Redundancy question: G3X approaches with GTN failure?

[mandm]

The question for tomorrow is whether to stick with my GTR205 backup comm or to upgrade that to a GNC215 backup comm/nav radio probably at a cost of another $3500.

Talking with my mechanic he asked what the backup is if the GTN650Xi failed. The G3X does have its own GPS and according to Google it can do some approaches with a GTN failure but not LPV approaches. Does anyone know what approaches the G3X Touch can do with a GTN650Xi failure or if a backup nav radio is necessary.

Initially I thought the VFR only G3X would not be capable of loading any approaches with a GTN failure and would solely provide GPS guidance, but if it can still load RNAV approaches, that sounds sufficient enough for my comfort level.

I also fly with Foreflight on an iPad and a Garmin Aera 760 although they are not primary navigation tools, in the event of a GPS failure that is an emergency and would allow me to use whatever tools I have available.

 

[TCABM]

To start with, if there’s GPS failure of some sort on the GTN, there’s still the VOR/ILS side of the box that should be operational.

Now, if the whole box fails, that’s when a second nav/com would be useful. What’s the MBTF of a GTN6xx/7xx?

 

[Pinecone]

The answer is legally NONE. The GPS in the G3X is VFR only.

That said, if all you have is the G3X, you declare an emergency and use it.

It does not have full approaches in the database. No missed approach procedures and nothing prior to the FAF. So you would need to hand program or get vectors.

Posted on another forum:

"Today's test was the using the G3X internal VFR GPS as a backup for the GTN 650Xi. The G3X allows entering waypoints and the final segment of an instrument approach for reference and also it also has a VTF capability similar to the GTN. The GPS is certified VFR only so it's not really legal for IFR but it would help out in a pinch to get me to the airport where I could use NAV2 to shoot a legal VOR or ILS approach. I had some issues getting the G3X to load an approach for my test, but eventually I figured it out.

First, I tried it in the hangar on ground power with the G3X switched to internal flight plan source and there was no Load Approach button on the menu. Turns out the button only becomes available when the G3X internal GPS is getting a signal. You can load any other waypoints -- just not an approach.

Second, if the external navigator is active -- even with the G3X flight plan source set to internal, the G3X will not display the Load Approach button on the active flight plan menu.

You can load an approach into a saved flight plan and then activate it regardless of the state of the internal and external GPS'."

 

[midlifeflyer]

Talking with my mechanic he asked what the backup is if the GTN650Xi failed. The G3X does have its own GPS and according to Google it can do some approaches with a GTN failure but not LPV approaches. Does anyone know what approaches the G3X Touch can do with a GTN650Xi failure or if a backup nav radio is necessary.

A good idea when making a decision of this type is to grab a Pilot Guide or AFMS to see what limitations something has. As the Limitations section of the G3X AFMS says, IFR operations require an external IFR approved navigator and, more specifically,

"IFR operations are prohibited using G3X Touch while FPL Source is selected to Internal GPS navigation as the navigation source on G3X Touch."​

If you have VLOC capability feeding the G3X, you can use that. In an emergency, you can use anything.

 

[flyingcheesehead]

A good idea when making a decision of this type is to grab a Pilot Guide or AFMS to see what limitations something has. As the Limitations section of the G3X AFMS says, IFR operations require an external IFR approved navigator and, more specifically,

"IFR operations are prohibited using G3X Touch while FPL Source is selected to Internal GPS navigation as the navigation source on G3X Touch."​

If you have VLOC capability feeding the G3X, you can use that. In an emergency, you can use anything.

My impression was that the OP was talking about an emergency, and trying to figure out what would work at all, not what was approved.

The G3X Touch has a VFR GPS for backup, but is it possible to fly an approach using that?