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Aviation Alerts and Advisories

Service Advisory 1555 Rev C: G600 Interfaced With KFC 275/KFC 325 Autopilot

 G600 Integrated Flight Deck Systems that are interfaced to a KFC 275 or KFC 325 autopilot system and include altitude capture (ALTC) mode and vertical speed (VS) control from the G600 Primary Flight Display (PFD) are affected.

 The issue affects the operation of the altitude capture (ALTC) and/or vertical speed (VS) modes of the autopilot.
 The following may occur:

  • Premature engagement of altitude capture mode (ALTC) resulting in inappropriate pitch up or pitch down commands
  • Pitch commands in vertical speed (VS) mode that are not appropriate for the selected vertical speed
  • Unintentional disengagement of altitude capture (ALTC) or vertical speed (VS) modes


  • Monitor the autopilot/flight director for proper operation at all times.
  • If inappropriate autopilot/flight director pitching is experienced, immediately disengage the autopilot/flight director and maintain aircraft control manually.

 Until the Software update is completed to address this issue, Garmin recommends minimizing the use of VS and/or altitude capture (ALTC) modes as follows:

  • Use pitch attitude hold or Indicated Airspeed mode (IAS) as an alternative to VS mode for climbs and descents.
  • Avoid climbs or descents with altitude capture mode armed. Disarm altitude capture mode using the ALT button on the G600 PFD. Manually level off the aircraft and engage altitude hold (ALT) mode at the desired altitude.

Download 1555C