EASA SIB CE-12-31: Garmin GRS 77/77H Attitude and Heading Reference System (AHRS) Units

What to do

Operators should avoid sustained bank angles exceeding 35 degrees when flying in regions prone to this AHRS reset condition. They should also consult the applicable Airplane Flight Manual or Rotorcraft Flight Manual Supplement for immediate actions in case of attitude or heading information loss. No mandatory compliance deadline is specified, but adherence to these recommendations enhances safety.

Summary

Special Airworthiness Information Bulletin SAIB: CE-12-31 is an FAA advisory concerning the Garmin GRS 77 and GRS 77H Attitude and Heading Reference System (AHRS) units used in Garmin G500/G500H/G600 systems and integrated flight decks such as G900X, G950, G1000, G1000H, Cirrus Perspective™, and Embraer Prodigy®. It informs operators about a potential unintentional reset of these AHRS units during sustained bank turns in certain geographic regions. This bulletin does not impose mandatory requirements but provides important safety information.

What changed

SAIB CE-12-31 introduces awareness of a condition where the Garmin GRS 77/77H AHRS units may reset during sustained bank turns exceeding 35 degrees at speeds over 150 knots, particularly in regions with near-vertical magnetic fields like northern Canada, northern Russia, and Antarctica. The reset causes a temporary loss of attitude and heading information lasting up to 45 seconds. This bulletin does not mandate corrective action but advises caution and operational limitations.

Why it matters

This information is critical for aviation professionals operating aircraft equipped with the affected Garmin AHRS units, as unexpected attitude and heading loss can impact flight safety during certain maneuvers. Operators, maintenance personnel, and compliance teams need to understand the conditions that trigger the reset to mitigate risks and ensure proper response. Awareness helps prevent incidents and supports informed decision-making in affected geographic areas.