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GPS Data and IFR

Sqrfrk

Member
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 :D

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?
 
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.
 
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.
 
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
 
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.
 
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.
 
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?
 
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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?

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.
 
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.
 
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
 
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.

It makes some tasks easier as everything is displayed in one place vs having to page around and it can free up screens to show other data, but that's primarily personal preference. For example, I have a 2 Screen non-touch G3X and a GTN 650. The moving map on the 650 is basically worthless. Enroute I display nearest airports on it, and on approach, the flight plan so I can make quick changes in routing if required. On my MFD enroute I typically display the moving map and the selected approach plate on approach. If I had a GTN 750, it would give me more options as to where and what I displayed at any given time.

I should note that I also have my tablet up with GarminPilot at the same time.
 
Not Eacctly Sure What You're Looking for, but...

As already mentioned, the TSO'd box feeds information into the EFIS, which is really just a display (I know, it can be wired to a GPS antenna as well,). When using the EFIS as your primary flight display, you should be able to display localizer and glide slope information in some fashion (needles or scales). All the information you need is right in front of you, unlike in the "old" days when we have to scan the six pack and then the OBS/GS display head.

You don't "need" 2 EFIS screens to safely fly IFR - one will do. You'll still need some backup though - a Garmin G5 or an GRT Mini will work well.

As for the approach charts, you don't need to display them on an EFIS. If you do, the EFIS has to have a large enough screen for you to read them. Many of us use Ipads or something similar to display plates. If you use something like Foreflight, the annual subscription cost is less than $200. When flying an approach, you shouldn't be staring at a plate anyway - you should have the MDA/DH and missed approach procedure committed to memory. You should be focused on flying the plane.
Terry, CFI
RV9A N323TP
 
My two cents...

Absolutely strictly speaking, a TSO for, say, my Garmin 420W, also specifies one or more specific antennas, and one or more specific CDIs. However, the FAA is content to accept your or your manufacturer?s assessment that it meets ?the performance standards?. For an indicator, this is pretty simple: when the box commands ?fly left?, does the needle move left? etc. Same for required indicators. You can roll your own colored lights as long as they work. So, bottom line, FAA is happy with non-TSO indicators as long as they work. They are suppose to be within the designated field of view.
 
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