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No ILS DME after 1.04


B320Max8

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  • 2 weeks later...

I looked at that ILS chart ILS or LOC Rwy 13 at LDZD.  The first thing I notice is that in the ILS frequency box it only denotes and ILS, not ILS/DME (Navigraph/Jepp charts).  All the DME fixes on the chart reference ZADAR 108.3.  You would need to have ZADAR tuned in on NAV2 for the DME information I believe.  ILS with integrated DME would show ILS/DME in the frequency box.  I will double check all this as I have not flown an ILS of any type in a while.  I mainly fly the RNAV approaches when I can't land visually.  

Looking at your VOR needles it looks like that VOR was autotuned (or perhaps you did it) and you were at 5 DME on the approach.  Based on your altitude and vertical deviation, I believe you were just passed LOM at the moment the picture was taken.  LOM is 6.2 DME from ZDA 4.5 DME from the threshold.  

I will check the FCOM when I get back later, but I believe you would only get the DME info on the PFD if you were on an ILS with integrated DME.  Try it at a runway that has ILS/DME noted in the ILS frequency box.  If you have charts, look at the ILS to runway 17C at KDFW for example. I know that is indicated on Jepp charts.  In standard FAA charts you can tell by the DME fix information referencing the ILS localizer.  It will say something like ZINGG I-FLQ 9.9.  I-FLQ is the designator for the ILS Rwy 17C at KDFW. 

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Mark "Crabby" Crabtree AAL311 | PHL
I7-9700KF | 2070 Super | Honeycomb Alpha/Bravo | MFG Crosswind

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1 hour ago, B320Max8 said:

In this case I wonder why I get a dme readout @lirn rwy24

Ok, I was wrong with the chart interpretation.  ILS DME means ILS with DME equipment REQUIRED.  Not wrong about the rest. 

 The FCOM says:

During approach
3. NAV-ILS-VOR switch............................................................................. ILS
The co-located DME frequency is automatically tuned by the FMS.
4. Associated PFD...............................................READ DME/ILS DISTANCE

It is clear that a co-located DME frequency is needed.  So, my guess is that the answer is in the nav data. At LIRN that would be NPC.  In the Navigraph data it is shown as an ILSD entry which indicates it is an ILS DME. 

In the other example above ZADAR is shown as a VORD, indicating a VOR with DME. Not collocated but a separate VOR 

So, the moral of the story is, if your ILS fixes reference the ILS identifier, then that ILS has a collocated DME.  The plane will tune the co-located DME source automatically.  If not, tune it and read it off the VOR needles.  At least this is what I gather from the FCOM.  

I will look to see if I can find the in-sim data as that is what the A310 uses but based on what I saw in Navigraph and the FCOM, what you saw was normal. 

  • Like 1
Mark "Crabby" Crabtree AAL311 | PHL
I7-9700KF | 2070 Super | Honeycomb Alpha/Bravo | MFG Crosswind

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Damn, can't edit anymore.  

I posed the question "How to tell if an ILS has a co-located DME or not" to an AAL pilot.  He said what I said above about fix reference, but that it is not always the case and the best way to tell is to tune in the ILS and if you see the DME with no further action, it has a co-located DME.  If you see 0.0 or a flag where it is read, it is not co-located, and you have to manually tune in the reference DME station".  

The engineer in me hates this answer, and I will continue to look into it although this could be a case of I'm thinking too much.  Either way in your two references, the first one did not have a co-located DME and the second one did, again based on what I see in the Navigraph database. 

  • Like 1
Mark "Crabby" Crabtree AAL311 | PHL
I7-9700KF | 2070 Super | Honeycomb Alpha/Bravo | MFG Crosswind

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