GTN650, G5’s, GNC255 upgrade

[Jdm]

Hello, I’d like to get your thoughts about a #2 indicator please. After way too many years of making due with our old avionics we are finally getting a new rack of IFR equipment.

Here’s the equipment:
GTN650 in the #1 position.
GNC 255 in the #2 position.
Two G5’s flush mounted. (Vacuum sys will be entirely removed, including the old DG)
GMA 345 audio panel.
GTX 345 transponder.

Here’s the situation:
The G5’s will be the new primary ADI and HSI. The GTN650 will provide all lateral and vertical guidance to these G5’s as our primary instrumentation source.

Here’s the confusing part:
The #2 nav/com (GNC 255) can also be connected to the G5’s which is source selectable from within the G5 menu. This allows the G5’s to suffice as the indicator for both our #1 and #2 units which saves the large expense of an additional indicator for our #2 nav. Obviously it will only allow one source to be displayed at a time, therefore preventing indicator redundancy, the ability to pull cross radials, compare courses, intersection holds, etc. We certainly have the option to add a #2 indicator which can be installed as a stand alone indicator or mirrored to the G5’s respective nav source. If I need to go this route I’m leaning towards the new GI 275 as it’s not that much more than a new 106B indicator.

Question: Based on the above information, what’s your general thoughts on the importance of a secondary indicator? Remember, the GNC 255 has a some built indications. It has a small, “lateral only” deviation scale with a TO/FROM indicator and OBS knob on it’s display.

Thanks,
Jdm

 

[Ryan Klems]

The G5 HSI can display bearing pointers, which should get you your cross radials, etc. The G5 STC does not allow for any other indicator to be connected to any nav source that is connected to it... nor can you connect a second nav source to the G5s unless you do not have a third party autopilot (though that sounds like your case... probably no autopilot?). You do get some redundancy in that the ADI will display course guidance, so you have that if the HSI goes TU.

How much do you really need crossing radials anyway though? With a GPS onboard you don't really have a need to identify fixes via crossing radials (and VORs are getting decom'd all the time) and if your GPS were to fail for other than jamming/interference reasons, you probably don't have that 2nd nav source available to get a fix anyway.

 

[WDD]

Just a general comment....

WoW What an amazing panel you're going to have.

How did you decide between the 650 and not the 650 xi? 750? At what point do you get rid of all of the 6 pack and put in a glass panel like a G500?

 

[chemgeek]

Impressive upgrade. Personally, I would like a redundant CDI display, which provides failure backup as well as seamless transition in case of same. An option is to obtain a used GI-106 indicator for the 255. With some owners pulling their GI-106 units when G5s go in, you might get a bargain. I'm in that boat with a spare GI-106, but I think I'm getting a 255 in the near future to replace an obsolescent #2 radio and CDI, so the 106 can go back in. I got it used in the first place for a very good price when another local owner put in a first gen Aspen years ago. Of course a GI275 would be $piffier.

 

[Jdm]

Ryan.

You appear to be correct about the G5 bearing pointer. I actually knew about that feature but forgot to mention it. You guessed correctly, we do not have an autopilot. It’s therefore ok to connect a second selectable nav source to our G5. My avionics guy is the one who suggested this set up. It’s starting to sink in. My main concern with not having a dedicated #2 indicator is not necessarily the cross radials, it’s primarily the lack of comparable raw data approach indications, and the lack of lOC/GS indications if the G5 itself were to fail.

I have to admit that this is a new way of GA flying for me. I’ve flown over 30 years of GA having 2 independent nav/coms w/indicators at a minimum. My commercial jet flying years totally spoiled me with redundancy.

Hey, you mentioned that I have some redundancy in that the ADI will display course guidance, if the HSI were to go TU. Do you happen to know the specifics on that? GPS course? Loc course? GS?

Thanks much! Very helpful.

 

[Jdm]

Just a general comment....

WoW What an amazing panel you're going to have.

How did you decide between the 650 and not the 650 xi? 750? At what point do you get rid of all of the 6 pack and put in a glass panel like a G500?

