Garmin GTS 855 Manual

GTS 8XX Series
Pilot’s Guide
Traffic Advisory System

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December 2009 Printed in the U.S.A.

i190-00587-02 Rev. A
Garmin GTS 8XX Series Traffic Advisory System
LIMITED WARRANTY
This Garmin product is warranted to be free from defects in materials or workmanship for two years from
the date of purchase. Within this period, Garmin will, at its sole option, repair or replace any components
that fail in normal use. Such repairs or replacement will be made at no charge to the customer for parts
and labor, provided that the customer shall be responsible for any transportation cost. This warranty does
not cover failures due to abuse, misuse, accident, or unauthorized alterations or repairs.
THE WARRANTIES AND REMEDIES CONTAINED HEREIN ARE EXCLUSIVE AND IN LIEU OF ALL OTHER
WARRANTIES EXPRESS OR IMPLIED OR STATUTORY, INCLUDING ANY LIABILITY ARISING UNDER
ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, STATUTORY OR
OTHERWISE. THIS WARRANTY GIVES YOU SPECIFIC LEGAL RIGHTS, WHICH MAY VARY FROM STATE TO
STATE.
IN NO EVENT SHALL GARMIN BE LIABLE FOR ANY INCIDENTAL, SPECIAL, INDIRECT OR CONSEQUENTIAL
DAMAGES, WHETHER RESULTING FROM THE USE, MISUSE, OR INABILITY TO USE THIS PRODUCT OR
FROM DEFECTS IN THE PRODUCT. Some states do not allow the exclusion of incidental or consequential
damages, so the above limitations may not apply to you.
Garmin retains the exclusive right to repair or replace the unit or software, or to offer a full refund of the
purchase price, at its sole discretion. SUCH REMEDY SHALL BE YOUR SOLE AND EXCLUSIVE REMEDY FOR
ANY BREACH OF WARRANTY.
To obtain warranty service, contact your local Garmin Authorized Service Center. For assistance in
locating a Service Center near you, visit the Garmin web site at http://www.garmin.com or contact
Garmin Customer Service at 800-800-1020.

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Garmin GTS 8XX Series Traffic Advisory System
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WARNINGS, CAUTIONS, AND NOTES
WARNING: The GTS 8XX Series Traffic Advisory System (TAS and TCAS I)
is intended for advisory use only to aid the pilot in visually acquiring
traffic. No avoidance maneuvers should be based solely upon TAS traffic
information. It is the responsibility of the pilot in command to see and
maneuver to avoid traffic.
NOTE: Pilots should be aware of TAS/TCAS system limitations. TAS/TCAS
systems require intruder transponders to respond to system interrogations.
If an intruder transponder does not respond to interrogations due to
antenna shading or marginal transponder performance, it will not be
displayed, or display may be intermittent. Pilots should remain vigilant
for traffic at all times when using TAS/TCAS systems for non-transponder
equipped airplanes or unresponsive airplanes.
TSO COMPLIANCE
GTS Unit Product Description Applicable TSO
GTS 800 Low Power TAS C147, C166a
GTS 820 High Power TAS C147, C166a
GTS 850 TCAS I C118, C166a
Table 1 GTS 8XX Series Family TSO Compliance

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Contents
LIMITED WARRANTY ........................................................................................i
Warnings, Cautions, and Notes.......................................................................ii
TSO Compliance..............................................................................................ii
Product Description........................................................................................2
Compatible Display Units.................................................................................. 4
GTS 800........................................................................................................... 5
GTS 820........................................................................................................... 5
GTS 850........................................................................................................... 5
Antennas ......................................................................................................... 5
General Antenna Information .................................................................... 5
GTS 8XX Series Antenna Configurations .................................................... 6
GA 58 Directional Antenna........................................................................ 6
Bottom Mounted Directional Antenna (optional)........................................ 6
Bottom Mounted Monopole Antenna (optional)......................................... 7
GPA 65 PA / LNA Module (GTS 820 & 850 only) ............................................... 7
Operation .......................................................................................................8
GTS 8XX Series Traffic....................................................................................... 8
Theory of Operation.......................................................................................... 8
TAS/TCAS Surveillance Volume .................................................................. 8
TAS/TCAS Symbology ................................................................................ 9
GTS 8XX Series Sensitivity Level............................................................... 11
Traffic Advisory (TA) Alerting Conditions................................................... 12
TAS/TCAS Alerts...................................................................................... 13
System Test ............................................................................................. 14
Power-Up .............................................................................................. 15
System Status ......................................................................................... 15
Q and A.........................................................................................................17
Glossary........................................................................................................19
Index.............................................................................................................20

