Distance to station from GPS versus DME.

[10driver]

I'm installing a Skyview HDX with an Apollo SL30 and a certified Garmin WAAS GPS. Is it my understanding that the Skyview will derive distance from the station tuned in the SL30 via GPS (GPS distance versus DME slant distance)? Obviously, DME info cannot be received via the SL30 unless you add something like a Garmin DB30 but it's not really needed. Am I correct?

 

[Danerazz]

Probably not an issue as you posted a while ago, but on CERTIFIED installations the Dynon manual states that function needs to be disabled (Unless they recently changed something)

 

[wilkersk]

I don't see too many DME receivers these days. If you have an IFR approved GPS navigator I don't believe you need a DME receiver. AIM 1-2-3 says "
Uses of Suitable RNAV Systems. Subject to the operating requirements, operators may use a suitable RNAV system in the following ways.

1. Determine aircraft position relative to, or distance from a VOR (see NOTE 6 below), TACAN, NDB, compass locator, DME fix; or a named fix defined by a VOR radial, TACAN course, NDB bearing, or compass locator bearing intersecting a VOR or localizer course.
2. Navigate to or from a VOR, TACAN, NDB, or compass locator.
3. Hold over a VOR, TACAN, NDB, compass locator, or DME fix.
4. Fly an arc based upon DME."

Here's further info from BoldMethod: https://www.boldmethod.com/blog/lists/2025/06/gps-vs-dme-distance-ifr-flying/

 

[Danerazz]

Understood, however the question was about the “virtual DME” on the Dynon PFD.

According to the Dynon manuals, that feature must be disabled on certified installations.

 

[wilkersk]

Understood, however the question was about the “virtual DME” on the Dynon PFD.

According to the Dynon manuals, that feature must be disabled on certified installations.

It looks to me like the question was whether or not the OP needed a DME receiver. Perhaps he or she will clarify.

 

[Danerazz]

The implication was it will display GPS derived “pseudo-DME” without actual DME equipment and based on the NAV frequency tuned in your radio, which it will, but that feature has to be disabled in certified installations.

Then there was a “do I need DME?” question, which in most cases you do not. Not sure where he is, but I believe it IS required in some non-US locales, and at least recently there were a (small) handful of approaches that do require DME. And in the event of GPS failure a NAV radio with DME could get you out of a bind, though that seems like a remote possibility.

 

[10driver]

Sorry was off-line for awhile. I'm keeping a KX-165 nav/com which was connected to a KN64. I'm also connecting the SL30 (thru a DB30) to the KN64 as I'm old school and like to have the ability to see info that's available. Also installing a toggle switch to flip between the two radio DME's that will be displayed on the KN64. I was inquiring about what "distance" info is shown on the HDX display but then I came up with another question regarding the statement: "but that feature has to be disabled in certified installations". I don't see where that feature is turned on in the installation manual. I do see where the indicator head type is supposed to be set to NONE. Is that what you referring to???

 

[Danerazz]

The skyview cannot display DME. The distance is a GPS based figure based on the decoded NAV identification (to determine the DME station being referenced) and GPS database of the SV. If you are keeping the KN64, that is the only place to display DME.

If you are referring to the “distance to next fix” that would come from either your connected GPS navigator or the SV flight plan (if that is currently the in-use GPS flight plan source).

The Skyview manual states that the “virtual DME” function is not allowed in certified installations.

My GUESS is this is because the NAV database in the SV is “for reference only” and not “certified” (note that any IFR navigation is based on a certified unit, and cannot be based on SV data). The “virtual DME” function is strictly a SV function (though it is getting its position from an IFR navigator, the database it uses to determine where the VOR/DME is located is SV).

 

[10driver]

Ah...got it. Was researching the statement in the Setup in the Installation Manual....should have realized it might have been in the User's Guide. Thanks!

 

[Danerazz]

Ah...got it. Was researching the statement in the Setup in the Installation Manual....should have realized it might have been in the User's Guide. Thanks!

The data is kind of scattered between the certified and “general” installation and user’s guides. Unfortunately you need to reference all of them for installation and initial setup.