B. MaintenancePractices (continued)
4. 50-Hour Inspection
(a)
Performentire deicer system operational checkfor each engine.
(b)
Removespinnerdome and upper engine cowl. With assistant observingdeicer ammeter and deicer switch on and groundtest switch activated,flex all accessible wiring. (particularly deicer lead straps, leads from slip ring assemblyand firewall electricalconnectorsand wiring.) If any movementof ammeter needle,otherthan 34 second flicker of cycling exists, locate and correct short or break immediately.Performtest for left and right systems.
5. 100-Hour Inspection
(a) Removeenginecowling.
(b)Conduct50-hourinspection.
(c)
Check for radio noise or radio compass interferenceby operating each engine at near takeoff powerwith radio gear on, while turning each deice switch on and off. If noise or interference occurswith deicer switchon and disappears when switch is off, see 30-20-00, Chart1 for fault isolation.
(d)
Ensure all clamps, clips, mountings,and electrical connectionsare tight. Check for loose, broken,ormissing safety wire.
(e)
Checkdeicer boots for wrinkled, loose, torn, or cut areas around ends of boots, where propeller bootstrap passes under strap retainer, especiallyalongleadingedgesand flat or thrust face propellerboots.If heater wires are exposed in damaged areas,or if rubber is tacky, swollen or deteriorated,replacedamageddeicer.
NOTE: Ensure strap restrainers are properly positioned and secured. Look for cracks or other damage.Operatepropellerfrom full pitch to feathering and ensure deicerlead straps arenot tensioned or pinched bypropellerblade.
(f)
Checkslip rings for gouges, roughenedsurface, cracks, burnedor discolored areas,and depositsof oil, grease or dirt as follows: (1.) Clean greasy or contaminated sliprings with CRC-2-26solvent.(See 91-00-00, Listof
ConsumableMaterialsfor vendor information.) (2.) If uneven wearexists or if wobble is noticed, set up dial indicator (Figure 501) to check slip ring to propeller shaft alignment.
SuggestedUse of Dial Indicator
Figure 501
EFFECTIVITY:
30-60-00 PAGE3Jan 10/90
PIPERAIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCE MANUAL
B. MaintenancePractices (continued)
5. 100-HourInspection (continued)
(g) Examinebrush block mounting bracketsand housing for cracks, deformation,orother physical damage. (1.) Ensure each brush rides fully on its slip ring over 360° (seeFigure 502). If alignment is
off, shim where brush block attaches to mounting bracket.(Shim is a series of laminates and can be peeled for proper alignment.) If old shim is not thick enough, install new one.
Slip Ring Brush Located
Slip Ring
NotchWornin Brush
Due to Misalignment
Centeringof Brushes on Slip Rings
Figure 502
(2.) Check for proper brush block to slip rings clearance (Figure 509). If incorrect, loosen mounting screws, place in proper elongated holes, and tighten securely. (3.) Check brushes for wear limitation (Figure 503).
°
(4.) Visually check block for approximately 2 angleof contact (Figure 509). If incorrect, loosen mounting screws, twist block, and ensure proper clearance limits when tightening.
CAUTION: DO NOT HOLD GROUND TEST SWITCH ON FOR ANY LENGTH OF TIME WHICHCOULDCAUSEOVERHEATING.
(h)Operatedeicersystems and whileassistantobservesammeter,inspectand physically flex wiring from brush block through firewall,to timer, to ammeter,toswitch, and to aircraft power supply.Theammetermust flicker as timer switches every34 seconds
approximately in cycle. Jumpsor flickers at other time intervals indicateloose or broken wiring. Check continuity in affectedharnesswhile flexing and prodding each wire in area causing problem. Use Wiring Diagram,30-20-00,Figure 2, to trace circuitry. Performsametest on engine inlet lip deicers withsystemsswitcheson and an assistantpressingground test switch.
6. Checking For Brush Wear
Insert small diameterwirethrough hole in rear of brush retainer assembly (refer to Figure 503). Replacebrushesif the length of the inserted portion of wire measuresmorethan 1 25/64 inches.
EFFECTIVITY: 040-999
Jan 10/9030-60-00
PIPERAIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCEMANUAL
B. Maintenance Practices (continued)
Measuring Brush Wear
NOTE:
Measure brush wear as shown,
X-dimension (inches) /
given indicateswhen
brushes must be replaced.
During measurement only
1/16 inch of brush should be
allowedto protrude from
modularbrush. This is the
normal position of the
brush when installedon the
aircraft.
ModularBrushAssembly X-Dimension(Inches) Must Replace 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：夏延飞机维护手册 Cheyenne IIIA PA-42-720 AMM 2(27)
