(2023) Service Alert 22027 Rev B: Autopilot Does Not Follow Guidance From Smart Glide

REVISION B:

Added Resolution

PRODUCTS AFFECTED:

GFC 500 Digital Autopilots with Smart Glide enabled on the GTN™ Xi navigator, that are installed on Grumman American AA-5, AA-5A, AA-5B, AG-5B airframes are affected.

ISSUE:

For GFC 500 installations with a G5 or G3X Touch™ that controls the autopilot:

NOTE
This is indicated by flight director modes shown on the G5 or G3X Touch.

When Smart Glide is activated, the autopilot and flight director do not engage automatically. If previously engaged the autopilot and flight director will remain engaged in the same lateral and vertical modes, rather than automatically switching to GPS or ROL and IAS modes.

For GFC 500 installations using a GI 275 that controls the autopilot:

NOTE
This is indicated by flight director modes shown on the GI 275.

When Smart Glide is activated, the autopilot will engage in GPS or ROL, and IAS modes, however the IAS reference speed will be the autopilot Minimum Engagement Speed of 75 knots and will not track the POH/AFM best glide speed target of 72 knots as stated in the Garmin AFMS and Pilot’s Guide.

NOTE
Glide range may be degraded when flying at an airspeed higher than the Best Glide Speed published in the POH/AFM.

ACTION:

When Smart Glide is activated, if the GFC 500 does not automatically engage in the desired lateral and vertical modes at the desired reference airspeed, manually select the desired modes and reference airspeed (75 knots minimum), or disconnect the autopilot (if engaged) and hand-fly the aircraft. The GTN Xi will display the active navigation course to the active Smart Glide airport.

RESOLUTION:

Refer to Garmin STC Service Bulletin 23046 for G3X Touch EFIS Software Version 9.15.

Refer to Garmin STC Service Bulletin 23047 for G5 Electronic Flight Instrument Software Version 8.20.

Refer to the appropriate GTN Xi GPS/SBAS Navigation System Airplane Flight Manual Supplement (190-01007-C2 Rev 7 or 190-01007-C3 Rev 7) for clarification on Smart Glide emergency procedures.