Garmin HTAWS User Guide - Page 61

Part Four: Section 3 HTAWS Alerts 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. 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 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 NAV - HTAWS page map. The alerts are annunciated aurally through a voice message indicating the potential threat, such as "Caution - Terrain, Terrain" or "Warning - Obstacle, Obstacle". 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" OR "Terrain Ahead; Terrain Ahead". Similarly, a "Caution Obstacle; Caution Obstacle" or "Obstacle Ahead; Obstacle Ahead" 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. Voice Call Out Aural Alert The purpose of the Voice Call Out aural alert messages are to provide an advisory alert to the pilot that the aircraft is between 500 feet and 100 feet above terrain in 100 foot increments. When the aircraft descends within the selected distance from the terrain, the aural message for the selected distance is generated. There are no display annunciations or pop-up alerts that accompany the aural message. 190-00356-30 Rev H 55