GNX 375 Install, keep DME?

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wilco

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wilco
Hey everyone, new to the forum. I've been lurking around on here for the last few months leading up to and after purchasing a new to me 1963 Comanche 250. Lots of great info and good people!

When I purchased the plane it had a working KN64 DME. Within a week it gave up the ghost and was showing gibberish on the display (welcome to airplane ownership!). Right now, I am in the midst of upgrading to a GNX 375/Dual G5's with some other goodies and the shop bench tested the DME and said it was shot. Like the title says, would you guys worry about replacing the unit?

Most of the reading I've done, people are saying to ditch it, especially if it's not working and needs to be replaced. I am in the middle of IFR training so I don't quite yet know the utility of the DME if I have a 375 in there. It seems useful to have as a backup if GPS failed for some reason. I also know it's unnecessary from a regulation standpoint so spending money for a used one doesn't sound appealing. For reference, I'm keeping my two KX-155 nav/com radios with CDI/glideslope on #1 and CDI on #2.

Any thoughts would be appreciated, thanks in advance!
 
Do you have a GPS in the mix? If so, the DME can be tossed.
 
wilco said:
Right now, I am in the midst of upgrading to a GNX 375/Dual G5's with some other goodies and the shop bench tested the DME and said it was shot. Like the title says, would you guys worry about replacing the unit?
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Dump it. If it's shot, ditch it.
 
If it doesn't work, why would you keep it?
Do you need/want a backup to the GPS for distance? If not, don't replace it with another DME, just use the GPS.
 
"Let it go!"

If you have two nav/com's and a glideslope, you'll still have plenty of options for gettin' down somewhere if the GPS goes kaput.
 
I put a Garmin 480 and other stuff in the panel 15 years ago. I kept the DME because it was a fairly recent addition and the FAA hadn't officially laid out the rules on DME/ADF substitution (and my home base made frequent use of an ILS/DME approach). In practice, other than for curiosity reasons, I've not turned it on hardly at all in all this time.
 
Hang 4 said:
Do you have a GPS in the mix? If so, the DME can be tossed.
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asicer said:
Dump it. If it's shot, ditch it.
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jrcox19 said:
If it doesn't work, why would you keep it?
Do you need/want a backup to the GPS for distance? If not, don't replace it with another DME, just use the GPS.
Click to expand...

kath said:
"Let it go!"

If you have two nav/com's and a glideslope, you'll still have plenty of options for gettin' down somewhere if the GPS goes kaput.
Click to expand...

flyingron said:
I put a Garmin 480 and other stuff in the panel 15 years ago. I kept the DME because it was a fairly recent addition and the FAA hadn't officially laid out the rules on DME/ADF substitution (and my home base made frequent use of an ILS/DME approach). In practice, other than for curiosity reasons, I've not turned it on hardly at all in all this time.
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Thanks for all the replies everyone, super helpful. My hesitation comes from the lack of IFR experience, so just trying to make sure I'm not missing something and regret leaving the DME out later on. Sounds like I'm about to save another couple pounds!
 
I just went through the same considerations during a panel upgrade, with a working DME. Dump it, especially if it’s not working. You won’t miss it.
 
I'm not IFR, but it seems that DME and ADF are something people have moved on from.

GNX 375 and Dual G5's sound like a great panel. That gives you a transponder with ADS-B, and GPS to power it's own mapping as well as the G5's.

So many combinations of Garmin gadgets - how did you settle on these?
 
I've got a functional DME, and it's getting yanked once I redo the aluminum panel itself.
 
AA5Bman said:
I just went through the same considerations during a panel upgrade, with a working DME. Dump it, especially if it’s not working. You won’t miss it.
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Thanks very much for the perspective, it sounds like everyone is in agreement that it's not worth keeping. Really appreciate your input!

WDD said:
I'm not IFR, but it seems that DME and ADF are something people have moved on from.

GNX 375 and Dual G5's sound like a great panel. That gives you a transponder with ADS-B, and GPS to power it's own mapping as well as the G5's.

So many combinations of Garmin gadgets - how did you settle on these?
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It took quite a while to settle on a plan, and of course snowballed out of something simple. It started with needing ADS-B onboard. The plane wasn't equipped with any kind of GPS equipment and the existing GTX 327 transponder wasn't working properly, so that steered me away from something like the uAvionix ADS-B solutions.

When you start looking at full-up transponders, you can get them with and without GPS (add money for integrated GPS) and I would of course need GPS. One of these is in the realm of 3-4 AMUs, which is about halfway to a GNX. I wanted GPS nav for IFR training so that decision got made pretty quick, since I didn't want to end up paying for a GPS receiver twice.

Then, researching the GNX and talking to the avionics shop, I learned that a G5 HSI can drive the stec 60-2 autopilot in my plane to add GPS approach capability to the autopilot. Was going to stop with one G5 but the "while you're in there" mentality took over and I pulled the trigger on the G5 attitude indicator as well. Allows me to delete the vacuum system and flying with the coupled G5 attitude indicator is super nice, I got to try it in a 172 I flew a while back.