Hi WDD. Thanks. Yes, this is actually the 650Xi. I didn’t think to mention the Xi portion. Pretty much the same as the legacy GTN650 but with a better processor, pixels, and maybe a new direct to button. The 6 pack is kinda gone already with this set up. The two vertically stacked squares become primary. Much cleaner now that the DG is gone. The nav indicators are both gone (unless I decide to put a #2 in). The vacuum gauge is gone. The old intercom is even gone. Much cleaner radio stack also. We had a lot of old nav junk in there. Very exciting for sure. No idea what it takes to stomach a full glass panel.

 

[Jdm]

Impressive upgrade. Personally, I would like a redundant CDI display, which provides failure backup as well as seamless transition in case of same. An option is to obtain a used GI-106 indicator for the 255. With some owners pulling their GI-106 units when G5s go in, you might get a bargain. I'm in that boat with a spare GI-106, but I think I'm getting a 255 in the near future to replace an obsolescent #2 radio and CDI, so the 106 can go back in. I got it used in the first place for a very good price when another local owner put in a first gen Aspen years ago. Of course a GI275 would be $piffier.

I like the way you think! I’m obviously having a hard time wrapping my head around the lack of redundancy, but It’s so much better than what we had before. I actually called a few of the big boy shops today about used indicators. They all told me the same thing. Good used indicators are hard to find. High demand. I’ll probably go new if we end up getting a #2 indicator. Thanks!

 

[Ryan Klems]

Hey, you mentioned that I have some redundancy in that the ADI will display course guidance, if the HSI were to go TU. Do you happen to know the specifics on that? GPS course? Loc course? GS?

Thanks much! Very helpful.

It’ll show all the time, not just in a failover mode, but the ADI will show course deviation for both VHF nav and GPS and glide path for both ILS and GPS approaches with glide path.

Here is a clip from pilots guide showing the course and glide path displays on the ADI.

 

[Jdm]

Understood. I thought you were referring to a failover that I wasn’t aware of. Thanks for clearing that up.

 

[pnancoz]

I upgraded to the exact same set-up last year. Do you have an existing CDI that you can reuse with the GNC 255 to save cost?

 

[Jdm]

No, I wish. My existing CDI is trash. Are you using an independent CDI for your CNC 255? The G5’s will support both. People seem to be about 50/50 in favor of that idea...

 

[Fracpilot]

Hello, I’d like to get your thoughts about a #2 indicator please. After way too many years of making due with our old avionics we are finally getting a new rack of IFR equipment.

Here’s the equipment:
GTN650 in the #1 position.
GNC 255 in the #2 position.
Two G5’s flush mounted. (Vacuum sys will be entirely removed, including the old DG)
GMA 345 audio panel.
GTX 345 transponder.

Here’s the situation:
The G5’s will be the new primary ADI and HSI. The GTN650 will provide all lateral and vertical guidance to these G5’s as our primary instrumentation source.

Here’s the confusing part:
The #2 nav/com (GNC 255) can also be connected to the G5’s which is source selectable from within the G5 menu. This allows the G5’s to suffice as the indicator for both our #1 and #2 units which saves the large expense of an additional indicator for our #2 nav. Obviously it will only allow one source to be displayed at a time, therefore preventing indicator redundancy, the ability to pull cross radials, compare courses, intersection holds, etc. We certainly have the option to add a #2 indicator which can be installed as a stand alone indicator or mirrored to the G5’s respective nav source. If I need to go this route I’m leaning towards the new GI 275 as it’s not that much more than a new 106B indicator.

Question: Based on the above information, what’s your general thoughts on the importance of a secondary indicator? Remember, the GNC 255 has a some built indications. It has a small, “lateral only” deviation scale with a TO/FROM indicator and OBS knob on it’s display.

Thanks,
Jdm

I have the same set up as you except I went with the Garmin 225 Comm instead of the Garmin 255 Nav/Com. I couldn’t see any reason for redundancy Nav when I use GPS 100% of the time. I would even shoot an LPV before an ILS now if the mins are the same.

I did decide to panel mount a Garmin Aera 660 and had it wired to a GDL51. All of it talks to each other and it’s great having XM and ADS B. I went with the 350C audio panel instead of the GMA345. It does more and was the same price, especially if you ever install a Garmin 750.

