EASA AD US-2021-08-07: ROCKWELL COLLINS - Global Positioning System GPS-4000S - Upgrade

What to do

Operators must identify and remove GPS-4000S units with part number 822-2189-100 from their aircraft by May 12, 2021. They may temporarily install these units for maintenance purposes until 24 months after the effective date, after which installation is prohibited without FAA approval. Replacement units must be approved for installation, and operators should coordinate with Rockwell Collins for service information and software upgrades.

Summary

Federal Aviation Administration Airworthiness Directive 2021-08-07 is a final rule addressing Rockwell Collins GPS-4000S Global Positioning Systems installed on various airplanes. The directive targets GPS units with part number 822-2189-100 that contain a software error causing inaccurate GPS positioning, potentially leading to misleading localizer performance with vertical guidance (LPV) glidepaths and controlled flight into terrain (CFIT).

What changed

This new airworthiness directive requires the removal of the affected GPS-4000S units with part number 822-2189-100 and prohibits their installation 24 months after the effective date. Operators may replace the affected units with any approved GPS-4000S system, not necessarily limited to part number 811-2189-101. The AD also adjusts installation prohibitions to allow temporary use of the affected units before compliance.

Why it matters

This AD is critical for aviation professionals because it addresses a latent GPS software error that can compromise approach safety by providing inaccurate position data, risking CFIT accidents. Operators and maintenance organizations must ensure affected GPS units are upgraded or replaced to maintain compliance and operational safety. Compliance teams need to track affected aircraft and parts to avoid installation of non-compliant GPS units after the grace period.