Pressurization System Checkout Procedure 17 Ground Operation Check 17 Safety Precautions 19 Pressurization System Flight Check 20 Absolute Pressure Regulator Removal 24 Absolute Pressure Regulator Installation 24 Outflow and/or Safety Valve Removal 25 Outflowand/or Safety Valve Installation 25 Outflowand Safety Valve Cleaning 25 Removal of Controller 26 Installation of Controller 26 Controller Filter Replacement 26
21-40-00
Heating and Cooling 1 General 1 Troubleshooting(EnvironmentalControl System) 1 Component Detailed Descriptions 3 Removal of Pressure Regulator and Shutoff Valve 4 Installation of Pressure Regulator and Shutoff Valve 4 Removal of Hot Air Bypass Valve 4 Installation of Hot Air Bypass Valve 5 Removal of Bleed Air Supply Overpressure Switch 5 Installation of Bleed Air Supply Overpressure Switch 5 Removal of Compressor Discharge Sensing Switch 5 Installation of Compressor Discharge Sensing Switch 5
EFFECTIVITY: 040-999
CONTENTS
PAGE 1
PIPERAIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL
CHAPTER21-AIR CONDITIONING
TABLE OF CONTENTS (continued)
SUBJECT CHAPTER PAGE
21-60-00
TemperatureControl 1 Removal of Duct Temperature Sensor 1 Installation of Duct Temperature Sensor 1 Removal of Cabin Temperature Sensor and Controller 1 Installation of Cabin Temperature Sensor and Controller 1
21-70-00
Moisture/Air Contaminant Control 1 Removal of Water Separator 1 Installationof Water Separator 1 Cleaning,Inspection and Repairs of Water Separator 1
EFFECTIVITY:
040-999
CONTENTS
Jan 10/9
PIPERAIRCRAFT
PA-42-720(Advanced Trainer)
MAINTENANCEMANUAL
Air Conditioning
A. General
The cabinis pressurized by enginebleedairthat is conditionedby an environmentalcontrolsystem (ECS). The bleed air is cooled as required for heating, air conditioning, ventilationand pressurizing the air in thecabin.
CAUTION: PERFORMPITOTANDSTATIC SYSTEM LEAKCHECKSBEFOREPERFORMING ANYPNEUMATICFUNCTIONALTESTS. CONDUCTINGCABINPRESSURETESTS WITHLEAKINGSTATICSYSTEMSCOULDDAMAGEDELICATEINSTRUMENTS.
The environmentalcontrolunit(ECU)uses bleed air from both enginesasthe primesourceof energy. This bleedair system has three parts:
1.
TheECU bleed air supply
2.
Theauxiliarybleedair supplyfor deicer bootsand gyros
3.
The emergency bleed air cabinpressurizationsystem.
NOTE: Tocapisobaricvalveambientlines,removeaccesscoversin the tail of the aircraft andcapfittings(adapters)on aft pressurebulkhead.
(a) Thecompressorand interstageturbinebleedairfrom eachengineis supplied througha variableejectormixingvalve directly to the ECU. A pressureregulatorandshutoffvalve controlspressureandflow of bleedair into the ECU,locatedin the righthandequipment compartmentandforwardoffuselagestation57.00pressurebulkhead.Referto Heating and
Coolingsectionsfor a more detailed descriptionof various components.
(b)
Auxiliarybleedair supplysystemis usedto operatethe cabinpressurecontrolsystem, inflatablecabin door seals,surfacedeicerbootsandvacuumgyrosystem. Thisbleedair is takenoff the enginebleedair ductingupstreamof eachbleedair shutoffvalveandcannotbe shutoff unlessthat particularengineis shutdown. A ram air-bleed air intercooleris installed at the firewallof each enginenacelleto coolthe bleed air supplyto the auxiliarysystembelow 250°F,priorto entering thefueltankareaaft of the firewall. A bleed air overtemperature switch,installedin the bleedair duct downstreamof the intercooler, closesat 425 ° ±5°Fand illuminatesthe BLEEDAIR HOTlightonthe pilot annunciatorpanel. Duringnormaloperation, bleedair to the auxiliarysystemvariesbetween10and 85 psi and/or150°Fand500F. Temperatureisreducedto below 250°Fby the intercooler.Refer to pressurizationcontrolfor moredetail,30-00-00for detailon the deicersystemand37-00-00onthe vacuum system.
(c)
Theemergencybleedair cabinpressurizationsystemconsistsof a solenoid shutoffvalve,jet pumpand pressure switch. The emergency bleedair is supplied fromthe right handauxiliary bleedair supply lineand activatedby the pilotwith the ECSSELECTORswitchon the comfort controlpanel. Withthe ECSSELECTORswitchedintothe EMERposition,the emergency pressurizationvalvein the right handwingrootis opened. At the sametime,the pressure regulatorand shutoffvalvede-energizes,shuttingoff bleed air flow to the ECU. The emergencypressurizationairservesasmotiveflowto the jet pumpin the right handwing root,
whichpulls in ambientairfrom a portin the wing rootfairing. A totalpressurizationflow up to 9 poundsper minuteis providedintothe righthand heaterduct,withinthe cabin,dependingon the righthandenginepowersettingandaltitude.
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