GTN625 install for dummies

[skirting_virga]

Not afraid to admit I don't know what I'm doing and these connectors are huge. My plane is down for months for engine work and an ok consolation prize would be the ability to shoot LPV approaches for practice when it's up and running again.

I can probably figure out how to cut a hole in the panel, but mounting a rack study enough to support the LONG and HEAVY chassis of the unit is something I need help figuring out.

Fabricating a connector and connecting to the GRT Sport EX EFIS is something that should be simple but I really need to see a step by step build log of someone else doing it and could use guidance on what pins I need to populate and what the connectivity should look like.

Ultimately a G5 backup or two is something I'm interested in (maybe instead of the Aera 660) but I want to start small and just get this GPS in the panel and working. Help?

I'd like to put it above the GTX 327 and maybe attach the two racks together for additional support.

 

[BobTurner]

Not afraid to admit I don't know what I'm doing and these connectors are huge. My plane is down for months for engine work and an ok consolation prize would be the ability to shoot LPV approaches for practice when it's up and running again.

I can probably figure out how to cut a hole in the panel, but mounting a rack study enough to support the LONG and HEAVY chassis of the unit is something I need help figuring out.

Fabricating a connector and connecting to the GRT Sport EX EFIS is something that should be simple but I really need to see a step by step build log of someone else doing it and could use guidance on what pins I need to populate and what the connectivity should look like.

Ultimately a G5 backup or two is something I'm interested in (maybe instead of the Aera 660) but I want to start small and just get this GPS in the panel and working. Help?

I'd like to put it above the GTX 327 and maybe attach the two racks together for additional support.

I don’t see what RV you have; my comments are specific to the -10. In the 10 there is a structural sub-panel maybe 8”(?) behind the instrument panel. As you note, the gps is deep so I had to cut an opening for the gps to pass thru. Vans suggests these openings be reinforced, with doublers or angles. If you plan ahead these angles can be tied to the rack with small flush head screws (heads inside the rack (rack may need countersinking)) which greatly reduces the load on the instrument panel fasteners.
As to wiring, it’s just one wire at a time. Make sure you have a decent wire stripper and pin crimper (I’m pretty sure the 625 has both regular and high density pins, you’ll need a crimper (and pins) that can do both.) The GRT web site has the connections you’ll need, although it’s written in engineering-speak and you may need to look around (e.g., 430W gps to Hx in the Hx manuals), it’s all there.
Finally, the location for the gps is sub-optimum for IFR use (the TSO wants the gps not to be so far below the EFIS, although I’ve never heard of an faa inspector actually complaining about it.) When you get around to your future G5 upgrade you may want to think in terms of building a new panel from scratch. The uncut panel from Vans is not expensive, and doing much of the work off the plane is much easier than crawling around under the panel.

 

[skirting_virga]

I don’t see what RV you have; my comments are specific to the -10. In the 10 there is a structural sub-panel maybe 8”(?) behind the instrument panel. As you note, the gps is deep so I had to cut an opening for the gps to pass thru. Vans suggests these openings be reinforced, with doublers or angles. If you plan ahead these angles can be tied to the rack with small flush head screws (heads inside the rack (rack may need countersinking)) which greatly reduces the load on the instrument panel fasteners.

Thanks for weighing in. This is an 8A, which I'm led to believe has fewer reinforcements/obstructions due to the narrow panel. Do you have photos of doublers/angles reinforcing the rack in some install (yours or other)?

As to wiring, it’s just one wire at a time. Make sure you have a decent wire stripper and pin crimper (I’m pretty sure the 625 has both regular and high density pins, you’ll need a crimper (and pins) that can do both.) The GRT web site has the connections you’ll need, although it’s written in engineering-speak and you may need to look around (e.g., 430W gps to Hx in the Hx manuals), it’s all there.

I have the manuals and figure it makes a little sense as written, but I'm not totally clear on it all. Do I need an ARINC 429 module if there's only one nav source? The manuals *seem* to depict no additional module. I'm wondering if I should rip the Aera 660 out and if it uses the data pins that are supposed to go into the GRT Sport EX...

Finally, the location for the gps is sub-optimum for IFR use (the TSO wants the gps not to be so far below the EFIS, although I’ve never heard of an faa inspector actually complaining about it.) When you get around to your future G5 upgrade you may want to think in terms of building a new panel from scratch. The uncut panel from Vans is not expensive, and doing much of the work off the plane is much easier than crawling around under the panel.

As an instrument rated pilot, this is something I've never considered. I did think a little bit about the ergonomics of use given that my right hand will be on the stick when hand-flying, so the GPS should be programmed with the left hand, and additional height is potentially fatiguing for the arm/shoulder. Keeping the 625 within a short enough distance to scan it makes sense, although I've flown plenty of beat up, old, retrofitted planes that have mediocre panel configuration w/r/t the GPS and the primary instruments.

Ultimately I want to get rid of the GRT because I don't love it, but a backup instrument or two, even if located sub-optimally, would be enough to fly in "real IMC" if I'm well adjusted to the panel and keep the conditions of that encounter reasonably conservative. Locating it to the right of the GRT is probably what I would elect. I do have a spare panel, which I could populate with instruments, but the goal of this project is to learn how to wire up the 625 with as little disruption to what presently works as possible.

