(2011) Service Advisory 1129 Rev A: Momentary loss of GRS 77/GRS 77H and GDC 74A/GDC 74B/GDC 74H functions

AFFECTED PRODUCTS

All GRS 77/77H Attitude Heading and Reference System (AHRS) and/or GDC 74A/74B/74H Air Data Computer units as installed with Garmin Integrated Flight Decks (G1000, G1000H, G950, G900X, G500, G500H, G600, Cirrus Perspective™, and Embraer Prodigy®) with the following software versions are affected:

GRS 77 (fixed wing) 3.01 or earlier
GRS 77H (rotary wing) 3.51 or earlier
GDC 74A/74B/74H 3.07 or earlier

This condition has existed in these products since they were initially fielded in 2004.

DESCRIPTION

Garmin has become aware of a condition that may cause momentary interruption of GRS 77/77H AHRS and/or GDC 74A/74B/74H Air Data operation. For each installed component, there is a limited possibility for a one to two-second interruption to occur once every 90 operating hours.

Depending on the installation and/or system configuration, the momentary interruption of these systems may: (a) result in the display of a red ‘X’ for up to two seconds in the affected data field(s) on the PFD; and/or (b) result in an annunciated disengagement or reversionary mode-change of the autopilot. Affected primary data fields include: Attitude, Heading, Slip/Skid, Airspeed, Altitude, and Vertical speed. This issue will not affect attitude and air data information at the same time.

The attitude and heading red ‘X’ may persist for up to 45 seconds to accommodate a reset of the GRS 77/77H AHRS.

PILOT ACTION

Refer to the applicable flight manual or flight manual supplement for information regarding immediate actions in the event of any system failure.

RESOLUTION

This issue will be corrected in a future system software release.