feedback
and
tradeoff
studiesin
which eachhad
anopportunity to
effect change andthus
arrive at an optimum solution.
Familiarity
withdata
content willreadily
show whether one organizational
group dominated
the
generation ofdata.
If
such were
the
casethen
it
wouldbe
necessary
to
re-evaluatethe data
andarrive at an optimum solution which was not so void of other
group
design
parameters.
For the
mostpart,
eachform
necessitatedthe
intergroup
19
Trade-off
study
is very
important.
Each
newdesign
must gothrough
phases of
detailed discussion
and analysis so asto
optimize allthe
interrelated
design
parameters.It is
the
desire
ofevery
engineering
organizationin
industry
to
define
all requirementsin
the
initial
system specification.The
hope is
then
that
no(or
minimal)
change willbe
required.Each
changeis
costly
in
time,
money,
material,
and ofcourse,
to
management scheduling.The later in
the
production phasethat
a changeis
made,
the
more expenseinvolved.
In the
extreme case a complete scrappageis
required andassembly
must start over again.
The
reader can now understandthe
need anddesire
by
each organizational group
to
have
moredata,
thus
effect a moredetailed
analysis andto
ultimately
be
more responsiveto
proposal andstudy
requests.Technology,
economics and
the
state of competitiondemands data
output which representsthe
company'scapability
to
meetthe design
requirementsimposed
by
military
contracts.
INPUT/OUTPUT
DATA
FORMAT
To
meetthis
needfor data
which representsdetailed
studies,
inter
action,
and optimization ofdesign
parameters,the
historical data
wascoUected.
The
major quantitativedata
entries were comparedto the
presentprediction request entries.
(Appendix
A
andFigure
H-2)
.This
comparisonwas made so as
to
answerthe
next questionconcerning data
retrieval.This
could
be
usedto
submitthe historical
data for
computerprogramming
and alsothe
format for data
retrieval.The
selecteddata
printout shouldbe
such asto
simplify
the
reading
ofthe
data
items.
It
wasdecided
to
have
a onehundred
thirty
-two(132)
character printoutformat from
the
computer program.This
means
that
to
maintain aneasy
to read,
one rowentry
ofdata,
that the
format
is
limited
to
132
characters(alpha/numeric symbols)
of print.Restriction
to
one row ofdata is
notreally
a constraint which mustbe
adhered
to
because
there
are other methods of printout such asprinting
severalrows of
data.
However,
the
one row conceptfacilitates
the reading
ofthe
data
entries and also permits
using
aformat
withheadings
under whichthe
variousdata
entries aredelineated
andeasy
to
locate.
This
is
even more evident asthe
number ofdata
entriesincreases.
The
resultantformat
for
transcribing
the historical data
for
usein the
computer program model
is
the
same asthat
specifiedfor the
data
printout.Figure II-3 is
the
Input Data Format
sheet usedfor
data inputs.
Interface
withthe
Program Data group
wasnecessary in
orderto
establishthe
feasibility
ofcomputer
programming initiation
andadaptability
to
presentcompany
computerfacilities.
The
format
numberis
assignedby
the
Data
Forms Control group
within
the
company.This
numberis
adocument
control number and mustbe
used when
requesting
copies.Briefly
stated,
the
form
is in
three
basic headings
.There
is the Header
Information
such as partnumber,
etc.,
then
the
General
Data
which containss
Y
S
P/N
&
)MENCLATURE01
OF
C
0
N
T
M
0
D
E
GENERAL
DATA
B-TBF
HR
MTBiA
HR
UHSCHED
MADJT
MAN-NUN
PER
OPER.
HR
ACTIVE DOWNTIME
MINUTES
UN-
I
SCHEDULED
SCHED
TIME
I
INTERVAL
D E
T
MAINTENAUC
UNSCHEDULED
(MIN.)
^TAILED
DATA
Input
Data Format
JCE
TASK
DATA
^'l
SCHEDULED
SPECIFICS
REPAIR
MAINT.
TIME
FACTOR
MINrMAX
I
MIN-MAX
22
then the
DetaHed Data
which reflectsin
moredetaU
those
entries underthe
General
heading.
