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GNS 530(A) Pilot’s Guide and Reference
190-00181-00 Rev. H
13-6
SECTION 13
TAWS
Table 13-3 shows system status annunciations that may also be issued:
Alert Type
TAWS Page
Annunciation
Pop-Up Alert Aural Message
TAWS System Test Fail None “TAWS System Failure”
TAWS Alerting is disabled None None
No GPS position or excessively degraded
GPS signal
None “TAWS Not Available”
“TAWS Available” is generated when sufficient
GPS signal is re-established.
System Test in progress None None
System Test pass None None “TAWS System Test OK”
Table 13-3 Additional System Annunciations
Forward Looking Terrain Avoidance
The Forward Looking Terrain Avoidance (FLTA) alert is used by TAWS and is composed of:
• Reduced Required Terrain Clearance (RTC) and Reduced Required Obstacle Clearance (ROC) -These alerts are
issued when the aircraft flight path is above terrain, yet is projected to come within the minimum clearance
values in Table 13-4. When an RTC or ROC alert is issued, a potential impact point is displayed on the TAWS
Page.
• Imminent Terrain Impact (ITI) and Imminent Obstacle Impact (IOI) - These alerts are issued when the
aircraft is below the elevation of a terrain or obstacle cell in the aircraft’s projected path. ITI and IOI alerts are
accompanied by a potential impact point displayed on the TAWS Page. The alert is annunciated when the
projected vertical ight path is calculated to come within minimum clearance altitudes in Table 13-4.
Phase of Flight Minimum Clearance
Altitude Level Flight (ft)
Minimum Clearance
Altitude Descending (ft)
Enroute 700 500
Terminal 350 300
Approach 150 100
Departure 100 100
Table 13-4 Minimum Terrain and Obstacle Clearance Values for FLTA Alerts
During the nal approach phase of ight, FLTA alerts are automatically inhibited when the aircraft is below 200
feet AGL while within 0.5 nm of the approach runway or below 125 feet AGL while within 1.0 nm of the runway
threshold.