Deicer System 100 Hour Inspection - Piper PA-44-180 SEMINOLE Maintenance Manual

100 HOUR INSPECTION.
1. Remove cowling.
2. Conduct 50 hour inspection.
3. Check for radio noise or radio compass interference by operating the engine at near takeoff power with
radio gear ON while turning deicer switch ON and OFF. If noise or interference occurs with deicer switch
ON and disappears when switch is OFF, see troubleshooting chart.
4. Ascertain that all clamps. clips. mountings and electrical connections are tight. Check for loose, broken or
missing safety wire.
5. Deicers: Closely check deicers for wrinkled. Loose or torn areas, particularly around the outboard end.
Check that terminals and terminal studs are not shorting out to each other or the propeller hub. Inspect wire
harness for evidence of chafing or shorting. Insure that all clamps and tie straps are properly installed.
Look for abrasion or cuts. especially along the leading edge and the flat or thrust face. If heater wires are
exposed in damaged areas or if rubber is found to be tacky, swollen or deteriorated (as from oil or solvent
contact). replace the damaged deicer in accordance with the appropriate information in this chapter.
Operate propeller from "full pitch" to "feathering" and check that deicer lead wires do
not come under tension or are pinched by propeller blade. (Refer to Figure 30-9.)
6. Slip Rings: Check slip rings for gouges, roughened surface, cracks, burned or discolored areas, and for
deposits of oil, grease or dirt.
A. Clean greasy or contaminated slip rings with CRC 2-26 solvent (This solvent is available from C.R.C.
Chemical Division, Webb Inc., C-J10 Limekiln Pike, Dreshner, Penna. 19025.) or with Stoddard
Solvent. If Stoddard Solvent is used, wipe off with a clean cloth dampened with MEK to avoid
leaving a film.
B. If uneven wear is found or if wobble is noticed, set up a dial indicator as shown in Figure 30-4 and
check alignment of the slip rings to the propeller shaft as explained in this section.
7. Modular Brush Assemblies - Brushes: Examine mounting brackets and housing for cracks. deformation or
other physical damage.
A. Test that each brush rides fully on its slip ring over 360°. Figure 30-5 shows the wear pattern if this
condition is not corrected. If alignment is off, shim where brush block is mounted to bracket or adjust
mounting bracket support arm.
The shim is a series of laminates and may be peeled for proper alignment of brushes to
slip ring.
B. Check for proper clearance of brush block to slip rings as shown in Figure 30-6. If not correct, loosen
mounting screws and move in elongated holes to correct block position before tightening securely.
C. Visually check brush block for approximately 2° angle of attack. (Refer to Figure 30-6) If not, loosen
mounting screws and twist block, but be sure to hold clearance limits shown when tightening.
8. System Wiring: With deicer system operating. have assistant observe ammeter while visually inspecting and
phycically flexing wiring from brush blocks through firewall. to timer, to ammeter. to switch and to aircraft
power supply. The ammeter will flicker as the timer switches approximately every 90 seconds in the cycle.
Jumps or flickers at other times indicates loose or broken wiring in the area under examination at that
moment. In such case, check continuity through affected harness, while flexing and prodding each wire in
the area that gave initial indication of trouble. Use the wiring diagram to trace circuitry.
PIPER AIRCRAFT
PA - 4 4 - 1 8 0 / 1 8 0 T
AIRPLANE MAINTENANCE MANUAL
— Note —
— Note —
2E12
3 0 - 6 5 - 0 2
Page 30-32
Revised: May 15, 1989