The
details
ofhow
and whereto
apply
the individual
data
entries will
be
containedin
aseparate
Procedures
andInstruction
manualto
be
generated and
distributed
to the
various project groups.DATA
RETRIEVAL EQUIPMENT
IDENTIFICATION
To
be
ableto
effectively
usethe
historical
data
requires apreliminary
identification
of equipment.The
first
step
ofthe
proposal orstudy
responseis
to
identify,
ashas
been
the
casebefore,
the type
of system requiredandthe
basic type
of equipmentfrom
whichthe
system willbe
made.This identification
includes the
basic
operational characteristics such as powerrequirements,
mode of
operation,
voltage and signal stimulusdevices,
control andrelay
transfer
units,
and measurement andindicator
devices.
As
statedpreviously in Chapter
II,
there is
a proposalmeeting held
with
representatives,
from
eachprojectgroup,
who willbe
requiredto
respondto
the
particular proposal orstudy
task.
It is
during
this meeting that the
identification
of system requirementsis
made.The meeting
attendees relatethe
proposed requirements with other systemitems
being
worked upon now orin
the
past.Therefore,
it
is the
pursuit ofthis
reflection or recall of similaritems
which mustbe
encouraged.To
maximizethe
use ofhistorical
data,
someone must
be
ableto
recognizethe
present needs and associatethis
withavailable
historical
data.
There
are several sources ofinformation
availablehas
some source ofdata
whichis
more relevantto
its
needsthan
other sourcesand
therefore
no attempt willbe
madehere
to
list
these
referencesfor
eachgroup.)
To
better
enable anidentification
of similarequipment,
alist
is to
be
supplied at eachproposal
meeting
whichdelineates
the
part number andnomenclature of each
item in the
historical data
records.This
list
shouldbe
kept
up-to-date as moreinformation
is
accumulated.
This
list
represents allthe items
whichwillbe
in the
historical data
modelboth
as a result ofthis
study
and as a result ofany further
recommendationsto
this
study.This
research also consideredthe possibility that
atsometime,
someone
may
notbe
ableto
make a comparativeidentity by
part number orname, between
a proposeditem
and one onthe
above referencedpart numberlisting.
Therefore,
anotherlist
Table
II-l
was generatedafter an analysiswas made of
the historical data items
andthe
various proposal and specialstudy
requestitems.
This
newlist
consists of equipment classifications.The
number of classifications was
purposely
kept
minimalto
enable rapidequip
ment
identification.
Therefore,
if
anidentity
cannotbe
madeby
item
partnumber or
name,
then
it
may
be done
by
equipment classification.In addition,
eachclassification was
further
defined
anddivided in
subclassifications.Table
II-l
is the
Equipment Classification List
and representsthe
class andsub-class of each equipment which
is
applicableto the
model and will aidin
24
TABLE II-l
EQUIPMENT
CLASSIFICATION
LIST
Stimulus
Devices
(a)
Power
(b)
Signal
(c)
RF
(d)
Microwave
(e)
Infrared
(f)
Synchro
&
Servo
(g)
Radar
Measuring
Devices
(a)
Microwave
(b)
Pressure
& Temperature
(c)
C
ontrol(d)
Ratio, Standard,
C
omparator(e)
Multimeters
(f)
Scopes
Display
Devices
(a)
Power
(b)
Test Data
Control
Devices
(a)
Microwave
(b)
Relay
(Switching)
(c)
Power
(d)
Indicator
(e)
Signal
(f)
Program
(g)
Temperature
(h)
RF
(g)
RF
7
Simulators
(h)
(i)
Audio
Recorder
(a)
Flight Control
Inte
srfaceDevice
(b)
Mechanical Movement
(c)
Receiver Transmitter
(a)
Terminal
& Distribution
Systems
(Includes
(b)
Adapters
Antenna
(c)
C
ontrol(d)
Radar
(d)
Signal
(e)
Navigation
(f)
Loads
Switching
Devices
(a)
Relay
Assembly
ANALYSIS OF RESEARCH
Chapter
I
defined the
purpose ofthe
researchstudy
as well asexplained
the
use of analysisdata.
Chapter
II
described
the type
ofdata
studied,
analyzedthe
data
andinputs that
wereavailable,
andthen
adaptedthe
data for
computer program modeling.It
now remainsto
be
determined
whether or not
the
research propositionis
supported as specifiedby
the
measurement criteria.
