GFC500 problem

[rbp]

The latest is that Garmin is looking for a J or K model that is having this issue to bring into the factory for testing. 

[ArtVandelay]

The latest is that Garmin is looking for a J or K model that is having this issue to bring into the factory for testing. 

And the factory is where?

[PeytonM]

Olathe, KS

[Marc Taylor]

Rather surprised on several references to the first flight after their avionics upgrade.  The technician that did the first upgrade was in the right seat when we flew after the upgrade, which included several approaches.  Following the most recent upgrade, (different shop, the first tech went to work for a known avionics manufacturer and closed his shop) the current avionics shop of choice for me had a Mooney experienced pilot fly the plane for about 1.5 hours.  Prior to picking the plane up, the shop owner told me to expect to fly with him before they released the Mooney.  About another 1.5 hours, demonstrating what the new avionics capabilities are.  The technician that did the installation has 15 years as Mooney technician.  The install was on time and on estimate.  This link is from AvWeb regarding retro’s.  

https://www.avweb.com/ownership/retrofit-checklists-test-flying-familiarity/

[PeytonM]

Can you believe 1 YEAR has passed since the first posting of oscillation issues with the GFC500?? 

The posting has gone silent, so I wonder if I’m the only one still having this issue. I have over 180 hours since installation April, 2022. All of my friends comment on the oscillation; one nicknamed my plane “Flipper;” you remember the show from the 60s, dolphin swimming…

Saddest of all, Mary finds the oscillation so uncomfortable, she’s done with anything longer than about half an hour in the Mooney. 
 

Fly safe. 

[kortopates]

56 minutes ago, PeytonM said:

Can you believe 1 YEAR has passed since the first posting of oscillation issues with the GFC500?? 

The posting has gone silent, so I wonder if I’m the only one still having this issue. I have over 180 hours since installation April, 2022. All of my friends comment on the oscillation; one nicknamed my plane “Flipper;” you remember the show from the 60s, dolphin swimming…

Saddest of all, Mary finds the oscillation so uncomfortable, she’s done with anything longer than about half an hour in the Mooney. 
 

Fly safe. 

I feel for you, that's pretty much why I upgraded to the GFC-500 but for a slight but noticeable porposing with the King KFC-150 AP.

If you've down all you can to make sure the trim system is fully lubricated from cockpit to tail, I'd be scheduling a flight to Kansas to get them to resolve the issue; especially given how bad it is. They're not that far from Il at Mooney speeds!

[PeytonM]

Mooney sent a Baron-full of experts to my installer’s airport a few months ago, went spinner to tail  and found nothing. Last I heard, Garmin is looking for a J/K to troubleshoot. (I was unwilling to give up my plane for a month or…regardless of what they’d offer me.)

[natdm]

I'm willing to lend them mine if they need practice installing and troubleshooting a GFC500.. It'll cost them one GFC500 :-D

[donkaye]

On 4/26/2023 at 8:58 AM, PeytonM said:

Mooney sent a Baron-full of experts to my installer’s airport a few months ago, went spinner to tail  and found nothing. Last I heard, Garmin is looking for a J/K to troubleshoot. (I was unwilling to give up my plane for a month or…regardless of what they’d offer me.)

You'd rather your wife not fly with you forever, and oscillate with the plane yourself than give up the plane for a month and get the problem resolved?

[PeytonM]

Garmin has their own J. 

[rbp]

Mine still oscillates in IAS mode, but only if I touch the thumbwheel. If I set it to climb with VS, then switch to IAS, it will hold the airspeed. If I adjust the hold IAS, it will oscillate. Garmin knows about this, and they are waiting for a J/K to bring to Olathe to test. I don't know what else to do but wait

 

people are still reporting it 
https://www.facebook.com/groups/833963897818892/posts/926741995207748/

 

[donkaye]

1 hour ago, PeytonM said:

Garmin has their own J. 

Unfortunately, each plane has their own idiosyncrasies.

[PeytonM]

That’s great news!!!

[PT20J]

This is a perplexing problem. I understand how frustrated those are that have it, but having been in product development for my entire career, I also understand why it has been hard to solve. First, the vast majority of installations do not oscillate. Trek told me that most of the ones that have problems are due to installation issues or airframe issues and once the root cause is determined they work fine. I had a slight oscillation in IAS that was corrected by re-tensioning the pitch servo bridle cable. 

However it seems that there are some hard cases where everything appears to be in spec and yet the problems persist. I'm sure this is why Garmin wanted to find an example to examine. Unless you can reproduce the problem, you are just guessing and trying things. And, even if you can reproduce the problem, it may take special software that is instrumented with more data collection than the production build to determine the root cause and proper fix. Remember that this is a closed loop control system and the fact of feedback can mask issues. 

If Garmin in fact has an aberrant airplane to work with, they should be able to figure this out. I think we can see now why there are not a lot of companies certifying new autopilots. It is not a simple product to make work with a fleet of aged airplanes. 

