Garmin G3X Touch Pilot's Manual page 253

The optional Garmin GTS 8XX is a Traffic Advisory System (TAS) and Traffic Collision
Avoidance System (TCAS I). It enhances flight crew situational awareness by displaying
traffic information for transponder-equipped aircraft. The system also provides visual
and aural traffic alerts including voice announcements to assist in visually acquiring
traffic.
The GTS 8XX is capable of tracking up to 45 intruding aircraft equipped with
Mode A or C transponders, and up to 30 intruding aircraft equipped with Mode S
transponders. A maximum of 30 aircraft with the highest threat potential can be
displayed simultaneously. No TAS/TCAS I surveillance is provided for aircraft without
operating transponders.
THEORY OF OPERATION
When the GTS 8XX is in Operating Mode, the unit interrogates the transponders of
intruding aircraft while monitoring transponder replies. The system uses this information
to derive the distance, relative bearing, and if reported, the altitude and vertical trend
for each aircraft within its surveillance range. The GTS 8XX then calculates a closure
rate to each intruder based on the projected Closest Point of Approach (CPA). If the
closure rate meets the threat criteria for a Traffic Advisory (TA), visual and aural alerting
is provided.
TAS/TCAS I SURVEILLANCE VOLUME
The GTS 8XX surveillance system monitors the airspace within ±10,000 feet of own
altitude. Under ideal conditions, the GTS 8XX unit scans transponder traffic up to 12
nm in the forward direction. The range is somewhat reduced to the sides and aft of
own aircraft due to the directional interrogation signal patterns. In areas of greater
transponder traffic density or when TCAS II (Traffic Alert and Collision Avoidance
System II) systems are detected, the GTS 8XX automatically reduces its interrogation
transmitter power (and therefore range) in order to limit potential interference from
other signals.
190-02472-00 Rev. D
Garmin G3X Touch ™ Pilot's Guide for Certified Aircraft
Hazard Avoidance
231