DISCUSSION
OF DATA ITEMS
To
adequately
relatethe
study findings
to
the
purposefor
whichthe
researchwas undertaken requires a
step
by
step
analysis ofthe
variousdata
items
which areincorporated
withinthe
systemdata
model.This
analysiscan
be
easier understoodby
referring
to
the
different data headings
depicted
in Figure II-3.
Establishing
the
scheduled maintenance(also
calledpreventivemaintenance)
tasks,
task
times,
equipment,
and personnelneeds,
aidsin
defining
the
overall equipment availability.This is
animportant
factor
in
responses
to
proposals and studies.Equipment avaHability is
animportant
factor
whenmaking
decisions
relativeto
time,
cost,
and quantity.Now
mostscheduled
tasks
referto
metercalibration, cleaning
of airfilters,
removing
26
calibration
standardfrom
the
syst em,
andthen
replacing
these
equipmentitems
withrecently
calibrateditems.
All
ofthese
calibration requirementsare such
that the
calibration accuracies mustbe
traceable
to
the National
Bureau
ofStandards
in
Washington,
D.
C.
The task time
to
performthe
calibration
of equipmentis usually
defined
within certainlimits.
The
only
exceptions which would
be
evident arethose
involving
the accessibility
to
the
item
withinthe
particular system and alsothe availability
ofthe necessary
calibration support equipment.
Some
systems contain equipmentwhich requiresvery
little
calibration while other systems require considerable calibration.The
amount and
type
of support equipment neededto
performthe
calibrationtask(s)
varies
from
systemto
system.(The
reader can referto
Military
Specification
MIL-C-45662A,
Calibration
System Requirements for
moreinformation
onthis
topic
.)It
wasfound
that the historical
data
provided a goodbase
ofdata for
reference and
the consistency
ofthe data
was suchthat it
wasreadily
adaptableto
the
data
analysis model.In
fact,
this
historical
scheduled maintenancetask
data
provides afirm
basis
for
establishing
proposal andstudy
data
asit has
fulfilled
the
requirements of variousmilitary
specifications.Having
determined
the
applicability
of scheduled maintenancedata
to
the
modelit
is
then
necessary
to
considerthe
unscheduled maintenancedata.
Repair
times
for removing
piece partsfrom
anassembly is usually
compatible
from
equipmentitem
to
equipmentitem.
Any
relevant variationin
task
time
wouldbe
primarily
due
to
the gaining
of accessto
performthe
when no consideration
has
been
givento
performing
a system analysis.However,
the
historical data
as appliedto
this
research analysis model representsmany
systems'
analyses and
thus
the time
variationis
minor.It is
quite evidentthat
time
andtask weighting
of severalitems,
over a period oftime,
for
severalsystems and
subsystems,
willeventually
show a quantitative relationship.This
quantitative
relationship has
alsobeen
recognizedby
the
military.There
aremiHtary
documents
listing
many items
whichhave been
studied over a period oftime
and which relateto
actualmilitary shop
practices. .Inthis
respectthe
military
recognizesthat there is
some sort of standardizationamong
similartypes
ofequipment.(The
readeris
referredto
Air Force Manual AFLCM-65-1
Electronics Maintenance
andRepair
Policy
for further reading.)
Where
the
real element oftime
difference is
significantis in
the
fault
localization
andisolation tasks.
To
help
simplify
the
understanding
ofthis
difference,
considerthe
task
oflocalizing
andisolating
a powerfailure
in
acar,
alocomotive,
and an airplane.Assume that localization
ofthe
malfunctionhas been
madeby
the
fact
that the
car motorhas
stopped orthe
jet
onthe
airplane
has
stopped orthe
locomotive
has
stopped.Actually
in
electronicequipment
this
localization is
not so apparent.Many
initial
malfunctionindications
areonly
anilluminated
light
which should notbe
on or vice versus.Once
localization has been
made,
it is
then necessary to
isolate the
cause ofthe
failure.
Suppose
each ofthe items has
apowerfailure.
The complexity
ofdesign
andthe
power requirements ofthe
three items demands different
28
the
powerfailure
on a car.Assuming
that
he has had
experience orknowledge
in
a similar carinstance in the
past,
there
is
an experiencefactor
which will aidhis
maintenancetasks.
Further
support ofthis
is
evident when an autorepair
shop
supervisor opens a maintenance manual and statesthat
the
standardbook time to
repair a particularfailure
requires somany
minutes.This book
time
is
a weighted standard whichhas been
achieved over a period oftime.
