Garmin GFC 500 Autopilot issues

[HIghpockets]

Not sure if I have reported this here before but I had to replace a roll servo due to a bad bearing. The GFC 500 was installed September 2019. Still under warranty part and labor was covered.Servo failed on a flight back from NH to NJ.

[ArtVandelay]

What is the length of Garmin’s warranty?

[FlySafe]

1 hour ago, ArtVandelay said:

What is the length of Garmin’s warranty?

 

On 5/30/2021 at 10:14 AM, Warren said:

Here is the link to the Garmin Warranty Policy

https://www.garmin.com/en-US/legal/aviation-limited-warranty/

The GFC500 is a non-TSO product.  Looks like this means 1 year, 400 hour warranty.

from an earlier post, take care

[HIghpockets]

3 hours ago, FlySafe said:

 

from an earlier post, take care

It'a a 2 year warranty.

[FlySafe]

Thank you for clarifying warranty time

[chan65]

On 5/24/2021 at 7:24 AM, alextstone said:

Garmin should be able to tell what the fault is from data logs.  In my case, I was having the same failure modes due to YD disconnects... Still not fully resolved.  Are you flying a long body?

Sorry, for slow response , no it’s a J , servo replaced but issues still exists , Garmin has had file for over a week, I think the servos are under powered I hope I’m wrong. 2 months with this issue 

[alextstone]

13 hours ago, chan65 said:

Sorry, for slow response , no it’s a J , servo replaced but issues still exists , Garmin has had file for over a week, I think the servos are under powered I hope I’m wrong. 2 months with this issue 

Yes, I suspect that is the case too at least with the YD servo.  I've learned that I must pay careful attention to re-setting the rudder trim in each phase of flight THEN engage the YD on the servo and even with that, I find that it still occasionally adversely disconnects.  

[chan65]

Thought I had posted update,  second servo replaced , and thus far about 10 hours in no issues. 

Servo was bad, replaced with a new one, that one was bad as well ( seems odd ) avionics sad they often use refurbished servos for warranty parts. This time avionics insisted on replacing it with brand new servo. My gut tells me this servos are underpowered and we will see failures between 200-300 hours. I hope I'm wrong and this is behind me, it cost me the whole summer of flying and several trips cancelled.

 

hoping this is behind me,  grateful for my Avionics man 

Edited September 13, 2021 by chan65

[carusoam]

Great follow-up Chan!

There is something going on with a few Garmin servos…

Best regards,

-a-

[ArtVandelay]

I wonder how much resistance is in the trim system when the trim servo is completely disconnected? I know mine has significant resistance (compared to a 172 ) when I use the trim wheel, but I assume that’s because of the electric trim servo.

[carusoam]

There is very little resistance in the trim system….

Older systems use a brake to keep it from changing on its own…

Not sure what the newer systems with an AP use… but the trim wheel moves pretty easily in the M20R…

Kind of amazing with all of the forces acting on the system…

Best regards,

-a-

[tmo]

6 hours ago, carusoam said:

There is very little resistance in the trim system….

The question might have been directed at the planes that have servo failures, with said resistance proposed as a factor contributing to the failures...

[PT20J]

GFC 500 servos have a torque setting (percent maximum) that is part of the STC installation configuration for each airplane. Does anyone happen to know what the values are (pitch, roll, yaw, trim) for Mooneys?

[201Mooniac]

4 hours ago, PT20J said:

GFC 500 servos have a torque setting (percent maximum) that is part of the STC installation configuration for each airplane. Does anyone happen to know what the values are (pitch, roll, yaw, trim) for Mooneys?

For the M20J, Pitch max torque 85%, Roll max torque 90%, Yaw max trim 100%

[PT20J]

Just now, 201Mooniac said:

For the M20J, Pitch max torque 85%, Roll max torque 90%, Yaw max trim 100%

Last part a little confusing: are you saying both yaw and pitch trim are 100%?

