G3X Touch EIS hacks

[PT20J]

One thing I did on my Mooney analog engine gauges was to put a grease pencil tick mark at the normal needle location so I could tell at a glance if something was amiss. Turns out that the G3X EIS will allow you to place tick marks at any location on the gauge, so I marked normal cruise fuel pressure and oil pressure. I also put a tick mark at 0 on the ammeter and at 2500 rpm and 15, 20 and 25" on the manifold pressure gauge. If you want to get fancy, you can make the marks different colors.

The EIS gauges can have two different types of yellow ranges denoted Yellow Range and Yellow Range + Alert. Both look the same on the gauge depiction. The difference is that if the parameter falls with Yellow Range + Alert, it generates a yellow CAS Caution message on the right side of the G3X display. A Caution message also pulls EIS Discrete Output 2 low to activate an external indicator. On my case, I connected it to PMA450B Flightmate input 3 which creates an aural "Master Caution" annunciation in the pilot's headset. As an example, Mooney specifies that my oil pressure gauge have yellow range from 25 to 60 psi. I wanted a CAS Caution for low oil pressure, but the pressure can fall below 60 during idle (which is permissible) and I didn't want a nuisance alert in this case. So I set a Yellow Range + Alert to 25 - 45 psi and a Yellow Range from 45 - 60 psi. I also created a Yellow Range + Alert at 425-475 F CHT which draws a yellow line at 425 across the CHT/EGT bar graph.

The same can be done for Red Range and Red Range + Alert. In this case, an alert generates a red CAS Warning message and pulls Discrete Output 1 low. I connected this output to the PMA450B Flightmate input 2 which currently annunciates the default "Oil Pressure" warning. These messages are field recordable and I plan to change it to say "Master Warning." 

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[Brent]

Skip, 

I just installed a clean all-Garmin glass panel, including a G3X, so I'm about to go through your learning curve. I managed the twenty-minute flight home last week (after four months of not flying anything), and I'm taking the plane out tomorrow to start figuring stuff out. I've read the manuals, but the only way I'll get it is flying and trying. So, a dumb question: the old ammeter gauge was net zero for normal. I understand net zero, and I understand all the equipment is going to draw some level of power. But the -24 amps or whatever it was caught me by surprise. Either way, I guess the absolute power draw rather than the net aero is normal for the Garmin EIS, yes?  

[PT20J]

My panel draws about 4 amps with everything turned on. There is a calibration for the shunt in the G3X configuration. I retained the Mooney shunt which is an EMPRO MLA-70A-100MV, so the shunt voltage is 100 mV at 70A. and the scale factor entered into the G3X is 100/70 = 1.4 mV/A.

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[PJClark]

I don't have EIS, EDM900 instead.  But with everything on including external lights I draw 8-10 amps. All my lights are led except the strobes. (Zoom in to see amps in the column of white data on the EDM under the rpm arc)

[Scottknoll]

Are the CAS messages able to replace the Mooney annunciator panel? Or is the annunciator panel part of the TCDS and thus required to stay?

[PT20J]

I don’t believe the certified version has the ability to generate CAS messages from external inputs.

[Ragsf15e]

On 12/11/2021 at 9:33 AM, PJClark said:

I don't have EIS, EDM900 instead.  But with everything on including external lights I draw 8-10 amps. All my lights are led except the strobes. (Zoom in to see amps in the column of white data on the EDM under the rpm arc)

Careful assuming the amp gauge shows amps currently drawn… the original design of older Mooney’s is to show the amps to/from the battery.  Thus with your alternator running, it shows charging amps to the battery which should be close to zero, but slightly positive.  It doesn’t show total amp draw of your electrical system.  Now that’s at least on vintage birds and it’s definitely possible to show total amp draw - the PA46 I fly at work shows total.

Just to be sure, turn on everything on the ground without the engine running and you should see a negative amperage that is indeed your total draw.

[PJClark]

Hmm. Well, it's an '86 Mooney but it's a 2019 panel.  the negative draw number has decreased every time I trade an LED for an old incandescent, and besides: if that was showing battery discharge I'd have killed at least 1 battery in the last 2 years of flying.  Plus the low voltage light would have been flashing at me 100% of the time for about 150 hours now.

