Gfc500 disconnect

[Ulysse]

13 hours ago, PT20J said:

a software “fix” for a hardware problem can introduce other issues since you are forced to address the symptom but not the root cause

 

10 hours ago, PT20J said:

All this actually makes me more comfortable with my decision to schedule a GFC 500 installation

It is maybe my poor understanding of English, so pardon me but aren't these 2 statements contradictory? On one hand you seem to point out a fundamental hardware problem and the risk of fixing it with software, and in the other hand you are confident in installing it in your aircraft although there are pending issues which are maybe addressed inadequately?

 

PS: I highly esteem your contributions to this site, so, please do not take this comment in a negative way

[carusoam]

Great work Ulysse I can understand your writing really well.  

I’m sure Skip will too…

Best regards,

-a-

[PT20J]

13 minutes ago, Ulysse said:

 

It is maybe my poor understanding of English, so pardon me but aren't these 2 statements contradictory? On one hand you seem to point out a fundamental hardware problem and the risk of fixing it with software, and in the other hand you are confident in installing it in your aircraft although there are pending issues which are maybe addressed inadequately?

 

PS: I highly esteem your contributions to this site, so, please do not take this comment in a negative way

It’s very common to fix hardware deficiencies with software in modern systems where much if the behavior is under software control. It’s faster and less expensive and often more convenient for the customer since it’s usually easier to download a software patch than swap out hardware. I merely meant to point out that the approach is an indirect solution to a problem and requires careful consideration of all factors and thorough testing.

We wish the products we pay so much money for, and bet our lives on, were perfect, but they are not. Look at how often Microsoft or Apple patch their software. 

So, once one accepts the fact that all products are imperfect to some extent, it becomes a matter of who do you trust to fix the problems once they are discovered. I just think that Garmin is likely to be able to maintain its products better than some other vendors.

Skip

[jamesm]

if your are a Hardware guy you would say "I am a Hardware guy stuck in a Software world" and of course if you are Software guy would say "I am a Software guy stuck in a Hardware world" 

Were you able to determine the cause of your AP disconnects ?

I don't know about the G3X touch and G5 configuration, but the 2 G5's that I have installed has data logging ability and creates CSV (Comma Separated Value ) file on a micro SD card provided the G5 configuration is enabled.  If recall correctly it is disable on the G5's configuration you have go into setup to enable the feature.  I believe someone has already posted a sample of the a CSV file in earlier post.

Hope this helps,

 

James

[Ulysse]

Yes, the data was actually stored in my g3x card, not in the g5

Every time the AP disconnects I see the following  error in both the "Autopilot State" and "Yaw damper State" columns:
Fail/Attitude comparator/00002004 00001000

Any clue in what the source of the error could be?

[Ulysse]

[dzeleski]

Does your g3x match your g5 in attitude exactly?

Ask you installer to check the calibration within the GMC-507 (the control unit for the AP) there is a 3rd AHRS unit in it that is used as a 3rd comparison. If not calibrated correctly it will kick the AP off due to it reading bad data between the units.

[carusoam]

Great insight DZel!

Thanks for sharing that…

Best regards,

-a-

[Ulysse]

7 minutes ago, dzeleski said:

Does your g3x match your g5 in attitude exactly?

Interesting! They actually do not. The g3x is off by more than 1/2 deg pitch (almost 1 deg) compared to the g5. 

But then, why doesn't it disconnect much earlier in the flight?

[Tom 4536]

9 hours ago, dzeleski said:

Does your g3x match your g5 in attitude exactly?

Ask you installer to check the calibration within the GMC-507 (the control unit for the AP) there is a 3rd AHRS unit in it that is used as a 3rd comparison. If not calibrated correctly it will kick the AP off due to it reading bad data between the units.

Does that AHRS problem exist only when you have the g3x? I ask, because 2 avionics installers and Garmin have not been able to find out why my new GFC500 keeps disconnecting every 15 minutes. I don't have YD. I don't have a g3x.  I have a GTX 345 that I believe has AHRS and I have a GI275 AI with AHRS. Could my problem be that the 2 AHRS's don't agree? My avionics shop tried a different 507 but the problem still exists. Thank you.

