TT21/TT22 Transponder Installation Manual
22 August 2017
00560-00
Issue AP
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Trig Avionics Limited
33
used by ATC to identify taxiing routes and potential conflicts. When
configured for ADS-B, the TT21/TT22 will ask for the aircraft length and
width (wingspan), in metres, and will calculate the appropriate size code for
transmission.
6.1.13
GPS Antenna Offset
The GPS antenna offset is used together with the aircraft length and width to
manage taxiway conflicts. A typical GPS installation does not report the
geographic position of the centre of the aircraft, or even the tip of the nose of
the aircraft; instead it usually reports the location of the actual GPS antenna
(not the GPS receiver). In normal flight operations this distinction is of no
practical importance at all, but if ADS-B is used to manage taxiway conflicts, a
significant offset in antenna position could mean that the aircraft is not in the
same place as the ADS-B reported position. Although primarily intended for
position correction on large transport aircraft, General Aviation aircraft can
also have a significant offset. For example, if the aircraft has a long tail boom
and the GPS antenna is on the top of the tail, the GPS position could be 4
metres or more from the nose of the aircraft.
Enter the position of the GPs antenna relative to the nose of the aircraft. The
position is stored and transmitted to the nearest 2 metres; great accuracy in
measurement is not required.
6.1.14
1090 MHz Receiver Installed
The ADS-B transmissions include an indication to the ground stations of
whether your aircraft includes a 1090 MHz ADS-B receiver. This can be used
by the ground stations to manage the volume of traffic they must send. Set this
to “Yes” if the aircraft has a 1090 MHz ADS-B receiver installed.
6.1.15
UAT Receiver Installed
The ADS-B transmissions include an indication to the ground stations of
whether your aircraft includes a UAT ADS-B receiver. This can be used by
the ground stations to manage the volume of traffic they must send. Set this to
“Yes” if the aircraft has a UAT receiver installed.
