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  #1  
Old 12-08-2017, 12:01 PM
Sqrfrk Sqrfrk is offline
 
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Location: Alameda, CA
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Default GPS Data and IFR

I'm still a long way off from having the need to plan for avionics (not to mention the market may look completely different by the time I get there), but I'm a little confused as to some aspects of using a homespun glass cockpit for a GPS approach. I'm trying to get a clearer picture of the use case so forgive me if I just regurgitate my thoughts all over the place

I have the understanding that you can't legally IFR navigate nor fly approaches via GPS unless it's a TSO'd unit like an IFD/GTN/KSN770, etc. If I was sitting behind a Skyview HDX, I can hook these devices together to get helpful features like an HSI on the PFD...but I still can't legally use the Skyview for enroute/approach (I'd have to be looking at the TSO'd unit). Without any backup IFR instruments to navigate, what would be the purpose of loading in an approach plate into the Skyview if it's presumably already loaded up on the GPS MFD? A lot of the user panels I'm seeing in various galleries seem to be going all in on an GPS IFR setup without any other way to perform an approach.

I was thinking of possibly using a KSN770 to take advantage of my existing Seattle Avionics chart subscription, with the understanding that I'll need to subscribe for nav/obstacle/terrain data through Wingman (which is sourced form Jeppesen?). It seems to me with my shallow understanding that having Skyview HDX + KSN770 would make the most sense considering the resources I have. On the other hand, I like the IFD interface from what little I've played with it and I've been reading that future support for the KSN is looking pretty shaky. Of course, going with an IFD unit would mean I'm on the hook for a Jeppesen subscription of 1k+ per year to stay legal (though there was someone on the forum who chose to only subscribe for navdata, while using the Skyview for obstacle/terrain - does this work out pretty well?).

What would be a good way to work out a system with the right amount of tradeoffs? I like the IFD but it's pricier for initial cost and data. I wouldn't mind the KSN but it seems to be fairly dated compared to other current offerings and future support is questionable. Or am I approaching this with the wrong perspective?
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  #2  
Old 12-08-2017, 12:06 PM
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bkervaski bkervaski is offline
 
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In the case of a GTN and a G3X, the GTN feeds the data to the G3X through the can-bus network.

The GTN is the "certified source" which makes it legal to fly the aircraft IFR.

The fact that it's feeding the data over to the G3X is just a convenience.
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  #3  
Old 12-08-2017, 12:08 PM
Sqrfrk Sqrfrk is offline
 
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Quote:
Originally Posted by bkervaski View Post
In the case of a GTN and a G3X, the GTN feeds the data to the G3X through the can-bus network.

The GTN is the "certified source" which makes it legal to fly the aircraft IFR.

The fact that it's feeding the data over to the G3X is just a convenience.
Fair enough, but in this case would it be legal to be looking mainly at the G3X to navigate and fly the approach (moving map, GPS approach plate)? I'm having trouble distinguishing the problem of having an aircraft "IFR legal" and the problem of legally flying the aircraft IFR.
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  #4  
Old 12-08-2017, 12:09 PM
YellowJacket RV9 YellowJacket RV9 is offline
 
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There?s no reason you have to be looking at the TSO unit for the approach. You can use the sky view just like as in any other phase or flight. There is certainly more to it than that, ie possibly indicator lights needed, but in essence, the TSO GPS unit is needed as a navigational source, not as a PFD.

Chris
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  #5  
Old 12-08-2017, 12:19 PM
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Auburntsts Auburntsts is offline
 
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Quote:
Originally Posted by Sqrfrk View Post
Fair enough, but in this case would it be legal to be looking mainly at the G3X to navigate and fly the approach (moving map, GPS approach plate)? I'm having trouble distinguishing the problem of having an aircraft "IFR legal" and the problem of legally flying the aircraft IFR.
Yes it's legal. The TSO'd navigator with a current database fills the navigation square and any EFIS, regardless of brand, that provides for the proper system annunciations and nav display (and all the major ones do) completes the system. Now if you want to look at just the navigator, that's fine too, but that's not nearly as practical, especially on the smaller boxes like the GTN 650 I have.
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  #6  
Old 12-08-2017, 12:24 PM
DGlaeser DGlaeser is offline
 
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Quote:
Originally Posted by Sqrfrk View Post
I have the understanding that you can't legally IFR navigate nor fly approaches via GPS unless it's a TSO'd unit like an IFD/GTN/KSN770, etc. If I was sitting behind a Skyview HDX, I can hook these devices together to get helpful features like an HSI on the PFD...but I still can't legally use the Skyview for enroute/approach (I'd have to be looking at the TSO'd unit).
Not true! The EFIS HSI is simply being used as your CDI. The TSO'ed unit has all the data (waypoints, approaches) and the IFR navigator, but the device to display the data can be the EFIS (doesn't have to be a certified unit).
When you say 'loading an approach plate into the Skyview', are you talking literally about the approach plate, or the navigation plan view of the approach? The plan view of the approach is provided by the IFR Navigator, and again can be displayed on multiple devices.
Looking at the published (NOS, JEPP) approach plate is typically done via paper or a tablet. It can be displayed on an EFIS screen if desired, but most don't find that as useful.
So you need 2 subscriptions - one for your IFR Navigator, the other is the NOS or Jepp approach charts.
Updating things like Terrain, Obstacles, surface features (cities, lakes, roads) is optional and done every few years by most folks.
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  #7  
Old 12-08-2017, 12:24 PM
Sqrfrk Sqrfrk is offline
 
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Thanks for the replies! Any opinion on possibly subscribing to just Navdata on an IFD and relying on Skyview and Dynon for terrain/obstacle data?

Last edited by Sqrfrk : 12-08-2017 at 12:26 PM.
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  #8  
Old 12-08-2017, 12:29 PM
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Auburntsts Auburntsts is offline
 
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Quote:
Originally Posted by Sqrfrk View Post
Thanks for the replies! Any opinion on possibly subscribing to just Navdata on an IFD and relying on Skyview and Dynon for terrain/obstacle data?
You could. Only the nav database is required for IFR flight. All of the other databases are just gravy and aren't legally required to be kept current.
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  #9  
Old 12-08-2017, 12:35 PM
Sqrfrk Sqrfrk is offline
 
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Quote:
Originally Posted by Auburntsts View Post
You could. Only the nav database is required for IFR flight. All of the other databases are just gravy and aren't legally required to be kept current.
I guess the last question I have then is the motivation for larger screen navigators, that is, what are practical use cases for pairing a large screen IFR navigator like the IFD550 or GTN750 with say a two screen EFIS? I know a few Cessnas in my club opted to have the GTN750 installed, but they had the standard instrument six pack.
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  #10  
Old 12-08-2017, 12:42 PM
YellowJacket RV9 YellowJacket RV9 is offline
 
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Quote:
Originally Posted by Sqrfrk View Post
I guess the last question I have then is the motivation for larger screen navigators, that is, what are practical use cases for pairing a large screen IFR navigator like the IFD550 or GTN750 with say a two screen EFIS? I know a few Cessnas in my club opted to have the GTN750 installed, but they had the standard instrument six pack.
I think you hit on the primary reason - most are installed in planes without the benefit of huge glass panels like we have. Now, if you only have a single screen display, it may be cheaper to bump up to the larger navigator and use that like a second screen if you want more screen real estate, rather than add another screen. IE, you could have PFD and engine data on your PFD, and a moving map or approach plate on your GPS/MFD.

Chris
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