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[pnancoz]

No, I wish. My existing CDI is trash. Are you using an independent CDI for your CNC 255? The G5’s will support both. People seem to be about 50/50 in favor of that idea...

I prefer to have the completely redundant nav.

 

[murphey]

I prefer to have the completely redundant nav.

View attachment 82899

Me too.
SL30 <-> CDI
GPS 355 <-> G5 HSI

And.....keeping the DME and ADF....just for grins.

I despise single point of failure.

 

[Fracpilot]

Me too.
SL30 <-> CDI
GPS 355 <-> G5 HSI

And.....keeping the DME and ADF....just for grins.

I despise single point of failure.

I guess so if it’s already installed. In my case I’m have not seeing the value of 2 VHF Nav’s. I already have 3 independent GPS sources and 1 VHF nav. I removed the DME. GPS is primary. Time to accept it. In the last 15 years of professional flying, I’ve never lost a GPS as primary Nav.


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[455 Bravo Uniform]

If I had a spare hole in my panel, I’d install a secondary independent indicator for NAV2.

Not sure about compatibility with any old CDI/GS. Doesn’t need to be fancy or expensive to work with the Garmin nav radio, does it?

 

[pnancoz]

Not sure about compatibility with any old CDI/GS. Doesn’t need to be fancy or expensive to work with the Garmin nav radio, does it?

My new GNC 255A works perfectly with the old KI 209 CDI.

 

[murphey]

I guess so if it’s already installed. In my case I’m have not seeing the value of 2 VHF Nav’s. I already have 3 independent GPS sources and 1 VHF nav. I removed the DME. GPS is primary. Time to accept it. In the last 15 years of professional flying, I’ve never lost a GPS as primary Nav.


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“3 independent GPS sources.”
Unless you have equipment for GNSS, Galileo, GLONASS, or BeiDou, (pick 3) you have 3 GPS receivers, not sources. Right now I have 3 - an iPad, a handheld hikers gps and my phone. But all three are receiving from the GNSS constellation.

[fixed spelling]

 

[Jdm]

Excellent points. Very much appreciated!

Right, it doesn’t have to be fancy to work with the GNC255. Unfortunately, my shop does not currently have anything decent available. Used ones from unknown sources have been hit and miss for them, sometimes costing more in repair/checkout labor than what it’s even worth.

We don’t mind going with a new indicator if it’s determined to be a needed item for this panel upgrade.

Interesting times. I’ve been in this business all my life, hold every rating/cert one could want and I still seriously underestimated the amount of owner/operator research needed to properly design a well-functioning modern panel. Avionics shops are even struggling to keep up with the stuff these days.

Nice panels there! Thanks for sharing the pics. I’m saving for reference.

 

[Grum.Man]

The GPS has it's own CDI as does the 255 and the G5. That's triple redundancy. Reality is if you lose a nav component there is no harm in declaring an emergency. They will give you radar vectors and you would have the GPS for Vnav if you lose your G5 or you can just fly a localizer/lpv/VOR approach and not need any vertical guidance. Worst case scenario you will have your tablet most likely which can get you down safely in a pinch.

 

[455 Bravo Uniform]

Imagine if shops had time to market and up sell!

I ended up finding and buying my own GS/CDI. It was a NOS KI209 from a guy on POA from Malaysia. Even came with the install kit still wrapped in original sealed plastic.

They’re out there. You just have to assist the avionics shop a little to save yourself money, cuz to them it’s not sensible to burn hours on that effort, while customers are piling up at the door.

 

[Fracpilot]

“3 independent GPS sources.”
Unless you have equipment for GNSS, Galileo, GLONASS, or Baidu, (pick 3) you have 3 GPS receivers, not sources. Right now I have 3 - an iPad, a handheld hikers gps and my phone. But all three are receiving from the GNSS constellation.

The iPAD receives GNS, GLONASS, and Galileo along with the GDL51 I believe. Not sure about the Aera 660 and Sentry.

If I need GPS information from a source/device when others have failed then I have three sources/devices to receive that information in the event I have any failures. GTN650, Aera 660, GDL51, IPAD and even the Sentry. All of them can independently review GPS information. 5 sources..lol

It’s all semantics.


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[ISU_Radar]

The iPAD receives GNS, GLONASS, and Galileo along with the GDL51 I believe. Not sure about the Aera 660 and Sentry.

