Significant ILS DME errors (primarily affects Europe)

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Are you using Developer Mode or made changes in it?


Brief description of the issue:

There are two big errors in the way the sim handles the DME element of ILS/DMEs.

1) The DME read incorrectly for approaches where it is supposed to be referenced to the runway threshold.

For example, London Heathrow 27R - the ILS DME is referenced to 0 NM at the threshold. The sim seems to be measuring from the runway mid-point and so the ILS DME over-reads by ~ 1 NM when comparing against GPS/VOR cross-cuts/distance-altitude checks (at 4 NM you expect to be at 1410 ft):

This issue seems to affect any airport where the ILS DME is meant to read zero at the threshold. The exact mis-match varies (I suspect based on runway length) at Newquay (EGHQ) it is ~ 0.7-0.8 NM out. It would seem like the sim is incorrectly referencing the runway mid-point.

The issue doesn’t seem to affect airports where there is only an ILS on one Runway, for example at Biggin Hill (EGKB) there is only an ILS to Runway 21 and in the sim the readings are within 0.1 NM of GPS and match altitude cross-checks (at 4 NM you expect to intercept the GS at 1800 ft):

Similarly, for approaches that don’t reference zero at the threshold (as is common in the USA) the sim seems to be providing a correct distance read-out. For example KJFK 4L:

It seems like the issue is at airports with an ILS to both runway ends (possibly where they share a frequency which is common in the UK) and the DME is referenced to zero at the threshold.

This is an issue because it significantly affects accurate IFR navigation and interactions with online ATC like VATSIM (you commonly get speed restrictions referenced to distance from touch-down based on an ILS DME which you cannot accurately comply with if the DME is incorrect.

2) For runways with an ILS to only one end and which have a suppressed back-course, the DME only reads in the 180 degree front-course sector.

I’ve detailed this before here:

This again is an issue primarily in Europe. There are airports with an instrument approach to the non-ILS runway that require the DME element of the ILS, ie. an NDB/DME approach to the opposite runway end. You also commonly require the DME for any missed approach procedures for the ILS approach. These are impossible to fly if you use any add-on scenery or navigation data that suppresses the back-course (correctly at the affected airports). Again, this significant affect IFR navigation and can make it impossible to fly certain IFR procedures.

Both of these are issues with the basic mechanics of how an ILS DME station works and both significant affect the experience for people trying to accurately emulate IFR procedures. I would be very grateful if they could be registered and fixed! :grinning_face_with_smiling_eyes: Thanks!

PC specs and/or peripheral set up if relevant:


Build Version # when you first started experiencing this issue:

Noted in multiple version - I suspect present since initial release

This is a good and very detailed report. Be sure to file each bug on Zendesk or Asobo won’t see your details.

I have also noticed some Ils problems across the world but didn’t think much of it. I thought it was an Ils issue with the airplane and not with the sim’ s nava…

Today flew the VORDME approach at santorini LGSR. Had to do 2 GAs. unflyable because of the wrong readouts.

Hi @NormalPrism6528. Welcome back to the community. Good to see you contributing experience to the conversation.

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Again, welcome back! Hope the DME issue get sorted for you all soon.

I have been using simbreif nav. , charts with little nav map and comparing the two I do get differences. I thought msfs got real nav aids but I see they don’t. very sad

Sorry, but I can’t follow you why you wrote this as an answer of GAs due wrong readouts?

What have this todo with your posting about using real navaids? The MSFS uses real world navaids (data) as LNM too …

Please can you give us an example, which navaid you mean that is not real and or missing?

Thank you

do you mean the dme distance with wrong read outs? What aircraft has you use?

I have tested the VOR15 approach with the standard stock A320 (Navigraph AIRAC 2205 installed, stock scenery) and the DMEs are all absolutely correct.

approaching KORAX at SNI/9.0

final MA15, SNI/2.0:

I can´t see any DME readout issues here sorry.


Hi there. Not sure what navigraph has to do with this but the Fenix a320 and whatever navdata pack tat came with. Believe it was SNI which should be almost on the aerodrome but was way off.

This is still an issue and I’ve submitted to zendesk.
Do things getting recorded as “bug-logged” rely solely on the number of votes received?
Is there anything else I can do to try to see this fixed, it’s truly the one gripe I have with the sim :sweat_smile: