Can KX-155 drive both a KI-206 and a GI-275?

[Flash]

I've got an IFD 540 as my No. 1 Nav/Com and a KX-155 as my backup, and I've got dual GI-275s plus a KI-206. My question is whether the KX-155 can be wired to drive both the KI-206 and the GI-275 HSI.

I know that the GI-275 is capable of displaying information from more than one Nav source and that it can take output from a KX-155. I like having the KI-206 because that gives me an independent source of Nav information display if my GI-275s fail. But it would be nice if my KX-155 can drive both the KI-206 and the GI-275, so that if my IFD 540 fails I can use the No. 2 Nav radio to drive the autopilot.

If the answer is that the KX 155 can drive both the KI-206 and the GI-275, how much work is involved in wiring it to do that?

Thanks in advance. 

Edited January 29, 2023 by Flash
fix typo

[Vance Harral]

Without looking at the installation manuals, I'm going to opine that you don't want to do this, because the KI-206 and GI-275 have independent OBS "knobs" (physical in the case of the KI-106, virtual for the GI-275).  Not sure what you're expecting to see on dual CDIs driven from the same source, if they don't have the same OBS knob setting.  Lots of potential for confusion and failure, and seems like a bad idea.

 

[N231BN]

Are you certain you have a KI-206? They are normally used with a KX-165. The KI-204 or KI-209 has the VOR/LOC converter for use with a KX-155.

The GI-275 takes the VOR composite signal from the KX-155/165 and can be combined with a mechanical CDI.

[Flash]

2 hours ago, N231BN said:

Are you certain you have a KI-206? They are normally used with a KX-165. The KI-204 or KI-209 has the VOR/LOC converter for use with a KX-155.

The GI-275 takes the VOR composite signal from the KX-155/165 and can be combined with a mechanical CDI.

Thanks. You're right. I must have a KI-209.

[Flash]

2 hours ago, Vance Harral said:

Without looking at the installation manuals, I'm going to opine that you don't want to do this, because the KI-206 and GI-275 have independent OBS "knobs" (physical in the case of the KI-106, virtual for the GI-275).  Not sure what you're expecting to see on dual CDIs driven from the same source, if they don't have the same OBS knob setting.  Lots of potential for confusion and failure, and seems like a bad idea.

 

Thanks, Vance. It's not that I'm expecting to see different things on the two displays; it would just be nice to be able to drive my autopilot off the No. 2 Nav if the IFD 540 were to fail.

The only potential for confusion I see here would be thinking I'm displaying the data from my IFD 540 on my GI-275 CDI when I'm actually displaying the data from the KX-155, or vice versa, but the GI-275 helpfully uses an outlined arrow rather than a solid arrow to represent the CDI from the No. 2 Nav radio.

I agree that if I were flying a VOR and had different OBS settings, I would get different deflections, but I don't know why I would use different OBS settings. One nice thing about the GI-275 is that it can show bearing from the No. 2 Nav VOR while flying the No. 1 Nav, so triangulation should be easier because you don't have to turn an OBS to see your bearing from the No. 2 Nav VOR.

The KI-209 (as N231BN pointed out I really have) will continue to act as usual. If I'm flying an ILS, the deviation indications on both displays should look the same, as the OBS on the KI-209 becomes just a heading bug. If I'm flying the No. 2 Nav VOR, I think I'd have the OBS set the same on both displays, so I'd see the same thing.

[N231BN]

The GI-275 and the KI-209 have their own VOR converters so they can each give you a different indication. The 275 will clearly say NAV2 and like you said have a hollow arrow.

[kortopates]

Isn’t the AP coming off the KI-275? In which case you use Nav with VOR-2 and not need the KI-209?
With dual GI-275’s just don’t see a need to keep the KI-209 - but don’t entirely understand your AP setup but it seems that’s what should be driving the AP.


