82046-PG-B1
ST3400H PILOT’S GUIDE
Page 6-1
6
TERRAIN AND OBSTACLE ALERTING
6.1
Alert Generation
FLTA is an acronym for Forward Looking Terrain Alerting. The FLTA
Alerting Area is an area mostly in front of and to both sides of the aircraft.
Through sophisticated look-ahead algorithms, alerts are generated if terrain
or an obstacle conflict with the path of the aircraft.
Position and altitude of the aircraft are computed along the projected flight
path twice per second. The projected position is based on current aircraft
location and the aircraft’s ground speed. The projected altitude is based on
current aircraft altitude and the aircraft’s vertical speed. The aircraft’s
projected position and each terrain cell and obstacle elevations are then
compared to check for conflicts.
During enroute operations, a caution alert typically occurs approximately
20 seconds ahead of the terrain or obstacle conflict. A caution alert will
turn into a warning alert if evasive action is not taken approximately 10
seconds ahead of the conflict.
The alert in question will be the closest cell or obstacle in which a threat is
detected.
Figure 6-1 “CAUTION TERRAIN” Annunciation