But it's a good tip for others with older Mooneys. I think the original ship's guage deflected right to show alternator draw and left to show battery discharge. However I confess to only having about 15 hours with that guage before avioncs and as everything was working I'm not entirely sure how that worked....

[PT20J]

A lot of Pipers have load meters and Cessna always favored ammeters. I think all the M20Js had ammeters. Not sure about earlier Mooneys. Ammeters show the current into or out of the battery with zero in the middle and discharge amps to the left and charging amps to the right. Load meters show the current being drawn from the electrical source (either the alternator or battery depending on which is powering the aircraft) and have zero on the left side and only read positive numbers.

[Ragsf15e]

2 hours ago, PJClark said:

Hmm. Well, it's an '86 Mooney but it's a 2019 panel.  the negative draw number has decreased every time I trade an LED for an old incandescent, and besides: if that was showing battery discharge I'd have killed at least 1 battery in the last 2 years of flying.  Plus the low voltage light would have been flashing at me 100% of the time for about 150 hours now.

But it's a good tip for others with older Mooneys. I think the original ship's guage deflected right to show alternator draw and left to show battery discharge. However I confess to only having about 15 hours with that guage before avioncs and as everything was working I'm not entirely sure how that worked....

You misunderstood me.  That 8 amps is likely feeding your battery, not discharge.  Look at it with the engine off and see what the amperage looks like.  It will likely be red and show discharge from your battery like my edm930.

Yeah, my panel is newer too but that doesn’t mean they changed how your shunt works.

[Brent]

So I went out to the airport during L.A.'s days of rain and revisited the amps reading on my G3X. I assume something needs calibrating or the display needs to be properly configured because this is what the G3X EIS amps meter showed (and, no, the battery minder was not connected) as I powered various items (actually unpowered in reverse, but it's easier to read this way):

16     G3X and nothing else powered 

17     GI 275 CDI

19     GI 275 standby AI

25     GTN 750

26     GFC 500

28     GTX 345

30     GMA 350

32     WX500

38     GNS 430

43     LED strobes

45     LED nav lights

56     Incandescent recognition lights

67     Boom beam landing light

94     Pitot heat

109    AOA probe heat

Since I believe that is about 2x the available amps on the airplane, something is off. It's on the squawks list for the shop, but I'm trying to educate myself.

 

[Niko182]

27 minutes ago, Brent said:

So I went out to the airport during L.A.'s days of rain and revisited the amps reading on my G3X. I assume something needs calibrating or the display needs to be properly configured because this is what the G3X EIS amps meter showed (and, no, the battery minder was not connected) as I powered various items (actually unpowered in reverse, but it's easier to read this way):

16     G3X and nothing else powered 

17     GI 275 CDI

19     GI 275 standby AI

25     GTN 750

26     GFC 500

28     GTX 345

30     GMA 350

32     WX500

38     GNS 430

43     LED strobes

45     LED nav lights

56     Incandescent recognition lights

67     Boom beam landing light

94     Pitot heat

109    AOA probe heat

Since I believe that is about 2x the available amps on the airplane, something is off. It's on the squawks list for the shop, but I'm trying to educate myself.

 

in cruise with all the lights and avionics on, I use about 12amps. Add the pitot heat and it adds another 10ish.

[ArtVandelay]

I have all LEDs, G5s, GTN, 255…it uses about 4 amps assuming radios are idle.
The 6 amps for an GTN seems off, assuming it was idle. Maybe 0.6 amps?

[PT20J]

Did you keep the original shunt?  If so, look in the IPC and find out what the specs are. For instance, my 28V J uses an EMPRO MLA-70-100MV. So this shunt drops 1.43 mV/A (100/70). Put the G3X in configuration mode, open the EIS page and enter the correct scale factor. My 28v system draws about 4A with all the avionics on. Expect a 12V system to draw about twice that.

