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Surveillance Systems

2. The cockpit equipment functionality required

by a TIS client aircraft to receive the service consists

of the following (refer to FIG 4−5−6):

(a) Mode S data link transponder with

altitude encoder.

(b) Data link applications processor with TIS

software installed.

(c) Control−display unit.

(d) 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).

3. 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


4. 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

ASR−8 analog primary radars, will provide TIS

pending modification or relocation of these sites. See

FIG 4−5−5, 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.

1. 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.

2. TIS, through the Mode S ground sensor,

provides the following data on each intruder aircraft:

(a) Relative bearing information in 6−degree


(b) Relative range information in 1/8 NM to

1 NM increments (depending on range).

(c) Relative altitude in 100−foot increments

(within 1,000 feet) or 500−foot increments (from

1,000−3,500 feet) if the intruder aircraft has operating

altitude reporting capability.

(d) Estimated intruder ground track in

45−degree increments.

(e) Altitude trend data (level within 500 fpm

or climbing/descending >500 fpm) if the intruder

aircraft has operating altitude reporting capability.

(f) Intruder priority as either an “traffic

advisory” or “proximate” intruder.

3. 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.

4. 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.