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The FAA has issued a Special Airworthiness Information Bulletin to advise you, owners and operators of the Garmin G500/G500H/G600 systems, and all G900X, G950, G1000, G1000H, Cirrus Perspective™, and Embraer Prodigy® Integrated Flight Deck Systems with GRS 77 software versions 2.10 through 3.02 and GRS 77H software version 3.50, of an unintentional reset during sustained bank turns.

At this time, this airworthiness concern has not been determined to be an unsafe condition that would warrant airworthiness directive (AD) action under Title 14 of the Code of Federal Regulations (14 CFR) part 39.

Background
Per Garmin Service Advisory No.: 1156, Rev. A, the GRS 77/77H Attitude and Heading Reference System (AHRS) may reset during sustained bank turns. The conditions that may initiate this reset occur when operating in regions where the earth’s magnetic field vector is close to vertical (e.g. northern Canada, northern Russia, and Antarctica). The reset may occur after 30 seconds of turning when bank angle exceeds 35 degrees and speed is greater than 150 knots. If the reset occurs, it results in a temporary loss of attitude and heading, typically not lasting longer than 45 seconds.

Recommendations
In the affected regions, the FAA recommends you refrain from operating at bank angles exceeding 35 degrees. Refer to the applicable Airplane Flight Manual, Airplane Flight Manual Supplement, or Rotorcraft Flight Manual Supplement for information regarding immediate actions in the event of any loss of attitude and/or heading information.

For Further Information Contact:
Roger A. Souter, Aerospace Engineer, FAA/Wichita ACO. 1801 Airport Road, RM 100, Wichita, KS 67209; phone: 316-946-4134, fax: 316-946-4107; e-mail: Roger.Souter@FAA.GOV.
(Optional) For Related Service Information Contact: Garmin, 1200 East 151st Street, Olathe, KS 66062, phone: 913-393-8200; fax: 913-397-8282

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