Garmin aera 795/796 Pilot’s Guide
190-01194-00 Rev. C
Appendix F
194
OverviewGPS NavigationFlight PlanningHazard AvoidanceAdditional FeaturesAppendicesIndex
better nor more accurate than the information used by ATC. TIS-A is intended only to
assist 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 be
considered 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-Aoperationmaybeintermittentduringturnsorothermaneuvering.
•TIS-Aisdependentontwo-way,line-of-sightcommunicationsbetweentheaircraft
and the Mode-S radar antenna. Whenever the structure of the aircraft comes
between the transponder antenna and the ground-based radar antenna, the signal
may be temporarily interrupted.
NOTE:
Refer to the TIS-A Limitations section of the Aeronautical Information
Manual (AIM) for a more comprehensive explanation of limitations and
anomalies associated with TIS-A.
NOTE:
TIS-A 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. Operation
of the ground stations is the responsibility of the FAA. Refer to the AIM for a
Terminal Mode S radar site map.
TIS-A information is collected during a single radar sweep. Collected information
is then sent through the Mode S uplink on the next radar sweep. Because of this,
the surveillance information is approximately five seconds old. TIS-A ground station
tracking software uses prediction algorithms to compensate for this delay. These
algorithms use track history data to calculate expected intruder positions consistent
with the time of display. Occasionally, aircraft maneuvering may cause variations in
this calculation and create slight errors on the Navigation Map which affect relative
bearing information and 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 to assist in spotting traffic. The following errors are common
examples:
