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MAINTENANCE MANUAL
(10) Detector, card, or associated wiring failures may not provide a valid fault output at the moment of failure. These inoperative loops can only be detected during a system test.
C. Test____
(1)
When a test occurs, the AFOLTS card sends out signals to both loops of the system. Returned signals indicate operating loops. If either loop is found faulty, AFOLTS reconfigures the system to operate on the remaining loop.
(2)
AIRPLANES WITH GRAVINER FIRE DETECTORS; If the remaining loop sustains an alarm or fault condition, then a fire warning results.
(3)
AIRPLANES WITH SYSTRON DONNER FIRE DETECTORS; If the remaining loop sustains an alarm condition, then a fire warning results. If the remaining loop sustains a fault condition
(4)
If both loops are found faulty, then a dual-loop fault indication is given by the following:
(a)
The amber FAIL P-RESET switchlight, on the P8 control stand, comes on.
(b)
The advisory message, FIRE/OVHT SYS, is displayed on EICAS (P2).
(c)
The status/maintenance messages, APU FIRE LP 1 and 2, are displayed on EICAS.
(d)
The FAIL P-RESET switchlight is pressed to reset the fault monitoring circuitry. This also turns off the FAIL P-RESET switchlight, and clears the EICAS advisory message, FIRE/OVHT SYS.
(5)
Power-up mode (TABLE 2):
~............................................................. | APU Fire Detection | | TEST LOGIC | | Table 2 | ............................................................... | INPUTS TO AFOLTS | | | | DURING | | | | SYSTEM TEST | AFOLTS | | ...................... CONFIGURATION | EICAS MESSAGE | | LOOP 1 | LOOP 2 | AFTER TEST | AFTER TEST | ............................................................... | ----| ----| DUAL LOOP | NONE | ............................................................... | ----| FAULT | LOOP 1 | APU FIRE LP 2 | ............................................................... | FAULT | ----| LOOP 2 | APU FIRE LP 1 | ............................................................... | FAULT | FAULT | FAIL | FIRE/OVHT SYS | | | | | APU FIRE LP 1 | | | | | APU FIRE LP 2 | 2.........…..........…................….......................1
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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757
MAINTENANCE MANUAL
(a) Whenever power is first applied, an automatic self-test occurs. Both single-loop APU status/maintenance messages are momentarily displayed on EICAS (P2). If either loop is found faulty, then the appropriate loop message remains on EICAS display, and the system is reconfigured to the other loop. If both loops are found faulty, then the FAIL P-RESET switchlight (on P8) comes on, EICAS displays APU FIRE LP 1 and LP 2 maintenance messages and the advisory message - FIRE/OVHT SYS. A fire warning will not be initiated by a power-up test.
(6)
Manual system test (TABLE 2):
(a)
When the ENG/APU/CARGO switch on the fire/overheat test panel (on P8) is pressed and held - the engine, APU, and cargo detection systems go through a self-test. Both APU loop messages are displayed on EICAS, and after a two to four-second delay, a successful test terminates with all APU fire indications.
(b)
When the ENG/APU/CARGO switch is released, all messages and indications should clear, except for any faulty-loop messages which will remain on EICAS. The FAIL P-RESET switchlight, and EICAS advisory message - FIRE/OVHT SYS, will also remain on if there is a dual-loop fault.
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