EASA AD US-2021-08-15: GARMIN INTERNATIONAL - GTS Processor Units - Software Update

What to do

Operators of aircraft equipped with Garmin GMN-00962 GTS processor units with software version 3.13 or earlier (except 3.12.1) must update the software to version 3.12.1 or later within 24 months of the directive's effective date. They should verify the affected units by part number and software version and coordinate with Garmin Aviation Support for the software update. Aircraft not listed but equipped with the affected units should also comply accordingly.

Summary

Federal Aviation Administration Airworthiness Directive 2021-08-15 is a final rule addressing certain Garmin International GMN-00962 GTS processor units (GTS 825, GTS 855, GTS 8000) installed on various aircraft including Textron Aviation Citation models, Embraer Phenom 100 and 300, Learjet 70 and 75, and Viking Air Limited Model SD3-60 Sherpa modified by Field Aerospace STC ST00865DE. The directive targets software versions 3.13 or earlier (except 3.12.1) of these units due to false resolution advisories that may cause unsafe conditions. It mandates a software update to correct this issue and improve flight safety.

What changed

This new airworthiness directive requires operators to update the software of affected Garmin GMN-00962 GTS processor units to version 3.12.1 or later to eliminate false resolution advisories. It clarifies applicability to all units with the specified part number regardless of marketing configuration and extends the compliance time to 24 months. The directive also adds the Viking Air Limited Model SD3-60 Sherpa modified by Field Aerospace to the list of known affected aircraft.

Why it matters

This directive is critical for aviation professionals because false resolution advisories can lead to unnecessary evasive maneuvers and increase the risk of mid-air collisions, especially in multi-aircraft encounters. Operators and maintenance organizations must ensure compliance to maintain airworthiness and safety of affected aircraft. Compliance teams need to track software versions and update schedules to meet regulatory requirements and avoid operational disruptions.