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757 MAINTENANCE MANUAL
(6)
A nacelle overheat indication is given by the following:
(a)
The appropriate amber engine overheat light - L or R ENG OVHT, on the P8 control stand, comes on.
(b)
The appropriate overheat caution message - L or R ENG OVHT, is displayed on EICAS (P2).
(c)
The amber master CAUTION lights, on glareshield panels P7, come on (inhibited when both fuel control switches are in cutoff).
(d)
The caution annunciation owl tone sounds, on the flight deck aural warning speakers (inhibited when both fuel control switches are in cutoff).
(7)
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 appropriate system status/maintenance messages are displayed on EICAS: 1) L ENG OH LP 1 and 2. 2) R ENG OH LP 1 and 2. 3) L ENG FIRE LP 1 and 2. 4) R ENG FIRE LP 1 and 2.
(8)
The FAIL P-RESET switchlight is pressed to reset the fault monitoring circuitry of the failed system. This also turns off the FAIL P-RESET switchlight, and clears the EICAS advisory message -FIRE/OVHT SYS.
(9)
A single-loop fault or alarm signal indication is given by EICAS displaying the appropriate status/maintenance message:
(a)
L ENG OH LP 1 or 2.
(b)
R ENG OH LP 1 or 2.
(c)
L ENG FIRE LP 1 or 2.
(d)
R ENG FIRE LP 1 or 2.
(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.
B. Test (TABLE 2)
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(2)
(3)
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757
MAINTENANCE MANUAL
~........................................................... | Engine Fire/Overheat Detection Test Logic | | Table 2 | ............................................................. | INPUTS TO AFOLTS | AFOLTS | EICAS | | DURING SYSTEM | CONFIGURATION | MESSAGE | | TEST | AFTER TEST | AFTER TEST | ......................... | | | LOOP 1 | LOOP 2 | | | ............................................................. | - - -| - - -| DUAL LOOP | NONE | ............................................................. | - - -| FAULT | LOOP 1 | EICAS LOOP 2 | ............................................................. | FAULT | - - -| LOOP 2 | EICAS LOOP 1 | .............................................................
| FAULT | FAULT | FAIL | FIRE/OVHT SYS |
| | | | EICAS LOOP 1 |
| | | | EICAS LOOP 2 |
2..........…............…..................…................1
AIRPLANES WITH SYSTRON DONNER DETECTORS; Refer to the data that follows:
(a)
When a test occurs, the AFOLTS cards send out signals to each loop of the detection systems. Returned signals indicate operating loops. If any loop is found faulty, AFOLTS reconfigures that system to operate on the remaining loop. If the remaining loop sustains an alarm , then a fire/overheat warning indication results. If the remaining loop sustains a fault, then a fail indication results.
AIRPLANES WITH GRAVINER DETECTORS; Refer to the data that follows:
(a)
When a test occurs, the AFOLTS cards send out signals to each loop of the detection systems. Returned signals indicate operating loops. If any loop is found faulty, AFOLTS reconfigures that system to operate on the remaining loop.
(b)
For engine fire detection loops, if the remaining loop sustains an alarm or fault, fire indications result. For nacelle overheat detection loops, if the remaining loop sustains an alarm, overheat indications result. If the remaining overheat loop sustains a fault, fail indications result.
Power-up mode:
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