(4)
Indication and Crew Alerting
(a) The digital pressure sensor in the automatic pressure controller which is primary control supplies cabin pressure information to the EIU's for display on EICAS. This information is used to determine cabin altitude (in feet), cabin rate of altitude change (in SL fpm), and cabin-to-ambient pressure difference (in psid). These values are continuously displayed on the main EICAS. When manual control is selected, the analog pressure sensor provides this information for display on EICAS.
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(5)
A
747-400
MAINTENANCE MANUAL
(b)
The elevation of the destination airport is normally entered via the FMC, and the value is forwarded by the automatic pressure controllers for display on the LDG ALT readout of the main EICAS. The elevation value is displayed followed by the word AUTO.
(c)
If landing altitude data from the FMC is not valid, the cabin pressure controller will assume a default landing altitude value of 2000 feet. In this case, the LDG ALT readout will display 2000 AUTO.
(d)
When manual control of one or both outflow valves is selected, the LDG ALT readout will go blank.
(e)
The flight crew may override the FMC-supplied destination elevation by entering another field level via the landing altitude selector. The selector has settings from -1000 to +14,000 feet in increments of 50 feet. When the landing elevation is entered manually, the elevation value is displayed followed by the word MAN.
(f)
Outflow valve position may be read off the dial gauges on the CPCS selector panel, or off the dials displayed on the ECS synoptic.
EICAS Messages
(a)
If cabin pressure rises above 10,000 feet, the EICAS warning message CABIN ALTITUDE will be displayed, an aural warning will sound, and the master warning lights will be illuminated. These indications will remain until the cabin altitude falls below 9500 feet.
(b)
If both automatic pressure controllers fail, the EICAS caution message CABIN ALT AUTO will be displayed, a caution aural will sound, and the master caution lights will illuminate. These same indications will also appear if the flight crew elects to operate both outflow valves manually.
(c)
If the primary pressure controller determines the landing altitude information from the FMC's to be invalid, the EICAS advisory message LANDING ALT will be displayed. The message is removed by entering a different field altitude via the FMC.
(d)
If the primary controller determines that an air turnback has occurred and it continues to receive the original landing altitude (not within 250 feet of takeoff altitude) two minutes after entering climb abort, the EICAS advisory message LANDING ALT will be displayed and the landing altitude display blanked. The message may be removed by entering a different field elevation via the FMC or by climbing 500 feet or more (which will exit the climb abort).
(e)
If you select the landing altitude manually, the EICAS message LANDING ALT will show on the display.
(f)
If automatic control of an outflow valve is lost, the EICAS advisory message OUTFLOW VALVE L or OUTFLOW VALVE R will be displayed.
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A
747-400 MAINTENANCE MANUAL
(g)
AIRPLANES WITH PACK TEMPERATURE CONTROLLER P/N S210U130-9; Pack number 2 shuts down automatically when either positive pressure relief valve opens and all 3 packs are in high flow, and the EICAS advisory message PACK 2 is displayed. If pack 2 fails to shut down automatically, the EICAS advisory message PRESS RELIEF is displayed.
(h)
AIRPLANES WITH PACK TEMPERATURE CONTROLLER P/N S210U130-31; Pack number 2 shuts down automatically when either positive pressure relief valve opens and all 3 packs are in normal or high flow, and the EICAS advisory message PACK 2 is displayed. If pack 2 fails to shut down automatically, the EICAS advisory message PRESS RELIEF is displayed.
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