C.A.R.D. 060 Troubleshooting Guide download pdf (Page 23)

EGPWS LINE MAINTENANCE MANUAL

CAGE CODE: 97896 SCALE: NONE SIZE: A DWG NO.: 060-4199-180 REV: G SHEET 23 of 68

3 FAULT ISOLATION (TROUBLESHOOTING)

3.1 GENERAL

The troubleshooting methods provided in this section identify system and sensor or subsystem faults to the lowest

level possible. Additional fault isolation in the installation or associated sensors or subsystem should be performed

using the aircraft installation and wiring diagrams and other supporting documentation in accordance with

established maintenance procedures.

Do not remove or replace the EGPWC until all associated sensors or subsystems and their interfaces have been

verified per established maintenance procedures and the fault is isolated to the EGPWC. If the troubleshooting

methods determine that the EGPWC is faulty, then the EGPWC should be replaced per Section 6. Route the faulty

EGPWC to an authorized repair facility for repair.

3.2 TROUBLESHOOTING GUIDE

In general, if any EGPWS Inoperative status is indicated, the EGPWC front panel LED’s should be checked. The

following table shows the recommended maintenance action in response to the front panel LED’s.

EXTERNAL

FAULT

COMPUTER

FAIL

CORRECTIVE ACTION

OFF GREEN OFF Normal operation.

YELLOW GREEN OFF Troubleshoot external faults using the Level 2 Self-

Test. DO NOT REMOVE OR REPLACE THE EGPWC

OFF OFF OFF Ensure that the EGPWC is installed in the rack

correctly and power to the EGPWC is turned on.

OFF OFF RED Record the Level 2 Self-Test, if possible. Remove and

replace the EGPWC if required.

OFF GREEN RED Record the Level 2 Self-Test, if possible. Remove and

replace the EGPWC if required.

YELLOW OFF OFF Troubleshoot external faults using the Level 2 Self-

Test. DO NOT REMOVE OR REPLACE THE EGPWC

YELLOW OFF RED Troubleshoot external faults using the Level 2 Self-

Test. Remove and replace the EGPWC if required.

YELLOW GREEN RED Record the Level 2 Self-Test, if possible. Troubleshoot

external faults using the Level 2 Self-Test. Remove

and replace the EGPWC if required.

A Terrain INOP light rarely implies an external or internal failure of the EGPWC. The Terrain INOP light may turn on

if the required accuracy of the position information is not being received from the GPS, IRS, or the FMC. Therefore,

if the Terrain INOP light is reported to be on (or was on), perform a Level 2 Self-Test. If no faults are present, verify

that position data from the GPS, IRS, or FMC is correct (note: this sentence does not apply to internal GPS

engines).

NOTE: The Computer Fail Light will illuminate during some ground test procedures that use the WinVIEWS

Software utility, even although no fault exists. The EGPWS Computer Fail Light will extinguish after testing

has completed.

The following sections detail the operation of the EGPWS Self-Test and its use in troubleshooting EGPWS faults,

when initiated by EGPWS Self-Test switches in the aircraft. Reference is made to a “short cancel” and a “long

cancel”. A “short cancel” is defined as depressing the Self-Test switch (either in the cockpit or on the EGPWC front

panel) for less than 2 seconds. A “long cancel” is defined as depressing the Self-Test switch (either in the cockpit or

on the EGPWC front panel) for more than 2 seconds (but not longer than 59 seconds or a fault is indicated and Self-

Test is exited). The affect of these is indicated in each section.

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