Tom

[dzeleski]

10 hours ago, Ulysse said:

Interesting! They actually do not. The g3x is off by more than 1/2 deg pitch (almost 1 deg) compared to the g5. 

But then, why doesn't it disconnect much earlier in the flight?

My G5’s are identical.

It’s possible all 3 of yours are off by a bit. It takes awhile but eventually the AP doesn’t like something and kicks off. From what I understand the gfc500 is made to be overly cautious (makes sense tbh) if it sees anything outside of very strict boundaries it kicks off.

I would start asking your installer to confirm all 3 calibrations are set correctly or have them re do all 3 so they match.

34 minutes ago, Tom 4536 said:

Does that AHRS problem exist only when you have the g3x? I ask, because 2 avionics installers and Garmin have not been able to find out why my new GFC500 keeps disconnecting every 15 minutes. I don't have YD. I don't have a g3x.  I have a GTX 345 that I believe has AHRS and I have a GI275 AI with AHRS. Could my problem be that the 2 AHRS's don't agree? My avionics shop tried a different 507 but the problem still exists. Thank you.

Tom

Keep in mind I’m not an avionics installer. I just happen to have had this conversation with my shop a few days ago when discussing things around my install.

I would ask if the 507 was actually calibrated, if a new one was installed but not calibrated you are in the same spot. I would think if garmin was involved this would’ve been gone over but who knows.

Pretty sure your gtx AHRS has nothing to do with it, it’s separate and not used for the AP.

No it matters for all GFC500 installs. They all need to be calibrated together from what I understand at least.

[carusoam]

Garmin’s person that can be conversationally helpful for this discussion is Trek Lawler…

He is big G’s social media guy…

Address here is @TrekLawler but most often found at BT.

Best regards,

-a-

[PilotX]

12 hours ago, Ulysse said:

Here is what I see when I get the YD disconnect (appears to be the same code). I think the YD is fighting the electric rudder trim setting. Since it centers the ball, there is no indication, in the cockpit, that they YD is doing anything or more specifically competing with the rudder trim. I think a technique readjustment, on my part, is in order. YD off until cruise or at least until cruise climb, center then YD. Then in cruise recenter with electric pitch trim, then reengage the YD.

 

[PT20J]

I don't believe that the G5 and G3X being slightly misaligned should cause a disconnect. Most of the autopilot logic is contained in the ADI. In  a G3X/G5/GFC 500 installation, either the G3X is controlling the servos or the G5 is controlling the servos, but not both at the same time. You can turn either ADI off and run the autopilot off the other which is a cool backup feature. The GMC 507 Mode Controller contains it's own attitude sensors that provide system monitoring functions. So, some sort of miscompare between the active ADI and the GMC 507 would be an issue. Pretty much anything that an autopilot monitoring logic detects as an issue results in a disconnect. 

Skip

[Davidv]

On 6/25/2021 at 10:51 PM, Ulysse said:

Interesting! They actually do not. The g3x is off by more than 1/2 deg pitch (almost 1 deg) compared to the g5. 

But then, why doesn't it disconnect much earlier in the flight?

You should get a yellow “ATT MISCOMP” warning on the G3X if they are truly out of sync…(I believe)

[Ulysse]

8 hours ago, PT20J said:

You can turn either ADI off and run the autopilot off the other which is a cool backup feature

So, since the g3x pitch is off by almost 1 deg, I could switch it off and fly with the g5 and see if the autopilot still disconnects ? I am so frustrated that I am currently traveling and will not be able to test anything before many weeks.

[PT20J]

5 hours ago, Ulysse said:

So, since the g3x pitch is off by almost 1 deg, I could switch it off and fly with the g5 and see if the autopilot still disconnects ? I am so frustrated that I am currently traveling and will not be able to test anything before many weeks.

I would certainly try that. If you switch off the G3X and fly on the G5 you are now using the autopilot logic in the G5. If it still disconnects then it says that it's not the G3X or G5 and that narrows it down to the servos or GMC 507. I would try it with the YD off and see if that solves it since that seems to be a known issue. If not, I'd try to get the GMC 507 replaced. 

