Garmin SAs 1307B and 1309B: Flight Decks may Display drifting Heading values

Summary of Service Alert:  

SA1309B:  Garmin G1000, G1000H, G950, G900X, G500, G500H, G600, Cirrus Perspective™, and Embraer Prodigy® Integrated Flight Deck Systems equipped with GRS 77/77H AHRS (Attitude Heading Reference System).
SA1307B:  King Air and Cessna Mustang aircraft with Garmin G1000 installations equipped with GRS 77 AHRS (Attitude Heading Reference System) may be affected.

Garmin has received a very limited number of reports of a temporary loss of heading and attitude (provided by the AHRS) displayed in the products noted above. There are two possible causes.

•    Moving the aircraft on the ground (e.g., towing operations) during the first 10 seconds after turning on power to the AHRS (when power is applied to a PFD, power is also applied to the associated AHRS)
•    Magnetic interference introduced near the magnetometer(s) during AHRS initialization (i.e. during the 60 seconds following power up of the AHRS)

Either of the above conditions can cause noticeably drifting heading to be displayed on the PFD (Primary Flight Display) prior to takeoff.  Noticeably drifting heading may induce a temporary loss of PFD displayed heading and/or attitude information after takeoff and during climb.

For the purpose of this alert, “noticeably drifting heading” occurs when the PFD heading is continuously turning in one direction at a rate of more than ½ degree per second when the aircraft is stationary.  A constant heading offset on the PFD prior to aircraft movement is not an indication of this issue.

Do not move the aircraft on the ground during the first 10 seconds after turning on the pilot and co-pilot (if present) PFD(s).  Do not take off if the heading displayed on the PFD is noticeably drifting.


35 years component-level Aviation/Electronics repair/Avionics retrofit experience. FCC General Radiotelephone with Ship Radar. Navcom-Audio, Transponder-Pulse-Radar, Autopilot expertise. IT Administration since 1983. Private Pilot since 1986. CAD designer since 1990. FAA Certified Repair Station Chief Inspector since 1994. Started 3 Avionics Shops. College: Business Administration/Marketing. Motorcycle enthusiast. 6 year USAF Veteran, Ground Radio Equipment Technician (30474, E-5). WordPress novice.

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