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Aviation Alerts and Advisories

Service Advisory 1805: NAV 2


GFC 600 installed with a GDU 620 and dual Garmin GNS/GTN products are affected.


When the pilot’s PFD CDI source is selected to display VOR/LOC 2 the following may occur:

  • VOR/LOC mode may appear to be armed but the autopilot may not capture and engage VOR/LOC mode when intercepting the VOR/LOC 2 course.
  • If the frequency or course for VOR/LOC 1 is changed while coupled to VOR/LOC 2, the autopilot may deviate from the VOR/LOC 2 course in an attempt to couple to the VOR/LOC 1 source.

Navigation information shown on the displays is correct, and the HSI/CDI operates correctly in all cases.

Coupling to GPS 2 is not affected.


Do not use the VOR/LOC 2 source on the pilot’s PFD for coupling to the autopilot.  If it is necessary to couple to VOR/LOC  2 in abnormal/emergency operations, closely monitor the autopilot modes and course deviation to ensure proper operation.


Garmin will address this issue in future software releases.

Service Advisory 1805A