[PT20J]

I reread @Davidv post above and looked this up in the G3X Pilot’s Guide and it creates a new wrinkle. Apparently, the ADAHRS source for the G3X can be set to AUTO in which case it will compare the GSU 25D with the G5 and report miscompares and give an annunciation. The system I have been flying to gain familiarity (my airplane won’t going in for installation until August) is in a c-172. I did verify that the GFC 500 will work with either the G3X or G5 powered down. I never got miscompare annunciations in either case. I don’t know if the G3X ADAHRS selection was set to AUTO, and I don’t know how to tell or where this gets set.

Skip

[PT20J]

Here is Garmin's description of COMPARISON ALERTS from the G3X Pilot’s Guide. This seems to have been written by a software engineer because it shows the typical error trap response: throw up a cryptic message and leave it to the human to determine what to do. So, if you get an attitude miscompare between the G3X and G5 in IMC you’re screwed because you are supposed to somehow figure out which ADAHRS is good and switch to it by some method that I cannot find in the manual anywhere. I really think one needs a third attitude source as a tie breaker.  Maybe the GTX 345 Bluetoothed to an iPad is enough, since it is independent UNLESS it’s possible that the source of the error is the GPS common to all three. I’ve got lots of panel space available. I may just keep the vacuum system and put in a vacuum attitude indicator which would be less expensive than other solutions.

[jamesm]

Interesting I am getting the same fault on a  '67 M20C with two 2 G5's with  GFC 500  that has 2 servo's and  stab trim servo installation.

Does yours happen right at take off ?  I have some right at take off and others failed when I am in the air.

I   have reset the breakers for the GAD and autopilot and trim that works sometimes but not last time.  This  before take I took it to the Installer.

Fail / Attitude comparator / 00002004 00001000

I also have a

Fail / Servo communication fault / 00000035 00000000

fault

The authorized Garmin installer/dealer swapped the G5's and couldn't get it to fail on the ground after they made the swap.

They were  thinking that it could  still possibly  be  in the GMC507  control head unit.

I guess my question to Garmin is:   what is the Autopilot comparing  which Attitude  module(s) ?

as it was point out me Garmin  has  several AHRS modules in various Garmin  products in the aircraft.

I am waiting for schedule to clear so I can fly.

Edited June 28, 2021 by jamesm

[Jim Peace]

I have an old Stec-30 and it works well.....

Just saying....

Time not spent on hold with Garmin is priceless....

[jamesm]

They seemed to have changed their customer service model within last year year and half. I was really surprised to hear that a Garmin installer that I have heard of was having the same problem getting support. It my understanding that these Garmin dealers a pay premium to be  a dealership to get virtually no support or valuable information.

[PT20J]

38 minutes ago, jamesm said:

They seemed to have changed their customer service model within last year year and half. I was really surprised to hear that a Garmin installer that I have heard of was having the same problem getting support. It my understanding that these Garmin dealers a pay premium to be  a dealership to get virtually no support or valuable information.

My dealer told me they get the same tech support we get when we call and wait on hold just as long. The dealers apparently can get an issue escalated to a higher level more easily, however.

Skip

[201Mooniac]

I was with my installer about 2 months ago when there was a software issue and he dialed a "Dealer specific" support phone number to get to a support person and within about 2 mins was connected to someone, that was much easier than I've gotten connected to anyone.

[Tom 4536]

On 6/12/2021 at 11:56 AM, Tom 4536 said:

Today was my first flight with my new GFC500. I have 275s. No YD. Throughout the flight the autopilot kept disconnecting after 15 minutes. I could restart it after 5 minutes. It happened in HDG, NAV and climb modes. It disconnected at some intersections but not all. The command bars were visible when the AP disconnected.

An update on my GFC 500 disconnect problem. My avionics shop replaced each GFC 500 component, one at a time, and checked all the wire connections and it did not solve the problem. Garmin recommended a “Factory Reset” of the GFC 500 and my three previously installed GI275s. It solved the problem but meant everything had to be re-calibrated. My avionics shop had promised to work on the problem until the autopilot worked and they kept their promise.