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[LANCECASPER]

3 hours ago, Brent said:

So I went out to the airport during L.A.'s days of rain and revisited the amps reading on my G3X. I assume something needs calibrating or the display needs to be properly configured because this is what the G3X EIS amps meter showed (and, no, the battery minder was not connected) as I powered various items (actually unpowered in reverse, but it's easier to read this way):

16     G3X and nothing else powered 

17     GI 275 CDI

19     GI 275 standby AI

25     GTN 750

26     GFC 500

28     GTX 345

30     GMA 350

32     WX500

38     GNS 430

43     LED strobes

45     LED nav lights

56     Incandescent recognition lights

67     Boom beam landing light

94     Pitot heat

109    AOA probe heat

Since I believe that is about 2x the available amps on the airplane, something is off. It's on the squawks list for the shop, but I'm trying to educate myself.

 

I hope you didn’t keep the incandescent recognition lights on long on the ground. Those projector lamps will melt your wingtip lenses in a hurry.

[Brent]

22 minutes ago, LANCECASPER said:

I hope you didn’t keep the incandescent recognition lights on long on the ground. Those projector lamps will melt your wingtip lenses in a hurry.

Not long. Would sure like to see an LED replacement for those, as I know many would.  

[carusoam]

20 minutes ago, Brent said:

Not long. Would sure like to see an LED replacement for those, as I know many would.  

Don’t forget to send a note to our Whelen guy and request the LED recog lights… 

+1 For identifying what shunt you have… your shop probably didn’t know what was there… or forgot to update the G system if they changed it out…

-a-

[Brent]

3 hours ago, ArtVandelay said:

I have all LEDs, G5s, GTN, 255…it uses about 4 amps assuming radios are idle.
The 6 amps for an GTN seems off, assuming it was idle. Maybe 0.6 amps?

You nailed what I'm trying to figure out. Based on tonight's Mooneyspace education, it appears the G3X EIS that I just had installed wasn't properly configured to account for whatever electrical shunt is in the plane, assumed to be the original. So now I'm trying to ID the shunt and specs (for M20J SN 24-1524) to determine the scale/ratio so I can input that into the G3X. I found only one shunt in the IPC, but it's for the prop de-ice. I see the shunt in the electrical schematic, but the only apparent ID there is the wire number. I might be able to swag a scaling number, but I'd definitely like to be more accurate than that. Or I can toss it back tot he avionics shop to get it right. If anyone knows the specs on the J model 14 Volt shunt, I'll be happy to have it.     

[Brent]

12 minutes ago, carusoam said:

Don’t forget to send a note to our Whelen guy and request the LED recog lights… 

+1 For identifying what shunt you have… your shop probably didn’t know what was there… or forgot to update the G system if they changed it out…

-a-

Re. recognition lights: already promised that guy I would be a ready and willing customer. 

[PT20J]

25 minutes ago, Brent said:

You nailed what I'm trying to figure out. Based on tonight's Mooneyspace education, it appears the G3X EIS that I just had installed wasn't properly configured to account for whatever electrical shunt is in the plane, assumed to be the original. So now I'm trying to ID the shunt and specs (for M20J SN 24-1524) to determine the scale/ratio so I can input that into the G3X. I found only one shunt in the IPC, but it's for the prop de-ice. I see the shunt in the electrical schematic, but the only apparent ID there is the wire number. I might be able to swag a scaling number, but I'd definitely like to be more accurate than that. Or I can toss it back tot he avionics shop to get it right. If anyone knows the specs on the J model 14 Volt shunt, I'll be happy to have it.     

According to the schematic for SN 24-1500 through 24-1528, your shunt is a 21DA01C which according to the SMM is a EMPRO MLA-60-100.

[Brent]

36 minutes ago, PT20J said:

According to the schematic for SN 24-1500 through 24-1528, your shunt is a 21DA01C which according to the SMM is a EMPRO MLA-60-100.

Thanks for that. I was hung up in section 39 of the IPC and an earlier section in the maintenance manual. And thanks for the other info, too. I didn't even know what an electrical shunt was until now.  

[rbp]

what the hell is this shunt thing, and what's it for?

[PT20J]

6 hours ago, rbp said:

what the hell is this shunt thing, and what's it for?

It’s a precision resistor used to measure the bus current. The voltage drop across it drives the ammeter.

[Brent]

Finally got back to the hangar and reconfigured the scale factor on the G3X with the MLA 60-100 shunt value. The amps readings make sense now.  

[carusoam]

Great follow-up Brent!

Thanks for sharing it.

-a-