Garmin GNC 420W Pilot's Manual Addendum

Also see for GDL 69: Pilot's guide addendum Pilot's guide addendum Activation Instructions Pilot's guide Activation Instructions

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Garmin GNC 420W Pilot's Manual Addendum Manual pdf 6 page image

2TIS Operation and SymbologyPart One: Section 1How TIS differs from TCASThe main difference between TIS and TCAS is thesource of surveillance data. TCAS uses an airborneinterrogator with a one-second update rate, while TISuses the terminal Mode S ground interrogator and itsData Link to provide about a five-second update rate.The range accuracy of TIS and TCAS is similar.TIS LimitationsNOTE: This section on TIS Limitations is not compre-hensive. Garmin recommends the user review the TISLimitations section of the Aeronautical InformationManual, Section 1-3-5.TIS is NOT intended to be used as a collisionavoidance system and does not relieve the pilot ofresponsibility to “see and avoid” other aircraft. TISshould not be used for avoidance maneuvers duringIMC or other times when there is no visual contactwith the intruder aircraft. TIS is intended only to assistin visual acquisition of other aircraft in VMC. No rec-ommended avoidance maneuvers are provided for, norauthorized, as a direct result of a TIS intruder displayor TIS advisory.While TIS is a useful aid to visual traffic avoid-ance, it has some system limitations that must be fullyunderstood to ensure proper use. Many of these limi-tations are inherent in secondary radar surveillance.In other words, the information provided by TIS willbe no better than that provided to ATC. TIS will onlydisplay aircraft with operating transponders installed.TIS relies on surveillance of the Mode S radar,which is a “secondary surveillance” radar similar to theATCRBS. TIS operation may be intermittent duringturns or other maneuvering. TIS is dependent ontwo-way, “line-of-sight” communication between theaircraft and the Mode S radar. Whenever the structureof the client aircraft comes between the transponderantenna (usually located on the underside of the air-craft) and the ground-based radar antenna, the signalmay be temporarily interrupted. Other limitations andanomalies associated with TIS are described in theAIM, Section 1-3-5.Garmin is not responsible for Mode S geo-graphical coverage. Operation of the groundstations is the responsibility of the FAA. Referto the Aeronautical Information Manual for aTerminal Mode S Radar Site Map covering theU.S.NOTE: TIS will be unavailable at low altitudes in manyareas of the U.S., particularly in mountainous regions.Also, when flying near the “floor” of radar coveragein a particular area, intruders below the client aircraftmay not be detected by TIS.TIS information is collected one radar scan prior tothe scan during which the uplink occurs. Therefore,the surveillance information is approximately fiveseconds old. In order to present the intruders in a “realtime” position, the TIS ground station uses a “predic-tive algorithm” in its tracking software. This algorithmuses track history data to extrapolate intruders totheir expected positions consistent with the time ofdisplay in the cockpit. Occasionally, aircraft maneuver-ing will cause this algorithm to induce errors in the400W/500W display. These errors primarily affect rela-tive bearing information and traffic target track vector(it will lag); intruder distance and altitude will remainrelatively accurate and may be used to assist in “see