1992 M20J Panel Upgrade / Advice

[carusoam]

G hit a really good point… (above)

Check where the steel tubes go…  the center tube turns into an inverted Y…

This is why the audio panel is always at the top of the stack… it is a really short box.

Best regards,

-a-

[Vance Harral]

Internet says GNX375 is 10.85" deep with backshell connectors.  That is definitely not going to fit at the top of an M20J panel as depicted in the OP's layout.  As carusoam says, the center tube that comes down the windshield branches out just below the glareshield, and winds up running behind the left radio stack in a manner that limits the depth of avionics that can be placed at the top of that stack.  You are going to have to put that GNX375 either below the G3X 7" display (if it will fit below it), or over in the right side stack.

[ArtVandelay]

If you’re going with 2nd G3X screen, you don’t need the G5.

[gevertex]

11 hours ago, carusoam said:

gever,

 

What is the estimated time to first flight?

Best regards,

-a-

 

First flight happened already . I've been flying it since mid December 2022.

[graham28105]

Give some thought to where your USB plugs are. The cords are going to get in the way of your access to the a/p.

[Pinecone]

Late to the party, but I would have done a GTN-750Xi and dropped the 7" G3X.

I think you need the G-5 as backup.  There is an upgrade ($$$) to have the 7" screen be a backup PFD with its own AHARS, but it is not cheap.  But then you need to power it separately.

And the G-5 has an internal battery good for 4 hours in case of electrical failure.

Of course, you could put in the 750Xi and also do the 7" G3X, but put it to the right for someone in the right seat to use as MFD or PFD.

 

[gevertex]

8 hours ago, Vance Harral said:

Internet says GNX375 is 10.85" deep with backshell connectors.  That is definitely not going to fit at the top of an M20J panel as depicted in the OP's layout.  As carusoam says, the center tube that comes down the windshield branches out just below the glareshield, and winds up running behind the left radio stack in a manner that limits the depth of avionics that can be placed at the top of that stack.  You are going to have to put that GNX375 either below the G3X 7" display (if it will fit below it), or over in the right side stack.

Thanks for the feedback on this all. Sounds like I have to make an adjustment.

[gevertex]

1 hour ago, Pinecone said:

Late to the party, but I would have done a GTN-750Xi and dropped the 7" G3X.

I think you need the G-5 as backup.  There is an upgrade ($$$) to have the 7" screen be a backup PFD with its own AHARS, but it is not cheap.  But then you need to power it separately.

And the G-5 has an internal battery good for 4 hours in case of electrical failure.

Of course, you could put in the 750Xi and also do the 7" G3X, but put it to the right for someone in the right seat to use as MFD or PFD.

 

As I understand it I need the G5 or GI275 for the GFC 500 anyway. Love the extra backup battery capacity also. I don't have the second air data computer for the 7" so it's just an MFD.

In a perfect world I'd add a 750XI and the second air data computer, but it was just more $ than I was willing to spend at this point. I did want the 7" as I am told it will operate in a reversionary mode as the PFD if the 10" fails. Then I still have full access to the audio panel, radios, etc. I also understood that the G5 will operate as the primary air data computer for the 7" or 10" if the one connected to the G3x fails.

[gevertex]

2 hours ago, graham28105 said:

Give some thought to where your USB plugs are. The cords are going to get in the way of your access to the a/p.

Makes a ton of sense. Any thoughts for where to place it instead?

[Pinecone]

2 hours ago, gevertex said:

As I understand it I need the G5 or GI275 for the GFC 500 anyway. Love the extra backup battery capacity also. I don't have the second air data computer for the 7" so it's just an MFD.

In a perfect world I'd add a 750XI and the second air data computer, but it was just more $ than I was willing to spend at this point. I did want the 7" as I am told it will operate in a reversionary mode as the PFD if the 10" fails. Then I still have full access to the audio panel, radios, etc. I also understood that the G5 will operate as the primary air data computer for the 7" or 10" if the one connected to the G3x fails.

Can you add the second AHRS later?  If so, I would have considered making the wiring setup for that.

Yes, as I understand it, the 7" can be reversion for the 10" failure.

I also am thinking that a 7" can be used by the right seater to fly.  With a 750, they would have nav/MFD handy

Although, I was just looking over at BT and one person put a 7" on the right with second G-5.  I don't think we have the panel space in a Mooney to do that

 

[rbp]

12 hours ago, ArtVandelay said:

If you’re going with 2nd G3X screen, you don’t need the G5.

the second G3X would use the same AHRS, the G5 has its own 

the second G3X does not have its own backup battery, but the G5 has a built-in battery rated for 4 hours

[Pinecone]

You can have the second G3X have its own AHRS.  But at a cost.

