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Human Error in Maintenance
Presented by:
Alabama & Northwest Florida Flight
Standards District Office
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Section Objectives
After you complete this section you will be
able to:
Define two different types of human error.
!plain why people commit errors.
!plain how human error affects A"#. Name the types of error pre$ention.
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Defining Human Error
!ample: %ohn dri$es into standing water and beginsto hydroplane.
. Slip ' (a$ing a good plan) but bad e!ecution.
!: %ohn *nows he should pump his bra*es) butmisses the bra*e and steps on the gas instead
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Defining Human Error
+. "ista*e ' A bad plan is performed) though
not on purpose.
!: %ohn thin*s that speeding up will gi$e
control o$er his car. (e steps on the gas.
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Defining Human Error
,. -iolation ' #he wrong procedure isperformed intentionally.
!: %ohn learned in dri$ers education classthat he should pump his bra*es in this
situation. (owe$er) %ohn heard from hisolder brother that acceleration is best) sohe steps on the gas.
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Error and Aviation Maintenance
#his section describes how human error
affects the a$iation community) a$iation
maintenance and more specifically theA"#.
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Valuejet flight !"
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Machine#Human $auses for
Accidents%Airline safety has impro$ed o$er the past /
years because of:
better aircraft.
better air traffic control.
better weather prediction.
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Machine#Human $auses for
Accidents% (uman error defined
byred line.
"achine error definedby yellow line.
0
20
40
60
80
100
120
1850 1900 1950 2000 2050
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Human Error Estimates&%
System 0 Due to (uman rror
Airlines 1/23/0
Air #raffic 4ontrol 5/0
Ships 3/0
6rocess 4ontrol 3/0
Nuclear 6ower 1/0
7oad #ransportation 380
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'able of Aviation Accident
$ausal (actors%Causal Factors (1982-
1991)
No. of
Accidents
Onoard Fatalities
4ontrolled Flight into
#errain 94F#;
,< +
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'able of Aviation Accident
$ausal (actors%@round Deicing>Anti2icing 5 ,3
ind shear / ,3
?n2contained ngine Fire 55
Out of 4onfiguration #a*e2off
33
Airport @round Ops.4ontrol
+, ,3
7eBected #a*e2off 5 8,
!O!A" #94 96#9
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)ntroduction to Human Error
CFor want of a nail) the shoe was lost)
for want of a shoe) the horse was lost)
for want of a horse) the rider was lost)
for want of a rider) the battle was
lost
22EenBamin Fran*lin22
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Heinrich *atio
Heinrich Ratio
Fatal Accident
Non2Fatal Accident /
7eportable ncident ,/
?nsafe Acts
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Active and +atent Errors
#here are two basic *inds of human errors:
acti$e errors and latent errors.
Acti$e rror ' An action that has an
immediate effect.
=atent rror ' An action that has a delayed
effect
7eason) %. 955/;. (uman rror) 4ambridge) ?G: 4ambridge 6ress.
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Active and +atent Errors
Acti$e errors' Actions that ha$e immediateeffect. 6eople are most familiar with acti$e
errors. An e!ample of an acti$e error wouldbe a pilot belie$ing his aircraft to be muchhigher than it really is and failing to adBusthis altitude accordingly. #his error leads tothe plane crashing into a mountainside) aneffect that is felt more or less immediatelyin the system.
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Active and +atent Errors%
=atent errors' Actions that ha$e delayed effect.=atent errors) on the other hand) are errors whoseeffects are delayed in time and space and may not befelt immediately. An e!ample would be an A"#neglecting to chec* a *ey bolt supporting an engine toa wing. #his bolt happens to be corroded. O$er time)the engine support wea*ens and fails altogether. (ad
the A"# not committed the latent error of neglect)the corroded bolt would ha$e been replaced and thesupport would not ha$e been compromised.
