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Surveillance Systems


The cockpit equipment functionality required

by a TIS client aircraft to receive the service consists
of the following (refer to FIG 4



Mode S data link transponder with

altitude encoder.


Data link applications processor with TIS

software installed.



−display unit.


Optional equipment includes a digital

heading source to correct display errors caused by
“crab angle” and turning maneuvers.


Some of the above functions will likely be combined into
single pieces of avionics, such as (a) and (b).


To be visible to the TIS client, the intruder

aircraft must, at a minimum, have an operating
transponder (Mode A, C or S). All altitude
information provided by TIS from intruder aircraft is
derived from Mode C reports, if appropriately


TIS will initially be provided by the terminal

Mode S systems that are paired with ASR

−9 digital

primary radars. These systems are in locations with
the greatest traffic densities, thus will provide the
greatest initial benefit. The remaining terminal
Mode S sensors, which are paired with ASR

−7 or


−8 analog primary radars, will provide TIS

pending modification or relocation of these sites. See

−5−5, Terminal Mode S Radar Sites, for site

locations. There is no mechanism in place, such as
NOTAMs, to provide status update on individual
radar sites since TIS is a nonessential, supplemental
information service.

The FAA also operates en route Mode S radars (not
illustrated) that rotate once every 12 seconds. These
sites will require additional development of TIS
before any possible implementation. There are no
plans to implement TIS in the en route Mode S radars
at the present time.

c. Capabilities.


TIS provides ground

−based surveillance

information over the Mode S data link to properly
equipped client aircraft to aid in visual acquisition of
proximate air traffic. The actual avionics capability of
each installation will vary and the supplemental
handbook material must be consulted prior to using

TIS. A maximum of eight (8) intruder aircraft may be
displayed; if more than eight aircraft match intruder
parameters, the eight “most significant” intruders are
uplinked. These “most significant” intruders are
usually the ones in closest proximity and/or the
greatest threat to the TIS client.


TIS, through the Mode S ground sensor,

provides the following data on each intruder aircraft:


Relative bearing information in 6




Relative range information in 1/8 NM to

1 NM increments (depending on range).


Relative altitude in 100

−foot increments

(within 1,000 feet) or 500

−foot increments (from


−3,500 feet) if the intruder aircraft has operating

altitude reporting capability.


Estimated intruder ground track in


−degree increments.


Altitude trend data (level within 500 fpm

or climbing/descending >500 fpm) if the intruder
aircraft has operating altitude reporting capability.


Intruder priority as either an “traffic

advisory” or “proximate” intruder.


When flying from surveillance coverage of

one Mode S sensor to another, the transfer of TIS is
an automatic function of the avionics system and
requires no action from the pilot.


There are a variety of status messages that are

provided by either the airborne system or ground
equipment to alert the pilot of high priority intruders
and data link system status. These messages include
the following:

(a) Alert.

Identifies a potential collision

hazard within 34 seconds. This alert may be visual
and/or audible, such as a flashing display symbol or
a headset tone. A target is a threat if the time to the
closest approach in vertical and horizontal coordi-
nates is less than 30 seconds and the closest approach
is expected to be within 500 feet vertically and
0.5 nautical miles laterally.

(b) TIS Traffic.

TIS traffic data is displayed.

(c) Coasting.

The TIS display is more than

6 seconds old. This indicates a missing uplink from
the ground system. When the TIS display information
is more than 12 seconds old, the “No Traffic” status
will be indicated.