If I need GPS information from a source/device when others have failed then I have three sources/devices to receive that information in the event I have any failures. GTN650, Aera 660, GDL51, IPAD and even the Sentry. All of them can independently review GPS information. 5 sources..lol

It’s all semantics.


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FYI, the Aera 660 can receive and use GLONASS.

 

[Fracpilot]

FYI, the Aera 660 can receive and use GLONASS.

Even better. Thanks.


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[TerryD]

Recently lost my GPS in flight (failed GPS antenna) so had to revert to VOR NAV. I have the same set up you are going to (Dual G5s, GTN650, GNC255), with the 650 and 255 connected to the G5s for CDI. In the first pic, I was able to use VOR1 and VOR2 to identify cross radials. In the second pic I was using VOR2 (GNC255) for navigation while using VOR1 (650) to identify cross radials. Used it for course navigation and flying an arrival procedure into DFW. No issues with both NAV CDIs being on the G5.

 

[Jdm]

Wow. Great example. Very well managed! Thanks for sharing that one. And the pics, perfect time to take camera break..Haha. That’s a clean G5 flush job you got there. We’re going for the same.

 

[Jdm]

Update: After weighing the research, options, and opinions, we decided to splurge. Ordered the GI275. MFD flavor. It allows the connection of 2 sources. In our case, it will serve as a dedicated CDI for the #2 GNC255A, or the #1 GTN650Xi whichever is selected via knob or touchscreen. It will display traffic and weather info from the GTX345. Mapping/terrain info via the GTN650Xi. The GI275 comes with a built in VERY VFR GPS for simple direct-to commands. This feature could be useful if the 650, or it’s antenna were to go “TerryD” on us... Ships with it’s own GPS antenna included. Nothing fancy, a simple hockey puck type that’s hard wired and mounted on the glare shield.
Our avionics man says the GI275 will not prohibit any of the G5’s normal functionality which was an initial concern of mine.
It appears to be a nice little standby instrument going forward. Very customizable. Could offer even more options later if we decide to sell or upgrade. It’s the 1st one installed by our shop. We are the guinea pig.

Thanks for the recommendations, really looking forward to flying with this package.

 

[asicer]

Update: After weighing the research, options, and opinions, we decided to splurge. Ordered the GI275. MFD flavor. It allows the connection of 2 sources. In our case, it will serve as a dedicated CDI for the #2 GNC255A, or the #1 GTN650Xi whichever is selected via knob or touchscreen. It will display traffic and weather info from the GTX345. Mapping/terrain info via the GTN650Xi. The GI275 comes with a built in VERY VFR GPS for simple direct-to commands. This feature could be useful if the 650, or it’s antenna were to go “TerryD” on us... Ships with it’s own GPS antenna included. Nothing fancy, a simple hockey puck type that’s hard wired and mounted on the glare shield.
Our avionics man says the GI275 will not prohibit any of the G5’s normal functionality which was an initial concern of mine.
It appears to be a nice little standby instrument going forward. Very customizable. Could offer even more options later if we decide to sell or upgrade. It’s the 1st one installed by our shop. We are the guinea pig.

Thanks for the recommendations, really looking forward to flying with this package.

I take it you got the non-AHRS version of the GI275?

 

[AA5Bman]

I just did this exact panel, with a GI275. Make the GI275 your HSI - it’s awesome. Really, awesome, and worth the extra coin over a G5, especially if you have an autopilot it can interface with and provide GPSS. For a secondary display, I’d pick up a used Ki206 or KI209 or something along those lines - I found a used Ki206 for $400.

 

[Jdm]

I’m sure it’s awesome but we got the non-AHARS version. No need for another attitude indicator with two G5’s running primary.

 

[Jdm]

We didn’t even opt for the $400 backup battery. The only way we would need that is if we have total elec failure. At that point we would have no nav to provide the GI275 anyway. Backup battery is only good for the internal VFR GPS, which is no better than a handheld or iPad. The G5’s should have plenty of backup for AHARS.
I’m really getting tired of tracking battery dates. Everything seems to have batteries that have to be tracked these days. 3 for the ELT alone!

