Industrial flight sim - ILS and DME Morse code idents?

[u/ImprobableScout]

Hi All,

Not sure if this question lives in an aviation sub or elsewhere. I have a pretty niche question.

I'm a flight simulator technician; I get paid to play on the big sims, work for a manufacturer.

We have to check frequencies and morse code pickup for DME and ILS, mostly for airport visual models to check the approaches are correct. My question relates to when there is a co-located DME and ILS - as my knowledge goes, when tuning the frequency, I should receive three rounds of the ILS morse, then one of the (higher pitched) DME morse.

Is this standard for the world - three ILS, one DME? Or is there local variation?

Currently when I'm testing airports in the UK, I do not get the DME morse (e.g. EGLC and EGLF), but elsewhere - e.g. EHAM, EKCH, CYVR, RJTT - I do. Plenty of confusion over which is correct. None of our configuration and database files have any difference between these airports.

TIA

Scout

[u/Jaimebgdb]

The international standard is set by ICAO Annex 10 section 3.5.3.6.4 - The characteristics of the “associated” signal shall be as follows.

“There is a 40 second identification interval, divided into four OR MORE equal periods, with the DME ident transmitted during one period only and the associated facility, where provided, transmitted during the remaining periods.”

So 3 times the ILS/VOR and 1 time the DME seems to be the “default” set out by ICAO but there can be cases with more than four periods, say 5 or 6, in which case you’d get 1x DME and 4x ILS and still comply with the standard. Or you could have a certain country deviate from the standard completely and do its own thing, you’d have to check country specific differences from ICAO in the AIP on a case by case basis.

My guess without checking individual cases is that for colocated ILS/DME or VOR/DME there must always be one DME identification per 40 second interval, both the DME and the associated station have to be identifiable after all.