All GTS Processor GTS 825/GTS 855/GTS 8000 units (011-02571-0( )) with software version 3.13 (or earlier) and interfaced to a Garmin GX000 Integrated Flight Deck are affected.
GTS Processors with software version 3.12.1 are not affected by this bulletin.
The FAA issued Airworthiness Directive (AD) mandates that all GTS Processor units (GTS 825/855/8000) comply within 24 months of the effective date by updating the GTS Processor software to version 3.14, 3.12.1 or later.
Since TAS and TCAS I installations do not exhibit the subject condition, an Alternative Method of Compliance (AMOC) may be proposed to the FAA describing how the subject condition is not possible (i.e. if the installation is not TCAS II capable). This would alleviate the requirement to update software.
The FAA has issued an AD against all installations using a GTS Processor (GTS 825/855/8000) effective May 17, 2021. The AD (Docket No. FAA-2020-0991) identifies a condition where a false RA could potentially result in loss of separation.
The subject condition only affects TCAS II installations, however the AD mandates compliance for all GTS Processor units because some TAS and TCAS I installations are capable of TCAS II with a software enablement.