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36-11-00
ALL ú ú 01P Page 9 ú Feb 18/02
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
A. The high pressure controller is installed on the engine in the 7:00 o'clock position on the forward face of the main gearbox. The high pressure controller senses high stage pressure, receives command inputs from the ASCTU, and sends pneumatic signals to the HPSOV. These signals will cause the HPSOV to open or close.
(1) The high pressure controller has the following components:
-a cast aluminum controller body
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an altitude biased pneumatic switch
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an internal sensing diaphragm
-a shutoff solenoid
-four pressure sensing switches
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a high stage pressure sensing port
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a signal pressure port that goes to the HPSOV.
(2) The valve control lever moves when high stage servo pressure acts on the servo pressure sensing diaphragm. A preset spring adjusts the lever to move when high stage engine pressure is 105 | 5 psi at or below 27,000 | 1,000 ft. Above 27,000 ft, an evacuated bellows expands to contact the control lever. This changes the switchover pressure linearly from 105 psig at 27,000 ft to 77 psig at 42,000 ft. The valve control poppet controls the servo pressure to the HPSOV. At high power engine operation, the servo pressure is sent to ambient. At low power engine operation, the servo pressure is sent to the HPSOV. The latch solenoid allows an override to the pneumatic switching. When the solenoid is energized it shuts off the high stage pressure and sends servo pressure to ambient. This will cause the HPSOV to close.
4. Intermediate Pressure Check Valve (Fig. 7)
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A. The intermediate pressure check valve is installed on the engine in the 9 o'clock position approximately three feet aft of the fan frame. The valve is an in-line check valve that prevents high stage reverse flow into the intermediate stage. The valve has the following components:
-
an outer shell
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an inner shell with strut supports
-tube guide
-a movable tube/valve plate assembly.
(1)
The valve is installed between the intermediate pressure manifold and the HP/IP manifold. The valve outlet flange is larger than the valve inlet flange. This prevents incorrect installation. An arrow on the body of the valve indicates the direction of air flow.
(2)
When the pressure upstream of the intermediate pressure check valve becomes more than the pressure downstream of the valve, the valve poppet assembly moves to the open position. The tube guide in the inner shell guides the poppet assembly. This will occur when the HPSOV is in the closed position. When the pressure upstream of the intermediate pressure check valve becomes less than the downstream pressure (HPSOV is opened), the poppet assembly moves to the closed position. This prevents reverse flow through the valve.
5. Pressure Regulating Valve (PRV) (Fig. 8)
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EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
36-11-00
ALL ú ú 01P Page 10 ú Feb 18/02
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
INTERMEDIATE
PRESSURE
CHECK VALVE
SEE A
OUTER SHELL
A
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