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Garmin GTS 8XX Series Traffic Advisory System
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PRODUCT DESCRIPTION
The GTS 8XX Series Traffic Advisory System (TAS) and Traffic Collision
Avoidance System (TCAS I) uses active interrogations of Mode A/C/S transponders
to provide Traffic Advisories to the pilot independent of the air traffic control
system. The system also uses passive surveillance by means of an Automatic
Dependent Surveillance – Broadcast (ADS-B) receiver which is enabled when
installed with an ADS-B link transmit class of equipment.
Figure 1 GTS 8XX LRU
The GTS 8XX Series of Traffic Advisory System (TAS) or Traffic Alert and
Collision Avoidance System (TCAS I) microprocessor-based sub-systems products
consist of the GTS 800, GTS 820 and GTS 850. The GTS 800 TAS product consists
of one LRU which has low power (40 Watts) transmit capability, and one GA 58,
or other Garmin-approved, directional antenna. The GTS 820 TAS and GTS 850
TCAS I products include one LRU paired with one GPA 65 PA/LNA Amplifier
Module, which allows high power (250W) transmit capability, and one GA 58 or
other Garmin-approved directional antenna. An optional second antenna may also
be installed with these systems. The optional second bottom mounted antenna
may be omnidirectional or a Garmin approved directional antenna.
For targets equipped with a 1090 MHz ADS-B transmit class of equipment, the
GTS 8XX series combines active (interrogated) and passive (ADS-B) surveillance
data to enhance the accuracy of target position on the display. The systems use
Garmin’s CLEAR CASTM technology to correlate ADS-B and actively interrogated
targets to provide pilots with the most accurate target position. Passive ADS-B
surveillance is enabled when the GTS 8XX is installed with an ADS-B transmit
class of equipment.

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Garmin GTS 8XX Series Traffic Advisory System
The GTS 8XX Series provides for expanded audio messaging in an ATC-like
verbal format: “Traffic. One o’clock. High (or Low or Same Altitude). Two miles.”
If surveillance bearing information is not available on the intruder, “Traffic, No
Bearing” is called out.
Bearing may be derived from either the top or bottom directional antenna
depending upon which antenna hears the response. A directional antenna is used
to derive bearing to the intruder aircraft, which is displayed with relative altitude
to own aircraft. Top antenna transmitted interrogations are directional, reducing
the number of transponders that receive the interrogation thus reducing potential
garble on the 1090 MHz band.
Note: GTS 8XX is used throughout this manual to refer to the GTS 800,
820, or 850 products. When a feature is unique to the GTS 800, 820, or
850 it will be specifically referenced as such.
Product GTS 800 GTS 820 GTS 850
Traffic Advisory System (TAS) X X
Traffic Alert and Collision Avoidance System
(TCAS I)
X
LRU X X X
GPA 65 PA/LNA X X
1090 ES ADS-B Receiver X X X
Transmit Power (Watts) 40 250 250
Top-Mounted Garmin-Approved Directional
Antenna
X X X
Optional Bottom-Mounted Garmin-Approved
Directional or Omnidirectional Antenna
X X X
Table 2 GTS 8XX Series Family Product Description
The GTS 8XX Series does not contain a display, but transmits traffic data to a
Garmin or third party multi-function display that is capable of displaying traffic
data. More information is located in the installation manual. The GTS 8XX Series
supplies data to a traffic display to indicate the presence and location of intruder
aircraft. The information provides the crew with the intruder’s range, bearing,
and, for altitude reporting intruders, relative altitude and vertical trend. TCAS I
symbology as defined in the FAA Advisory Circular entitled “Airworthiness

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Garmin GTS 8XX Series Traffic Advisory System
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Approval of Traffic and Collision Avoidance Systems (Active TCAS I)” is utilized
to depict traffic information.
Compatible Display Units
The following table lists compatible display units. As products may
continually be added to the list of compatible display units, always refer to the
GTS 8XX Installation Manual for a complete list. Some displays may require
the purchase and installation of additional modules and/or software to support
traffic displays. Check with your installer to ensure an existing display supports
traffic prior to installation.
Manufacturer Model
Garmin GMX 200/MX20
Garmin GNS 400/500 Series
Garmin GNS 400W/500W Series
Garmin GNS 480
Garmin GDU 620
Avidyne EX500 (MFD Only)
Honeywell Bendix/King KMD 550/850
Sandel SN3500/SN4500
Table 3 GTS 8XX Series Compatible Display Units

