82046-PG-B1
ST3400H PILOT’S GUIDE
Page 3-2
3.3
What it isn’t
The ST3400H is not the pilot. Remember: it is a tool, and it isn’t perfect.
Neither the terrain data nor the obstacle data on which alerting is based is
guaranteed to be 100% accurate, nor are the sensors feeding the system.
There is no substitution for good judgment by the pilot. The pilot should
always exercise prudent caution, with or without the ST3400H.
Again, it is NOT designed for navigation.
3.4
What it does
During normal flight operations the system remains essentially silent. It
uses GPS, Radar Altitude, barometric altitude, and other relevant data in
combination with its internal database information to provide the pilot with
a full-time terrain display. The look-ahead function compares the aircraft
flight path to terrain and obstacle database information and distance to
known runways and landing zones.
A built-in caution and warning system provides visual annunciation and
aural alerts. Provided are downward-looking Ground Proximity Warning
System (GPWS) alerts, Forward Looking Terrain Alerts (FLTA), and
various advisories.
FLTA provides predictive “look ahead” warnings by comparing its internal
terrain and obstacle database to position information provided by the GPS
receiver.
The internal terrain and obstacle database provides the basis to detect
terrain or obstacle conflicts. This is accomplished using the aircraft
position, phase of flight, vertical speed, ground track, and ground speed
relative to the terrain database image.
Through sophisticated look-ahead algorithms, alerts are generated if terrain
or an obstacle conflict with the flight path of the aircraft. This potential
conflict area projects forward of the aircraft. During enroute operations, a
Caution Alert typically occurs approximately 20 seconds ahead of the
collision conflict. A caution will turn into a warning if evasive action is
not taken after approximately 10 seconds of Caution.
During other operations the alert times may be shorter but Cautions are
always designed to occur prior to Warnings. A Warning does not indicate
a higher severity of threat, but simply that immediate action must be taken.
The Topographic (TOPO) and Relative Altitude (REL) display modes
provide the pilot with fast access to visual information to maximizing the
pilot’s understanding of the relationship between the aircraft and the
