(e)
If there is no electrical signal from the EEC, the HPT and LPT air valves are moved to the closed position.
(f)
If the TCC air valve actuator fails to function correctly, a record of the messages that follow will be in the central maintenance computer system (CMCS), depending on the area of actuator failure: ENG-# TCC TORQUE MOTOR WIRING/ACTUATOR FAIL (CH-X), ENG-# TCC ACTUATOR FAIL (CH-X), or ENG-# TCC LVDT WIRING/ACTUATOR FAIL (CH-X).
NOTE: "ENG-#" is engine 1, 2, 3, or 4; "CH-X" is channel A or
____ channel B of the EEC.
(2)
Turbine Vane and Blade Cooling System
(a)
ENGINES WITHOUT PHASE 3; Cooling air from the 12th-stage HPC flows to the 2nd-stage HPT vanes and blades. The cooling air flow through the blade cooling air ducts and through two vane cooling air ducts is controlled by two TVBCA valves. The cooling air flow through the other two vane cooling air ducts is continuous.
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TURBINE VANE COOLING AIR DUCT
MECHANICAL LINKAGE
HPC SECONDARY FLOW CONTROL VALVE AND TURBINE VANE AND BLADE COOLING AIR VALVE SOLENOID
TURBINE VANE AND BLADE COOLING AIR VALVE FILTER TURBINE VANE AND BLADE COOLING AIR VALVE POSITION SWITCH
RIGHT TURBINE VANE AND BLADE COOLING AIR VALVE TURBINE VANE COOLING AIR DUCTS HPT CASE COOLING COLLECTOR
15 LPT CASE COOLING COLLECTOR
Turbine Cooling System Simplified Schematic
Figure 2 (Sheet 1)
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E72019
////////////////////////A / PW4000 SERIES /747-400 / ENGINES /MAINTENANCE MANUAL ////////////////////////
FILTERED HPC
TURBINE VANE
15TH-STAGE AIR
TURBINE VANE COOLING AIR DUCTTURBINE CASE COOLING AIR VALVE CONTROL CABLE
LPT CASE COOLING MANIFOLDS (7 AIR TUBES)
TURBINE VANE COOLING AIR VALVE AND TURBINE VANE AND BLADE COOLING AIR VALVE SOLENOID HPT CASE COOLING MANIFOLDS (4 AIR TUBES) TURBINE VANE AND BLADE COOLING AIR VALVE SOLENOID HPT CASE COOLING AIR SHUTOFF VALVE TURBINE VANE COOLING AIR VALVE LPT CASE COOLING AIR SHUTOFF VALVE
12 RIGHT TURBINE VANE AND BLADE COOLING AIR VALVE TURBINE CASE COOLING AIR INLET DUCT TURBINE VANE COOLING AIR DUCTS LEFT TURBINE VANE AND BLADE COOLING AIR VALVE HPT CASE COOLING COLLECTOR TURBINE CASE COOLING AIR VALVE CONTROL CABLE 15 LPT CASE COOLING COLLECTOR TURBINE CASE COOLING AIR VALVE ACTUATOR
Turbine Cooling System Simplified Schematic
Figure 2 (Sheet 2)
E72018
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(b)
ENGINES WITH PHASE 3; Cooling air from the 12th-stage HPC flows to the 2nd-stage HPT vanes and blades. The cooling airflow through the blade cooling air ducts and through two vane cooling air ducts is controlled by two TVBCA valves. The cooling airflow through one of the other two vane cooling air ducts is controlled by the TVCA valve. The airflow through the other vane cooling air duct is continuous.
(c)
During low power operation, the TVBCA/TVCA valve solenoids are supplied energy by an EEC command.
(d)
When energy is supplied to the solenoids, it permits muscle air (servo pressure), supplied from the 15th-stage HPC, to flow to the valves.
(e)
The muscle air, cleaned by the TVBCA/TVCA valve filters before it gets to the valves, operates the normally opened TVBCA or TVCA valve to the closed position, which stops the cooling air flow.
(f)
When the valves close, the visual indicator pin retracts and the position switch for the valve supplies the EEC with an electrical feedback signal.
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