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Garmin GTS 8XX Series Traffic Advisory System
GTS 800
The GTS 800 is a TAS system that can track up to 45 Mode A/C/S targets,
and display up to 30 intruder threats at a time, depending on the display being
utilized. Offering 40 watts of transmit power, a ±10,000 foot vertical separation
maximum, and an active interrogation range of up to 12 NM in the forward
direction, the GTS 800 system will interface with a variety of compatible system
displays in the cockpit.
GTS 820
The GTS 820 is a TAS system that can track up to 45 intruding aircraft
equipped with Mode A/C transponders, and up to 30 intruders equipped with
Mode S transponders. A GTS 820 TAS has an active surveillance range of up to
40 NM in the forward direction, dependent upon interference limiting techniques
based on the number of TCAS II interrogators in the area. Interrogation power
and range in the left, right, and aft quadrants is reduced in a manner similar to
TCAS II systems. It includes a GPA 65 PA/LNA Module that is remotely installed
near the top directional antenna to boost the interrogation range.
GTS 850
The GTS 850 is a fully compliant TCAS I certified system. Operational
capabilities are similar for airborne traffic surveillance for both the GTS 820 and
GTS 850 systems.
Antennas
General Antenna Information
A top-mounted directional antenna is used to derive bearing to the intruder
aircraft. Top antenna transmitted interrogations are directional, reducing the
number of transponders that receive the interrogation thus reducing potential
garble on the 1090 MHz band.
Optional bottom monopole or directional antenna transmit interrogations are
omnidirectional. Intruder bearing can be determined from the top directional
antenna or an optional bottom directional antenna for retractable gear aircraft.

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Garmin GTS 8XX Series Traffic Advisory System
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GTS 8XX Series Antenna Configurations
• Toponlydirectionalantenna.
• Topdirectionalwithbottommonopoleantennas(recommendedforxed
gear aircraft) provides improved intruder visibility. The type of antenna used
will be primarily limited by the amount of space available on the bottom
of the airplane. Any aircraft that can utilize the directional antenna on the
bottom would benefit from its use.
• Top directional with bottom directional antennas (recommended for
retractable gear aircraft) provides benefit of intruder bearing visibility for
targets that are shaded from the top directional antenna.
GA 58 Directional Antenna
The GA 58 directional four element antenna is included with the basic GTS
system to provide altitude, distance, and bearing of threat aircraft. A single antenna
installation uses top-mounted placement. A second GA 58 may be bottom-
mounted to optimize coverage.
Figure 2 GA 58 Directional Antenna
Bottom Mounted Directional Antenna (optional)
A directional antenna may be used as an additional antenna for bottom-
mounting to reduce shading and provide altitude and distance of threat aircraft.
Interrogations from the bottom directional antenna are transmitted in an
omnidirectional pattern, but it still allows bearing determination from replies
received on the bottom antenna.

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Garmin GTS 8XX Series Traffic Advisory System
Bottom Mounted Monopole Antenna (optional)
The addition of an optional bottom-mounted monopole antenna will improve
visibility of intruder aircraft by reducing shading and providing altitude and
distance of threat aircraft. Bearing cannot be determined from replies received
on a bottom-mounted monopole antenna.
Figure 3 Bottom-Mounted Monopole Antenna
GPA 65 PA / LNA Module (GTS 820 & 850 only)
The GPA 65 is a combined Power Amplifier and Low Noise Amplifier module
used in the higher power GTS 820 and 850.
Figure 4 GPA 65 PA/LNA Module

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Garmin GTS 8XX Series Traffic Advisory System
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OPERATION
GTS 8XX Series Traffic
The Garmin GTS 8XX Series unit is a Traffic Advisory System (TAS - GTS 800
and GTS 820) or Traffic Alert and Collision Avoidance System (TCAS I - GTS 850).
The GTS 8XX Series enhances flight crew situational awareness by displaying traffic
information for transponder-equipped aircraft. The GTS 8XX Series also provides
visual and aural traffic alerts including voice announcements to assist in visually
acquiring traffic. The GTS 800 and GTS 820 are TAS systems, the GTS 850 is a
TSO-approved TCAS I system. The GTS 8XX uses active interrogations of Mode
A/C/S transponders to provide Traffic Advisories.
Theory of Operation
When the GTS 8XX Series is in Operating Mode, the unit interrogates the
transponders of intruding aircraft while monitoring transponder replies. The
GTS 8XX Series uses this information to derive the distance, relative bearing, and
if reported, the altitude and vertical trend for each aircraft within its surveillance
range. The GTS 8XX Series then calculates a closure rate to each intruder based
on the projected Closest Point of Approach (CPA). If the closure rate meets the
threat criteria for a Traffic Advisory (TA), visual and aural alerting is provided.
TAS/TCAS Surveillance Volume
The GTS 8XX Series surveillance system monitors the airspace within ±10,000
feet of own altitude. Under ideal conditions, the unit scans transponder traffic
up to 40 NM (GTS 820 and GTS 850) or 12 NM (GTS 800) in the forward
direction using top and bottom-mounted antennas similar to TCAS II systems.
In areas of greater transponder traffic density or when TCAS II systems are
detected, the GTS 820 and GTS 850 systems automatically reduce interrogation
transmitter power (and therefore range) in order to limit potential interference
from frequency congestion. The GTS 800’s range is 12 NM in the forward direction
and the maximum interrogation transmitter power remains constant. There is
also a minimum alerting threshold for range to allow alerting in situations where
traffic is slowly converging. Alerting may be caused by closure rate or minimum
distance to the intruder.