 

[BobTurner]

I’ll look and see if I have any photos of the rack install, but I think not.
Yes, you’ll definitely want ARINC data capability. You can get enough data over a rs232 line to do horizontal nav, but for precision approaches, or autopilot flown PT or holding patterns, you’ll need arinc data.
I hear you about using your left hand. I’m a cfii and frequently fly right seat and use a gtn650 with my left. I swear, I miss the correct touch screen button half the time with my left fingers (I’m very right hand dominant). I don’t think I’ve ever felt fatigued, though. You don’t need to mess with it that often.
Sorry you don’t care for your GRT. Of course these choices are very individual. I love my GRT Hx’s. The main limitation of the Sport is the small number of RS232 ports, it’s not hard to not have enough. Part of your planning will be to carefully count up how many you’ll need.

 

[BobTurner]

Okay, I found a photo. You'll see large square hole in the sub panel, where racks for transponder, Garmin 420W, and SL30 all passed thru. 4 aluminum angle opening-reinforcing pieces (primed with blue paint) around the hole, 2 aft, 2 fore. All 3 racks (not shown) were tied together with an aluminum "strap". Just visible on the lower left side of the vertical angle is a hole, where the strap was bolted to the angle. Not visible is a hole on the right side piece. You can also see cooling fans under the glare shield, and the copper ground buss bar going over the bottom blue angle.

 

[BobTurner]

Okay, I found another photo.

Just paper layouts. GPS is actually a picture of the Apollo unit, and the plain white paper to the right is the size of the second GRT Hx. To the far left is a Dynon D6 EFIS (with stand-alone Li battery). Point is, a simple left-right scan brings all 3 EFIS units, plus the gps, into view. Note too that normally one would try to mount these somewhat higher, for minimal head/eye movement when going from visual to instruments and back. However, I wear graded index glasses (sort of like bifocals). I sat in the plane, and moved the paper cutouts up and down, while holding my head level, in the usual position for looking out the windscreen thru the top of the glasses. The paper cutouts were then positioned where they were in best focus, moving only my eyes, not my head. Just a precaution against vertigo.

 

[gkochers]

Different unit and different airframe, but here are some photos of the supports I made for a GTN750 on an RV-10 that might be useful. I used angle stock to support to front end of the tray at the panel with #6 countersunk screws installed from inside the tray. I used angles to reinforced the holes I needed to cut in the sub panel and then just fabricated some plates to attach to the angles and support the rear of the tray, again with #6 screws from the inside.

Took a lot of thinking and trial fitting but it all came out ok.

 

[skirting_virga]

I’ll look and see if I have any photos of the rack install, but I think not.
Yes, you’ll definitely want ARINC data capability. You can get enough data over a rs232 line to do horizontal nav, but for precision approaches, or autopilot flown PT or holding patterns, you’ll need arinc data.

The wiring diagram from GRT (HX - not sure about EX) doesn't show an intermediate box - it just looks like pins out on the GTN650 and pins in on the GRT EFIS. What do the external ARINC 429 boxes get used for? For some reason I figured that was used with multiple inputs or something. I have no problem buying one if it is needed (and it seems like there might be a connector modularity benefit), I just want to make sure it's needed.

I hear you about using your left hand. I’m a cfii and frequently fly right seat and use a gtn650 with my left. I swear, I miss the correct touch screen button half the time with my left fingers (I’m very right hand dominant). I don’t think I’ve ever felt fatigued, though. You don’t need to mess with it that often.

I tried programming a GTN 650 from the right seat in occasional light turbulence with my left hand last week and it didn't go well. I'm also wildly right-hand-dominant, but assume I can adjust over time.

Sorry you don’t care for your GRT. Of course these choices are very individual. I love my GRT Hx’s. The main limitation of the Sport is the small number of RS232 ports, it’s not hard to not have enough. Part of your planning will be to carefully count up how many you’ll need.

I'm not opposed to replacing the Sport EX with a Sport 10.1 or Horizon 10.1 (because screen real estate is king) but I'm trying to avoid a ton of rewiring. Basically laziness and "minimum viable product" right now - because I don't want to break my panel trying to reinvent the whole thing. I honestly don't know what extra serial ports would get used for in my application, since I didn't build my panel. If I only have two is it likely to be one for the autopilot servos and for the GPS?


Anyhow, thanks for your willingness to chip in information. I may be slow to digest and my availability to work on it is infrequent due to other obligations, but I want to chip away at the knowledge to the point where I feel confident about doing this end-to-end.

 

[JDA_BTR]

I'm pretty sure you have to have the ARINC so that the air data and other go-between data is properly shared between the devices. In general a device ARINC interface has to go to an ARINC adapter, not another ARINC device. From the ad page for your EFIS:

"The Connectivity You Need
Three serial ports in and out (optional with six), a USB port, and a dedicated magnetometer port, allow for great flexibility within your panel design. An optional ARINC 429 interface can also be added, while still retaining all serial ports, for connectivity with IFR GPS navigators, such as the G430/650/750."

 

[BobTurner]

My Hx unit has a built-in ARINC, but I think most newer boxes do not. You need to get an external arinc box from grt. It plugs into a serial port. The box then has arinc and a serial port, although I think grt recommends only low speed data on the serial line.