LOM/MM DME GPS

brien23

brien23

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With LOM/MM going away now require DME or Radar GPS miles are not the same as DME and I believe they are the center position of the airport. What are GPS airport positions based on and how would you find the exact location on a airport.
 
If you have Jepp charts the airport reference point is marked, and you can get the lat/long from that.

The other problem is that you need to know where the DME that you're substituting is located...if it's a localizer DME, that can be difficult.
 
When you are substituting for DME with a GPS, you must use the location of the DME and not the location of the airport. The approach chart will define what DME station is being used to determine a distance, it can be an ILS DME or a VOR/DME or VORTAC/DME. An ILS DME will have a four letter identifier that begins with I, such as IUZA. These ILS DME will be in most GPS databases. Usually the DME distances are needed to determine localizer waypoints and are often not used as part of the full ILS approach with a GS. If you are using a separate ILS receiver, the GPS can be used by direct to the name of the DME station. If you are using a GNS430/530 or other GPS integrated navigation system for both the ILS and the GPS, you are going to have to probably fly the ILS the old fashioned way and not have the benefit of loading and activating the ILS approach, IOW tune the ILS, identify the localizer and use your CDI/HSI to fly the course. Set the GPS direct to the DME facility name and use the distance readout on the GPS in lieu of DME. If all your needed waypoints are named fixes and show on the loaded approach procedure, you can use the names instead of the DME.
 
brien23 said:
With LOM/MM going away now require DME or Radar GPS miles are not the same as DME and I believe they are the center position of the airport. What are GPS airport positions based on and how would you find the exact location on a airport.
Click to expand...

Do you have an example of an IAP where this is an issue?
 
I've never tried looking for the I-DME facilities (when applicable) as a waypoint, I've always assumed that's the one navaid that was never cataloged in GPS databases. Does the G430 include them? I've always been under the impression they do not.
 
mkosmo said:
But it's only going to be using the correct reference if you have the approach loaded and active.
Click to expand...
So contrary to John's post, you're saying that you can't enter IUZA, or some other localizer with DME, as a waypoint for distance?
 
AC 90-108 has the info for substituting GPS for a LOM/MM. If the procedure is called up by name in the GPS database you can be assured that the location of both the fix (via dme) and the GPS location of that fix will be the same.
 
MauleSkinner said:
So contrary to John's post, you're saying that you can't enter IUZA, or some other localizer with DME, as a waypoint for distance?
Click to expand...

You can and this was how it was done for GPSes that DIDN'T have the ILS/LOC/VOR procedures in the database - for example, the Garmin GNC300XL, which only had GPS procedures in its database. You would tune in the ILS/LOC/VOR the old-fashioned way with your NAV radios, but then could set the GPS Direct-To IABC and it would give you the distance to that DME source.

On a more modern GPS there is no reason to do this, of course. You just load/activate the ILS/LOC/VOR procedure from the database and it shows distance to all waypoints on the procedure. This is an approved substitution for DME, intersections, OMs, etc.
 
RussR said:
You can and this was how it was done for GPSes that DIDN'T have the ILS/LOC/VOR procedures in the database - for example, the Garmin GNC300XL, which only had GPS procedures in its database. You would tune in the ILS/LOC/VOR the old-fashioned way with your NAV radios, but then could set the GPS Direct-To IABC and it would give you the distance to that DME source.

On a more modern GPS there is no reason to do this, of course. You just load/activate the ILS/LOC/VOR procedure from the database and it shows distance to all waypoints on the procedure. This is an approved substitution for DME, intersections, OMs, etc.
Click to expand...
Maybe my impression is incorrect, but the impression I got from the OP is that he didn't have a "modern" GPS.
 
At the angle of a glide slope (typically 3 degrees) the discrepency between slant range and the ground distance is trivial, less than 1%.
 
For things like DME arcs for example, I have always used the nearest VOR page for DME, I have also loaded in the ILS into the GPS as a point and used that for DME. Its worth noting that I have two 430's in the plane so one is used to shoot the approach and the other is used for DME.
 
