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Aviation Alerts and Advisories

Software Version 8.04 is available for GTX 23, GTX 328, GTX 33(D)(ES)(H), and GTX 330(D)(ES) Products (not applicable to G900X, G950, G1000, Cirrus Perspective®, or Embraer Prodigy® installations)


This bulletin is applicable to GTX 23, GTX 328, GTX 33(D)(ES)(H), & GTX 330(D)(ES) units with software version 8.03 or previous software versions that are not installed in a Garmin Integrated Flight Deck system (G1000, G1000H, G950, G900X, Cirrus Perspective®, and Embraer Prodigy® Integrated Flight Deck Systems). The GTX 328/GTX 330(D)(ES) current software version is displayed at power up, on the unit’s front panel. The GTX 23/GTX 33(D)(ES)(H) software version is displayed on the remote screen of the controlling LRU (e.g. GTN) Startup/Self-Test Page.


TSO Authorization


Garmin recommends that this service bulletin be incorporated in the affected products at the next scheduled service interval.


This Service Bulletin incorporates new unit software version 8.04 for GTX 23, GTX 328, GTX 33(D)(ES)(H), and GTX 330(D)(ES) units.

Software version 8.04 incorporates the following updates:

  • Addressed air/ground determination issues and added the ability to configure the aircraft stall speed.
  • Addressed FAA note to manufacturers regarding the use of geometric type codes when operating in ON mode.
  • Updated the ADS-B Out CPR encoding to improve position accuracy near latitude zone transitions.
  • Improved ARINC 743A input data processing.
  • Added the GNS serial format, to accept GPS and height above terrain data from GNS 400W/500W Series devices.
  • Expanded the air/ground determination algorithm to utilize additional sensor data such as Height Above Terrain and nearest airport data, when available.
  • Added the ability to disable the automatic transition to ALT mode on takeoff, by configuration.
  • Updated the outside air temperature and density altitude displays to improve consistency with other Garmin equipment.

Service Bulletin 1734A ASDN