This
standard
is
still subjectto
variationbut,
the
variationis
not asfar
from
the
weighted standard as an estimate made
by
someone withoutbackground data
andexperience.
And
this
is important because the
personrequiring
the
services ofthe
maintenanceshop
personnelmay very
well want a good estimate(analysis)
before
deciding
whetherto
repairthe
faulty
item
orbuy
a new one.This
is
where
trade-off
studies arevery important in
helping
in
the
managementdecision
processes andthe
needfor
experiencedata is important.
It is this
basis
ofdata
accumulation andthe relevancy
ofthe
similartypes
of equipmentitems that strongly
supportsthe
application ofhistorical
quantitativedata
for
usein
a systemdata
modelfor better responding
to
proposals and special studies.
The
accumulatedhistorical
data
notonly
represents analyses of actual
types
ofequipment,
but
alsobears the
application andincorporation
ofmany design
considerations andtrade-off
studies whichwere required
to
approachthe
optimum system analysis as reflected within each analysis usedfor the
system model.The
application ofthis
historical
data
and
its many design
aspects outweighsdata
whichlacks
experiencefactors
andinformation
which mustbe
obtained and/or estimated within alimited time
The
proposal orstudy
response,
aspreviously
stated,
must notonly be
timely
but
containdata
which mostaccurately
reflectsthe
anticipated characteristics
ofthe
proposedsystem.
Two
points are madein the
utilization ofhistorical data
which aidsin
assuring
that
realisticdata
has
been
provided.One
is that the
data
is
existing
and notsimply
an estimatedfactor.
Two,
the
historical data
reflectsactual,
ratherthan
fictitious
items
and canbe further
supported
by
availabledocuments
such asdrawings,
etc.SPECIFIC
MODEL
APPLICATION
Having discussed,
in
Chapter
II,
the type
ofhistorical data
availableand
having
relatedthe
purposefor
whichthe
data
items
areused,
it is
noweasier
for
the
casual readerto
read and understand an actual computer printoutof analysis
data.
To
provide abasis for
discussing
the criteria,
asdefined in Chapter
I,
a
trial
computer printout was obtained.This
printout,
titled
Newsystem
Simulation,
is found in Appendix B
ofthis
report.In
an effortto
comparethe
research model applicationwith a situationusing
previousanalysismethods,
aproposed new system was simulated.It
wHlbe
rememberedfrom
Chapter I that
an analysisinvolving
nine(9)
major subassemblies required
three
days
of analysistime.
This
referenced analysis wasalso subjlect
to time
anddata
constraints as well as possiblebiased
decisions
on30
Past
data
indicates that the
majority
ofsystems
contain,
as aminimum,
a power control
panel,
switching
devices,
a system operation controlpanel,
measurement
devices,
a powersupply,
a signalgenerator,
and acooling
fan.
This
researchstudy
proposed a n ew systemsimulating
nine(9)
equipmentitems.
The types
of equipment simulated are self evident uponreading the
printout
in
Appendix B.
(The
only
items
notreadily
recognized,
by
the
casualreader,
arethe
wordsDATAC
andCONT. TP.
DATAC is the
main operationalcontrol panel.
CONT.
TP
is
atest
pointswitching
device.)
This
new systemclosely
approximatesthose
system requirements referencedin the
analysisrequiring
three
days.
The time
requiredto
identify
and associatethe
proposed nineitems
witha simHar
item
having
historical
data,
requiredfour hours.
It
is believed that
this time
couldhave been
shortenedhad
several peoplebeen involved in the
equipment
identification
and selection.It is the
opinion ofthe
researcherthat
the task
ofassociating
proposeditems
withhistorical items
willbe
performedat
the
various proposal meetingspreviously
mentioned.The
task
time
requiredfor
item
association shouldthen
be
reduced.Once
the
particularhistorical data item
was selectedthen
the
data
relevant
to
each ofthe
nineitems
was adaptedto the
computerinput
format
(Figure
II-3).
The data
sheet wasthen
taken to
data processing
to
key
punchthe
data
cardsto
be
usedby
the
computer.This
key
punchtask
requiredforty
(40)
minutesby
the
researcher.However,
it is
believed,
based
upon actualten
(10)
minutesto
do
the
sametask.
Both
ofthese times
are givento
providean
idea
of whatmay
be
involved
whenthere is
a morelengthy
requestfor
data.
