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TIS is NOT intended to be used as a collision avoidance system
and does not relieve the pilot responsibility to “see and avoid”
other aircraft. TIS should not be used for avoidance maneuvers
during IMC or other times when there is no visual contact with the
intruder aircraft. TIS is intended only to assist in visual acquisition
of other aircraft in VMC. No recommended avoidance maneuvers
are provided for, nor authorized, as a direct result of a TIS display or
While TIS is a useful aid to visual trafﬁc avoidance, it has some
system limitations that must be fully understood to ensure proper
use. Many of these limitations are inherent in secondary radar
surveillance. In other words, the information provided by TIS will
be no better than that provided to ATC. TIS only shows aircraft with
operating transponders installed.
TIS relies on surveillance of the Mode S radar, which is a
“secondary surveillance” radar similar to the ATCRBS. TIS
operation may be intermittent during turns or other maneuvering.
TIS is dependent on two-way, “line-of-sight” communications
between the aircraft and the Mode S radar.
Whenever the structure of the client aircraft comes between the
transponder antenna (usually located on the underside of the aircraft)
and the ground-based radar antenna, the signal may be temporarily
interrupted. Other limitations and anomalies associated with TIS are
described in the AIM, Section 1-3-5. Refer to
page 159 for wiring
NOTE: Garmin is not responsible for Mode S geographical
coverage. Operation of the ground stations is the responsibility
of the FAA. Refer to the Aeronautical Information Manual for a
Terminal Mode S Radar Site Map covering the U.S.
NOTE: TIS is unavailable at low altitudes in many areas of the
U.S., particularly in mountainous regions. Also, when ﬂying near
the “ﬂoor” of radar coverage in a particular area, intruders below
the client aircraft may not be detected by TIS.
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TIS information is collected one radar scan prior to the scan during
which the uplink occurs. Therefore, the surveillance information
is approximately 5 seconds old. In order to present the intruders
in a “real time” position, the TIS ground station uses a “predictive
algorithm” in its tracking software. This algorithm uses track
history data to extrapolate intruders to their expected positions
consistent with the time of display in the cockpit. Occasionally,
aircraft maneuvering causes this algorithm to induce errors in the
GPSMAP 496 screen. These errors primarily affect relative bearing
information and trafﬁc target track vector (it will lag); intruder
distance and altitude remains relatively accurate and may be used to
assist in “see and avoid.” Some of the more common examples of
these errors include:
• When client or intruder aircraft maneuvers excessively or abruptly, the tracking algorithm can report incorrect horizontal
position until the maneuvering aircraft stabilizes.
• When a rapidly closing intruder is on a course that crosses the
client aircraft course at a shallow angle (either overtaking or
head on) and either aircraft abruptly changes course within
¼ nm, TIS may show the intruder on the opposite side of the
client than it actually is.
These are relatively rare occurrences and are corrected in a few
radar scans once the course has stabilized.
Users of TIS can render valuable assistance in the correction
of malfunctions by reporting their observations of undesirable
performance. Reporters should identify the time of observation,
location, type and identity of aircraft, and describe the condition
observed; the type of transponder processor and software in use can
also be useful information. Since TIS performance is monitored
by maintenance personnel rather than ATC, it is suggested that
malfunctions be reported in the following ways:
• By telephone to the nearest Flight Service Station (FSS) facility.
• By FAA Form 8000-7, Safety Improvement Report, a postage-paid card designed for this purpose. These cards can
be obtained at FAA FSSs, General Aviation District Ofﬁces,
Flight Standards District Ofﬁces, and General Aviation Fixed
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The GPSMAP 496 supports TIS input from a Garmin Mode S
transponder, such as the GTX 330. To conﬁgure TIS input:
1. Press MENU twice. The Main Menu appears.
2. Highlight the
3. Use the
ROCKER to select the Interface sub tab.
4. Highlight the Serial Data Format ﬁeld, and use the
to select TIS In.
The status ﬁeld indicates one of the following messages:
• Waiting For Data—searching for a valid TIS data stream.
• Data Available —receiving TIS data from the transponder.
• Data Unavailable—connection to transponder established,
but TIS service is unavailable.
• Lost Connection—an error occurred or the connection to the
transponder was lost.
TIS trafﬁc is shown on the GPSMAP 496 according to TCAS
symbology, graphically shown on an alert window, and on the
moving Map Page. A Trafﬁc Advisory (TA) symbol appears as a
solid yellow circle. All other trafﬁc is shown as a hollow white
diamond. Altitude deviation from own aircraft altitude is shown
above the target symbol if trafﬁc is above own aircraft altitude, and
below the symbol if they are below own aircraft altitude. Altitude
trend is shown as an up arrow (>+500 ft/min), down arrow (<-500
ft/min), or no symbol if less than 500 ft/min rate in either direction.
A TIS audio alert is generated whenever the number of Trafﬁc
Advisories on the GPSMAP 496 screen increases from one scan to
the next. Limiting Trafﬁc Advisories only reduces the “nuisance”
alerting due to proximate aircraft. For example, when the ﬁrst Trafﬁc
Advisories appear on the TIS display, the user is alerted audibly.
So long as a single aircraft remains on the TIS display, no further
audio alert is generated. If a second (or more) aircraft appears on the
screen, a new audio alert is sounded.
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TIS > TIS SYMBOLOGY
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If the number of Trafﬁc Advisories on the TIS display decreases and
then increases, a new audio alert is sounded. The TIS audio alert is
also generated whenever TIS service becomes unavailable.
The following TIS audio alerts are available:
• Trafﬁc—TIS trafﬁc alert received.
• Trafﬁc Not Available—TIS service is not available or out of
NOTE: TIS audio alerts can be turned off in the Main Menu
Trafﬁc Ground Track
Trafﬁc ground track is indicated on the GPSMAP 496 screen by a
“target track vector”, a short line shown in 45-degree increments,
extending in the direction of target movement.
Trafﬁc Warning Window
When a trafﬁc threat is imminent, the Trafﬁc Warning Window is
shown. The Trafﬁc Warning Window shows a small thumbnail map.
Press QUIT to go back to the previous page.
NOTE: The Trafﬁc Warning Window is disabled when the
aircraft ground speed is less than 30 knots or when on the
approach leg of a route.
Trafﬁc Target Track Vector
Trafﬁc Warning Window
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TIS trafﬁc can be shown on the Map Page.To conﬁgure TIS Trafﬁc on the Map Page:
1. Press PAGE until the Map Page appears.
MENU. The Map Page options menu appears.
Set Up Map, and press ENTER.
4. Highlight the
Map sub tab.
5. Select TIS Trafﬁc
, and use the ROCKER to change the
Highlighting TIS Trafﬁc Using Map Page Panning
Another Map Page feature is panning. Refer to page 31 for more
When the target pointer is placed on trafﬁc, the trafﬁc range and
altitude separation are shown.
Displaying trafﬁc range and altitude separation
using the Map Panning feature.
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TIS > MAP PAGE