Jan10/9030-40-00

PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL

A. Windows, Windshields and Doors (continued)
WireWrappedAroundNut
Wire-P/N 151 295 (MS20995-C20)-

Twisted Wire Centered Under Arm
Wire WrappedAroundArm
WiperBlade
TvoicalWindshieldWiperBlade
10.Bolt,Washer,Nut

12.Blade
7. Wiper Shaft Cover
6. Converter

10.Bolt, Washer, Nut
9. Wiper
Mounting
Bracket-4. Drive Assembly
3. Bolt,7. Wiper

Shaft 5. Drive Assembly 2. Motor
Cover

1.

6. Converter
WindshieldWiperInstallation Figure 401

EFFECTIVITY:
040-999
PAGE30
Jan 10/90
PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCEMANUAL

A. Propellers-Description and Operation
The propeller deicer system consists of two individual systems. One for each engine is linked together by an ammeter containing a selector switch which enables it to monitor operation of the left or right system.
For propeller deicer cycling sequence, see cycle sequence (91-60-00). The system can be used continuouslyin flight, if needed.
NOTE: Heating can begin at any phase in cycle depending on timer position when switch was turned off previously.
B. Maintenance Practices
1. DeicerSystem Operational Check
CAUTION: THE LIP CAN BE DESTROYED WITH THE COMBINATION OF THE PARTING STRIP ELEMENT BEING CONTINUOUSLY ON THE HEAT INTENSITY OF THE LIP DEICER ELEMENTS. OBSERVE BOOT CLOSELY WHILE TESTING FOR OVERHEATING.
(a)
Chock wheels and operate engine at near takeoff power.

(b)
Tum deicer system switch on for side being checked. Activate ground test switch.

(c)
With ammeter selector switch in proper position, observe ammeterfor at least 2 minutes.

(d)
Ensure ammeter needle flickers approximately every 34 seconds when operating timer step switch. Ensure needle is in green arc during all four cycle phases.

(e)
Stop engine, remove top engine cowl, and unplug lip deicer boot at plug and ground lead disconnect.

(f)
Plug auxiliary power in, turn deicer switch on, and check operation of ice deflector door underneath air inlet screen by looking back through air inlet and down each engine side. Also check operation of bypass door on underside of bottom engine cowl at rear of engine.

(g)
Have assistant activate ground test switch. Adjustpropeller deicer boot outboard elements followed by inboard elements.

NOTE: Because the lip deicer is inoperative, the ammeter does not read through two phases of the two minute cycle and reads slightly lower than that observed with engine running, during two prop deicer phases.

(h)
Two ways to safety check operation of lip deicer are as follows: (1.) Obtain 28 Vdc power source capable of supplying 30 amps. Connect negativelead to deicer ground lead and touch positive lead individually to three terminals of deicer plug.

(2.) Connect deicer ground wire at quick-disconnect terminal,positioncockpitmaster and deicer switches on, and activate ground test switch. Have assistant connect deicer plug to mating plug supplyingsystem power long enough to notice temperature rise in boots. Finally, disconnect plug and wait until second lip deicer phase begins.
WARNING: DO NO HOLD CONNECTION SO DEICER BECOMES TOO HOT TO TOUCH.
NOTE: The timer only operates as long as ground test switch is activated.
riseof boots must be noticeable. If local hot spots are apparent, and must be replaced.
(i) Temperature boot is damaged
EFFECTIVITY:
30-60-00 PAGE
Jan 10/90

1.

PIPERAIRCRAFT
PA-42-720(Advanced Trainer)
MAINTENANCEMANUAL

B. MaintenancePractices (continued)
2. Usingthe Ammeter
Inflight or duringgroundtesting,useammeterto indicateconditionof mostelectricalproblems. Thetroubleshootingchart isbasedon ammeterresults.
NOTE: Whentroubleshooting,useammeterandheattesttodeterminecircuitsinvolved.Use circuitdiagramtocheckvoltagesorcontinuity.
3. HelpfulTips
(a)
If ammeterreadingdropsto one-thirdnormalcurrent,one heatercircuitis open.

(b)
Excesscurrentreadingon ammeteralwaysindicatespowerleadisshortedto ground. Locate and correctgroundedpowerleadimmediately.

NOTE: Manytimersare returnedfor repairandfoundfully workablewhentested. Complete testdescribedin TimerTestbeforediscardingtimer.
7. LeftCircuitBreakerPanel 
DeicePowerControlRelays 
2. PropellerDeicerBoot 
Propellerand EngineAir InletLipDeicerSystem 
Figure1 
EFFECTIVITY: 
040-999 

10/9030-60-00
Jan
　
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