10-44
GTN 625/635/650 Pilot’s Guide
190-01004-03 Rev. P
Terrain
10.7.6 HTAWS Alerts
Alerts are issued when flight conditions meet parameters that are set within
HTAWS software algorithms. HTAWS alerts employ either a CAUTION or a
WARNING alert severity level. When an alert is issued, visual annunciations
are displayed. Aural alerts are simultaneously issued. Annunciations appear in a
dedicated field in the lower left corner of the display.
Annunciations are color-coded according to the HTAWS Alert Summary
table. Pop-up terrain alerts occur if an HTAWS alert is activated while not on the
HTAWS page. There are two options when an alert is active.
To acknowledge the pop-up alert and return to the currently viewed page:
Touch the
Close
key.
To acknowledge the pop-up alert and quickly access the HTAWS Page:
Touch the
ENT
key.
NOTE:
To further capture the attention of the pilot, HTAWS issues aural
(voice) messages that accompany visual annunciations and pop-up alerts.
For a summary of aural messages, refer to the HTAWS Alert Summary table.
NOTE:
HTAWS Caution Alerts are displayed as constant black text on a
yellow background; HTAWS Warning Alerts are displayed as constant white
text on a red background.
10.7.6.1 Forward Looking Terrain Avoidance
The unit will issue terrain alerts not only when the aircraft altitude is below
the terrain elevation but also when the aircraft is projected to come within
minimum clearance values of the terrain. This alerting, called Forward Looking
Terrain Avoidance (FLTA), is also provided for obstacles.
The FLTA functionality looks ahead of the aircraft using GPS position
information and the terrain and obstacle databases to provide alerts when
the predicted flight path does not clear the terrain or obstacle by the required
clearance. The amount of clearance required varies depending on position
relative to airports and heliports, in order to reduce the occurrence of nuisance
alerting.
Any threat locations are depicted on the display. There are 2 levels of severity
for FLTA alerts. They are cautionary (amber) and warning (red) in nature and are
described in further detail below.
Summary of Contents for GTN 625
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