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[N231BN]

Isn’t the AP coming off the KI-275? In which case you use Nav with VOR-2 and not need the KI-209?
With dual GI-275’s just don’t see a need to keep the KI-209 - but don’t entirely understand your AP setup but it seems that’s what should be driving the AP.


Sent from my iPhone using Tapatalk

Yes, the 275 sends the deviations to the autopilot. There really isn't a reason to leave the KI-209 except it's already there.

[Vance Harral]

If the goal is to run the autopilot from NAV2, seems like the simpler and better way to achieve it is to just install a DPDT switch that selects between the GI-275 and KI-209 analog deviation wire pairs, for the autopilot's deviation inputs.  Label it "autopilot nav source".  Set to NAV1 for IFD-540/GI-275, NAV2 for KX-155/KI-209.  This sort of setup used to be common, e.g. our old Brittain autopilot setup has a NAV 1/2 select.  You don't say what autopilot you have, but if it's a somewhat older model, the installation manual almost certainly contains provisions for a nav input select like this.  Materials cost would be a few bucks for the switch and a couple feet of 22AWG wire.  Probably less than 1 hour of labor to install, modulo the usual "Mooney tax" for difficulty accessing stuff behind the panel.  The only downside is that the switch becomes a potential failure point, so spend a few bucks extra for a high-MTBF unit.

Based on what N231BN says, sounds like it's technically possible to drive two CDIs from a single KX-155.  But I still think the pilot interface for that is confusing, and the potential for error high (you say you don't intend to set the OBS knobs differently on the two indicators, but sooner or later that will happen).  Note also that you may or may not get an avionics shop to agree to perform the work.  Some shops won't install anything on a certified airplane for which there is a not a specific drawing in the installation manual for the devices being connected, and there aren't any "dual CDI output" drawings for nav radios.

[N231BN]

1 minute ago, Vance Harral said:

If the goal is to run the autopilot from NAV2, seems like the simpler and better way to achieve it is to just install a DPDT switch that selects between the GI-275 and KI-209 analog deviation wire pairs, for the autopilot's deviation inputs.  Label it "autopilot nav source".  Set to NAV1 for IFD-540/GI-275, NAV2 for KX-155/KI-209.  This sort of setup used to be common, e.g. our old Brittain autopilot setup has a NAV 1/2 select.  You don't say what autopilot you have, but if it's a somewhat older model, the installation manual almost certainly contains provisions for a nav input select like this.  Materials cost would be a few bucks for the switch and a couple feet of 22AWG wire.  Probably less than 1 hour of labor to install, modulo the usual "Mooney tax" for difficulty accessing stuff behind the panel.  The only downside is that the switch becomes a potential failure point, so spend a few bucks extra for a high-MTBF unit.

Based on what N231BN says, sounds like it's technically possible to drive two CDIs from a single KX-155.  But I still think the pilot interface for that is confusing, and the potential for error high (you say you don't intend to set the OBS knobs differently on the two indicators, but sooner or later that will happen).  Note also that you may or may not get an avionics shop to agree to perform the work.  Some shops won't install anything on a certified airplane for which there is a not a specific drawing in the installation manual for the devices being connected, and there aren't any "dual CDI output" drawings for nav radios.

The GI-275 does all of that internally, you are really only adding another point of failure. And as you said, it is not an approved configuration per the GI-275 IM.

[Vance Harral]

1 hour ago, N231BN said:

The GI-275 does all of that internally, you are really only adding another point of failure.

No argument there, but the OP wanted to retain his KI-209.  If the KI-209 is removed (or just bypassed and disabled), and the KX-155 connected directly to the GI-275 instead, that would certainly work, and eliminates the mechanical switch.

1 hour ago, N231BN said:

And as you said, it is not an approved configuration per the GI-275 IM.

Fair point that there's no drawing which shows a GI-275 driving analog autopilot deviation signals to a switch instead of directly to an autopilot.  I hypothesize a good avionics shop or freelancer might be comfortable claiming the GI-275's deviation outputs are just an "omni output" in accordance with older autopilot installation manuals - since they conform to the analog voltage standard - and therefore pronouncing it kosher to connect them to an approved autopilot via a completely passive switch that presents an equal or higher impedance load to the GI-275 under all conditions.  Driving two CDIs from a KX-155 seems a little sketchier, and I hypothesize fewer installers would put their name on something like that.  But it's not my opinion that matters.  These are good questions for the OP to ask an installer.

[Flash]

5 hours ago, kortopates said:

Isn’t the AP coming off the KI-275? In which case you use Nav with VOR-2 and not need the KI-209?
With dual GI-275’s just don’t see a need to keep the KI-209 - but don’t entirely understand your AP setup but it seems that’s what should be driving the AP.


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Paul, the theory for keeping the KI-209 is that if my GI-275s fail I still have ILS capability. I'd technically be partial panel, but I've got a Dynon D3 to give me attitude information. I think the odds are low that the GI-275s both fail, but if even one fails the other becomes an attitude indicator and I'd no longer have the HSI. 

Autopilot is a King 150. The GI-275 drives it.

[Flash]

Thanks for all of the feedback. I think I'll just keep the No. 2 Nav wired to the KI-209. I don't really need it to drive the autopilot; I can hand fly. Having the redundancy is the most important thing to me.

[kortopates]

15 minutes ago, Flash said:

Paul, the theory for keeping the KI-209 is that if my GI-275s fail I still have ILS capability. I'd technically be partial panel, but I've got a Dynon D3 to give me attitude information. I think the odds are low that the GI-275s both fail, but if even one fails the other becomes an attitude indicator and I'd no longer have the HSI. 

Autopilot is a King 150. The GI-275 drives it.

Once you get to know all of the great capabilities of the GI-275 I doubt you'll feel the same need for the old KI-209

Even without changing the #1 GI-275 out of Attitude mode, which you could do or toggle between HSI and ADI given you have the D3 for attitude also. But even in ADI mode you can enable both lateral and vertical deviation indicators - see page 41 of the GI-275 Pilots Guide, here is the pertinent extract:

When valid navigation data is available, the 'CDI', 'HSI', and 'HSI Map' Pages always show
deviation information. On the 'ADI' Page, lateral and vertical deviation indicators are not
enabled by default. If deviation indicators on the 'ADI' Page are enabled before unit poweroff,
deviations will be displayed after unit restart. Units configured as a Standby HSI cannot
disable deviation indication display on the 'ADI' Page.
Enabling/disabling deviation display on the 'ADI' Page:
1) From the 'ADI' Page, open the menu and select Options > NAV Options.
2) Select the CRS Devs Button to toggle displaying lateral and vertical deviation
information.

And if you have Synthetic Vision enabled on the ADI you get something even more powerful once your on final approach - the Flight Path Marker. The Flight Path Marker provides a 3D lateral and vertical deviation indication in the form a small green circle  and is simple and intuitive to use. By just adjusting heading and pitch/descent rate such that the Flight Path marker is pointing to the threshold of the runway, it will keep you on center lines and GP before a deviation is even registered. Its a very powerful tool you'll want to master. Check it out on page 242 of the same manual

 

[Minivation]

I've tried this in a Cessna 172 with a dual GI-275 setup, GNS430W as Nav/Comm/GPS #1 and KX155 as Nav/Comm #2. I wired the KX155 Composite Nav output to a KI-209 CDI and GI275 (HSI) in parallel as Garmin's IM at the time made no mention against such a setup and the KX155 IM implies the ability to do this in its sample wiring schematics.

However, this did not turn out well. The KI-209 did its job okay on its own but whenever the GI-275 was configured to accept the KX155's composite nav data, indications on both units went haywire. (Simulated LOC/GS outputs were OK) I'm not a real electrical engineer so I can't comment on the exact reason why, but I speculate that the KX155 output impedance is unable to deal with both units.

