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: 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.
3.3 LEVEL 1 SELF-TEST - GO/NO GO TEST
Level 1 Self-Test provides an overview of the current operational capability of the EGPWS. It is divided into 3 functions - the Preamble, Short Level 1 Self-Test, and Long Level 1 Self-Test as described in the following sections.
During Level 1 Self-Test, a Short Cancel terminates the Self-Test level and “CURRENT FAULTS” is enunciated to indicate activation of Level 2 Self-Test. A Long Cancel terminates the entire Self-Test sequence exiting Self-Test.
3.3.1 SELF-TEST PREAMBLE
When Self-Test is initiated, the Preamble is performed. This first step in the Self-Test process checks for configuration errors before starting the Short or Long Level 1 Self-Test process. If any are detected, the condition is enunciated and the Self-Test process is automatically terminated (inhibited). These are listed below with the associated probable cause and action.
TABLE 3-1: POSSIBLE PREAMBLE RESULTS
POSSIBLE SELF-TEST PREAMBLE RESULTS 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：增强型近地警告系统 Enhanced Ground Proximity Warning 航线维护手册 Systems Line Maintenance Manual(21)
