G-5 AI AND HSI COMBO

[bucko]

I have the dual G-5 setup with magnetometer and both are working well (HSI is a new install).

I want the HSI is continue to be slaved to show the magnetic heading with the magnetometer, but am wondering if the AI can be separately adjusted to show TRK (the ground track the plane is actually flying).

Can that be done easily?

Thanks,

Bucko Strehlow

[mcarterak]

The small magenta carrot shown on the HSI should be your GPS ground track. Figure 16 in this image. 

[Greg Ellis]

Looking in the User manual, the G5 will apparently automatically show ground track if it is not receiving info from the Magnetometer.  Any chance of disconnecting the Magnetometer from the AI but leaving it attached to the HSI?  Otherwise there may be a way to change the config in the configuration menu.  Hold the knob in when you power it up and you will get to a config menu.  There maybe something in there but I’m not sure.  @PT20J may be able to help.  He is quite knowledgeable with this stuff.  Probably more than most Garmin reps…

[PT20J]

I believe ADAHRS in the G5 requires the magnetometer. The G5 Pilot’s Guide seems to say that you can enter a menu and select HDG or TRK, but I haven’t experimented with it. The G3X has a setting to display TRK unless the GFC 500 is in HDG.

[Vance Harral]

It appears the OP had the G5 ADI originally, and recently added the HSI, and is now missing the way track was displayed on the ADI.  We had this same experience.

The short answer is, you still have track information on the ADI, it's just not as prominent.  It's the little tiny magenta triangle in the top "tape", shown at 290 degrees in the picture below.  It's easy to miss if you don't know to look for it, but it's there.  This particular image shows the aircraft on a heading of 282, and a track of 290.

 

[Vance Harral]

16 hours ago, Greg Ellis said:

Any chance of disconnecting the Magnetometer from the AI but leaving it attached to the HSI?

11 hours ago, PT20J said:

I believe ADAHRS in the G5 requires the magnetometer.

The G5 ADAHRS works fine without a magnetometer, as evidenced by the fact that a single G5 ADI installation doesn't require the magnetometer.  Once you've got the magnetometer, though, you don't want to try to disconnect it from either G5.  The reason is that all this stuff talks to each other through a CANBUS backbone.  If you remove the CANBUS connection from your G5 ADI, then in addition to losing the magnetometer data, you'll also lose the CDI display, and the mechanism that allows one G5 to detect the other has failed.

[EricJ]

1 hour ago, Vance Harral said:

It appears the OP had the G5 ADI originally, and recently added the HSI, and is now missing the way track was displayed on the ADI.  We had this same experience.

The short answer is, you still have track information on the ADI, it's just not as prominent.  It's the little tiny magenta triangle in the top "tape", shown at 290 degrees in the picture below.  It's easy to miss if you don't know to look for it, but it's there.  This particular image shows the aircraft on a heading of 282, and a track of 290.

 

This is the main way to see track on the AI, and the little magenta triangle is the same as the little magenta track dot on the HSI.   It's harder to see on the AI, but it's there if you're looking for it.

[EricJ]

1 hour ago, Vance Harral said:

The G5 ADAHRS works fine without a magnetometer, as evidenced by the fact that a single G5 ADI installation doesn't require the magnetometer.  Once you've got the magnetometer, though, you don't want to try to disconnect it from either G5.  The reason is that all this stuff talks to each other through a CANBUS backbone.  If you remove the CANBUS connection from your G5 ADI, then in addition to losing the magnetometer data, you'll also lose the CDI display, and the mechanism that allows one G5 to detect the other has failed.

This is also why the installation manual shows the HSI and AI on different power buses.    The HSI goes on the avionics bus, and the AI goes on the main power bus.    If you shut off the avionics bus, you lose the HSI (well, it goes to its internal battery) and the GMU11, but the AI will continue to work on the master bus power.

 

[Vance Harral]

34 minutes ago, EricJ said:

This is also why the installation manual shows the HSI and AI on different power buses.    The HSI goes on the avionics bus, and the AI goes on the main power bus.    If you shut off the avionics bus, you lose the HSI (well, it goes to its internal battery) and the GMU11, but the AI will continue to work on the master bus power.

Yes, though interestingly, the requirement for the ADI and HSI to be on different busses didn't show up until later revisions of the G5 installation manual.  Specifically, that requirement is found in rev. 17 of the G5 installation manual, but not in rev. 13.  I can't find any copies of the revisions in-between those two, but the revision notes in rev. 17 cover back through rev. 13, and yet don't make any note of the power distribution requirements.  Seems like this requirement was sorta "slid in" to the manual without any fanfare.

