1990 M20J Panel Upgrade to G3X

[DC_Brasil]

Hello everyone.

My M20J has tarted a panel upgrade this week. I share the ownership with a friend and after much research and talking to the avionics shop we've decided (like most posts we've seen here) to go with the G3X family.

We'll install:

• G3X 10 inch main display with full EIS
• G5
• GFC500 with all 4 servos (pitch, roll, pitch trim and YD)
• GMA245R Audio box
• GSB-15 USB power outlet

Unfortunately we didn't have enough cash to goo the full way and upgrade more stuff, so our navigator will remain the GNS430. If avionics are already expensive in the US, here in Brazil we still have to consider currency exchange and importing taxes. Perhaps in a year or so, I plan to add a GTN650, new ADSB transponder and LED NAV/Strobe/Landing lights.

Consequently, we're removing all analog instruments, all current engine instruments, ADF (it had two ahahahah), DME, Audio Panel, KAP150 autopilot (controller, alt selector and annunciator).

I have a few question for all you Garmin savvy out there. I've tried looking these up on the G3X user manual and even install manual without much luck. Some information is even a little ambiguous.

1 - Will our KX-155 Nav 2 send CDI data to the G3X or will I need to keep the backup NAV 2 CDI?

2 - Will I be able to change COMM 1 frequency (COMM1 is the GNS430) in the G3X screen?

3 - I know I can use Connext to send my flight plan from the iPad to the G3X, however, will it send it to the GNS430?

I am attaching a pic of the panel as it was and after the first day of instrument removal.

Have a great day!

DC

[PT20J]

I would post the question on Beechtalk. Several Garmin dealers hang out there. For sure Terry Markovich would know. 

I’m pretty sure the answer to 1 is no and 3 is yes. Not sure about 2, but I don’t think so.

[ArtVandelay]

I think 2 is no, I can’t change the GTN frequencies, but I can with 255.

But that may be because I don’t the necessary connection, all my GTN RS232 ports are being used.

[toto]

On 9/28/2024 at 6:31 AM, DC_Brasil said:

1 - Will our KX-155 Nav 2 send CDI data to the G3X or will I need to keep the backup NAV 2 CDI?

Hopefully one of the resident avionics experts will chime in, but my #2 navcom is a KX-155 and I had to keep the legacy indicator for it.

[ArtVandelay]

Hopefully one of the resident avionics experts will chime in, but my #2 navcom is a KX-155 and I had to keep the legacy indicator for it.

If you want interoperability with other older equipment, you should get G500 TXi, the G3X I think only works with modern digital equipment.

[toto]

7 minutes ago, ArtVandelay said:

If you want interoperability with other older equipment, you should get G500 TXi, the G3X I think only works with modern digital equipment.

Definitely don’t want. I would rather spend the money on a new navcom than integrate an old King radio with a TXi.

I’m very happy with a standalone KX-155 and a standalone indicator for my backup radio, and when it finally dies I’ll buy something new from Garmin

 

[DC_Brasil]

On 9/29/2024 at 8:07 PM, toto said:

Definitely don’t want. I would rather spend the money on a new navcom than integrate an old King radio with a TXi.

I’m very happy with a standalone KX-155 and a standalone indicator for my backup radio, and when it finally dies I’ll buy something new from Garmin

 

That's the way we're moving. We'll probably keep an old VOR CDI for NAV2.

Next year, after my pockets (hopefully) recover from - and my wife (hopefully) forgets about -  this upgrade, I'll try to add a GNT650txi and my current GNS430 will be NAV2. So I'll be able to throw out the analog CDI.

[DC_Brasil]

Hello Everyone!

Posting an update here about the evolution of the panel upgrade.