[rbp]

4 hours ago, Pinecone said:

You can have the second G3X have its own AHRS.  But at a cost.

I’ve been going on skip’s knowLedge @PT20J is this still true?

[PT20J]

16 minutes ago, rbp said:

I’ve been going on skip’s knowLedge @PT20J is this still true?

To my knowledge, and current Garmin documentation, the G3X Touch certified system permits one GDU installed as a PFD and a second installed as a MFD. Only one GSU 25 ADAHRS is allowed. If either GSU fails, there is a reversionary mode. However, because there is no battery backup and no second ADAHRS, standby instruments are still required.

Skip

[gevertex]

13 hours ago, PT20J said:

To my knowledge, and current Garmin documentation, the G3X Touch certified system permits one GDU installed as a PFD and a second installed as a MFD. Only one GSU 25 ADAHRS is allowed. If either GSU fails, there is a reversionary mode. However, because there is no battery backup and no second ADAHRS, standby instruments are still required.

Skip

Makes sense. Thanks!

[graham28105]

On 1/26/2023 at 10:34 AM, gevertex said:

Makes a ton of sense. Any thoughts for where to place it instead?

I'd probably keep them off the panel entirely. Place them below the throttle controls maybe. Depends on what you're plugging in to them.

[rbp]

On 1/26/2023 at 10:45 PM, PT20J said:

To my knowledge, and current Garmin documentation, the G3X Touch certified system permits one GDU installed as a PFD and a second installed as a MFD. Only one GSU 25 ADAHRS is allowed. If either GSU fails, there is a reversionary mode. However, because there is no battery backup and no second ADAHRS, standby instruments are still required.

Skip

so, I have heard you say this before, and when I went looking for more info, I came up with a few things that contradict this. both of the are taken from "Garmin G3X TouchTM Pilot’s Guide for Certified Aircraft 190-02472-00 Rev. D"

https://static.garmin.com/pumac/190-02472-00_d.pdf

[gevertex]

45 minutes ago, rbp said:

so, I have heard you say this before, and when I went looking for more info, I came up with a few things that contradict this. both of the are taken from "Garmin G3X TouchTM Pilot’s Guide for Certified Aircraft 190-02472-00 Rev. D"

https://static.garmin.com/pumac/190-02472-00_d.pdf

I believe this is showing a backup communication bus not a backup GSU 25. Normally GSU 25 communicates via arnic or canbus afaik. This shows backup RS-232 connection. Does the diagram show a second GSU 25 block?

[gevertex]

1 hour ago, graham28105 said:

I'd probably keep them off the panel entirely. Place them below the throttle controls maybe. Depends on what you're plugging in to them.

Interesting idea. I wonder if they could go where the suction gauge is now. 

[PT20J]

3 hours ago, rbp said:

so, I have heard you say this before, and when I went looking for more info, I came up with a few things that contradict this. both of the are taken from "Garmin G3X TouchTM Pilot’s Guide for Certified Aircraft 190-02472-00 Rev. D"

https://static.garmin.com/pumac/190-02472-00_d.pdf

I believe @gevertex’s explanation is correct. The normal communication path between the GDU and the GSU 25D is CAN bus and the RS-232 is a backup path. 

The single GSU 25D limitation for a certified system is in the installation manual. I don’t have the most current version, but here’s a page from an old one.

As Garmin is wont to say, this doesn’t mean that you cannot do it - it just means that you cannot use their STC as the approval basis. 

[rbp]

I buy that the STC says only one GSU, but what about this? doesn't that mean that if the G3X PFD on there LHS goes and takes the GSU with it, that the G3X on the RHS will go into reversion with the G5's ADAHRS?

definitely needs to be tested 

[PT20J]

1 hour ago, rbp said:

I buy that the STC says only one GSU, but what about this? doesn't that mean that if the G3X PFD on there LHS goes and takes the GSU with it, that the G3X on the RHS will go into reversion with the G5's ADAHRS?

definitely needs to be tested 

I believe it should work as you describe, but I would definitely test it.

[ArtVandelay]

I'd probably keep them off the panel entirely. Place them below the throttle controls maybe. Depends on what you're plugging in to them.

I put 12v outlet on far left, so a short (1’) usb cable keeps things nice and tidy.

[ZuluZulu]

On 1/31/2023 at 6:29 AM, gevertex said:

Interesting idea. I wonder if they could go where the suction gauge is now. 

I wouldn’t put the ports in the middle. Unless you want to contort yourself to avoid snagging cords every time you climb in and out of the left seat. I have mine low and to the left of where I sit to keep the cords out of my way. 

[PT20J]

I ditched the cigar lighter. I put a dual panel mount USB port on the right side for passengers. The only thing I power is my iPad on the yoke and for that I had a USB power cube mounted behind the panel and the ran a cable under the yoke shaft.