4 GPSMAP 496 Owner’s ManualTIS > TIS LimitationsTIS LimitationsTIS is NOT intended to be used as a collision avoidance systemand does not relieve the pilot responsibility to “see and avoid”other aircraft. TIS should not be used for avoidance maneuversduring IMC or other times when there is no visual contact with theintruder aircraft. TIS is intended only to assist in visual acquisitionof other aircraft in VMC. No recommended avoidance maneuversare provided for, nor authorized, as a direct result of a TIS display orTIS advisory.While TIS is a useful aid to visual traffic avoidance, it has somesystem limitations that must be fully understood to ensure properuse. Many of these limitations are inherent in secondary radarsurveillance. In other words, the information provided by TIS willbe no better than that provided to ATC. TIS only shows aircraft withoperating transponders installed.TIS relies on surveillance of the Mode S radar, which is a“secondary surveillance” radar similar to the ATCRBS. TISoperation may be intermittent during turns or other maneuvering.TIS is dependent on two-way, “line-of-sight” communicationsbetween the aircraft and the Mode S radar.Whenever the structure of the client aircraft comes between thetransponder antenna (usually located on the underside of the aircraft)and the ground-based radar antenna, the signal may be temporarilyinterrupted. Other limitations and anomalies associated with TIS aredescribed in the AIM, Section 1-3-5. Refer to page 159 for wiringinformation.notE: Garmin is not responsible for Mode S geographicalcoverage. Operation of the ground stations is the responsibilityof the FAA. Refer to the Aeronautical Information Manual for aTerminal Mode S Radar Site Map covering the U.S.notE: TIS is unavailable at low altitudes in many areas of theU.S., particularly in mountainous regions. Also, when flying nearthe “floor” of radar coverage in a particular area, intruders belowthe client aircraft may not be detected by TIS.
