User's Manual

TT21 Transponder Installation Manual 19 January 2009
00560-00 Issue AA
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Page 28 Trig Avionics Limited
12. ADS-B Compliance
TT21 transponders include support for Extended Squitter ADS-B out. The TT21 is a DO-260A
change 2 compliant category B0 broadcast-only participant.
12.1 ADS-B Parameters Supported
The following table lists the ADS-B parameters that are transmitted by the TT21 transponder when
connected to an appropriate GPS receiver.
Parameter BDS Register
SPI 0,5
Emergency Indicator 0,5
Barometric Altitude 0,5
Quality Indicator (NIC) 0,5
Latitude 0,5
Airborne Position
Longitude 0,5
Quality Indicator (NIC) 0,6
Latitude 0,6
Surface Position
Longitude 0,6
Surface Ground Speed 0,6
Surface Ground Track 0,6
Aircraft Identification 0,8
Airborne Ground Velocity 0,9
Emergency Status 6,1
Quality Indicator (NACp) 6,5
Quality Indicator (SIL) 6,5
Version Indicator 6,5
Surface Length/Width 6,5
In addition the TEST message with 4096 squawk code information can also be transmitted to support
coordination with ATC radar systems. TEST message transmission status is an installation option.
12.2 ADS-B Service Levels
ADS-B forms part of the future plans for airspace management, and is being deployed in certain
limited applications. The following summary of the ADS-B service is current at the date of publication
of this manual, but you should be aware that regulatory changes are taking place in this area, and the
most recent regulatory information should be consulted.
There are currently three levels of service that an ADS-B transmitter can provide.
Operational ADS-B Surveillance
EASA has published the certification requirements for using
ADS-B position information for Air Traffic Control services in a
non-radar environment, AMC20-24. AMC20-24 includes both
technical attributes of the individual components of an