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31-52-00
ALL ú ú 04 Page 17 ú Oct 18/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
(4)
Master Warning/Caution Lights
(a)
Two master warning lights illuminate when any warning occurs and two master caution lights illuminate when any caution occurs. The lights remain on as long as the warning or caution exists. However, pushing either master warning/caution reset switch extinguishes both master warning or caution lights for the duration of the warning or caution.
(b)
Pushing the reset switch silences the fire bell and the cabin altitude siren.
(c)
Pushing the reset switch may also silence the landing configuration siren, depending on the reason for activation.
(5)
Inhibits
(a)
Portions of the crew alerting system are inhibited or deactivated to prevent distractions during certain phases of flight.
(b)
The fire bell and the master warning lights are inhibited for fire warnings, overspeed, cabin pressure and pilot response during a portion of the takeoff. The inhibit begins at V1 (or 80 kt optional) and ends at either 25 seconds (or 50 seconds when 80 kt selected) elapsed time or the first penetration of 400 feet radio altitude, whichever occurs first. If a fire exists when the inhibit is removed, both master warning lights and the bell activate.
(c)
The beeper and the master caution lights are inhibited, for all cautions, during a portion of the takeoff. The inhibit lasts between a speed of 80 knots and either 20 (or 30) seconds elapsed time after nose gear strut extension or the first penetration of 400 feet radio altitude, whichever occurs first. If a takeoff abort is initiated above 80 knots, the inhibit lasts until the aircraft is slowed down to below 75 knots airspeed. If a caution exists when the inhibit is removed, both master caution lights and the beeper activate.
D. Control
_______
(1)
Primary operating power for Aural Warning System is provided through the MAWEA by the MAWEA POWER A circuit breaker thru the 115 volt STANDBY BUS 3 and the MAWEA POWER B circuit breaker thru the 115 volt F/O INST BUS.
(2)
The MAWEA performs a BITE test each time power is applied to the system which tests the applicable PC cards for the Aural Warning System. The CMC continuously monitors the system and faults are displayed on the CMC and EICAS.
(3)
Printed circuit card and power supply removal and installation procedures are shown in chapter 31-51-0X/401. For faults of LRU's that interface with the Aural Warning System, refer to the appropriate chapter and section for removal and installation procedures.
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
31-52-00
ALL ú ú 01 Page 18 ú Jun 18/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
AURAL WARNING SYSTEM - ADJUSTMENT/TEST
______________________________________
1. General_______
A. This procedure has one task. The task is a test of the aural warning system. The test has four parts: a takeoff warning test, a fire warning test, a BITE test, and an autopilot disengage test.
(1)
The takeoff warning test is started from the Central Maintenance Computer (CMC). This test will make sure the aural warning system operates correctly for a takeoff warning if the airplane is not in a takeoff configuration.
(2)
The fire warning test will make sure the aural warning system operates correctly to supply a fire bell warning.
(3)
The BITE test does a check of all the components and functions in the MAWEA necessary for the operation of the aural warning system. All failures are sent to the CMC. The aural warning speakers will sound a test tone that does a check for speaker operation.
(4)
The autopilot disengage test checks the aural warning to make sure it sounds immediately upon disengagement.
TASK 31-52-00-725-024
2. Aural Warning System Test_________________________
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