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Active and +atent Errors
Eecause of the time delay between error and
conseHuence) latent errors and their causes
are much more difficult to trace than areacti$e errors.
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Human Error in Maintenance
#he a$erage cost of an in2flight engine shutdown is
I8//)///.
#he a$erage cost of a flight cancellation is I8/)///. #he a$erage cost of a return to gate is I8)///.
#he Airline #ransport Association estimates that ground
damage costs I38/ million>year.
#he a$erage ground damage incident costs I1/)///. One Airline estimates between I182I// million>year is
wasted on error
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A Hangar e,am-le
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E,am-le: *esulting Damage
=eft2hand horiJontal stabiliJer.
7udder.
7ear doc* stands.
(angar wall.
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E,am-le: $ost (actors
"aterial
7egular and o$ertime labor.
7epair to doc* stands and hangar wall. =oss of bay during e!tra repair duration.
Delayed or third party maintenance for other aircraft.
Operational complications due to aircraft a$ailability.
n$estigation and remediation.
stimated total cost K I5//)///.
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E,am-le: $ost )m-lications
Annual airline re$enue K I+)///)///)///.
7e$enue>day K I,,)///)///.
stimated profit margin K 80
6rofit per day K I)associated costs K I5//)///.Summary: Error Consumed day of total
profit!
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'o- Seven $auses of )n.(light
Shutdo/ns. ncomplete installation 9,,0;.
+. Damage on installation 9.80;.
,. mproper installation 90;.
. Huipment not installed or missing 90;.
8. Foreign obBect damage 9
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Other Maintenance 0 *elated
$auses of )n.(light Shutdo/ns "issing parts.
ncorrect parts.
orn parts. 4areless installation of O2ring.
E2nuts not safety wired.
E2nuts wired bac*wards.
Nuts not torHued O$er torHuing.
Not loosening both ends of connections.
7eplacing tube assembly without brea*ing connections.
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'o- Seven $ommon Maintenance
Errors. ncorrect installation of components.
+. #he fitting of wrong parts.
,. lectrical wiring discrepancies 9including cross2connection;.
. =oose obBects 9tools) etc.; left in aircraft.
8. nadeHuate lubrication.
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1hy Do 1e Ma2e Errors3
L
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Mental +imits: Disassembly
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Mental +imits: *eassembly
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Definition of $ulture
Culture' A pattern of beliefs and
e!pectations shared by an organiJation and
its members.
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$ulture
hat would happen if an air carrier made
on2time departure its number one priorityL
(ow would that affect safetyL
Do you thin* management would gi$e you
the time to ser$ice an airplane the right
wayL
Do you thin* you would be pressuredL
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$ulture
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+ist of Organi4ational and +ocal
(actors%OrganiJational =ocal
#raining and selection ofpersonnel. Gnowledge and s*ill ofpersonnel.
Muality of resources asdistributed.
Muality of resources onhangar floor.
OrganiJational Structure (angar en$ironment.
Opportunities for careerde$elopment.
"orale & personalities ofemployee.
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A Human (actors Accident
Scenario%Defenses
@aps
#eamwor*
7eliable "aintenance
@ood "anagement
Ambiguous instruction9goes unchallenged;
oung F>O lets it go
"is2Budgment by senr. 4apt.
"issing component
Operational pressure
(igh wor* load.
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Error Prevention
#hree Easic Strategies
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'y-es of Prevention Design
. !clusion Design ' #he design of a component
ma*es it impossible to commit an error.
+. 6re$ention Design ' #he design of a componentma*es it difficult) but not impossible for error.
,. Fail2Safe Design ' #he design of a component
reduces the conseHuences of errors without
necessarily reducing the li*elihood of errors.
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E,am-les of Prevention Design
. !clusion design
+. 6re$ention design
,. Fail2Safe design
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$onclusion
Flying is not inherently dangerous, but
to an even greater extent than the
sea, it is terribly unforgiving of
carelessness, incapacity, or neglect