LOM/MM DME GPS

Discussion in 'Cleared for the Approach' started by brien23, Aug 6, 2017.

  1. brien23

    brien23 Line Up and Wait

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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.
     
  2. MauleSkinner

    MauleSkinner En-Route

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    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.
     
  3. John Collins

    John Collins Pattern Altitude

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    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.
     
  4. roncachamp

    roncachamp Final Approach

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    Do you have an example of an IAP where this is an issue?
     
  5. MauleSkinner

    MauleSkinner En-Route

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    I've never flown with GPS and no DME, but I didn't know that...thanks!
     
  6. mkosmo

    mkosmo Pattern Altitude PoA Supporter

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    But it's only going to be using the correct reference if you have the approach loaded and active.
     
  7. hindsight2020

    hindsight2020 Pattern Altitude

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    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.
     
  8. MauleSkinner

    MauleSkinner En-Route

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    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?
     
  9. hangar-birdstrike

    hangar-birdstrike Filing Flight Plan

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    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.
     
  10. RussR

    RussR Line Up and Wait

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    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.
     
  11. MauleSkinner

    MauleSkinner En-Route

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    Maybe my impression is incorrect, but the impression I got from the OP is that he didn't have a "modern" GPS.
     
  12. flyingron

    flyingron Touchdown! Greaser! PoA Supporter

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    At the angle of a glide slope (typically 3 degrees) the discrepency between slant range and the ground distance is trivial, less than 1%.
     
  13. OMGIFORGOTHOWTOLAND

    OMGIFORGOTHOWTOLAND Filing Flight Plan

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    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.
     
  14. brien23

    brien23 Line Up and Wait

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    KLN-89
     
  15. MauleSkinner

    MauleSkinner En-Route

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    Been about 20 years since I flew one of those, but no approach capability? Only enroute & terminal?
     
    Last edited: Aug 6, 2017
  16. brien23

    brien23 Line Up and Wait

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    Should have been KLN-89B
     
  17. mtuomi

    mtuomi Pattern Altitude

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    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.
     
  18. aterpster

    aterpster Pattern Altitude

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    TERPs ignores DME slant range for design of instrument approach procedures.
     
  19. aterpster

    aterpster Pattern Altitude

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    I believe localizers are in the database only if they have collocated DME.
     
  20. John Collins

    John Collins Pattern Altitude

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    As far as I am aware, all the localizer DME are in the database for GNS430 as I-xxx.
     
  21. John Collins

    John Collins Pattern Altitude

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    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.
     
  22. RussR

    RussR Line Up and Wait

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    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.
     
  23. luvflyin

    luvflyin En-Route PoA Supporter

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    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.
     
  24. luvflyin

    luvflyin En-Route PoA Supporter

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    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."
     
  25. aterpster

    aterpster Pattern Altitude

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    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.
     

    Attached Files:

  26. azure

    azure Final Approach

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    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.
     
  27. RussR

    RussR Line Up and Wait

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    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.
     
  28. aterpster

    aterpster Pattern Altitude

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    Look forward to seeing it. Could you do a pic of KCRQ?
     
  29. RussR

    RussR Line Up and Wait

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    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.
     
    denverpilot likes this.
  30. aterpster

    aterpster Pattern Altitude

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    That is interesting. Thanks! I'm sure it would be the same at KCRQ.
     
  31. luvflyin

    luvflyin En-Route PoA Supporter

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    Any idea what Jepps "corporate 'think' " is on why they don't like displaying stepdown fixes inside the FAF?
     
  32. John Collins

    John Collins Pattern Altitude

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    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.
     
  33. aterpster

    aterpster Pattern Altitude

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    Did you look at RussR's third screen shot above?
     
  34. luvflyin

    luvflyin En-Route PoA Supporter

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    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?
     
  35. John Collins

    John Collins Pattern Altitude

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    I sure did. It is the Localizer option, not the ILS option. Two procedures instead of one.
     
  36. aterpster

    aterpster Pattern Altitude

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    I must of misunderstood your previous post. As nice as this separate LOC option is, it eats up that database limit even faster.
     
  37. aterpster

    aterpster Pattern Altitude

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    Keeps more management positions.