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Aviation Alerts and Advisories

Service Alert 1381 Rev A: GDL 88 Non-Diversity Transmitter Self Test


GDL 88 non-diversity units (single bottom mounted antenna) with Software Version 2.01 or 2.05.

GDL 88D diversity units (top and bottom mounted antennas) are not affected.


GDL 88 non-diversity units with affected software will not send a failure message to the displays in the unlikely event the unit fails to transmit. This condition does not impact the overall reliability of the GDL 88, but can result in the lack of an indication to the pilot in the event of a failure.


Pilots should be aware of the potential for a loss of TIS-B traffic services which depend on ADS-B out transmissions without an appropriate failure indication. Use the availability of TIS-B while within the service volume of an ADS-B ground station as an indicator of a functioning UAT transmitter whenever practical.

Note that the only affected services in the event of a GDL 88 transmitter failure would be loss of TIS-B traffic data for your own aircraft. The ability to receive traffic information directly from other ADS-B participating aircraft, TIS-B data applicable to other aircraft, or FIS-B data would not be affected.


This issue will be corrected in a future GDL 88 software release.

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