GNX 375 talk to GNC 255 and GI-275

[RobertGary1]

When I select an ILS approach in the 375 it doesn't talk to the other modules. I have to then manually tune the 255 and then manually spin the HSI on the 275 and change the source. In other Garmin installs this was all automatic. Am I missing something? They are all on the same data buss and otherwise talk to each other.

 

-Robert

[KLudwick]

Have you talked to your dealer yet, Robert?

[jamesm]

Not sure if the GI375 has the GAD29B equivalent  builtin but in to the unit. However in the case Of 2 G5'S G5'S GNC-255 (Nav/Com) and GNC-355 (GPS/Com)setup. There's is a bit Of Symantec's in terminology and physical location different navigation unit. My case the GNC-255 sits above GNC-355.  so physically the GNC-255 is my com#1 on the audio panel .  but as I recall I think it's SDI on the G5 it see it and Nav signal number 2. Once working correctly you really don't even think twice which nav signal is #1 and #2. It's either being  driven by GPS or the VOR/LOC/ILS signal on the G5 it tells Which you have selected as well Color code symbol  for Each different nav signals. I am pretty sure the GI375 would works the same way.

Hope this Helps,

James '67C

[RobertGary1]

21 hours ago, KLudwick said:

Have you talked to your dealer yet, Robert?

Yes

[JimB]

22 hours ago, RobertGary1 said:

When I select an ILS approach in the 375 it doesn't talk to the other modules. I have to then manually tune the 255 and then manually spin the HSI on the 275 and change the source. In other Garmin installs this was all automatic. Am I missing something? They are all on the same data buss and otherwise talk to each other.

 

-Robert

Robert,

I have a similar set up with dual G5s, a GNX 375 and a GNC 255. Are you asking that when you select an ILS approach in the GNX 375, you're expecting it to autotune the GNC 255 and change the NAV selection in the HSI? I don't think it works like that. They are both independent NAV sources and you have to select which NAV source you want on the G5/GI 275. The GNX 375 is only going to provide you situational awareness for the ILS approach. 

I wish it would do want you want and maybe I am wrong but I have been messing around with it lately and if you want an ILS, tune the freq on the 255 and select NAV on the HSI. If you want to monitor the approach with the GPS, you can select that on the 375....

I think with the more integrated flight decks it will do what you want but even the G1000 systems I am familiar with, you still have to select a NAV source on the HSI. 

[RobertGary1]

1 hour ago, JimB said:

 

I think with the more integrated flight decks it will do what you want but even the G1000 systems I am familiar with, you still have to select a NAV source on the HSI. 

The older systems were like that. In the current g1000’s it automatically switches the nav source as you turn procedure turn inbound. 
 

-Robert 

[carusoam]

@KLudwick stuff that might interest you...

-a-

[jamesm]

Purely speculative on my part.  But as others have said or eluded to. being that G1000 is more Of integrated unit where as The  G5's or GI275's and  having separate  navigation sources such as GNC-255 and  GNX375|GNC-355|GPS175. I couldn't see how 3 separate and independent systems could possibly negotiate what the pilot is thinking and when to make the switch from GPS signal to ILS signal. I think that would be hard problem to solve and integrate into independent systems. I would be Great if they reliably do it.

[carusoam]

In the 90s...

Mooneys used a switch with a single throw, bazillion terminals... and a blue light...

When GPS data was sent to the HSI... the GPS was the source, the blue light was on...

When ILS data was sent to the HSI... the VOR / ILS nav box was the source, the blue light was off...

 

My first O squawk... replace the blue light.   The bulb went out and wasn’t indicating anything...  

There are so many little gotchas in the IFR environment...

Making sure what is being displayed, is actually being supported by the box you think it is...

PP thoughts only, not a CFII...

Best regards,

-a-

[RobertGary1]

7 hours ago, jamesm said:

Purely speculative on my part.  But as others have said or eluded to. being that G1000 is more Of integrated unit where as The  G5's or GI275's and  having separate  navigation sources such as GNC-255 and  GNX375|GNC-355|GPS175. I couldn't see how 3 separate and independent systems could possibly negotiate what the pilot is thinking and when to make the switch from GPS signal to ILS signal. I think that would be hard problem to solve and integrate into independent systems. I would be Great if they reliably do it.

It’s when you select “activate approach” it knows what the pilot is thinking. It’s identical to the g1000. These units all talk on the shared data buss. 
the g1000 is no more integrated. It’s an independent series of line replaceable units that communicate over the same data buss. 

[jamesm]

Hum I must be  misunderstanding you...  So I get the part  when say you hit “activate approach”  on the GPS since there is no activate approach on the GNC-255. Still in my case, where I have two  independent G5's displays and  two independent  navigation sources plus a GAD29B that make all this happen.  Say for the sake of argument that the Pilot  had the GPS slaved to the CDI needle on the G5  but you wanted to do an ILS approach. Someone (other than the Pilot) on the CAN bus would have to over ride the Pilot's input of the previous selected  GPS option for CDI on the G5 to now be slaved to ILS.  My way of thinking  you have just over ridden the pilot's input whether it be intentional  or unintentional if the G5 switches to ILS without the Pilot's consent or interaction. if you had say GNS or a GTN navigator  with ILS/GPS built in and you hit "activate approach" since both nav sources are in the same unit has some method (relays) of  selecting  ILS as the approach. That unit would know to put out the ILS signal since the was"activate approach" was select telling it ILS/GPS . As I understand it for Bus topology typically 2 kinds are a round robin  approach where everybody gets a turn talking on the bus and master/slave where there is essentially there is a traffic cop or symphony conductor that  controls who is on the bus talking. So in a scenario where you have two older  GNS  navigators or one GNS and maybe KX155/156 combination configuration. it is my understanding that they would used those really expensive relay switch annunicators units to switch the signal controlling the CDI source which requires pilot interaction through button push on the annunicator panel.

I guess comes down to design philosophy of whether or not to keep the Pilot in the loop or not. 

 

I could be way way out there on this. I find the different approaches to system design really interesting.

 

James '67C

[RobertGary1]

6 minutes ago, jamesm said:

Hum I must be  misunderstanding you...  So I get the part  when say you hit “activate approach”  on the GPS since there is no activate approach on the GNC-255. Still in my case, where I have two  independent G5's displays and  two independent  navigation sources plus a GAD29B that make all this happen.  Say for the sake of argument that the Pilot  had the GPS slaved to the CDI needle on the G5  but you wanted to do an ILS approach. Someone (other than the Pilot) on the CAN bus would have to over ride the Pilot's input of the previous selected  GPS option for CDI on the G5 to now be slaved to ILS. 

Yes, that's how it works. For instance in the G1000 (that has the same buss connecting the LRU's) when you activate the approach it steers you around with the GPS as the nav source until it finishes the procedure turn then it auto changes to the ILS. The entire time youre sitting there with your arms folded just watching the whole thing.

-Robert

Edited December 18, 2020 by RobertGary1