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190-01004-03 Rev. P
GTN 625/635/650 Pilot’s Guide
Terrain
10.6.6.7 Altitude Voice Call Out (VCO)
TAWS-B provides aural advisory alerts as the aircraft descends, beginning at
500 feet above the terrain, as determined by the radar altimeter (if greater than
5 NM from the nearest airport) or 500 feet above the nearest runway threshold
elevation (if less than 5 NM from the nearest airport). Upon descent to this
altitude, TAWS-B issues the aural alert message “Five-hundred.”
10.6.6.8 TAWS-B Not Available Alert
TAWS-B requires a 3-D GPS position solution along with specific vertical
accuracy minimums. Should the position solution become degraded or if the
aircraft is out of the database coverage area, the annunciation “TAWS N/A”
is generated in the annunciation window and on the TAWS-B page. The
aural message “TAWS Not Available” is generated. When the GPS signal is
re-established and the aircraft is within the database coverage area, the aural
message “TAWS Available” is generated (when the aircraft is airborne).
10.6.6.9 TAWS-B Failure Alert
TAWS continually monitors several system-critical items such as database
validity, hardware status, and GPS status. If the terrain/obstacle database is not
available, the aural message “TAWS System Failure” is generated along with a
“TAWS FAIL” annunciation.
10.6.7 TAWS-B System Status
During power-up, TAWS-B conducts a self-test of its aural and visual
annunciations. The system test can also be manually initiated. An aural alert is
issued at test completion. TAWS System Testing is disabled when ground speed
exceeds 30 knots.
Alert Type
Alert
Annunciation
Aural Message
TAWS Available
None
“TAWS Available”
TAWS System Test in Progress
None
TAWS System Test Pass
None
“TAWS System Test OK”
TAWS N/A
TAWS Not Available
TAWS Alerting is Disabled
None
TAWS System Test Fail
“TAWS System Failure”
Table 10-16 TAWS-B System Test Status Annunciations
Summary of Contents for GTN 625
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