The
personrequesting
a computer printout of analysisdata
mustconsider various other
factors
such as shared use ofthe keypunch
machinesandwhether or not
he
plansto
preparethe
data himself.
If
he does
notdo the
keypunch
himself,
then
he
must considerwaiting time
whenrequesting the
workbe done
by
an experienced operator.Some
tasks
have
priorities andin
those
instances the time
factor
couldbe less.
In any
eventit has
been
mentionedhere
as anitem to
be
considered.Waiting
time
is
also afactor
whenobtaining
an actual computer printout.This waiting time is the
period whenthe
keypunch
cards arepresentedto
the
computer programmer untH
the time
the
actual printoutis
received.Once
again,
there
are othercompany
requirements whichdemand
computertime
andeach
has its
particularpriority
as well as computer usagetime.
APPLICATION OF
MEASUREMENT
CRITERIA
Returning
nowto the Appendix B
computer printoutit
is
seenthat
there
are nine
items
withinthe
simulated new system.All
the
pertinentdata
such asMTBF, MTBMA,
maintenancetimes,
availabilities,
etc.,
are printedin
aform
which
may
be
directly
incorporated
as anAppendix
orAttachment to any
proposal or special study.
The data is
alsodelineated
so asto
facilitate
reading
as well as rapid
item identification
whichis especiaUy
useful when severalpeople are
discussing
the
particulardata items
priorto
making
management32
Note
the
availability data
onthe
second page ofAppendix
B,
the two
items
nextto the
last.
For example, the
Ai,
Inherent
Availability,
is
0.99745.
This
meansthat
the
newsystem,
comprised ofthe
nine majorsubassemblies,
is
expectedto
be
operational99.74%
ofthe
time.
The
other0.26%
ofthe time
the
systemis
expectedto
be inoperative due
to
unscheduled maintenance.Earlier,
scheduled maintenancetasks
werediscussed.
These
tasks
requirethat the
new systembe
removedfrom functional
use.The
Aa,
Achieved
Availability,
is
0.99328.
This
meansthat the
new system willbe
removedfrom
operational
use,
due
to
scheduled and unscheduledmaintenance,
0.67%
ofthe
time
.Many
proposal andstudy
requirements set adesign
goal which willrealize a
90
to
98
percentAa.
From the
presented modeldata
it is
evidentthat
the
new system withthe
nine major subassemblies shown willin
fact
meetthe
availability
requirements.The
otherdata
items,
asdefined in the
printout,
aid
in the
computation ofthe avaHability
factors.
The
particular equations arereferenced on
the
printout,
however,
all computationis
performedby
the
computer and eliminates
human
computational errors.The
actualtime
requiredby
the
computerto
performits
task,
whichincludes reading
data
cards, performing
computations andprinting the
actualoutput
in
Appendix
B,
is
printed on a separatedata
sheet.In
otherwords,
the
computer output not
only
providesthe desired
printoutbut
also provides alist
of
the
variousprogramming
steps as well as adata entry
which showsthe
actualcomputer
time.
This time
entry
is
usedby
the
company
in its
recordsrelating
and not
the
other sheetsbecause
they
are not pertinentto
the
research.
However,
it
shouldbe
notedthat the
actual computertime
was3
minutes and44
seconds.
Measurement
criterionNo.
1
statedthat
a computer analysisprintout,
and
the time
expendedto
obtainthe
data,
would require no morethan
one eighthour
day.
The
actual printoutin
Appendix
B
requiredfour hours
ofitem
identification
andassociation,
forty
minutes ofpreparing the
data for
computeruse,
andfour
minutes of actual computer runtime.
This
is
atotal
offour
hours
andforty-four
minutes whichis
well underthe
eighthour
criterion.(There
was an actualwaiting time
of onehour before
the
printout wasactually
received.
As
statedpreviously, this time
canvary,
depending
upon a numberof
items)
.Waiting
time
has
notbeen included in the total time
measurementof
meeting
criterionNo.
1.
If it
had,
criterionNo.
1
would stillhave been
satisfied.
The
second measurement criterion statedthat
a second computerprintout,
shouldit
be required, representing
alternative analysisdata
will notrequire more
than
onehour
more effort oncethe
originaldata
requirementshad been
established.Another
computer printoutwith alternativedata
was notactually
obtained.However,
assumethe
most complicated case wherein allnine of
the
items
wereto
be<