Garmin GNC 420W Pilots Guide - Page 186

SECTION 10 TERRAIN Table 10-3 shows system status annunciations that may also be issued: Alert Type TERRAIN System Test Fail TERRAIN Page Annunciation Pop-Up Alert None TERRAIN Alerting is disabled None No GPS position or excessively degraded None GPS signal System Test in progress None System Test pass None None Table 10-3 Additional System Annunciations Forward Looking Terrain Avoidance The Forward Looking Terrain Avoidance (FLTA) alert is used by TERRAIN 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 10-4. When an RTC or ROC alert is issued, a potential impact point is displayed on the TERRAIN 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 TERRAIN Page. The alert is annunciated when the projected vertical flight path is calculated to come within minimum clearance altitudes in Table 10-4. During the final approach phase of flight, 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. Phase of Flight Minimum Clearance Minimum Clearance Altitude Level Flight (ft) Altitude Descending (ft) Enroute 700 500 Terminal 350 300 Approach 150 100 Departure 100 100 Table 10-4 Minimum Terrain and Obstacle Clearance Values for FLTA Alerts 10-6 GNC 420(A) Pilot's Guide and Reference 190-00140-20 Rev. K