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Garmin GTS 8XX Series Traffic Advisory System
TAS/TCAS Symbology
The GTS 8XX Series supports displays that depict intruding traffic using the
symbols shown in the following table. Refer to the documentation for the specific
display to confirm the supported symbology. Symbol colors may vary depending
on the display product.
TAS Symbol Description
Non-Threat Traffic
(intruder is beyond 6 NM and greater than 1200 feet vertical
separation)
Proximity Advisory (PA)
(intruder is within 6 NM and less than 1200 feet vertical separation)
Traffic Advisory (TA)
(closing rate, distance, and vertical separation meet TA criteria)
Traffic Advisory Off Scale
Table 4 TAS Intruder Symbol Description
A Traffic Advisory (TA), displayed as a yellow circle, alerts the crew to a
potentially hazardous intruding aircraft if the closing rate, distance, and vertical
separation meet TA criteria. A Traffic Advisory that is beyond the selected display
range is indicated by a half TA symbol at the edge of the screen at the relative
bearing of the intruder.
A Proximity Advisory (PA), displayed as a solid white diamond, indicates the
intruding aircraft is within ±1200 feet and is within a 6 NM range, but is still not
considered a TA threat.
A non-threat symbol, shown as an open white diamond, is displayed for all
other traffic beyond 6 NM that does not meet the criteria to be a TA or PA.
Relative altitude, when available, is displayed above or below the corresponding
intruder symbol in hundreds of feet. When this altitude is above own aircraft,
it is preceded by a “+” symbol; a minus sign “-” indicates traffic is below own
aircraft.
A vertical trend arrow to the right of the intruder symbol indicates climbing or
descending traffic with an upward or downward-pointing arrow respectively.

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Intruder Altitude
and Vertical Trend
Figure 5 Intruder Altitude and Vertical Trend Arrow
The GTS 8XX Series automatically suppresses the display of altitude-reporting
aircraft on the ground under either of the following conditions:
• On-groundaircraftisequippedwithaModeS transponder that reports the
on-ground state.
• On-ground aircraft is equipped with a Mode C transponder, and own
aircraft’s radar altimeter (if installed) is displaying 1700 feet AGL or less.

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Garmin GTS 8XX Series Traffic Advisory System
GTS 8XX Series Sensitivity Level
The GTS 8XX Series issues Traffic Advisories according to the current Sensitivity
Level (SL). To prevent nuisance alerts near airports, the GTS 8XX Series has two
sensitivity levels available, Sensitivity Level A (SLA) and Sensitivity Level B (SLB).
Refer to Table 5 for Sensitivity Level definitions. SLA is used to reduce sensitivity
levels in airport environment and avoid nuisance traffic alerts.
The logic for choosing the sensitivity level is based on aircraft configura-
tion. SLA is determined according the following order:
1. Ownship is below 2,000 feet AGL (if equipped with a radio altimeter)
2. Landing gear is extended (no radio altimeter is installed on retractable gear
aircraft)
3. Ground speed is below 120 knots (no radio altimeter installed in a fixed-gear
aircraft)
The GTS 8XX Series will remain in SLB at all other times. In the event a
fixed-gear aircraft is not equipped with a radio altimeter and ground speed is not
available, the GTS 8XX Series will remain in SLB at all times.
Note: If the GTS 8XX Series is interfaced to a radio altimeter, or if the gear/
wheel is configured as fixed, the system will ignore the GEAR DOWN AND
LOCKED discrete input.
In both SLA and SLB, audio alerts are suppressed only under the following
conditions:
1. If radio altimeter is installed and own altitude is less than 400 feet AGL.
2. If no radio altimeter is installed in a retractable gear aircraft and gear is
extended.

