Gfc500 disconnect

[Ulysse]

I have a gfc500 + gtn7t0xi +g5 + g3x

I am having many AP disconnection issues. I have been able to repeat at least one instance: every time there is an important change in heading from one leg to the other, the AP disconnects.

Is this a normal behavior? 

 

 

[ArtVandelay]

I believe this is a known issue, some thought it might be only for those with YD servos.

Garmin is reportedly working on a software fix.

[Ulysse]

3 minutes ago, ArtVandelay said:

some thought it might be only for those with YD servos.

yes I have YD also

[dzeleski]

What mode are you in? NAV? My install is less then 10 hours old but I have not had this happen. What steps are you using to get it to reproduce?

Definitely not normal though.

[201Mooniac]

I have 250 hours on my install (with YD) with no disconnects at all in any condition including moderate turbulence and turns greater than 90 degrees.  I would say it is most definitely not normal behavior.  It would be best to put a micro SD card in the G5 and collect the logs for Garmin to examine.

[StevenL757]

5 hours ago, Ulysse said:

I have a gfc500 + gtn7t0xi +g5 + g3x

I am having many AP disconnection issues. I have been able to repeat at least one instance: every time there is an important change in heading from one leg to the other, the AP disconnects.

Is this a normal behavior? 

Nearly 75 hours into my install, and not a single glitch.  A few questions…

• Is your YD engaged when you’ve experienced the anomaly?
• Which roll mode are you typically in when it disconnects…NAV or HDG SEL?
• Are there any messages on the FMA (Flight Mode Annunciator, or “scoreboard”…either on the G3X and/or the G5) when you experience a disconnect?
• Is the problem happening at every waypoint/fix/intersection/navaid change, or just some?

Steve

[ArtVandelay]

yes I have YD also

Okay then this is a known issue, I would call Garmin support


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[M20C_AV8R]

Sounds oddly familiar, I had the GfC 500 installed this spring, when I picked up the plane and did my first use test, no issue with altitude climb, hold etc, however as soon as I reached any Nav point that was annunciated, the GFC 500 would go automatically into TOGA mode. I talked with Garmin support and told them I either need their assistance or to call a Priest.  It made no sense and had a mind of its own. Garmin had nothing for me other than to escalate internally and wait, however, I called my installer and explained what was going on, they talked with Garmin and quickly figured out that the instructions for one of the pin outs and a configuration in the GTN 650 was causing this, took the plane back a few days later, took an hour or two to fix it, and all is well now. The point is, work with your installer/dealer, they get to work with Garmin in a way we do not, and if your installer is pushing you off onto Garmin, then that is a different discussion. Hope you get it sorted soon, this AP is amazing.

[carusoam]

There was an early report when installations started occurring...

Make sure the controls get cleaned and lubricated... for smooth operation...

Best regards,

-a-

[Ulysse]

19 hours ago, ArtVandelay said:

Okay then this is a known issue

So this is a known issue but not all units are concerned. I am not sure if those who do not have any issues also have YD? is the problem due to poor installation? Faulty component?

On 6/11/2021 at 4:15 PM, dzeleski said:

What mode are you in? NAV?

 

21 hours ago, StevenL757 said:

A few questions…

It happens in different situations:

- Level flight, NAV mode, turn >90°

- HDG mode, straight IAS climb. Random disconnect during the climb

11 hours ago, M20C_AV8R said:

The point is, work with your installer/dealer

My installer is in another continent ...

I hope to get support from a local Garmin dealer

21 hours ago, 201Mooniac said:

 It would be best to put a micro SD card in the G5

How do you for that? I have a micro SD in the G5 but nothing gets written in it. Do you have to activate logging somewhere?

[Tom 4536]

3 hours ago, Ulysse said:

So this is a known issue but not all units are concerned. I am not sure if those who do not have any issues also have YD? is the problem due to poor installation? Faulty component?

 

It happens in different situations:

- Level flight, NAV mode, turn >90°

- HDG mode, straight IAS climb. Random disconnect during the climb

My installer is in another continent ...

I hope to get support from a local Garmin dealer

How do you for that? I have a micro SD in the G5 but nothing gets written in it. Do you have to activate logging somewhere?

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.

[201Mooniac]

On 6/12/2021 at 7:54 AM, Ulysse said:

So this is a known issue but not all units are concerned. I am not sure if those who do not have any issues also have YD? is the problem due to poor installation? Faulty component?

I do not have the issue and I have the YD so it isn't a function of YD.

On 6/12/2021 at 7:54 AM, Ulysse said:

How do you for that? I have a micro SD in the G5 but nothing gets written in it. Do you have to activate logging somewhere?

 

If you boot into config mode, on the device information page you should be able to enable Diagnostics/Data Logging.

[Tom 4536]

12 hours ago, 201Mooniac said:

I do not have the issue and I have the YD so it isn't a function of YD.

If you boot into config mode, on the device information page you should be able to enable Diagnostics/Data Logging.

Can the GI 275 log the error data?

[PilotX]

The GI275 logs tons of data. I was looking at my logs from the flight where I first experienced the FD pitching the plane 5deg up and GA annunciating. Getting to it is another matter. My GI275 keeps destroying thumb drives.

 

[carusoam]

That looks like more fun than a roller coaster at Universal! 

Yikes!

Great data set. Thanks for sharing it…

Best regards,

-a-

[Ulysse]

On 6/14/2021 at 4:40 AM, 201Mooniac said:

Quote

If you boot into config mode, on the device information page

Thank you. I am unfortunately traveling now, but I'll try that as soon as I return

[Tom 4536]

11 hours ago, PilotX said:

The GI275 logs tons of data. I was looking at my logs from the flight where I first experienced the FD pitching the plane 5deg up and GA annunciating. Getting to it is another matter. My GI275 keeps destroying thumb drives.

