Garmin G3X Pilot’s Guide 190-01115-00 Rev. KAppendix E416SystemOverviewFlightInstrumentsEISCNSInterfaceGPSNavigationFlightPlanningHazardAvoidanceAdditionalFeaturesAFCSAnnun/AlertsAppendixIndexTIS-A LIMITATIONSTIS-A relies on surveillance of the Mode-S radar system, which is a “secondarysurveillance” radar system similar to that used by ATCRBS. Many limitations areinherent in secondary radar surveillance. Information provided by TIS-A is neitherbetter nor more accurate than the information used by ATC. TIS-A is intended only toassist in visual acquisition of other aircraft in visual meteorological conditions (VMC).While TIS-A is a useful aid for visual traffic avoidance, system limitations must beconsidered to ensure proper use. No recommended avoidance maneuvers are given,nor authorized, as a direct result of a TIS-A intruder display or TIS-A advisory.• TIS-A operation may be intermittent during turns or other maneuvering.• TIS-A is dependent on two-way, line-of-sight communications between the aircraftand the Mode-S radar antenna. Whenever the structure of the aircraft comesbetween the transponder antenna and the ground-based radar antenna, the signalmay be temporarily interrupted.NOTE: Refer to the TIS-A Limitations section of the Aeronautical Informa-tion Manual (AIM) for a more comprehensive explanation of limitations andanomalies associated with TIS-A.NOTE: TIS-A is unavailable at low altitudes in many area of the United States.This is often the case in mountainous regions.NOTE: Garmin is not responsible for Mode S geographical coverage. Opera-tion of the ground stations is the responsibility of the FAA. Refer to the AIMfor a Terminal Mode S radar site map.TIS-A information is collected during a single radar sweep. Collected informationis then sent through the Mode S uplink on the next radar sweep. Because of this, thesurveillance information is approximately five seconds old. TIS-A ground station trackingsoftware uses prediction algorithms to compensate for this delay. These algorithmsuse track history data to calculate expected intruder positions consistent with the timeof display. Occasionally, aircraft maneuvering may cause variations in this calculationand create slight errors on the Map Page which affect relative bearing information andthe target track vector and may delay display of the intruder information. However,
