AD 2021-08-15 Requires Updating The Software Version Of The Affected GTS Processor Units

The FAA is adopting a new airworthiness directive (AD) for certain Garmin International (Garmin) GMN-00962 GTS processor units (GTS 825, GTS 855, GTS 8000).

This AD was prompted by reports of GTS processor units issuing resolution advisories (RAs) when no risk of collision or loss of separation exists between the airplanes involved. This AD requires updating the software version of the affected GTS Processor units. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective May 17, 2021.

Supplementary Information: The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to Garmin GMN-00962 GTS processor units (GTS 825, GTS 855, GTS 8000) with part number 011-02571-0( ) and software version 3.13 or earlier (except version 3.12.1). The NPRM published in the Federal Register on December 14, 2020 (85 FR 80696). The NPRM was prompted by seven reports of false RAs involving aircraft equipped with Garmin GMN-00962 GTS processor configured for traffic collision avoidance system II (TCAS II) (configuration marketed as GTS-8000 units). The Garmin GMN-00962 GTS processor units are marketed by Garmin as the GTS 825, GTS 855 or GTS 8000, with the marketing name representing the traffic system configuration.

A false RA occurs when there is no risk of collision or loss of separation of the airplanes. These false RAs result from the GTS Processor software potentially calculating incorrect range rates. This results in traffic advisories or RAs being generated when targets are greater than 10 nautical miles (NM) away. A TCAS event involving three or more airplanes can result in mid-air collision by increasing the risk that the TCAS, in resolving the false RA with the initial airplane, will create an actual loss of separation with a third airplane. This condition, if not addressed, could result in an RA being generated when no risk of loss of separation or risk of collision exists between the airplanes involved, which can lead to a mid-air collision with a third airplane.

In the NPRM, the FAA proposed to require updating the GTS processor unit software. The FAA is issuing this AD to address the unsafe condition on these products.

The affected GTS processor units were installed on the airplanes listed below during production and via an STC; however, the affected units may have been installed on other airplane models as a supplemental type certificate (STC). Although the names found in parenthesis may not be listed on the type certificate, the manufacturer may use those names as marketing names for the airplanes.

• Textron Aviation Inc. (type certificate previously held by Cessna Aircraft Company) Model 525 (Cessna Citation M2), Model 525B (Cessna Citation CJ3+), Model Model 680 Sovereign, Model 680A Latitude, and Model 700 (Cessna Citation Longitude);
• Embraer S.A. Model EMB-500 (Phenom 100) and Model EMB-505 (Phenom 300);
• Learjet Inc. Model 45 (Learjet 70) and Model 45 (Learjet 75); and
• Viking Air Limited (type certificate previously held by Shorts Brothers PLC, Shorts Brothers Limited) Model SD3-60 SHERPA, modified by Field Aerospace STC No. ST00865DE.

FMI: www.regulations.gov