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Garmin GTS 8XX Series Traffic Advisory System
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Traffic Advisory (TA) Alerting Conditions
Sensitivity
Level
Intruder Altitude
Available
TA Alerting Conditions
AYes Intruder closing rate provides less than 20
seconds of vertical and horizontal separation.
Or:
Intruder closing rate provides less than 20
seconds of horizontal separation and vertical
separation is within 600 feet.
Or:
Intruder range is within 0.2 NM and vertical
separation is within 600 feet.
A No Intruder closing rate provides less than 15
seconds of separation.
BYes Intruder closing rate provides less than 30
seconds of vertical and horizontal separation.
Or:
Intruder closing rate provides less than 30
seconds of horizontal separation and vertical
separation is within 800 feet.
Or:
Intruder range is within 0.55 NM and vertical
separation is within 800 feet.
B No Intruder range is less than 20 seconds.
Table 5 TA Sensitivity Level and TA Alerting Criteria

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TAS/TCAS Alerts
When the GTS 8XX Series detects a new TA, the following occur:
• A single “Trafc!” voice alert is generated, followed by additional voice
information about the bearing, relative altitude, and approximate distance
from the intruder that triggered the TA. The announcement “Trafc!
12 o’clock, high, four miles,” would indicate the traffic is in front of own
aircraft, above own altitude, and approximately four nautical miles away.
• ATAisannunciatedonthedisplayasaTAsymbolorannunciation.Refer
to the display pilot’s guide for details.
If the bearing of TA traffic cannot be determined, a yellow text banner will
be displayed on the Traffic Page instead of a TA symbol. The text will indicate
“TA” followed by the distance, relative altitude, and vertical trend arrow for the
TA traffic, if known.
A TA will be displayed for at least eight seconds, even if the condition(s) that
initially triggered the TA are no longer present.
No-Bearing TA Traffic
Annunciation
Figure 6 Traffic Annunciation
Bearing Relative Altitude Distance
“One o’clock” through
“Twelve o’clock”
or “No Bearing”
“High”, “Low”, “Same
Altitude” (if within 200
feet of own altitude), or
“Altitude not available”
“Less than one mile”,
“One Mile” through “Ten
Miles”, or “More than ten
miles”
Table 6 TA Descriptive Voice Announcements

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System Test
NOTE: GTS 8XX Series traffic surveillance is not available during the system
test. Use caution when performing a system test during flight.
The GTS 8XX Series provides a system test mode to verify the TAS system is
operating normally. The test takes ten seconds to complete. When the system test
is initiated, a test pattern of traffic symbols is displayed on the Traffic Page. If the
system test passes, the aural announcement “TAS System Test Passed” is heard,
otherwise the system announces “TAS System Test Failed.” For the GTS 850,
the aural announcement is “TCAS System Test Passed/Failed.” When the system
test is complete, the GTS 8XX Series enters Standby Mode. The system may be
installed so that the system test is unavailable during flight.
Figure 7 Self-Test Mode

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Power-Up
NOTE: The GTS 8XX Series automatically transitions from STANDBY to
OPERATE mode eight seconds after takeoff. The unit also automatically
transitions from OPERATE to STANDBY mode 24 seconds after landing.
After power-up, the GTS 8XX Series is in Standby Mode. The GTS 8XX Series
must be in Operating Mode for traffic to be displayed and for TAs to be issued.
System Status
The traffic mode is annunciated on the display product. The symbology
may vary by display product. See the particular pilot’s guide for specific details.
Mode Traffic Mode Annunciation
(Traffic Page)
Traffic Display
Enabled Icon
(Other Maps)
Self-test Initiated TEST
Operating OPERATING
Standby STANDBY
(also shown in white in center of page)
Failed* FAIL
Table 7 Example TAS/TCAS Modes
If the traffic unit fails, an annunciation as to the cause of the failure is shown
on the display product. During a failure condition, the Operating Mode cannot
be selected.
Traffic Map Page Annunciation Description
NO DATA Data is not being received from the TAS/
TCAS I unit
DATA FAILED Data is being received from the TAS/
TCAS I unit, but the unit is self-reporting
a failure
FAILED Incorrect data format received from the
TAS/TCAS I unit
Table 8 TAS/TCAS Failure Annunciations

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The annunciations to indicate the status of traffic information appear in a
banner on the traffic display. The annunciations may vary by display product.
See the particular pilot’s guide for specific details.
Traffic Status Banner Annunciation Description
TA OFF SCALE A Traffic Advisory is outside the selected
display range.
Annunciation is removed when traffic
comes within the selected display range.
TA X.X ± XX System cannot determine bearing of
Traffic Advisory.
Annunciation indicates distance in NM,
altitude separation in hundreds of feet,
and altitude trend arrow (climbing/
descending).
Table 8 TAS Traffic Status Annunciations