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How to fly an ILS approach in the US way (no DME) on a GTN

Just 3 tiny details

@lbra agree in the main, actually on an ILS missed approach is when you reach decision altitude, you wouldn’t use DME for that. My understanding is that on an ILS system the use of DME is to carry out the Glide Slope check. It may then define missed approach points, or lead in/arc routes to intercept.

Oxford (EGTK), United Kingdom

Ibra wrote:

Do you have the example? surely that DME is collocated with VOR/DME or NDB/DME

If it’s ILS/DME or LOC/DME it will be calibrated to runway threshold

Perhaps I’m lucky and found the only example – but it’s just the last approach I’ve flown…

Check EDGS ILS 31: DME is .5 nautical miles from threshold.

Germany

Sound like an example but it’s not even collocated ILS/DME with same frequency? so not surprising it reads differently? Southend DME I-ND will read 283nm on EDGS threshold or touchdown zone the plate states “DME required”, the point about GPS overlays is moot !

I just looked at Germany plates, I can’t find a DME that is collocated with ILS (ILS frequency = DME frequency), is this the norm? you never use “remote mode” and you always have to set the standalone DME frequency…

Elsewhere DME & ILS frequencies are identical, the two nav aids are collocated in one single package called ILS/DME on same frequency, you get both activated when you load ILS overlays from GPS DB, then you tend to read same 0nm distance in both GPS and DME near threshold: no surprise as the DME gets calibrated by flight calibration aircraft that will use GPS data to get threshold or touchdown offsets

Last Edited by Ibra at 04 Jul 20:08
Paris/Essex, France/UK, United Kingdom

Ibra wrote:

I just looked at Germany plates, I can’t find a DME that is collocated with ILS (ILS frequency = DME frequency), is this the norm? you never use “remote mode” and you always have to set the standalone DME frequency…

Elsewhere DME & ILS frequencies are identical,

I don’t know where “elsewhere” is – just saying that your earlier statement :

Ibra wrote:

2/ the DME in Europe on an ILS/DME or LOC/DME is always calibrated to give 0nm distance on live threshold (not at DME or VOR/DME)

is not always true. And btw.: This is not only the case in Germany. And it is not only the case if the DME has a different identifier than the ILS. Look at LFPG ILS 08L: The DME for the ILS GLE is .2 NM behind the threshold.

Germany

The DME for the ILS GLE is .2 NM behind the threshold.

It’s just TDZ vs TCH as @gallois previously mentioned, we don’t care about that level of noise in GA aircraft? we are talking 6seconds at 120kts no one with Cat1 IR give a hoot about that level of details, maybe relevant for someone with Cat2 sign-off? I doubt people will fall out of the sky making 0.2nm mistakes on private IR…

Last Edited by Ibra at 04 Jul 22:03
Paris/Essex, France/UK, United Kingdom

Ibra wrote:

Do you have the example? surely that DME is collocated with VOR/DME or NDB/DME

If it’s ILS/DME or LOC/DME it will be calibrated to runway threshold

Even if you’re right, I don’t see that it’s very relevant. There are lots of ILSes that require the use of a DME which is not colocated with the ILS GP. In some cases a DME colocated with the opposite direction ILS is used, in some cases the DME of a VOR/DME located on or close to the airport.

ESKC (Uppsala/Sundbro), Sweden

Hi. Thanks for interest for all ;)
My question was intended to be more technical/practical about this. I tried it and I find that I can’t setup gtn to show always distance to fixed point (for example dme from map) also distance box on my g5 goes off when I switch from gps to vloc display.

http://www.Bornholm.Aero
EKRN, Denmark

Zagreb LDZA, ILS22 uses DME LUK located some 4 NM from threshold.

LDZA LDVA, Croatia

From plates Zagreb ILS does not require DME at all (it’s for LOC )

 There are lots of ILSes that require the use of a DME which is not colocated with the ILS GP. In some cases a DME colocated with the opposite direction ILS is used, in some cases the DME of a VOR/DME located on or close to the airport.

Why? if you have the glidepath & altimeter, why you need DME on straight-in ILS? what is the logic?

You need DME on LOC for obvious reasons (also you need DME for missed, arc…)

Last Edited by Ibra at 05 Jul 07:24
Paris/Essex, France/UK, United Kingdom

From plates Zagreb ILS does not require DME at all (it’s for LOC)

And for ILS if OM and/or MM are U/S.

LDZA LDVA, Croatia
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