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B. The air bled off from the turbine case cooling (TCC) air inlet duct decreases the temperature of the exciter-to-igniter plug cables and the right side of the start valve. The ducted fan air on the right side of the engine supplies cooling air to the EEC alternator and starter as well as the EEC electrical connector on the right HPC secondary flow control valve. In addition, fan air bled off from the pneumatic duct on the inner wall of the right thrust reverser also decreases the temperature of the IDG.
C. The fan air bled from the upper left side of the fan case supplies cooling air to the oil quantity transmitter and the EEC electrical connector on the left HPC secondary flow control valve. The fan air bled from the lower left side of the fan case supplies cooling air to the left side of the start valve.
D. The nacelle zone ventilation system bleeds fan air and supplies cooling air to the nacelle zone area. The system includes the shutoff valve for the nacelle zone ventilation, duct for the nacelle zone ventilation, and barometric switch.
2. Nacelle Zone Ventilation Shutoff Valve (Fig. 2)
______________________________________
A. The shutoff valve for the nacelle zone ventilation is installed on the inner wall of the left thrust reverser half.
B. The shutoff valve is an electrically actuated, pneumatically operated butterfly type air shutoff valve. It includes an actuator, body and vane assembly, solenoid, actuator pressure relief valve, valve position indicator, and a manual override lock.
C. The manual override lock lets the shutoff valve be manually locked open.
3. Nacelle Zone Ventilation Duct (Fig. 2)
_____________________________
A. The duct for the nacelle zone ventilation is attached to the aft end of the shutoff valve for the nacelle zone ventilation. The duct is a perforated discharge duct that lets cooling fan air be bled into the nacelle area.
4. Barometric Switch (Fig. 2)
_________________
A. The barometric switch is installed in the forward fairing of the nacelle strut.
B. The barometric switch is an electrically operated, pneumatically actuated switch. It controls the position of the shutoff valve as a function of altitude.
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////////////////////////A / PW4000 SERIES /747-400 / ENGINES /MAINTENANCE MANUAL ////////////////////////
HPC SECONDARY FLOW CONTROL VALVE
START
OIL QUANTITY VALVE
TRANSMITTER
INTEGRATED DRIVE GENERATOR
COOLING AIR DUCTS - LEFT SIDE
HPC SECONDARY
TCC AIR
FLOW CONTROL
INLET DUCT VALVE
START
STARTER VALVE
EEC
ALTERNATOR
EXCITER-T0-IGNITER
PLUG CABLES
COOLING AIR DUCTS - RIGHT SIDE
Engine External Accessories Cooling Air Ducts Figure 1 (Sheet 1)
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Engine External Accessories Cooling Air Ducts
Figure 1 (Sheet 2)
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////////////////////////A / PW4000 SERIES /747-400 / ENGINES /MAINTENANCE MANUAL ////////////////////////
THERMAL ANTI-ICE (TAI) VALVE ACCESS DOOR
SEE B
SEE A
LEFT THRUST REVERSER HALF INNER WALL
NACELLE ZONE VENTILATION DUCT
FWD
NACELLE ZONE VENTILATION SHUTOFF VALVE
A
FWD BAROMETRIC SWITCH
B
Nacelle Zone Ventilation System Component Location Figure 2
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