GX55 doesn't have approach capability, but you can use it to sub DME on ILS approaches, just choose the 4-character I-xxx to use.
 
flyingron said:
At the angle of a glide slope (typically 3 degrees) the discrepency between slant range and the ground distance is trivial, less than 1%.
Click to expand...
TERPs ignores DME slant range for design of instrument approach procedures.
 
hindsight2020 said:
I've never tried looking for the I-DME facilities (when applicable) as a waypoint, I've always assumed that's the one navaid that was never cataloged in GPS databases. Does the G430 include them? I've always been under the impression they do not.
Click to expand...
I believe localizers are in the database only if they have collocated DME.
 
hindsight2020 said:
I've never tried looking for the I-DME facilities (when applicable) as a waypoint, I've always assumed that's the one navaid that was never cataloged in GPS databases. Does the G430 include them? I've always been under the impression they do not.
Click to expand...

As far as I am aware, all the localizer DME are in the database for GNS430 as I-xxx.
 
RussR said:
You can and this was how it was done for GPSes that DIDN'T have the ILS/LOC/VOR procedures in the database - for example, the Garmin GNC300XL, which only had GPS procedures in its database. You would tune in the ILS/LOC/VOR the old-fashioned way with your NAV radios, but then could set the GPS Direct-To IABC and it would give you the distance to that DME source.

On a more modern GPS there is no reason to do this, of course. You just load/activate the ILS/LOC/VOR procedure from the database and it shows distance to all waypoints on the procedure. This is an approved substitution for DME, intersections, OMs, etc.
Click to expand...

Not all of the waypoints on the ILS localizer course are in the GNS database. The ones between the FAF and the MAP are not included, so you need to use a different strategy when loading the ILS procedure from the database in these cases.
 
John Collins said:
Not all of the waypoints on the ILS localizer course are in the GNS database. The ones between the FAF and the MAP are not included, so you need to use a different strategy when loading the ILS procedure from the database in these cases.
Click to expand...

You are correct for the Jeppesen database. It's an interesting technical decision by Jeppesen to not include waypoints between the FAF and MAP, however, it's not a bad one if you're flying the ILS - as you know, fixes between the FAF and MAP do not apply to the ILS, and are asterisked "LOC only".

However, if you need these fixes because you're going to fly the LOC-only portion of the procedure, you have to use a different solution (such as "direct-to" the I-ABC DME source), but only if you're using the Jeppesen database. If on your 430W/530W you get the database from Garmin, they have split apart the "ILS OR LOC RWY xx" into two procedures - ILS RWY xx and LOC RWY xx. The LOC version has all the fixes between the FAF and MAP, which seems to me to be the smart way to code the procedures.
 
RussR said:
You are correct for the Jeppesen database. It's an interesting technical decision by Jeppesen to not include waypoints between the FAF and MAP, however, it's not a bad one if you're flying the ILS - as you know, fixes between the FAF and MAP do not apply to the ILS, and are asterisked "LOC only".

However, if you need these fixes because you're going to fly the LOC-only portion of the procedure, you have to use a different solution (such as "direct-to" the I-ABC DME source), but only if you're using the Jeppesen database. If on your 430W/530W you get the database from Garmin, they have split apart the "ILS OR LOC RWY xx" into two procedures - ILS RWY xx and LOC RWY xx. The LOC version has all the fixes between the FAF and MAP, which seems to me to be the smart way to code the procedures.
Click to expand...
Heres another interesting look at Jeppesen's take on things. LOC-D approach at KSEE. Sorry, I cant link it. The Planview note says "DME required. (For Procedure Entry from the Enroute Environment)
But you need DME for the entire approach. There is no timing table, it's needed for the MAP, and there is a stepdown fix, DEBEY. The GOV charts have it kind of messed up to. DME REQUIRED is in the Planview but not in the notes which implies the same thing the Jepp note says.
 
RussR said:
You can and this was how it was done for GPSes that DIDN'T have the ILS/LOC/VOR procedures in the database - for example, the Garmin GNC300XL, which only had GPS procedures in its database. You would tune in the ILS/LOC/VOR the old-fashioned way with your NAV radios, but then could set the GPS Direct-To IABC and it would give you the distance to that DME source.

On a more modern GPS there is no reason to do this, of course. You just load/activate the ILS/LOC/VOR procedure from the database and it shows distance to all waypoints on the procedure. This is an approved substitution for DME, intersections, OMs, etc.
Click to expand...
Yeah. It not only gives the distances, it gives the Name and tells ya when you're right smack dab over it. Not that you should, but you could fly it without paying attention to the "numbers."
 
