TVBCA VALVE CROSS-SECTIONAL VIEW  TVBCA VALVE POSITION SWITCH 
A-A  CROSS-SECTIONAL VIEW 
B-B 

Turbine Cooling System Component Location
Figure 1 (Sheet 3)

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SOLENOID FOR THE 
HPC SECONDARY  INTERMEDIATE 
FLOW CONTROL  CASE 
VALVE  1
OR 
TVCA VALVE  2 

SERVO FUEL SERVO FUEL L-A2578 SUPPLY PORT RETURN PORT
TURBINE CASE COOLING
AIR VALVE ACTUATOR

TVBCA VALVE SOLENOID
E
FWD
HPC SECONDARY
FLOW CONTROL OR TVCA VALVE AND
TVBCA VALVE SOLENOID

F
2.9 BLEED
VALVE DUCT
(REF)

TOP LEFT PS3 AIR FILTER
FWD
LOWER LEFT PS3 AIR FILTER
VALVE FOR THE TURBINE VANE COOLING AIR
G
TVCA VALVE H2
Turbine Cooling System Component Location Figure 1 (Sheet 4)
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////////////////////////A / PW4000 SERIES /747-400 / ENGINES /MAINTENANCE MANUAL ////////////////////////
SOLENOID FOR THE TVBCA 
VALVE AND IDG AIR/OIL
HEAT EXCHANGER VALVE 
INTERMEDIATE 
CASE 
FAN EXIT 
LINER 
SEGMENT 

IDG AIR/OIL HEAT EXCHANGER VALVE OVERRIDE PRESSURE SWITCH  FWD 
I SOLENOID FOR THE TVBCA VALVE AND IDG/AIR OIL HEAT EXCHANGER VALVE 
RIGHT 2.9 BLEED VALVE 
PS3 AIR FILTER TOP RIGHT 
LOWER RIGHT PS3 AIR FILTER 
FWD J Turbine Cooling System Component Location Figure 1 (Sheet 5) 

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6.  High Pressure Turbine Case Cooling Manifolds (Fig. 1)
____________________________________________
 A.  The HPT case cooling manifolds (air tubes) include many air bleed holes
 which flow cooling air externally on the HPT case. The cooling air
 decreases the turbine case growth due to thermal expansion.

 B.  The manifold for the HPT case cooling includes four air tubes, which are
 installed circumferentially around the HPT case. Each air tube is made
 of two halves. The four air tubes, or eight air tube halves, are
 longitudinally split which makes replacement of individual tube sections
 easier.

 7.  Low Pressure Turbine Case Cooling Manifolds (Fig. 1)
___________________________________________
 A.  ENGINES WITH PHASE 3 OR PRE-PW-SB 75-53; The manifold for the LPT case cooling includes seven air tubes (or 14 air tube halves), which are installed circumferentially around the LPT case.
 B.  ENGINES WITHOUT PHASE 3 OR POST-PW-SB 75-53;
 The manifold for the LPT case cooling includes six air tubes (or 12 air
 tube halves), which are installed circumferentially around the LPT case.

 C.  The function of the LPT case cooling manifolds are similar to the HPT
 case cooling manifolds.

 8.  Turbine Case Cooling Air Valve Actuator (Fig. 1)
_______________________________________
 A.  The TCC air valve actuator, which is hydraulically operated, mechanically moves the shutoff valves for the HPT and LPT case cooling air through a push-pull cable.
 B.  The TCC air valve actuator, which is installed on the HPC forward case at the 2 o'clock position, is installed on a free floating bracket in case of thermal growth of the control cable.
 C.  The TCC air valve actuator includes a dual coil torque motor, a pilot valve, actuator, and dual linear variable differential tranformers (LVDT) which supply redundant feedback signals of the actuator position to the electronic engine control (EEC).
　
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