Save the money and just buy a GTR255 Comm/Nav instead of the 650. Everyone I’ve talked that has a 750/650 combo said the 650 was a waste since they always just use the 750 and use the 650 just as Comm 2.
No desire to remote mount the audio panel or transponder?
Personally, I'd rather have a GNX375/GTR225 combo rather than a GNC355/GTX345 combo. Plus, you can get sub out the GTR-225 for a GNC255 to add back NAV2 (you can't get a ADS-B In/Out transponder with integrated NAV).
@iamtheari I would also think that a GTN750/GNX375/GNC255 combo would get you the same functionality as the GTN750/GTN650/GTX345 combo for a few bucks cheaper, no?
I've thought long and hard about other radio options as well as remote mounting things. My RV-14 has the GTR 20, GTX 45R, and GMA 245R. I love the panel having less avionics clutter and having the G3X Touch to control all the back-end stuff from one screen.
If there were a GTR 20 equivalent for the TXi system, I would jump on it immediately. But as far as I can tell, the only current Comm radios that the TXi can remote-tune are the GTNs. And being able to do that is a huge workload reduction. Bring up the destination waypoint info on the MFD (TXi or 750), tap the frequency you want, and then tap where you want it to come up. I would go with the 635, but I already have the nav antenna and wiring from the 430W that is coming out of the plane. That's more of a struggle.
In the 310, I really like having physical buttons for PILOT ISO and CREW ISO. I have flown with my sister's whole family: two parents plus three kids age 3, 6, and 9 at the time. They could all visit or soothe the youngest kid while I was talking to ATC, and with just one button push my "co-pilot" could switch between the family conversation and the crew to be my liaison and make sure everyone was doing okay. That's not an issue in the RV-14, so the remote intercom isn't a problem at all.
I already have the GTX 345, otherwise a remote transponder would be on order. But since I already have one, I can't quite push myself into trading it in for a same-functionality remote unit.
That's how I ended up with dual GTN combo. This entire project is an exercise in making the plane safer by reducing the single-pilot workload, so spending "a little" more for a dual GTN setup just to avoid manually tuning ATIS on Comm 2 is okay. It was a struggle, for sure. But I should also get database sync across the entire panel, so there's that as a bonus.
But I am still not quite sure where to put all the stuff. I like putting the PFD controller close to the PFD of course. Above it is fine. In my RV-14, I have the GMC 507 control head and it's below the GTN 650, just above the throttle and flap switch. But I'm sure I can adjust to having the heading and altitude select knobs above the PFD.
Between the 750 on the map page and the 650 on the default nav page, I think I get 11 data fields always on screen. So that's a factor in where I put those two units. I'll probably set the 650 up the same as the one in the RV-14, and then use the 750 to show the data fields that I have on the G3X Touch so both planes have the same information at hand.
I can put the GFC 600 control head above the throttle quadrant so the most important button (the AP button) is handy. I wonder if I can fit the 750, 650, and GFC all in the left column and then just put the audio panel and transponder in the right column. It will look asymmetrical but the audio panel and transponder are the two things a non-pilot right-seater is most likely to be able to help with, and I shouldn't have any trouble reaching the buttons on the audio panel to switch comm radios or hit the ISO buttons. Putting it at the top of the stack makes it easier to find and push a button in turbulence, in my experience.