 

[Smoked2long]

I have the same set up as you except I went with the Garmin 225 Comm instead of the Garmin 255 Nav/Com. I couldn’t see any reason for redundancy Nav when I use GPS 100% of the time. I would even shoot an LPV before an ILS now if the mins are the same.

I did decide to panel mount a Garmin Aera 660 and had it wired to a GDL51. All of it talks to each other and it’s great having XM and ADS B. I went with the 350C audio panel instead of the GMA345. It does more and was the same price, especially if you ever install a Garmin 750.

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Nice Panel. I’m looking at the same thing but adding Garmin autopilot.

 

[Smoked2long]

I just did this exact panel, with a GI275. Make the GI275 your HSI - it’s awesome. Really, awesome, and worth the extra coin over a G5, especially if you have an autopilot it can interface with and provide GPSS. For a secondary display, I’d pick up a used Ki206 or KI209 or something along those lines - I found a used Ki206 for $400.

Could you explain the benefits over a dual G5 setup? Thank you.

 

[Hang 4]

One other small point, the GTN will also provide lateral guidance and distance for a RNAV approach on it's own screen. (not sure if it will also do ILS). That would let you fly a dive and drive to a MDA at LPV mins. That's what I had to do for my IFR practical. The GNC 255 can do that with an ILS, but it needs to be configured by the installer during set up.

 

[WannFly]

the GTN will also provide lateral guidance and distance for a RNAV approach on it's own screen.

something i will definitely miss coming from 480 is 480 has both lateral and vertical guidance on its own page.

 

[AA5Bman]

Could you explain the benefits over a dual G5 setup? Thank you.

The main benefits are a better fitting instrument, a brighter and more colorful display, and the big one, HSI map mode, which plots out your course and provides topo/terrain mapping just like an additional screen for your GPS. Sounds kinda gimmicky but it's nice.

 

[Smoked2long]

The main benefits are a better fitting instrument, a brighter and more colorful display, and the big one, HSI map mode, which plots out your course and provides topo/terrain mapping just like an additional screen for your GPS. Sounds kinda gimmicky but it's nice.

Thanks, I’m just wanting to try and make a good decision.

 

[flyingcheesehead]

Here’s the confusing part:
The #2 nav/com (GNC 255) can also be connected to the G5’s which is source selectable from within the G5 menu. This allows the G5’s to suffice as the indicator for both our #1 and #2 units which saves the large expense of an additional indicator for our #2 nav. Obviously it will only allow one source to be displayed at a time, therefore preventing indicator redundancy, the ability to pull cross radials, compare courses, intersection holds, etc. We certainly have the option to add a #2 indicator which can be installed as a stand alone indicator or mirrored to the G5’s respective nav source. If I need to go this route I’m leaning towards the new GI 275 as it’s not that much more than a new 106B indicator.

After reading what you wrote above, I was going to tell you to do exactly what you did:

Update: After weighing the research, options, and opinions, we decided to splurge. Ordered the GI275. MFD flavor.

That should be a really nice setup. If I were to recommend anything, it'd be that you set up the 275 to display stuff that might kill you in the next 5 minutes: Zoom level set at 10 miles, displaying traffic, terrain, and obstacles and wires. Then, use the 650 and/or your iPad for the "strategic" view with weather and such.

 

[Jdm]

It’s working out very well. I’ve made 6 or so flights with the new panel. The GI275 is the coolest instrument of them all. And we almost didn’t even get it because it wasn’t necessary! The G5’s are nice, but if I had it to do over again I would definitely opt for a couple more 275’s instead. It’s really hard to pick which page to hang out on, they are all so great. I truly believe the 275 will cause the G5’s to become obsolete. That’s pretty crazy I know.

 

[Jeff Constantine]

I prefer to have the completely redundant nav.

View attachment 82899

Hi, I realize your comment on this thread is old, but do you have the gnc255 connected to the G5 AND the separate CDI (GI 106)? I’m upgrading to two gi275s and replacing an ancient com #2 and nav #2 with a gnc255. I’m trying to decide whether to keep my GI 106 and would love to have my NAV2 connected to both the gi275 AND the GI106. The installer is telling me the 255 has to connect to the GI 275 OR the GI 106 but can’t link to both…