(g)
Retighten fitting and turn on aircraft electrical power.

(h)
Slowly open control valve and increase pressure to 14 -16 psig. Ensure wing boot indicator light on copilot circuit breaker panel comes on at 15 ± 1 psig. Replace pressure switch by removing turtleback cowl on left nacelle.

(i)
Release system pressure. Remove test apparatus.

(j)
Reconnect system pressure line to solenoid valve.

(k)
Complete same test for inboard wing and tail boots solenoid control valve.

Clean 
Oil Free 
Air Supply  0-100 psig PressureGauge 
Manual  (SystemPressure)  ControlValve 
Regulator  Gauge No. 1 
15-30 psig 

0-100 psig
PressureGauge (LeakPressure) GaugeNo. 2
To Aircraft System Connection

Boots Test Apparatus Figure 501
EFFECTIVITY:

040-999

Jan
Jan 10/9030-10-00
PIPER AIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCE MANUAL

A. Airfoil -Description and Operation (continued)
4. PneumaticRegulator Adjustment
To gain access to the pneumatic pressure regulator on the right of the fuselage centerline, remove
the floorboard access panelat Fuselage Station 156.00.
The adjustable regulator provides appropriate pressurefor the pneumatic system. An adjustment screw on the outboard end of the valve body is accessible by removing the thermoplastic vent cap
fromthe outboard end of the regulator. Proceed as follows to check regulator operation:
WARNING: ALL SAFETYPRECAUTIONSMUST BE OBSERVED WHEN STARTINGAND OPERATINGENGINES.ENSURE AIRCRAFT IS PROPERLY RESTRAINEDWHEN USING FULL POWER SETTINGS. REFERTO PILOT'S OPERATING HANDBOOK FOR OPERATING INFORMATION.
(a)
Start both engines and place both right and left engine bleed air switches in the ON position. Establish steady airflow in cabin. If door is closed, ensure door seal inflates.

(b)
Cycledeicer boots and observe system pressure on cockpit pneumatic gauge. With engines at maximum power 90% Ng, the pressure must not exceed 20 psig. With one engine operating at 85%Ng, pressure mustnot go below 16 psig.

(c)
To adjust regulator, proceed as follows: (1.) Remove appropriate floor access panel. (2.) Loosen clamp and slide plastic vent cap off outboard end of regulator, exposing

adjustmentscrew. (3.) Loosen jam nut on screw and rotate screw clockwise to increase pressure,
counterclockwiseto decrease pressure.
(4.) Lock screw in position with jam nut.
(5.) Reinstall plastic vent cap on regulator and tighten clamp.

CAUTION: ENSURE VENT CAP IS REINSTALLEDPROPERLYON REGULATOR. ENSURE HOSE FROM CAP TO FUSELAGE IS SECURE AND IN GOOD CONDITION.IF CAP IS LEFT OFF OR NOT PROPERLY SECURED, REGULATOR IS REFERENCED TO CABIN PRESSURE, NOT AMBIENT PRESSURE, CAUSING REGULATOR TO ALLOW EXCESSIVE PNEUMATIC PRESSURE TO BUILD UP IN DEICERS AND DOOR SEAL.
NOTE: New aircraft contain a pressure regulatorincorporatingan overboard ventfitting, eliminatingthe vent cap used on earlier aircraft. Regulator adjustment is unaffected.
5.
Timer Maintenance

No field maintenance is recommended. See parts catalog for replacement or vendor for repairs.

6.
Inspections

Complete a ground check of entire deicer system at least every 100 hours. To ground check
systemwithout operating engine, disconnect pneumatic system line (3/4-inch branch line upstream
of bleed air shutoff valve) at engine and connect hose from shop air to pneumatic line with air
regulated to 22 psig. The shop air supply must be capable of delivering air 3 pounds per minute at
22 psig.
Beforechecking system, inspect all deicers for damage and repair according to cold patch or
vulcanized repair procedures in this section. To check system, use deicer piping diagram drawing
to determine the operating pressure and inflation time allotted for deicers.
EFFECTIVITY:
040-999
30-10-00Jan10/90
JaPAGE7

PIPER AIRCRAFT
PA42-720(Advanced Trainer)
MAINTENANCE MANUAL

A. Airfoil-Description and Operation (continued)
7. GroundTestProcedure
After establishing test pressure range, connectan external air pressure sourceto the 3/4-inch
engine pneumatic line. A check valve in the line prevents air from being forced back through the
oppositeenginebleedair ports. Activatesystem and check operating pressure.Thepressure
must be within 1 psig of the recommended operatingpressurewitheach inflation.
If deicers do not reach operating pressure,check solenoid valves.If boots deflate slowly, lines or
ejectorscould be plugged. Ensure systeminflates in approximately
6 +0.5 seconds. (See OutboardWings,Inboard Wings and Empennage section.)
CHART 2
　
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