1. All instruments removed and cabling being reworked
2. Removal of old KAP150 servos
3. A lot of work being done
4. First fitting test for panel plate
5. A lot of old cabling removed
6. New Garmin AP servos installed (we've added YD as well)
7. Avionics fitting test and fine tuning before painting

It is a remarkable difference between the old panel and the new. Can't wait to fly it 

 

One question for all of you Garmin flyers out there: now we'll have the GMA-245R remote audio panel controllable within the G3X. If we have a G3X failure, what communications capabilities do we retain? Do we lose intercom? Comm 2?

Cheers!

[KSMooniac]

Did they actually remove a tailcone skin???

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[ArtVandelay]

Did they actually remove a tailcone skin???

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I think they dropped the 1 piece belly.

[kortopates]

I think they dropped the 1 piece belly.

The one piece belly doesn’t go beyond the rear seats - not too avionics bay and battery area.


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[DC_Brasil]

1 hour ago, KSMooniac said:

Did they actually remove a tailcone skin???

Sent from my motorola edge plus 2023 using Tapatalk
 

I am not sure as I didn't go to the shop. The mechanics sent me these pics. I think they only removed the tail inspection panels under the horizontal stabilizer.

[kortopates]

I am not sure as I didn't go to the shop. The mechanics sent me these pics. I think they only removed the tail inspection panels under the horizontal stabilizer.

I think the question comes from the second picture where the light appears like it might be on the ground. But I think it’s an illusion created by the Avionics shelf and the light is actually in the belly, not on the ground.


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[KSMooniac]

I think you're correct, Paul. It sure looked like a hangar floor at first glance!

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[DC_Brasil]

Almost ready!

Went to the shop today. The idea was to review all installation and do a thorough runnup and a quick test flight with the mechanic to review the GFC500 autopilot. All avionics working but we had a malfunction with the voltage regulator.

Having it checked the  next couple of days and see if we can fly the plane Saturday morning. However, we got to spend some time playing with the new screen.

The G3X is indeed a very nice piece of equipment. 

[Stanton R]

On 10/11/2024 at 8:04 AM, DC_Brasil said:

 

I wish I had noticed this sooner but the rudder servo cable is wrapped around the servo incorrectly. The cable should be more parallel with the control rod (see attached). It's hard to tell but the elevator servo may be wrong also. I'm pretty sure if it wasn't changed that they would have had to program the yaw servo backwards to get it to work correctly. However it is kind of hard to check the Yaw servo for proper movement on the ground so it may be actually going the wrong way.

Edited November 8 by Stanton R

[DC_Brasil]

@Stanton R thanks for the heads-up. I will definitely talk to the mechanics about it. Wednesday I was there to test everything. Pitch, roll and trim controls worked on the ground. I didn't test the YD, but will do tomorrow morning.

Do you have any suggestions on how to actually test if the YD is working correctly? I have never flown with YD.

[Stanton R]

If it is working correctly the ball will stay centered in the turns and high power climbs. If it is backwards you will get into a crab and turns will be super uncoordinated. 

[EricJ]

Good catch.   At a minimum there appears to be an installation error that doesn't conform to the drawing.  If it is functioning correctly it may have been reversed in software configuration.

[201Mooniac]

Actually if it is reversed, you will get a dutch roll behavior, very easy to notice and quite alarming.  You won't notice it until flying and then just remember you can push the YD button to disable the yaw damper if that happens.

[Aerodon]

Always a good idea to know exactly which circuit breaker to pull if you get unexpected behaviour.  I flew a C172 that had the aileron programmed the wrong way and it was interesting.  Easy enough to change in the setup.

 

Aerodon

[Aerodon]

And here's a thread with good installation pictures:

 

 

[DC_Brasil]

@Stanton R thanks for the warning. The servos had indeed been rigged the wrong way and the YD behaved as expected: Dutch roll.

However two other things were wrong during the test flight and the shop is assessing the issues: 

1 - whenever engaged, the Autopilot commanded very aggressive right turns, even on ROLL lateral mode.

2 - the G3X tachometer is showing less than the real RPM. I guess this can be some incorrect config of the magneto type (Rated RPM is 2700 and the G3X is showing 2470).

Having these checked today.