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[LANCECASPER]

17 hours ago, PeytonM said:

Garmin has their own J. 

They have an Ovation. I'm not aware of a J that they own. What is the tail number?

[PeytonM]

Don’t know. They have both. 

[rbp]

11 hours ago, PT20J said:

However it seems that there are some hard cases where everything appears to be in spec and yet the problems persist. I'm sure this is why Garmin wanted to find an example to examine. Unless you can reproduce the problem, you are just guessing and trying things. And, even if you can reproduce the problem, it may take special software that is instrumented with more data collection than the production build to determine the root cause and proper fix. Remember that this is a closed loop control system and the fact of feedback can mask issues. 

If Garmin in fact has an aberrant airplane to work with, they should be able to figure this out. I think we can see now why there are not a lot of companies certifying new autopilots. It is not a simple product to make work with a fleet of aged airplanes. 

 

My A&P spent 12 shop hours going over every recommendation made by Garmin to flush out any airfare issues. 

I offered up my plane, but they wouldn't take it because its not a J/K

[PT20J]

35 minutes ago, rbp said:

I offered up my plane, but they wouldn't take it because its not a J/K

Did they explain why? I wonder if most of the problems have been with J and K models?

According to the FAA aircraft registry, Garmin International owns N430G (M20R) and N5272K (M20J).

[EricJ]

I don't think this has to do with aging airplanes as much as Garmin is doing something different than most autopilots.    Many aging Mooneys fly very stable with aging autopilots, and then seem to have this issue with the GFC500.    My 77 M20J was very solid with the Century III when it was working.    I miss it. 
 

 

[kortopates]

I don't think this has to do with aging airplanes as much as Garmin is doing something different than most autopilots.    Many aging Mooneys fly very stable with aging autopilots, and then seem to have this issue with the GFC500.    My 77 M20J was very solid with the Century III when it was working.    I miss it. 
 
 

What are you thinking is different with Garmin AP’s?
Most autopilots installed by Mooney where the BK variety which Garmin pretty much copied for their installation. Your Century was the exception. Quite possibly the BK might of performed better if they used the pushrods install method that Century did. But BK still had the superior performance.
Given many porpoising issues where fixed by better lubrication of the pitch controls it seems control stiffness and free play could be a factor.


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[rbp]

1 minute ago, kortopates said:

What are you thinking is different with Garmin AP’s?

Garmins have pitot pressure input, which other do not. its primary for IAS mode, but who knows how it is used in other modes

[ArtVandelay]

Can you believe 1 YEAR has passed since the first posting of oscillation issues with the GFC500?? 
The posting has gone silent, so I wonder if I’m the only one still having this issue. I have over 180 hours since installation April, 2022. All of my friends comment on the oscillation; one nicknamed my plane “Flipper;” you remember the show from the 60s, dolphin swimming…
Saddest of all, Mary finds the oscillation so uncomfortable, she’s done with anything longer than about half an hour in the Mooney. 
 
Fly safe. 

Does it always do it, or like @rbp it oscillates after using the thumb wheel?

[kortopates]

Garmins have pitot pressure input, which other do not. its primary for IAS mode, but who knows how it is used in other modes

True, but that’s a mode most others didn’t support and my BK KFC-150 didn’t support it till it was driven by my Garmin GAD-43e, using pitot. Do any support IAS or FLC without pitot?


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[EricJ]

9 minutes ago, kortopates said:

What are you thinking is different with Garmin AP’s?
Most autopilots installed by Mooney where the BK variety which Garmin pretty much copied for their installation. Your Century was the exception. Quite possibly the BK might of performed better if they used the pushrods install method that Century did. But BK still had the superior performance.
Given many porpoising issues where fixed by better lubrication of the pitch controls it seems control stiffness and free play could be a factor.

Everything could be different.   Because their system is software based they can do all kinds of things that aren't done in other autopilots.   It'd be tougher to assume that two systems from two sources are the same than that they're different.

They could be doing an entirely different type of control system (P, PI, PID, PD, varying orders, etc.), they could be doing adaptive control, they could do clever strategies to fuse inputs from air data, AHRS, GPS, etc., etc.    Whatever they're doing, it's not working as well on some of the same airplanes as some other autopilots.

Their servos seem to have issues across all types of airplanes.   It could still be related to their servos, who knows?

[PT20J]

The KAP/KFC 150 was digital with a microprocessor and thus software controlled.

The GFC 500 is a distributed system. Some of the software is in the PFD, some is in the servos. Only Garmin knows exactly how it works. I think it was pretty much a clean sheet design. The servos often seem implicated when problems arise. I don't recall such problems with the GFC 600 or GFC 700; does anyone else?

The GFC 500 was originally designed for the experimental market where airplanes are usually smaller with lighter control forces. Curious if anyone has followed the experimental threads to see if they have similar issues?

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