RussR said:
However, if you need these fixes because you're going to fly the LOC-only portion of the procedure, you have to use a different solution (such as "direct-to" the I-ABC DME source), but only if you're using the Jeppesen database. If on your 430W/530W you get the database from Garmin, they have split apart the "ILS OR LOC RWY xx" into two procedures - ILS RWY xx and LOC RWY xx. The LOC version has all the fixes between the FAF and MAP, which seems to me to be the smart way to code the procedures.
Click to expand...
That's not been my experience with Garmin navigators. Attached is a screen shot of the KCRQ ILS or LOC Rwy 24 from Foref light. Note the LOC procedure has HUSET step-down in the final segment. Also attached is a screen shot of the IAP options at KCRQ. Only one ILS, no LOC. Finally, a screen shot of the ILS active in the VTF mode. Note no HUSET.
 

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RussR said:
You are correct for the Jeppesen database. It's an interesting technical decision by Jeppesen to not include waypoints between the FAF and MAP, however, it's not a bad one if you're flying the ILS - as you know, fixes between the FAF and MAP do not apply to the ILS, and are asterisked "LOC only".

However, if you need these fixes because you're going to fly the LOC-only portion of the procedure, you have to use a different solution (such as "direct-to" the I-ABC DME source), but only if you're using the Jeppesen database. If on your 430W/530W you get the database from Garmin, they have split apart the "ILS OR LOC RWY xx" into two procedures - ILS RWY xx and LOC RWY xx. The LOC version has all the fixes between the FAF and MAP, which seems to me to be the smart way to code the procedures.
Click to expand...
It's not only navaid-based procedures that have this issue; the step down fixes inside the FAF seem to be missing for RNAV approaches as well, at least in the 480 database (which I get from Jepp). I don't know if it's true for all RNAV approaches but it is for the ones I fly frequently. It's not a serious issue since distances of the fixes from the MAP waypoint are given on the plate, so it's pretty easy to tell when you can descend by monitoring the distance to next WP.
 
aterpster said:
That's not been my experience with Garmin navigators. Attached is a screen shot of the KCRQ ILS or LOC Rwy 24 from Foref light. Note the LOC procedure has HUSET step-down in the final segment. Also attached is a screen shot of the IAP options at KCRQ. Only one ILS, no LOC. Finally, a screen shot of the ILS active in the VTF mode. Note no HUSET.
Click to expand...

Who supplied the navigation database for that GPS? Used to be there was only one choice, Jeppesen. Now that Garmin is also offerring its own database subscriptions, they have added the LOC version of ILS or LOC procedures as well, at least in the instances I've seen with Garmin-supplied data.

I will try to get a pic of a 430W I'll be flying with tomorrow that I know has the Garmin subscription.
 
RussR said:
I will try to get a pic of a 430W I'll be flying with tomorrow that I know has the Garmin subscription.
Click to expand...
Look forward to seeing it. Could you do a pic of KCRQ?
 
aterpster said:
Look forward to seeing it. Could you do a pic of KCRQ?
Click to expand...

Sorry, Wally, I didn't see your CRQ request until just now.

These are some pics from a 430W, current database supplied by Garmin (not Jeppesen). Airport is KOKC.

First listed are the ILS procedures:

IMG_20170813_140508646[1].jpg

Then listed are the LOC procedures (to the same runways, so, the "OR LOC" part of the "ILS OR LOC RWY xx"):

IMG_20170813_140514372[1].jpg

Loading the LOC RWY 35L, the final stepdown fix ZOPRO is listed as one of the fixes:

IMG_20170813_140609948[1].jpg

Again, this is, as far as I can tell, only when the database subscription is coming from Garmin. I first noticed this a couple of months ago when I flew back-to-back similar training flights in two different airplanes and saw the LOC procedures listed in only one of them. Turns out one had Jeppesen data, the other, Garmin data.
 
RussR said:
Again, this is, as far as I can tell, only when the database subscription is coming from Garmin. I first noticed this a couple of months ago when I flew back-to-back similar training flights in two different airplanes and saw the LOC procedures listed in only one of them. Turns out one had Jeppesen data, the other, Garmin data.
Click to expand...
That is interesting. Thanks! I'm sure it would be the same at KCRQ.
 
RussR said:
Sorry, Wally, I didn't see your CRQ request until just now.

