75-23-00
ALL ú ú N01 Page 4 ú Jun 10/88
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
5. Operation_________
A. Functional Description (Fig. 3)
(1)
The nacelle zone ventilation system is controlled by the barometric switch for the nacelle zone as a function of altitude.
(2)
With higher altitude, the shutoff valve stays open until the airplane is at an altitude of 23,000 |600 feet (7,010 |183 meters). At this altitude, the low ambient pressure operates the barometric switch, which supplies a ground to energize the solenoid on the shutoff valve with 28 volts dc.
(3)
When energy is supplied, the solenoid lets pneumatic pressure close the shutoff valve, which stops cooling fan air to the duct for the nacelle zone ventilation.
(4)
With lower altitude, the barometric switch removes the energy from the solenoid at an altitude of 22,600 |600 feet (6,888 |183 meters). This stops the pneumatic pressure and lets the shutoff valve open. The shutoff valve opens and lets the cooling fan air in the ventilation duct.
(5)
The shutoff valve is made for all modes of failure to open the shutoff valve.
(6)
The shutoff valve can be operated manually when a wrench is installed to the flats on the bottom of the butterfly shaft to open the shutoff valve and engage a lockpin in the actuator shaft.
(7)
Less than 35,000 feet (10,668 meters), a disagreement between the shutoff valve position and the barometric switch positon will cause the valve disagree relay to send a signal to the central maintenance computer system (CMCS). The CMC will then make a record of the ENG-X NACELLE VENT VALVE FAIL message.
NOTE: The CMC message "ENG-X NACELLE VENT VALVE FAIL" will be
____ set when the aircraft is operated between 23,000 feet and 35,000 feet, and the associated engine bleed system is turned off. For this condition, the system is operating as designed, and no troubleshooting is required.
NOTE: "ENG-X" is engine 1, 2, 3, or 4.
____
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75-23-00
ALL ú ú N01 Page 5 ú Feb 15/99
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / PW4000 SERIES /747-400 / ENGINES /MAINTENANCE MANUAL ////////////////////////
M7353
Nacelle Zone Ventilation System Simplified Schematic
Figure 3
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ALL ú
ú N01 Page 6
ú Jun 10/88
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
ENGINE EXTERNAL ACCESSORIES COOLING - ADJUSTMENT/TEST
_____________________________________________________
1. General
_______
A. This procedure gives a task to do a system test of the ventilation system of the nacelle zone.
B. A pneumatic ground cart or the auxiliary power unit (APU) can be used to supply the pneumatic source for the system test. Instructions for the two pneumatic sources are given in the task.
TASK 75-23-00-705-001-N00
2. System Test - Nacelle Zone Ventilation (Fig. 501 and 502)
______________________________________
A. Standard Tools and Equipment
(1)
Gauge - Vacuum, can read an altitude of 25,000 feet, accurate to |50 feet
(2)
Pump - Vacuum, can supply a pressure of 10 psia (25,000 feet altutude)
(3)
Ground Cart - Pneumatic, can supply pnuematic pressure, optional to APU
(4)
Multimeter - Digital, Fluke 8000A (8010A, 8012A, or 8050A can be used in place of 8000A), John Fluke Mfg. Co., Inc., P.O. Box C9090, Everett, WA 98206
B.
References
(1)
AMM 06-09-09/201, Nacelle and Engine-to-Wing Fairing Access Doors and Panels
(2)
AMM 24-22-00/201, Manual Control
(3)
AMM 31-61-00/501, Integrated Display System
(4)
AMM 36-00-00/201, Pneumatic System
(5)
AMM 71-11-04/201, Fan Cowl Panel
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