(1.) Clean deicer thoroughly with Isopropyl Acetate.
(2.) Roughen entire surface of boot with fine grit sandpaper.
(3.) Clean surface again with clean, lint-free cloth moistened with cleaning solvent.
(4.) Apply masking tape beyond upper and lower trailing edges leaving 1/4-inch gap of bare
metal. (5.) Mask off any legible deicer brands. (6.) Apply one brush coat of A-56-B cement to deicer. Allow to dry at least 1 hour. Apply
second coat and allow to dry at least 4 hours before operating deicers. Plane can be flown as soon as cement is dry.
NOTE: If A-56-B cement is 3 months old or more, dilute cement with Isopropyl Acetate to obtainproper brushing consistency.Mixthoroughly 5 parts cement
withapproximately to 1 part Isopropyl Acetate.
EFFECTIVITY:
30-10-00 Jan 10/90
PIPERAIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCEMANUAL
A. Air Intakes-Descriptionand Operation
The PA-42-720containsan engineinletLipDeicesystemin the nacelle.
The lip deicersystemconsistsof two individualsystemsonefor eachenginelinkedtogetheran
ammeteranda selectorswitchthat enablesit to monitoroperationof either leftor rightsystem.
Eachlipdeicesystemconsistsof an electricallyheatedlip,a timer shunt,circuitbreakers,anda switch
to controlsystemoperation.
Toconserveelectricalpowerdrawnfromaircraftelectricalsystem,currentis cycledto deicerheaters
at timed intervals,notcontinuously.
NOTE: Heatingcan beginat anyphasein the cycledependingon timerpositionwhen switchwas turnedoff fromprevioususe.
B. Fault Isolation
Problemspeculiarto deicingsystemare listedin Chart1 alongwith probablecausesandsuggested remedies.
CHART 1 (Sheet 1 of 5) FAULT ISOLATION (ENGINE DEICING SYSTEM)
Fault Cause Remedy
Ammetershowszero Trippedcircuitbreaker. Locateandcorrectshort
current. (All4 phases beforesettingcircuit
of the 2 minutecycle.) breaker.
Defectivepowersource. If novoltageintoswitch,
locateandcorrectbreak.
Ammeterselectswitch If novoltageat switchoutput
faulty. with voltageat switchinput,
replacethe switch. If voltage
is satisfactoryat switchoutput,
go to nextstep.
Ammeterfaulty. (If some Testforvoltageupto andout
or all deicersheatwith of ammeter. If lowor zero
ammeterat zero,replace outputand inputsatisfactory,
the ammeter.) replaceammeter. If no voltage
to ammeter,locateandfix
breakbetweenswitchand
ammeter.
Breakbetweenammeter Disconnectharnessattimer
andtimer. andcheckvoltageat PinB
(ofharness)to ground. If
none,locateandcorrect
break.
EFFECTIVITY:
040-999
30-20-00Jan 10/90
Jan
PIPERAIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCEMANUAL
B. FaultIsolation(continued)
CHART1 (Sheet2 of 5) FAULTISOLATION(ENGINEDEICINGSYSTEM)
Fault
Ammetershowsnormal currentpartof cycle, zerocurrentrest of cycle.
Ammetershowsnormal currentpartof cycle, lowcurrentrestof cycle.
Cause
Opencircuitbetweentimer andheatingelement.
Burnedout lip deicer.
Breakbetweenbrushblock assemblyandprop deicer leadstraps.
Nogroundcircuit,one
engine.
Elementsof different phases heatinginthesamephase.
Breakin deicer orslipring
leads.
High resistancein circuit
with low current.
SheddingAreaI and/or
SheddingAreaII phases
oflipdeicerinoperative
butPartingStripheater
working.
Remedy
Useheattestto find deicers notheatingandtestfor voltageonthatcontactof wireharnessplug.(At brushblockassemblyor connector.)Ifzeroover2 minutes,locateand fix breakin wiring fromtimer to wire harnessplug.
Replace.
Ifthereisvoltageto brush
blockwireharnessplug,
tryvoltageat junction of
deicerleadandslipring
lead. Ifnovoltage,find
andcorrectbreakinwiring
withinbrushblockorno
contactof brushto slipring.
Ifvoltageisfoundat deicer
leads,locateandfixbreak
fromdeicerto ground.
Locateandrepairincorrect connections.
Disconnectdeicersto
checkheaterresistance.
If satisfactory, locateand
fixbreakin slipringleads.
Ifnotin contact of brush
to slipring(including
groundbrush),tracewiring
todeicerandto timer tofix
partiallybrokenwire,loose
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