11.4.12 Forward Looking Terrain Avoidance - Garmin GTN 725 Pilot's Manual

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.

11.4.12 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 potential impact points 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.
FLTA CAUTION—Estimated potential impact in approximately 30 seconds after a caution
pop-up alert and annunciation. FLTA caution alerts are accompanied by the aural message
"Caution Terrain; Caution Terrain". Similarly, a "Caution Obstacle; Caution Obstacle" alert
is also provided. The time to an alert can vary with conditions, therefore there is no guarantee
of a 30 second caution alert being issued.
FLTA WARNING— Warning pop-up alerts are issued 15 seconds prior to an estimated potential
impact in normal mode and approximately 10 seconds in RP Mode. FLTA warning alerts are
accompanied by the aural message "Warning - Terrain, Terrain" . Similarly, a "Warning -
Obstacle, Obstacle" alert is also provided. The time to an alert can vary with conditions,
therefore there is no guarantee of a 15/10 second warning alert being issued.
The alerts are annunciated visually through the annunciator status bar, a
pop-up alert box, and the red and yellow X' s on the HTAWS page. The alerts
are annunciated aurally through a voice message indicating the potential threat,
such as "Caution - Terrain, Terrain" or "Warning - Obstacle, Obstacle".
190-01007-03 Rev. D Garmin GTN 725/750 Pilot's Guide
Foreword
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Appendix
11-33
Index