747-400 AMM 飞机维护手册 大气 AIR 2(50)

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 E.  For more information on the 2.5 bleed valve, refer to Compressor Section, AMM 72-30-00/001.
 3.  2.5 Bleed Valve Actuator (Fig. 1)
________________________
 A.  The 2.5 bleed valve actuator is installed on the intermediate case at the 7 o'clock position.
 B.  The actuator includes a pilot valve, actuator piston, dual coil torque motor, and dual rotary variable transducers (RVDT's).
 C.  The actuator is controlled by the electronic engine control (EEC) and is hydraulically actuated by finely filtered engine fuel from the fuel metering unit. The EEC command signal to the torque motor moves the pilot valve. The position of the pilot valve determines the direction and rate the actuator piston travels with available fuel pressure. The actuator piston rod end is sealed against fuel leakage by dual-stage ring seals. Fuel, which could leak pass the ring seals, is drained overboard through a drain tube.
 D.  The actuator piston position is detected and the feedback signal is sent to each channel of the EEC by the dual RTVs.
 4.  2.9 Bleed Valve (Fig. 1)
_______________
 A.  The right 2.9 bleed valve (start valve) and the left 2.9 bleed valve (start/stability valve) are found at the 1 and 10 o'clock position on HPC case respectively.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / PW4000 SERIES /747-400 / ENGINES /MAINTENANCE MANUAL ////////////////////////
EEC ELECTRICAL 
CONNECTOR 
SEE  B  SERVO FUEL 
SUPPLY TUBE 
SEE  A 
INTERMEDIATE 
CASE 
SERVO FUEL 
RETURN TUBE 
DRAIN TUBE 
LEFT 2.9  2.5 BLEED VALVE ACTUATOR 
BLEED DUCT 
A  FWD 
BLEED VALVE 
SIGNAL TUBE 

FWD
LEFT
2.9 BLEED
VALVE
B
Compressor Bleed Control System Component Location
Figure 1 (Sheet 1)

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
RIGHT 2.9 
BLEED DUCT 
SEE  C 
BLEED VALVE 
SIGNAL TUBE 
SEE  D 
RIGHT 2.9 
BLEED VALVE 

FWD  STABILITY BLEED PNEUMATIC RELAY VALVE SEE F 
C  INTERMEDIATE CASE 
2.9 BLEED VALVE SOLENOID SEE E 
SPEED TRANSDUCER (N1) (REF) EEC 
FWD 
D 
Figure 1 (Sheet 2) Compressor Bleed Control System Component Location 

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////////////////////////A / PW4000 SERIES /747-400 / ENGINES/MAINTENANCE MANUAL ////////////////////////
B.  The 2.9 bleed valves, when opened, route 9th-stage compressor airflow into the fan airstream to increase compressor stability during starting and transient operation.
 C.  Each valve is a two position (open/closed) poppet type valve, which is spring loaded (fail-safe) open. The valves are pneumatically actuated to the closed position by compressor discharge pressure (15th-stage air), and are regulated by the 2.9 bleed valve solenoid.
 5.  2.9 Bleed Valve Solenoid (Fig. 1)
________________________
 A.  The 2.9 bleed valve solenoid includes two solenoids installed on a common valve housing, which is found on the intermediate case at the 5 o'clock position.
 B.  The 2.9 bleed valve solenoid is an electrically operated, dual coil, pneumatic type solenoid valve. Each solenoid controls muscle pressure (15th-stage air), filtered by PS3 air filter, to the 2.9 bleed valves. Solenoid No. 1 controls muscle pressure to the right 2.9 bleed valve directly, while solenoid No. 2 controls muscle pressure to the left 2.9 bleed valve through the stability bleed pneumatic relay valve. For more information on PS3 air filter refer to HPC Secondary Flow Control System, refer to AMM 75-33-00/001.
　
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