GFC 500 "Fail / System not usable"

[Rick Junkin]

Garmin has an open ongoing engineering tag on this issue with no resolution as of yet. Apparently I'm not the first to report it. Has anyone else seen this behavior?

My GFC 500 threw a fault (AP in a red box in the AFCS status box) and disengaged the autopilot. I was able to re-engage it and it worked ok for the rest of the flight. On a subsequent flight it failed in the same way and continued to fail immediately after my trying to re-engage it multiple times. I sent the flight data logs, which show "Fail / System not usable" in the AFCS Status data field at the time of the failures, to Garmin for assistance.

I flew a 2.5 hour flight yesterday and didn't experience any issues with the autopilot. I exercised every function including VNAV without a single hiccup. I hate intermittent problems.

The failures have occurred after about 2 hours of flight, but I question whether that's relevant. 

Has anyone else seen this type of failure?

Cheers,
Rick

[ArtVandelay]

Yes, I think I saw this when I tried to engage the AP while in an usual attitude. Normally I engage when wings are level and in a moderate pitch attitude, but I was playing around.

[PT20J]

I've never had it fail, but I have had three or four random disconnects that Garmin couldn't explain.

[PeteMc]

Probably unrelated to this issue, but I just recently learned that buried in the manual is a few lines that explains that GPS is REQUIRED for the Auto Pilot to operate normally.  If GPS is lost, the G500 will go in Roll Mode and Pitch Mode.  Makes one wonder about MON, ILS or LOC approaches.  (Yes, you can hand fly, but sort of not the point when buying a G500.)

 

From page 3-6 of the AFMS – GFC 500 Autopilot:

LOSS OF GPS INFORMATION (GPS position information is lost to the autopilot.)

NOTE

If GPS position data is lost while the autopilot is tracking a GPS, VOR, LOC or BC course, the autopilot will default to roll mode (ROL). The autopilot will default to pitch mode (PIT) if GPS information is lost while tracking an ILS. The autopilot uses GPS aiding in VOR, LOC and BC modes.

1. Autopilot ................................................ SELECT different lateral and vertical mode (as necessary)

If on an instrument approach:

AP DISC / TRIM INT button ................................... PRESS, Continue the approach manually

Or

Missed Approach Procedure .......................................................... EXECUTE (as applicable)

  

[Fly Boomer]

13 minutes ago, PeteMc said:

Probably unrelated to this issue, but I just recently learned that buried in the manual is a few lines that explains that GPS is REQUIRED for the Auto Pilot to operate normally.  If GPS is lost, the G500 will go in Roll Mode and Pitch Mode.  Makes one wonder about MON, ILS or LOC approaches.  (Yes, you can hand fly, but sort of not the point when buying a G500.)

 

From page 3-6 of the AFMS – GFC 500 Autopilot:

LOSS OF GPS INFORMATION (GPS position information is lost to the autopilot.)

NOTE

If GPS position data is lost while the autopilot is tracking a GPS, VOR, LOC or BC course, the autopilot will default to roll mode (ROL). The autopilot will default to pitch mode (PIT) if GPS information is lost while tracking an ILS. The autopilot uses GPS aiding in VOR, LOC and BC modes.

1. Autopilot ................................................ SELECT different lateral and vertical mode (as necessary)

If on an instrument approach:

AP DISC / TRIM INT button ................................... PRESS, Continue the approach manually

Or

Missed Approach Procedure .......................................................... EXECUTE (as applicable)

  

 

G500:

 

[PeteMc]

20 minutes ago, Fly Boomer said:

G500:

So the pic is a simulation of what the G500 does when it looses GPS?  By itself the pic does not give me any context.  

[jamesm]

not  sure what your setup is that you have with your GFC500...

My setup is 2 G5's GNC255(Nav/Com), GNC355(GPS/Com), L3 NGT9000 +(transponder /ADS-B), GFC500  2 axis with pitch trim, GMU11(Magnetometer to CAN), GAD29B(A429 to CAN),GAD13(OAT to CAN)  in a '67C Mooney.

I really haven't too many problem with the G5 system which have installed since 2016 for the G5 ADI and 2017 G5 HSI display.  just tough ones.

I have experienced two different types of G5 failures.

The first was just shortly after the GFC500 was installed which was about 2 years ago. The G5 ADI display would randomly fail. The Garmin Service Center and the avionics Guy was ready to give the plane back to me since they where having hard time reproducing the problem. They happen to catch G5  fail during the self test. This was intermittent failure and would randomly fail so it wasn't every flight it failed. It was bugger to catch. Garmin sent a  RMA G5 which failed  then they  sent a recondition G5 which lasted about 2 years absolute trouble free until about 2 to 3 months ago. you could reset the electrical power to The G5 and GAD29, GMU11, GAD13 it work fine for the most part but then it start failing at more random bias. This is where I learned about value of the Data Log files on the G5's.  Their data logging seems to be pretty bullet proof. While I don't know how to interpret the error codes of the Data Log files their error logging happen at the time of the failure.

This last time which was about 2 months ago I had to take into Garmin Approved service center again for help.  It was slightly different error codes than the 1st time failures it was more common but at different flight regimes. The HSI G5 display would revert to the ADI  display without user input. you could power off the  HSI  G5 display then back then it would be ok.  The two times I  did catch the HSI fail i noticed that the OAT would pop up a red "X" just before the HSI G5 would revert to ADI display. between G5 system failures and while trying to get it to more predictable failure mode.  <unrelated>  I decided to removed L3 NGT9000 (transponder /ADS-B) The L3 NGT9000 would continually drop traffic on the Ipad and annoying TAS fail message. So I installed GNX375(transponder /ADS-B) so get more screen fields. <back to the story> My Avionics Guy gave the plane back to me, along with the help from the Garmin couldn't reproduce the problem or come up inclusive evidence  of the cause of the failure. Garmin had them open all the connectors and realign the GMU11 and go through the G5 installation and setting procedures. It would fail just about every flight prior to me taking it into my avionics shop. it has been about 6 flights but has not failed yet.

 

Hope this helps,

James '67C