In the end I deleted the connection between the KX155 and GI275.

[N231BN]

5 hours ago, Minivation said:

I've tried this in a Cessna 172 with a dual GI-275 setup, GNS430W as Nav/Comm/GPS #1 and KX155 as Nav/Comm #2. I wired the KX155 Composite Nav output to a KI-209 CDI and GI275 (HSI) in parallel as Garmin's IM at the time made no mention against such a setup and the KX155 IM implies the ability to do this in its sample wiring schematics.

However, this did not turn out well. The KI-209 did its job okay on its own but whenever the GI-275 was configured to accept the KX155's composite nav data, indications on both units went haywire. (Simulated LOC/GS outputs were OK) I'm not a real electrical engineer so I can't comment on the exact reason why, but I speculate that the KX155 output impedance is unable to deal with both units.

In the end I deleted the connection between the KX155 and GI275.

That is interesting, I have a similar setup but with a KI-204. I haven't had a chance to test it yet but if it doesn't work I'll probably ditch the KI-204.

[N231BN]

I got a quick test flight in this morning to test the GI-275's, they make that 44 year-old Century III fly like new.

The VOR 2 indication did wander a little on the GI-275, it was steady on the KI-204. Next time I'll un-plug the KI-204 and see if it makes a difference.

[Minivation]

On 2/9/2023 at 1:02 AM, N231BN said:

I got a quick test flight in this morning to test the GI-275's, they make that 44 year-old Century III fly like new.

The VOR 2 indication did wander a little on the GI-275, it was steady on the KI-204. Next time I'll un-plug the KI-204 and see if it makes a difference.

Let us know how things go after your tests - I'd love to know how other setups work (or not).

As for the autopilot - the GPSS functionality of the GI275 teaches some serious new tricks to those old A/P's. Glad to hear it works with your Century. The owner of the 201 I've been flying has since installed dual GI-275's as well but it doesn't seem to play nicely with the S-Tec System 60. He suspects it's an issue with the A/P though.

[N231BN]

Let us know how things go after your tests - I'd love to know how other setups work (or not).
As for the autopilot - the GPSS functionality of the GI275 teaches some serious new tricks to those old A/P's. Glad to hear it works with your Century. The owner of the 201 I've been flying has since installed dual GI-275's as well but it doesn't seem to play nicely with the S-Tec System 60. He suspects it's an issue with the A/P though.

He needs to make sure the GI-275 autopilot settings match the type of HSI that was previously connected to the STEC(NSD 360, KI-525, etc.).

I'm still working on the NAV2 issue.

[Minivation]

13 hours ago, N231BN said:

He needs to make sure the GI-275 autopilot settings match the type of HSI that was previously connected to the STEC(NSD 360, KI-525, etc.).

I'm still working on the NAV2 issue.

Turns out I posted slightly incorrect information. The autopilot works okay in lateral mode but cannot seem to hold altitude. So it's an issue independent of the GI275. (He did mention though that the GI275-STec connection worked a lot better when the GI275 was set to emulate the KI-525 rather than the NSD360 - The S-Tec can take either)

[Fly Boomer]

On 2/11/2023 at 11:35 PM, Minivation said:

Turns out I posted slightly incorrect information. The autopilot works okay in lateral mode but cannot seem to hold altitude. So it's an issue independent of the GI275. (He did mention though that the GI275-STec connection worked a lot better when the GI275 was set to emulate the KI-525 rather than the NSD360 - The S-Tec can take either)

Curious about the color code on your "states visited" map.

[Minivation]

On 2/15/2023 at 6:37 AM, Fly Boomer said:

Curious about the color code on your "states visited" map.

Green - lived there -or- flown to many, many parts of the state
Blue - flown in a few times across multiple places
Orange - flown in, looked around a bit (in AK's case, I flew a Citabria around the Matanuska Glacier area)
Red - fuel stop