[201Mooniac]

3 minutes ago, PT20J said:

Last part a little confusing: are you saying both yaw and pitch trim are 100%?

Sorry, fumble fingers, I meant Yaw max torque is 100%.  It so happens Pitch Trim max torque is also 100%.

[ArtVandelay]

For the M20J, Pitch max torque 85%, Roll max torque 90%, Yaw max trim 100%

I would have expected the pitch 100% for a couple of reasons.
We’ve had some members that had pitch oscillation issues.
Js have springs on the elevators controls.

[PT20J]

32 minutes ago, ArtVandelay said:

I would have expected the pitch 100% for a couple of reasons.
We’ve had some members that had pitch oscillation issues.
Js have springs on the elevators controls.

Actually, they all have springs: Up through the J trim assist bungees were used which provide both up and down springs with with a variable centering connected to the trim system. Starting with the more nose heavy K, bobweights with a variable downspring attached to the trim system were used. But, near the trim point, the springs have little effect.

There are also aileron/rudder interconnect springs.

Two sources of control friction in Mooneys are the control column eyeballs and poorly lubricated trim components.

Skip

[Fly_M20R]

On 9/14/2021 at 8:35 PM, PT20J said:

 

Two sources of control friction in Mooneys are the control column eyeballs and poorly lubricated trim components.

Skip

 I found the same in my 1995 Ovation. By luck I found out that if I trim the elevator to a down position after shut down that the noticeable friction (slight binding) that occurs mid-position on the yoke when you push or pull on it is much less than if I leave the trim in the nose up position which is typical after a landing. Of course, adequate lubrication as Skip states is important in minimizing the friction. Not sure why trimming the pitch down before tying down or hangaring the plane decreases the binding vs leaving it trimmed up. That binding may add extra resistance to the servo and if not up to par in torque may cause it to fail. (???) 

Chris

P.S. I am scheduled to upgrade my panel to add a GTN750Txi and a GFC500 in January and therefore interested in GFC500 experiences.

[Davidv]

Just an FYI for others with the GFC500, after months of troubleshooting some very minor pitch changes in cruise, a Garmin dealer determined that both my Pitch and Roll servo were defective.  They replaced both last week and now everything works perfect.  Don't spend a ton of money troubleshooting this before seeing if the servos are defective.  I'm told this is a big problem and they are replacing a ton of them.

[PT20J]

32 minutes ago, Davidv said:

Just an FYI for others with the GFC500, after months of troubleshooting some very minor pitch changes in cruise, a Garmin dealer determined that both my Pitch and Roll servo were defective.  They replaced both last week and now everything works perfect.  Don't spend a ton of money troubleshooting this before seeing if the servos are defective.  I'm told this is a big problem and they are replacing a ton of them.

There was a range of servo serial numbers that Garmin identified as defective a while back. My dealer says that’s behind them, but who knows? Do you know if yours were from bad batch?

[Niko182]

On the preflight check, my autopilot doesnt turn on anymore. YD and PT work, however AP is crossed out. Any ideas? It started happening a few weeks ago. It always however started properly with the CB being pulled and reset. I thought the AP just wouldn't turn on. Now i realize that it would fail the AP preflight check and cross it out. 

[PT20J]

Could be any number of things. If you have enabled data logging from a G3X or G5 to SD cards, the logs might give a clue.

[PJClark]

On 6/2/2021 at 7:12 AM, chan65 said:

Ran about 3 hours with SD card and sent in for data, it seems to be pointing to the pitch trim servo, the whole system is less than 2 years old , so it will be interesting to see what they come up with 

I just went through exactly this with my G3X/G5/GFC500.  Trim servo was bad, replaced free under 2 year Garmin warranty (free part, I paid labor to diagnose and R2).  Pitch trim servo clutch had failed.

[Ragsf15e]

You guys are doing a great job working out the bugs on these things! My stec been awesome for 8 years, I’m hoping the Garmin servos are eventually that good when I go for the upgrade to the gfc, thanks guys!