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Aviation Alerts and Advisories

Service Alert 1307 Rev B: Potential loss of PFD displayed heading and/or attitude for G1000 systems installed in King Air and Cessna Mustang Aircraft


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 PFDs.
Do not take off if the heading displayed on the PFD is noticeably drifting.


Download 1307