VNAV on GFC500 Autopilot not working - suggestions?

[201Steve]

1 minute ago, Ragsf15e said:

What cdi did you have up on the arc?

GPS guidance to the G5, then it auto swiitches just prior to the loc course, but doesn’t auto slew. 

[Ragsf15e]

11 minutes ago, 201Steve said:

GPS guidance to the G5, then it auto swiitches just prior to the loc course, but doesn’t auto slew. 

Interesting. You’ve obviously got smart guys looking at it, maybe @PT20J could comment too though?  Seems that he knows more about the gfc500 and g3x than Garmin does at times.

[PT20J]

Make sure that the GTN is not in OBS mode.

Since the auto switching from GPS to LOC occurs, the GTN appears to be working properly. If the G5 HSI isn't autoslewing, it might be a misconfiguration of some sort. I'd have the dealer figure it out.

[201Steve]

Well, I've resolved the auto-slewing mystery. I hit the ILS for 6 laps on each navigator (650 and 430) and the G5 HSI auto-slewed to the final approach course during the auto switch from GPS to LOC. What did I do differently? I have no idea, but I could not get it to not auto-slew so, there you have it. I did figure out that APR mode puts the localizer (along with the GS) into standby mode, so you do not need to reactivate the autopilot into nav mode after it switches. I was previously under the impression that APR mode only qued up the GS, but it qill que up the switch for the autopilot from GPS to LOC and the GS. Good to know.

 

Back to the VNAV, for a final review. Maybe with pics someone can see something I don't. Otherwise, I believe the GTN is doing it's job, but either the Autopilot or the G5 (or both) is not. Will have to have the dealer figure that one out.

Here you can see the route. I am at 2,700' and would like to be at 1,700' crossing BERTT (the iaf for ILS7 at BQK). Well before TOD, plenty of room to loose the 1,000'.

The GTN appears to know what we are trying to do in the preview:

 

But the G5 will not show a Vertical nav card, and the button on the AP head will not engage.

 

 

 

 

 

[carusoam]

Let’s see if a fresh pair of eyes can help….

I can invite @midlifeflyer and see if he is around…. (GTN, G5, and GFC quirky behavior…)

Best regards,

-a-

[midlifeflyer]

15 hours ago, carusoam said:

Let’s see if a fresh pair of eyes can help….

I can invite @midlifeflyer and see if he is around…. (GTN, G5, and GFC quirky behavior…)

Best regards,

-a-

Weird. I thought I respond earlier but it's not showing up.

What specifically might be wrong is above my pay grade.  And I always find it hard to troubleshoot without being there - I'm not that good. 

But off the top of my head, In addition to not getting a vertical path indicator, I do notice that the "scoreboard" on the G5 does not show VNV armed (white) or engaged (green), which should be happening when pressing the VNV button on the GFC500 if they are communicating. Whether it's a misconfiguration, installation error, or an earlier G5 software release which didn't support VNAV, I haven't a clue.

Edited August 22, 2022 by midlifeflyer

[201Steve]

@midlifeflyer thanks, yeah it’s my assumption at this point that it’s just not configured correctly.  All the updates should be well within capability. the autopilot head is not communicating the desire to arm vnav to the g5 or otherwise, the g5 isn’t receiving the message. 
I’m going to take a trip to the shop.  Thank you for the feedback.  

 

[carusoam]

Good call @midlifeflyer!

 

We have all the big guns on this thread!

Go MS!

Best regards,

-a-

[201Steve]

Heading to the radio shop in the morning. Will advise the resolution. 

[201Steve]

CCF08312022.pdfArinc 429 data selection in the G5 configuration was set to the wrong field. 
 

this has resolved the issue. 

[carusoam]

Great follow-up Steve!

Thanks for sharing the detail.

+1 for @midlifeflyer’s input from a few states away…

Best regards,

-a-

[TommyFlies]

This was a great thread! I'm having the exact same issue in my airplane. I called the avionics shop to explain the issue and, after some digging, they called me back and had we switch ARNIC 429 to Garmin 429. I haven't had a chance to fly the airplane to test it yet but this thread has me pretty hopeful. 

For reference:
- 1965 M20E
- Dual G5's
- GTN750
- GFC500

[201Steve]

It took the shop 3 test flights telling me good to go until this config was fixed. Goes to show, there are a bunch of little tiny details to follow to make it all simpatico. Good luck and glad it helped! Too many threads leave the outcome unknown, so I try to add in the findings later for this reason.