Anyway, if you get in an airplane with dual G5s and they both power up on the main bus, that doesn't necessarily mean the installer didn't follow the manual.  It may have been installed in accordance with an earlier manual.  It's not entirely clear to me if you can legally update the G5 software in such an installation without re-wiring the power distribution, but that's a nitpick, and I'm certainly not going to hassle anyone about it.

[EricJ]

21 minutes ago, Vance Harral said:

Yes, though interestingly, the requirement for the ADI and HSI to be on different busses didn't show up until later revisions of the G5 installation manual.  Specifically, that requirement is found in rev. 17 of the G5 installation manual, but not in rev. 13.  I can't find any copies of the revisions in-between those two, but the revision notes in rev. 17 cover back through rev. 13, and yet don't make any note of the power distribution requirements.  Seems like this requirement was sorta "slid in" to the manual without any fanfare.

Yeah, there are often changes like this in manuals.    Like Mooneys using a prop stand for gear swings or not. 

21 minutes ago, Vance Harral said:

Anyway, if you get in an airplane with dual G5s and they both power up on the main bus, that doesn't necessarily mean the installer didn't follow the manual.  It may have been installed in accordance with an earlier manual.  It's not entirely clear to me if you can legally update the G5 software in such an installation without re-wiring the power distribution, but that's a nitpick, and I'm certainly not going to hassle anyone about it.

If they're on the same power bus I think you can manually power both down with the button, and then bring them up individually to do the updates.   

[Vance Harral]

1 hour ago, EricJ said:

If they're on the same power bus I think you can manually power both down with the button, and then bring them up individually to do the updates. 

What I'm getting at is that each revision of G5 software is associated with a set of documents.  i.e. when you go to https://support.garmin.com/en-US/?partNumber=K10-00280-01&tab=manuals, you must select a specific version of software to get the corresponding documents.  If you upgrade your G5 software, you're definitely supposed to print the AFMS associated with the new version of software and put it in your POH/AFM, and I think we'd all agree that makes sense.  But I don't know what to make of corresponding changes in the installation manual.

For the sake of discussion, let's say your G5s were installed with software revision 4.0 in 2017.  That installation would have been associated with installation manual rev. 9, and maybe has both units on the primary bus.  If you finally get around to installing software revision 8.0 this month, that's associated with installation manual rev. 29.  Because of that, the rev 8.0 software could, theoretically, contain code that assumes the dual G5s are installed on separate primary/avionics busses.  But your airplane isn't going to be wired that way unless you update your wiring.

I'm not suggesting there's any kind of "real" problem here, and I don't think anyone should lose sleep over it.  It just piques my interest because I'm involved in a line of work that has similar hardware/software/manual versioning concerns.

[EricJ]

9 minutes ago, Vance Harral said:

What I'm getting at is that each revision of G5 software is associated with a set of documents.  i.e. when you go to https://support.garmin.com/en-US/?partNumber=K10-00280-01&tab=manuals, you must select a specific version of software to get the corresponding documents.  If you upgrade your G5 software, you're definitely supposed to print the AFMS associated with the new version of software and put it in your POH/AFM, and I think we'd all agree that makes sense.  But I don't know what to make of corresponding changes in the installation manual.

For the sake of discussion, let's say your G5s were installed with software revision 4.0 in 2017.  That installation would have been associated with installation manual rev. 9, and maybe has both units on the primary bus.  If you finally get around to installing software revision 8.0 this month, that's associated with installation manual rev. 29.  Because of that, the rev 8.0 software could, theoretically, contain code that assumes the dual G5s are installed on separate primary/avionics busses.  But your airplane isn't going to be wired that way unless you update your wiring.

I'm not suggesting there's any kind of "real" problem here, and I don't think anyone should lose sleep over it.  It just piques my interest because I'm involved in a line of work that has similar hardware/software/manual versioning concerns.

I'm not sure what power wiring would affect for software revisioning.   Either unit will have to assume that power can be interrupted to the other, or some other catastrophic failure can happen to the other, regardless of which bus they're connected to.   They're on separate CBs, at a minimum, so can be interrupted independently.   They share the CAN bus the same way regardless of how power is connected, so from that standpoint I'd think it shouldn't matter.    Garmin would be making their own lives more difficult if they made software releases dependent on which installation manual was used, but I've certainly seen worse done.