GFC 500 in a PA28-181 - New install problems

In that case, suggest you try Garmin directly. Google "Trek Lawler". He's a Garmin guy who is active on almost every aviation board, except this one. Get on one of the other boards and send him a PM. He can at least point you in the right direction. There just aren't that many possible problems and most of them have been touched on.
- Servo issues on early GFC500's - but it sounds like yours were replaced
- Sensitivity settings - Haven't heard too many folks needing to make adjustments, most fly well out of the box
- Out of rig - Based on your video, you'd have a hard time hand flying the plane if that was the cause
- Sticking yoke/controls - You said that wasn't an issue
- Static leak/kink or other issue. That would explain the porpoising, but not sure about the turns
- Operator error - might explain the weird turn, but not the porpoising.
- Cable tensions and/or servo mounting. cable tension is a classic AP issue

Others with more experience than me can chime in, but I'd ask the shop for their troubleshooting procedure and what specific steps they've taken. My money is on the servo replacement introducing the issue.
 
Michael Rellinger said:
The problem is that the Avionics are still under warranty and I am trying to get Garmin involved with the shop to get this resolved.
They are a Garmin dealer
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Any garmin dealer will honor that warranty. You will have to for the labor though. If I were you, I would try a diff shop
 
Hang 4 said:
In that case, suggest you try Garmin directly. Google "Trek Lawler". He's a Garmin guy who is active on almost every aviation board, except this one. Get on one of the other boards and send him a PM. He can at least point you in the right direction. There just aren't that many possible problems and most of them have been touched on.
- Servo issues on early GFC500's - but it sounds like yours were replaced
- Sensitivity settings - Haven't heard too many folks needing to make adjustments, most fly well out of the box
- Out of rig - Based on your video, you'd have a hard time hand flying the plane if that was the cause
- Sticking yoke/controls - You said that wasn't an issue
- Static leak/kink or other issue. That would explain the porpoising, but not sure about the turns
- Operator error - might explain the weird turn, but not the porpoising.
- Cable tensions and/or servo mounting. cable tension is a classic AP issue

Others with more experience than me can chime in, but I'd ask the shop for their troubleshooting procedure and what specific steps they've taken. My money is on the servo replacement introducing the issue.
Click to expand...
 
To All,

Today I flew and had all the above problems replicated, however when I tried the alternate static port, things got a lot better and it didn't bank over 20 degrees and never overshot any desired course in the Nav mode! We also flew an RNAV approach and it brought us right down to the runway .....Yey !!!
Tomorrow morning we will fly a short Cross Country and see if she holds the altitude.
Keep your fingers crossed that this is the solution to my problem and I will report back tomorrow after the flight!!!
 
When was the pitot static check done? It’s interesting that alternate static helps with not overshooting magenta line.
 
Well so much for that idea, flew today and before we could test again I had many AP abnormal disconnects and AP fail messages as well as Ptrim notice!
Garmin finally called me and now I am going to go back up with my G5 data logging enabled so I can send them the Log file and they can diagnose it from the files!
What a hassle but with Garmin involved now I am sure we will get to the root cause!
By the way my pitot static system was last checked in Aug 2018, so it is due to me checked as well
 
After 3 separate flights and data logging on my G5, yes it will keep a log, I sent all the data to Garmin Support!
They are off tomorrow for the 4th and most likely will not speed to them until Monday.
I will keep this blog posted !!
 
Michael Rellinger said:
After 3 separate flights and data logging on my G5, yes it will keep a log, I sent all the data to Garmin Support!
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If you (this means anyone-you, not just Michael you) have any gadgets in your panel capable of logging data, it's a great idea to make sure they're doing so. Especially engine monitors! So be sure you always have a card in them and have logging turned on. Glass panel displays, engine monitors, you name it.
 
Well all, today Garmin called and told me they are contacting my avionics shop and sending them a new GFC 500 AP head and ask them to essentially do a new setup on the plane!
Waiting for the appointment to get this done and I will let everyone know how it turns out!
 
Michael Rellinger said:
Well all, today Garmin called and told me they are contacting my avionics shop and sending them a new GFC 500 AP head and ask them to essentially do a new setup on the plane!
Waiting for the appointment to get this done and I will let everyone know how it turns out!
Click to expand...

Hmmm. Interesting... When you say "GFC 500 AP head" what exactly do you mean?

The GFC 500 doesn't work like other autopilots, where the brains live inside the control or "head" unit. The GFC 500 system is controlled by the G5 - That's where the brains are. The GMC 507 where the autopilot controls are doesn't contain the brains - GMC stands for Garmin Mode Controller, all it does is tell the G5 which mode(s) you want to be in.

Now I'm really curious as to what they found in the log, and whether it's the GMC 507 or your G5 AI that they're replacing...
 
flyingcheesehead said:
Hmmm. Interesting... When you say "GFC 500 AP head" what exactly do you mean?

The GFC 500 doesn't work like other autopilots, where the brains live inside the control or "head" unit. The GFC 500 system is controlled by the G5 - That's where the brains are. The GMC 507 where the autopilot controls are doesn't contain the brains - GMC stands for Garmin Mode Controller, all it does is tell the G5 which mode(s) you want to be in.

Now I'm really curious as to what they found in the log, and whether it's the GMC 507 or your G5 AI that they're replacing...
Click to expand...

While that is true that the brains are the G5, the GMC507 is not quite just a mode controller. It requires pitch and roll calibration as well as setting yaw offsets, indicating that it has sensors in it as well, which is confirmed by this snippet from the install manual.

Screen Shot 2020-07-07 at 1.29.50 PM.png

So I could see that if that was generating bad info, it could cause some bad behavior.
 
Well I did a 60 mile jump for lunch and all seems well! Looks like Garmin made the correct call and replaced the GMC507 and my avionics shop rebalanced the plane and did a new setup on the G5!
Thanks for all the feedback and suggestions,
Greatly appreciated!
 
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