Garmin aera 795/796 Pilot’s Guide 190-01194-00 Rev. AAppendix F154OverviewGPS NavigationFlight PlanningHazard AvoidanceAdditional FeaturesAppendicesIndex• TIS operation may be intermittent during turns or other maneuvering.• TIS is dependent on two-way, line-of-sight communications between the aircraft andthe Mode-S radar antenna. Whenever the structure of the aircraft comes betweenthe transponder antenna and the ground-based radar antenna, the signal may betemporarily interrupted.NOTE:Refer to the TIS Limitations section of the Aeronautical InformationManual (AIM) for a more comprehensive explanation of limitations andanomalies associated with TIS.NOTE:TIS is unavailable at low altitudes in many areas of the United States.This is often the case in mountainous regions.NOTE:Garmin is not responsible for Mode S geographical coverage. Operationof the ground stations is the responsibility of the FAA. Refer to the AIM for aTerminal Mode S radar site map.TIS information is collected during a single radar sweep. Collected information isthen sent through the Mode S uplink on the next radar sweep. Because of this, thesurveillance information is approximately five seconds old. TIS ground station trackingsoftware uses prediction algorithms to compensate for this delay. These algorithms usetrack history data to calculate expected intruder positions consistent with the time ofdisplay. Occasionally, aircraft maneuvering may cause variations in this calculation andcreate slight errors on the Navigation Map which affect relative bearing informationand the target track vector and may delay display of the intruder information. However,intruder distance and altitude typically remain relatively accurate and may be used toassist in spotting traffic. The following errors are common examples:• When the client or intruder aircraft maneuvers excessively or abruptly, the trackingalgorithm may report incorrect horizontal position until the maneuvering aircraftstabilizes.• When a rapidly closing intruder is on a course that intercepts the client aircraftcourse at a shallow angle (either overtaking or head-on) and either aircraft abruptlychanges course within 0.25 nm, TIS may display the intruder aircraft on the incorrectside of the client aircraft.
