Garmin GTS 820 TAS, Pilot'S Manual, Page: 25 / 40

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190-00587-02 Rev. E Garmin GTS Traffic Systems
6.4 Traffic Alerting
GTS provides visual and aural alerts to assist in visually acquiring traffic.
Aural and visual alerts are provided as a Traffic Advisory (TA) for conflicting
traffic. A TA is generated based on range and altitude closure rate (time until
collision) or if the intruder aircraft encroaches within a minimum distance.
When an intruder aircraft is tracked with active surveillance, TAS/TCAS I
alerting is used for that aircraft. If an intruder cannot be tracked with active
surveillance but is tracked by ADS-B In, then ADS-B alerting is used for that
aircraft. Intruder aircraft can only be tracked by ADS-B In when ADS-B In is
installed and operating.
NOTE : The GTS Traffic System does not provide the ADS-B Traffic Awareness
System (ATAS) application defined by TSO-C195b.
6.4.1 TAS/TCAS I Alerting
6.4.1.1 Sensitivity Level
To prevent nuisance TAs in the airport environment, there are two sensitivity
levels available: Sensitivity Level A (SL A) and Sensitivity Level B (SL B). The
Sensitivity Level determines what criteria will be used for TAs. SL A is less
sensitive and traffic must be closer before it will generate an alert. SL B is more
sensitive and traffic may be farther away to generate an alert. The logic for
choosing the sensitivity level is based on available system inputs. If none of the
inputs described below are available, the system will always remain in the most
sensitive level, SL B.
6.4.1.1.1
Height Above ground
If the aircraft is equipped with a radar altimeter, it will be used as the source
of height above ground. If the aircraft is not equipped with a radar altimeter,
calculated height above ground (see below) will be used. SL A will be used
when the height above ground is less than 2,000 feet. SL B will be used when
the height above ground is greater than 2,000 feet.
NOTE : Calculated Height Above Ground is used for sensitivity level selection
in GTS 800, GTS 820, and GTS 850 systems with software version 4.00 and
later; and in GTS 825 and GTS 855 systems with system software version
3.00 and later. In earlier software versions, only radar altimeter is used for
sensitivity level selection.