These are some pics from a 430W, current database supplied by Garmin (not Jeppesen). Airport is KOKC.

First listed are the ILS procedures:

View attachment 55561

Then listed are the LOC procedures (to the same runways, so, the "OR LOC" part of the "ILS OR LOC RWY xx"):

View attachment 55562

Loading the LOC RWY 35L, the final stepdown fix ZOPRO is listed as one of the fixes:

View attachment 55563

Again, this is, as far as I can tell, only when the database subscription is coming from Garmin. I first noticed this a couple of months ago when I flew back-to-back similar training flights in two different airplanes and saw the LOC procedures listed in only one of them. Turns out one had Jeppesen data, the other, Garmin data.
Click to expand...
Any idea what Jepps "corporate 'think' " is on why they don't like displaying stepdown fixes inside the FAF?
 
luvflyin said:
Any idea what Jepps "corporate 'think' " is on why they don't like displaying stepdown fixes inside the FAF?
Click to expand...

Neither does Garmin, what Garmin does is add a new procedure in the database for the Localizer option. This increases the number of procedures in the database and the World Wide database for Jeppesen is already eliminating procedures below a certain runway length, I think 4000 feet.
 
John Collins said:
Neither does Garmin, what Garmin does is add a new procedure in the database for the Localizer option. This increases the number of procedures in the database and the World Wide database for Jeppesen is already eliminating procedures below a certain runway length, I think 4000 feet.
Click to expand...
Did you look at RussR's third screen shot above?
 
John Collins said:
Neither does Garmin, what Garmin does is add a new procedure in the database for the Localizer option. This increases the number of procedures in the database and the World Wide database for Jeppesen is already eliminating procedures below a certain runway length, I think 4000 feet.
Click to expand...
Ah. It's about storage. While were on the subject, what was the rationale in changing from naming approaches as ILS approach and having localizer only minimums, to naming them ILS or LOC. I know there are a few approaches out there where theres an ILS without loc only minimums and a separate LOC approach. Often because theres so many notes to add for the loc only. But what was accomplished by renaming all of the ILS approaches with loc only minimums to ILS or LOC?
 
John Collins said:
I sure did. It is the Localizer option, not the ILS option. Two procedures instead of one.
Click to expand...
I must of misunderstood your previous post. As nice as this separate LOC option is, it eats up that database limit even faster.
 
luvflyin said:
Ah. It's about storage. While were on the subject, what was the rationale in changing from naming approaches as ILS approach and having localizer only minimums, to naming them ILS or LOC. I know there are a few approaches out there where theres an ILS without loc only minimums and a separate LOC approach. Often because theres so many notes to add for the loc only. But what was accomplished by renaming all of the ILS approaches with loc only minimums to ILS or LOC?
Click to expand...
Keeps more management positions.
 
luvflyin said:
Any idea what Jepps "corporate 'think' " is on why they don't like displaying stepdown fixes inside the FAF?
Click to expand...
This is the response I received from my contact at Garmin:

There is no literature that explains that LOC IAPs are separate from ILS IAPs and contain the final segment step-down(s) in the Garmin database. Part of the reason for the lack of literature is that we had hoped to already have this difference eliminated.


There are plans for future Jeppesen databases to have separate LOC IAPs and ILS IAPs where the LOC IAPs include the final segment step-down(s). Jeppesen has an option for its ARINC 424 data to have the separated procedures. However, we have determined that we need to proceed with caution before enabling this option due to possible database storage limitations, particularly among legacy avionics. At the very least, we hope to allow the additional ILS approaches to appear in our newer avionics that aren’t as storage limited.


As you have noted, the Garmin navigation database does include separate ILS and LOC IAPs. This is primarily due to the fact that there is no "worldwide" version of that database that needs to be supported. Consequently, the Garmin database does not have the storage space limitation issue that exists with Jeppesen databases.
Click to expand...
 
So what would be the problem for inclusion of these step down fixes inside the FAF on an a single ILS/VOR. It would require increased storage slightly but no where close to that needed for a separate approach.
 
MajorTurbulence said:
So what would be the problem for inclusion of these step down fixes inside the FAF on an a single ILS/VOR. It would require increased storage slightly but no where close to that needed for a separate approach.
Click to expand...
I am not a database expert but I suspect the database records make a separate LOC selection a full IAP, as required by ARINC 424 coding specifications.
 
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