Garmin GTS 800 Traffic Advisory System (TAS)

The GTS 800 interrogates the transponders of nearby aircraft and determines bearing, distance, relative altitude and, for aircraft that report altitude, vertical trend. At least one compatible traffic display is required; it shows a top-down view of the targets.

A traffic advisory is issued from the closure rate in range and altitude or when an intruder comes within a minimum distance. The spoken alert gives the bearing from one o’clock to twelve o’clock, high, low or same altitude (within 200 ft), and the distance in miles. Mode S traffic that reports being on the ground is not displayed.

Besides active surveillance, the unit contains a 1090 MHz Extended Squitter receiver. The ADS-B In function is enabled at installation. According to Garmin, full ADS-B In functionality needs system software 4.00 or later; earlier versions only use ADS-B position data to derive the bearing of traffic that is already tracked actively.

Unlike the GTS 820 and GTS 850, the GTS 800 needs no interface to a transponder. An ARINC 429 connection to the transponder is needed only when the transponder is the barometric altitude source.

A directional antenna on top of the aircraft is always required; it determines the bearing. Garmin’s GA 58 is a four-element directional antenna for the top and/or bottom position. An optional bottom antenna can be directional or an omni-directional monopole, which gives no bearing.

The unit mounts in a vertical rack 115-00781-00 or a horizontal rack 115-00784-00, supplied separately together with the QMA connector kits. Required inputs are a pressure altitude source (serial encoder or digital air data computer) and an audio interface for the spoken alerts. Landing gear position, GPS and an air/ground switch are optional.

The system normally powers up in Standby, where no traffic surveillance runs. Operate is the normal mode with active and ADS-B In surveillance. If a fault prevents normal operation, the unit enters Fail mode and stays there.

The self-test is started manually from Standby and takes about ten seconds. A pattern of test traffic appears on the display, and the result is announced as “TAS System Test Passed” or “TAS System Test Failed”. Traffic surveillance is not available during the test. The installation can be configured so that the self-test cannot be started in the air.

P/N 010-00519-00 is the new GTS 800 with processor unit 011-01356-00. The same unit 011-01356-00 is also offered serviceable/overhauled and as a repair. The unit has no display; rack, connector kits and display are separate.

The GTS 820 (011-01446-00, 250 W, with GPA 65 amplifier) and the GTS 850 (011-01553-00, TCAS I) are different units with their own part numbers.

Garmin service bulletin 1855 names the GTS 800 among the units installed under EASA AML STC 10067437; the FAA equivalent SA02121SE applies in the US only. Whether a given aircraft type is covered depends on the approved model list of the STC.

A Certificate of Release to Service closes the installation. AIR TEAM service performs certified installations in Kunovice under EASA Part-145 (CZ.145.0094).