Sorry for the long response, hopefully it makes sense. It was a combo of existing equipment driving decisions, budget and wanting to deal with it once and be done with it. The other route with the GTN series is nice but I had working nav/com radios and it's quite a bit more expensive when you tally up the external transponder.

rbridges said:
I've got a functional DME, and it's getting yanked once I redo the aluminum panel itself.
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Nice, thanks for the input!
 
Even if the DME works--ditch it. You'll end up ditching it soon anyway. I even made the decision to pull my KX-155s even though they were working well and sounding amazing. But I knew it was a matter of time before I would have an expensive repair to my 30+ yr old radios...
 
So. Do we all still need 2 nav radios? Heck - do we need one at al?

And do we need a back up GPS nav system? That is - any need for 2 gps nav units ?
 
WDD said:
So. Do we all still need 2 nav radios? Heck - do we need one at al?

And do we need a back up GPS nav system? That is - any need for 2 gps nav units ?
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That's an oft debated topic and you'll find many that who will never fly IFR without ground based NAVAIDS. I pulled all of them and haven't looked back. Ultimately it's very much a personal choice that weighs risk and cost. I wanted to upgrade once and to not pay for rework of a piecemeal approach. My mission and risk management approach allows me to cancel without much risk. Meanwhile everything is clean and reliable.

Good luck--you have lots of choices to make.
 
WDD said:
So. Do we all still need 2 nav radios? Heck - do we need one at al?
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For VFR, I don't need any. For IFR, I'd want at least one. Can't use the MON without it. However, 2 would be nice, especially if the home field doesn't have a VOR checkpoint on the ground or a VOT. I'd have to have a pretty good reason to ditch #2.
And do we need a back up GPS nav system? That is - any need for 2 gps nav units ?
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They all have a single point of failure (the satellite constellation) anyway.
 
I replaced the ADF with an XM receiver. That way I can still hear the ball games.
 
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kath said:
"Let it go!"

If you have two nav/com's and a glideslope, you'll still have plenty of options for gettin' down somewhere if the GPS goes kaput.
Click to expand...
This. Exactly.
 
I kept my DME after putting in my GNC 355. Call me old fashioned. But I did yank my ADF.
 
From a new pilot’s perspective with no IFR experience -

I’ve read where some never use or don’t have nav radio at all, let alone ADF or DME.

Given the ability of some com radios to allow you to listen to ATIS while also on ATC, etc. Do you really even need a 2nd com ?

Back up? Carry a hand held com in your bag for $200. Carry a Sentry for back up AHRS, GPS, traffic for $500.

Thoughts??
 
WDD said:
From a new pilot’s perspective with no IFR experience -

I’ve read where some never use or don’t have nav radio at all, let alone ADF or DME.

Given the ability of some com radios to allow you to listen to ATIS while also on ATC, etc. Do you really even need a 2nd com ?

Back up? Carry a hand held com in your bag for $200. Carry a Sentry for back up AHRS, GPS, traffic for $500.

Thoughts??
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If you are on a busy frequency the monitored frequency will be silenced while transmissions are in progress. It could take some time before you get the complete ATIS or AWOS information (it seems that transmissions will always occur during the same information). I've found my hand held is difficult to hear on its own over the airplane noise and radio. That said I only have a single comm radio with the monitor function. I use a Stratux with AHRS but have found that on warmer sunny days the iPad is not that reliable due to heat and will either dim excessively or shutoff entirely. I suppose that wouldn't be as much an issue in IMC and could possibly be resolved with a fan cooled case.
 
I fly professionally and have a 310. I pulled my 20 lb DME when I put in the dual G5’s and GTN650. I never use DME professionally and certainly never use it in my 310. Once you fly IFR everywhere and have GPS, you’ll never use DME.

If you have a DME arc approach, the GTN’s have them and a good autopilot can fly them beautifully. The only places I see DME arcs are in Mexico. They use them everywhere there.

Good luck and congrats on the panel install.


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Slightly off topic
Do you get a free database with initial installation of a GNX-375?
TIA
 
I was going to ask why the G5 and not the G275 - I’m guessing it is because the G5 works with your current auto pilot and the newer g275 won’t. Close?
 
WDD said:
I was going to ask why the G5 and not the G275 - I’m guessing it is because the G5 works with your current auto pilot and the newer g275 won’t. Close?
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Yes, that's part of the reason I went with the G5 as the HSI, though the Gi 275 is compatible with the stec 60-2. I seriously considered the Gi 275 but the increase in price isn't justifiable in my opinion. It's a super neat looking instrument but there is SO MUCH stuff going on and it's a lot of info that will either be up on my tablet or on the GNX screen. Another big downside is the GI 275 has an optional one hour backup battery, whereas the G5 comes standard with a 4 hour backup battery. Going with the G5s essentially allowed me to stay within budget and get the AI done at the same time as the HSI, rather than a single Gi 275 HSI.
 
I have a KN64 in my Warrior and a Garmin 430w. I would definitely replace mine if it went south just for the redundancy. I am also based under Class B airspace and I use it alot to confirm which ring I am in. Now, I am thinking about ditching my old ADF.
 
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