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GFC 500 wandering off course

jneves

Well Known Member
OK so this has happened 2 times now. , Avionics configuration in my signature. I'm cleared the approach, engage approach mode, start to slow things down. All is fine, GPS switches from TERM to LPV coming down final and then the autopilot starts to turn off track and doesn't return. Both times I had my CFI with me so we were both there to recover and continue the approach hand flown, GPS and G5's agree and are all good with data, track displayed on my Area 660 from the 430W is correct, but the autopilot is not flying the track it should.

I cant figure out why this would happen. Both times we shot another approach shortly after with no issues. I can say the only common thing between the 2 times was that I was getting a bit slow and the pitch of was getting a bit high, I needed to apply power and (I'll admit it) I was a bit uncoordinated. Could this have caused the wandering? Anyone have any input, thoughts, ideas?

Anything from the Garmin Experts on the forum?
 
Johnny,

When you say "the autopilot starts to turn off track and doesn't return", is it accurate to say that it moves off the course line, flies roughly parallel to the course line, but never returns to the course line?

This can be caused by flying uncoordinated. The roll steering guidance calculations performed by the 430W assume a coordinated aircraft, so if you fly without the ball centered, especially with some cross winds, it is not uncommon to end up to one side or the other of the course line.

Try it again with the ball always centered and see if that corrects the issue.

I flew a lot of coupled approaches in an RV-7A for 5 years. That plane took a lot of right rudder, and if I was being lazy and not keeping the ball centered, I would be rewarded with a runway arrival that was off the centerline.

Steve
 
Johnny,

When you say "the autopilot starts to turn off track and doesn't return", is it accurate to say that it moves off the course line, flies roughly parallel to the course line, but never returns to the course line?

This can be caused by flying uncoordinated. The roll steering guidance calculations performed by the 430W assume a coordinated aircraft, so if you fly without the ball centered, especially with some cross winds, it is not uncommon to end up to one side or the other of the course line.

Try it again with the ball always centered and see if that corrects the issue.

I flew a lot of coupled approaches in an RV-7A for 5 years. That plane took a lot of right rudder, and if I was being lazy and not keeping the ball centered, I would be rewarded with a runway arrival that was off the centerline.

Steve

I went back and watched the flight track with my CFI on his iPad. The autopilot started to intercept final, over flew it a bit and turned back to re-intercept and overflew final again. At that point I disconnected and started to hand fly her down. We have flown about 20 approaches together and twice we have seen this happen, the rest were solid all the way down, no issues with holds or procedure turns. As you can see in this screen shot the plane is on final again and you can see the prior track heading straight toward final interception, the over shoot, the return and overshoot again, then my manual turn back onto final approach.

We landed, hand lunch and debriefed, then headed back to home base with an ILS approach and no issues at all. The autopilot has never done anything odd except for these 2 times, 1st one in VMC this last one in IMC. I have no issues hand flying, but this should not be happening randomly IMHO.
 

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Johnny,

You should contact Garmin. They will probably want to see the data log file from the G5.

Where is the max torque set for the roll servo? One possibility is that it barely has enough roll authority to fly the plane well in all conditions, and giving it a little more torque would do the trick.

The data log file should tell Garmin if this is the issue.

Make sure you have enabled data logging and have a micro SD card installed as explained in the Pilot Guide before you fly.

DataLogEnable.png

Steve
 
Johnny,

You should contact Garmin. They will probably want to see the data log file from the G5.

Where is the max torque set for the roll servo? One possibility is that it barely has enough roll authority to fly the plane well in all conditions, and giving it a little more torque would do the trick.

The data log file should tell Garmin if this is the issue.

Make sure you have enabled data logging and have a micro SD card installed as explained in the Pilot Guide before you fly.

View attachment 20789

Steve

I'll dig into the data log setup and make sure I have data captured to share. I do plan to contact Garmin, also planning to swap the 430 for the 650Xi, but really want to understand the issue before I make changes.
 
AP Approach Performance

I'll dig into the data log setup and make sure I have data captured to share. I do plan to contact Garmin, also planning to swap the 430 for the 650Xi, but really want to understand the issue before I make changes.

Johnny,

As Steve mentioned, grab the datalog file off of the microSD card and email it to us, at [email protected]. We'll be able to provide some insight as to what is causing this. The card does have to be in the unit during the flight to record flight data, there is no way to retroactively dump it to a card after the flight. If there was no card in the unit during these flights, you will want to install a card in the G5 and perform a test flight to gather some data for us to analyze.

Thanks,

Justin
 
Johnny,

As Steve mentioned, grab the datalog file off of the microSD card and email it to us, at [email protected]. We'll be able to provide some insight as to what is causing this. The card does have to be in the unit during the flight to record flight data, there is no way to retroactively dump it to a card after the flight. If there was no card in the unit during these flights, you will want to install a card in the G5 and perform a test flight to gather some data for us to analyze.

Thanks,

Justin

Thanks Justin, there was in fact no card in either G5. I'll pick one up today an make sure to get it in for the next flight and then send logs over for review once this happens again.

Question, would I need cards in both G5s or will one or the other suffice?

Thanks for the GREAT support!
 
Datalogging Card

Thanks Justin, there was in fact no card in either G5. I'll pick one up today an make sure to get it in for the next flight and then send logs over for review once this happens again.

Question, would I need cards in both G5s or will one or the other suffice?

Thanks for the GREAT support!

Just 1 card will be sufficient, but its not a bad idea to keep one in each unit at all times. You will need a 32 GB or smaller microSD card.

Thanks,

Justin
 
Scrap the panel and convert to Advanced Flight Systems.

So your suggestion is spend 20K to make this go away..... Thanks but, no thanks. I've flown behind the G5's, AFS and G3X. I'd go G3x way before AFS, that's not the point of this thread.

There is no perfect system, in researching this issue I've read of folks having similar problems regardless of brand, Dynon, AFS, Garmin, EFIS - Avidyne and Garmin GPS, it doesn't matter issues do pop up across the board. I actually read AFS/Dynon systems with all the bells and whistles and no outside avionics brands suffering from Autopilot holding course problems.
 
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