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New engines operate within a tolerance band either above or below charted parametervalues
and tend to deviate more with time and deteriorationof gas path components. Abrupt,or
gradual increased rate of change of normal deviationsfromcharted parameter values indicate
criticalchanges in gas path component conditions.In many cases such changes are
detectablebefore any drastic failure occurs. It is to this end that this system is directed.
The monitoring system should be introduced whenthe engine is new or has just been overhauled. For specific procedure to be used, refer to Pratt & Whitney Canada Publication "Aircraft Gas Turbine OperationInformationLettersNumber 22 and 23."
NOTE: Refer to Pratt and Whitney Maintenance Chapter 71 for
Manual,p/n 3034342, informationon Engine Condition Trend Monitoring.
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CHAPTER 79

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CHAPTER79 -OIL

TABLEOFCONTENTS

SUBJECT
Oil
DescriptionandOperation
Distribution ThermostaticBypassand CheckValve Oil-to-FuelHeater Removalof Oil Cooler Installationof Oil Cooler Oil Filter Element Maintenance Oil Cooler ExhaustDoor
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1 1 79-20-00 1 1 1 1 1 3 3

Removalof Oil Cooler DoorTransmission 3 Installationof Oil Cooler DoorTransmission 3 Cleaning,Inspection,and Repairof Oil CoolerDoorTransmission 3 Adjustmentof the Oil CoolerDoor 4
79-30-00 Indicating 1 Oil Temperature Probe 2
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MAINTENANCE MANUAL

Oil
A. Description and Operation
Enginelubrication is provided through a pressure type system. The oil tank is an integral part of the compressorinlet case and houses the main oil pump. A plunger pressure relief valve, located on top of the main oil pump, regulatesoil pressure. For overhaul or maintenance procedures of the engine, refer to the Pratt and Whitney Maintenance Manual, p/n 3034342.
The oil cooler is mounted to its cooling duct underneath the engine. A door to control air flow is built into the rear of the duct and functions through an electric screw jack.
Two other important service items are the oil drain and breather line. A T type fitting, located on the rightside of each engine compartment, is used for draining oil. The oil breather line, connected to the overboardbreatherport on the right side of the accessorycase, is routed to the right side of each rear, bottom nacelle panel.
NOTE: When replacing or repairing any assemblies, engine nuts, bolts, or screws, use thread lubricant, engine oil, or equivalent when retorqueing parts.
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A. Description and Operation (continued)
RETURNFROMCOOLER

OILSUPPLY
TOPROPELLER

ThrustBearing

OilTransfer
Sleeve

PRESSUREOIL PROPELLERSUPPLYOIL SCAVENGEOIL BREATHERAIR TORQUEMETER
PRESSURE
Engine Oil System
Figure 1

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A. Distribution
1. ThermostaticBypassand CheckValve
Thethermostaticbypassandcheckvalve,sometimesreferredto asthe oil divertervalve,is
locatedin the systembetweenthe oil to fuel heateroutletandthe engineoiltank. It directsoil
comingfromthe oil to fuel heaterto eitherthe oil tankoroil cooler,dependingon oil temperature.
Higherthan normaloil temperatureswill indicatea malfunctionof eitherthe bypassvalveorthe checkvalveassembly.
Referto Prattand WhitneyMaintenanceManual,p/n3034342,Chapter79for detailson removing, inspecting,repairing,replacing,andinstallingthethermostaticbypassand checkvalve.
2. Oil-to-FuelHeater
Theoil-to-fuelheateris a heatexchangerwhichusesheatfrom enginelubricatingoil systemto preheatfuelfor the fuelsystem. Theassembly,mountedto the rearengineflange,also interconnectswith the divertervalveand oiltank.
　
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