Air - Component Location (Details from Sht 2)
Figure 102 (Sheet 3)

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////////////////////////
A / PW4000 SERIES /
747-400 / ENGINES /FAULT ISOLATION/MAINT MANUAL ////////////////////////
HPC SECONDARY  INTERMEDIATE 
FLOW CONTROL  CASE 
VALVE AND  (REF) 
TVBCA VALVE 
INTERMEDIATE  SOLENOID 
CASE 
(REF) 

FWD
2.5 BLEED VALVE ACTUATOR FWD
F
E  HPC SECONDARY FLOW CONTROL VALVE AND
INTERMEDIATE IDG AIR/OIL HEAT STABILITY BLEED CASE (REF) EXCHANGER VALVE PNEUMATIC RELAY OVERRIDE SOLENOID
VALVE
INTERMEDIATE CASE (REF)
NO. 3 BEARING BUFFER AIR COOLER IDG AIR/OIL HEAT EXCHANGER
2.9 BLEED VALVE OVERRIDE FWD
VALVE PRESSURE SWITCH
SOLENOID
EEC

(REF)
SPEED

G
TRANSDUCER
(N1) (REF)

FWD
H
INTERMEDIATE CASE (REF)
FWD
I
Air - Component Location (Details from Sht 2) Figure 102 (Sheet 4)
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A / PW4000 SERIES /
747-400 / ENGINES /FAULT ISOLATION/MAINT MANUAL ////////////////////////
FWD
PS3 AIR 
FILTER 
SEE  R 
LEFT TURBINE  SHT 6 
VANE AND BLADE  FWD 
COOLING AIR (TVBCA) 
VALVE  J  FROM SHT 2 
LEFT 
2.9 BLEED VALVE 
PNEUMATIC MANIFOLD (REF)  K  FROM SHT 2  2.9 BLEED VALVE RIGHT 

FUEL/OIL COOLER (REF)
LEFT HPC SECONDARY FWD PS3 AIR
FLOW CONTROL VALVE FILTER SEE R
L FROM SHT 2 FWD SHT 6
TURBINE CASE
COOLING AIR VALVE
FROM SHT 3 CONTROL CABLE
M
TURBINE CASE COOLING AIR VALVE ACTUATOR
FWD N FROM SHT 3
Air - Component Location Figure 102 (Sheet 5)
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A / PW4000 SERIES /
747-400 / ENGINES /FAULT ISOLATION/MAINT MANUAL ////////////////////////
RIGHT HPC SECONDARY
INTERMEDIATE FLOW CONTROL VALVE
CASE (REF)
BELLCRANK
(REF)

FUEL PUMP (REF) FUEL FLOW TRANSMITTER (REF)  O  FWD FUEL METERING UNIT (REF) FROM SHT 3  VARIABLE STATOR VANE ACTUATOR  FWD  P  FUEL FLOW TRANSMITTER (REF) FROM SHT 3  HEAD 
MAIN FUEL SUPPLY LINE (REF) 
TURBINE VANE COOLING AIR TUBE  TVBCA VALVE POSITION SWITCH RIGHT TVBCA VALVE  ELEMENT FILTER 
FWD  CASE 
Q  FROM SHT 3  R  FROM SHT 5 
Figure 102 (Sheet 6) Air - Component Location 

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ENGINE BEARING COOLING SYSTEM - DESCRIPTION AND OPERATION
_________________________________________________________
 1.  General (Fig. 1)
_______
 A.  The engine bearing cooling system includes bearing carbon seal
 pressurization and the No. 3 bearing cooling system.

 B.  The main bearing carbon seals are pressurized by compressor air to make sure that oil does not go into the air stream. The No. 1 and 2 bearing carbon seals are pressurized by low pressure compressor (LPC) bleed air. The No. 1.5 bearing carbon seals are pressurized by 9th-stage high pressure compressor (HPC) bleed air. The No. 3 bearing carbon seals are pressurized by cooled 12th-stage HPC bleed air. The No. 4 bearing carbon seal is pressurized by LPC air that goes into the low pressure turbine (LPT) shaft forward of the No. 1 bearing.
　
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