 

Does the data logged include what triggered the AP disconnect?

[PilotX]

18 minutes ago, Tom 4536 said:

Does the data logged include what triggered the AP disconnect?

There are so many fields that are logged and I haven't been through them all. I was trying to isolate the reason the FD when into uncommanded GA mode. The AP disconnected when I pushed the button (but no disconnect tone) - trying to see if there was a trigger that put it into GA, I was enroute between points, no procedure was loaded. It was disconcerting because me and my PNF (17 year old voice activated AP) had the seats all the way against the stops to the rear to stretch our legs for a minute. Fortunately it was CAVU.

[Tom 4536]

Just now, PilotX said:

There are so many fields that are logged and I haven't been through them all. I was trying to isolate the reason the FD when into uncommanded GA mode. The AP disconnected when I pushed the button (but no disconnect tone) - trying to see if there was a trigger that put it into GA, I was enroute between points, no procedure was loaded. It was disconcerting because me and my PNF (17 year old voice activated AP) had the seats all the way against the stops to the rear to stretch our legs for a minutes. Fortunately it was CAVU.

Interesting! I noticed at the time of one disconnect that the command bars were at about 45 degrees and the wings were level in HDG mode.

[Rmag]

I have a Garmin dealership, I have experienced this problem. It is the Yaw Damper. It is not an install problem, it is a software problem that will be fixed later this year. 

Garmin’s response to me was, “What has happened in short, is when the units are built they’re using surface mount components that have tolerances to them just as any component does. With the software tolerance being so tight and these components ranging we’re running into random disconnects like this especially with the Yaw damp servos in these systems which is why it will fly perfectly with it not engaged.”

This is why you will have some but not all people experiencing this. I have been flying with the YD off and have never had disconnects since.

[PT20J]

21 minutes ago, Rmag said:

I have a Garmin dealership, I have experienced this problem. It is the Yaw Damper. It is not an install problem, it is a software problem that will be fixed later this year. 

Garmin’s response to me was, “What has happened in short, is when the units are built they’re using surface mount components that have tolerances to them just as any component does. With the software tolerance being so tight and these components ranging we’re running into random disconnects like this especially with the Yaw damp servos in these systems which is why it will fly perfectly with it not engaged.”

This is why you will have some but not all people experiencing this. I have been flying with the YD off and have never had disconnects since.

Thanks. It’s kind of a strange explanation. Both surface mount and through hole components have tolerances and it should make no difference how the PCBs are manufactured. Having designed many such systems, I suspect that the worst case tolerance build up in some critical circuit was not adequately considered in the design. It’s a hardware problem that will get a software workaround because that’s a whole lot cheaper than redesigning and retrofitting the hardware. But, it’s tricky because a software “fix” for a hardware problem can introduce other issues since you are forced to address the symptom but not the root cause. The software patch has to be very thoroughly tested. There’s an old engineering axiom that goes: There is no such thing as a single change.

I talked to my Garmin dealer about this yesterday and they didn’t know about it although they have installed many GFC 500s. Apparently Garmin doesn’t give its dealers a heads up about known issues unless they specifically run into a problem.

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[Tom 4536]

52 minutes ago, Rmag said:

I have a Garmin dealership, I have experienced this problem. It is the Yaw Damper. It is not an install problem, it is a software problem that will be fixed later this year. 

Garmin’s response to me was, “What has happened in short, is when the units are built they’re using surface mount components that have tolerances to them just as any component does. With the software tolerance being so tight and these components ranging we’re running into random disconnects like this especially with the Yaw damp servos in these systems which is why it will fly perfectly with it not engaged.”

This is why you will have some but not all people experiencing this. I have been flying with the YD off and have never had disconnects since.

I don't have the YD and I get the disconnect.

[PT20J]

2 hours ago, Tom 4536 said:

I don't have the YD and I get the disconnect.

It may not be the same problem. In complex systems, there are often multiple issues that can precipitate the same result. The standard response for any autopilot when it gets confused is to disconnect. This is a safety measure to prevent the autopilot for driving the aircraft outside the safe envelope. 

By the way, this is why it is a good idea to keep your hand lightly on the yoke when the autopilot is flying in any critical situation such as low altitude or during an approach. If it does something wonky or disconnects you are "in the loop" to take control immediately and prevent an excursion.

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[PilotX]

Pulled up the log file that I downloaded from the EIS. You can see where the GFC500 uncommanded GA  and the resultant pitch rates. The csv doesn't play nice on my Mac but there is more information than I know what to do with. 

They are troubleshooting found a chafed wire (install issues - I told them where I wanted the TO/GA button and they wrapped it but it might have rubbed through), we are going to fly again shortly. 

 

[PT20J]

All this actually makes me more comfortable with my decision to schedule a GFC 500 installation. The autopilot is the most complex system on the airplane. It's part mechanical, part analog, part digital and a lot of software. I would expect issues when it first gets out into the field and meets the real world of old airplanes. And, I'm not too concerned that the tech support people we talk to don't have all the answers. I've run tech support. No one puts skilled design engineers at a desk answering a phone (they usually hate talking to customers anyway and will sometimes embarrassingly let the customer know that).

So, I expect problems. The important thing is how well the company addresses them. Given that Garmin has the capability to design an autonomous landing system, I'm pretty confident that they have a lot of depth in the engineering ranks to solve any issue that arises. I'm not at all confident that I'd get the same support from B-K if I bought an Aerocruz.

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