I was never taught to do this during training and it seems like it would be pretty apparent if you were receiving another DME using the same frequency pair since there wouldn’t be a similar pairing within such a distance. It wasn’t until flying in the UK that I learned they do it differently there (shocker) and identify the DME separately (using audio) from the ILS (which the G1000 does nicely).
So do you guys identify the DME separately and have I missed something, or do you find this unnecessary?
I think DME require continuous ident as DME suffer from max aircraft pairing (I have seen it increasing distance while flying toward PTV, switch ON/OFF and it worked fine)
Sometimes DME has an ident for each threshold even on same frequency, the case in UK when collocated with an ILS, if you look at Southend DME 111.35 it has two names (I-SO and I-ND) with two morse codes, when ATC flip the switch 23/05 for “runway in-use” the morse code will change…
That’s the theory, in practice you have an iPad running ForeFlight or SkyDemon, you also load VOR, NDB, ILS from database: GPS threshold distance comes to rescue if DME is giving wrong indication of distance or ident (also one validates with ILS glide path by giving range checks at 4DME or at FAF/FAP)
I think DME require continuous ident as DME suffer from max aircraft pairing (I have seen it increasing distance while flying toward PTV, switch ON/OFF and it worked fine)
On a DME which wasn’t duff?
It wasn’t until flying in the UK that I learned they do it differently there (shocker) and identify the DME separately (using audio) from the ILS
I have no recollection of ever seeing the DME having a different ident to the LOC. On VOR approaches this is often the case.
So do you guys identify the DME separately
I do, because it is a separate button on the intercom, and if you pressed both buttons together you can’t tell which you are identing. Although if you do enable both idents concurrently, they will still be spaced in time appropriately.
I have heard of IR examiners who want to see the ident running continuously during an approach. I think that’s ridiculous. But maybe the automatic monitoring equipment on an ILS system does suppress the ident if it detects a failure.
you have no way of ensuring that the NDB is still alive otherwise.
The needle goes perpendicular and does not dip or wiggle in turbulences 
Ibra wrote:
I think DME require continuous ident as DME suffer from max aircraft pairing
I’ve never heard this before… Wouldn’t it be obvious by your DME distance dropping out after it’s memory clears (10 seconds I believe)? Also the station would automatically desensitize, responding only to those aircraft nearest the station (ie. the one on approach). This brings up another question (I can’t seem to find the answer in my books so maybe there’s a radio guru that knows the answer). Does the DME identifier broadcast on VHF or UHF?
Peter wrote:
I have no recollection of ever seeing the DME having a different ident to the LOC.
The same for me, however, the rationalization given to me was that the G1000 auto identification is identifying the LOC and not its DME pairing (ie. that you aren’t sure you are receiving the correct DME unless you hear the identifier over the DME ident on the intercom.
I disagree with this for the reasons above, mainly 1. You shouldn’t be within range of another DME/ILS pairing (granted you’ve identified the correct LOC) and 2. If for whatever freak reason you picked up a distant DME while correctly identifying the LOC, the distance error would give it away (assuming your DME equipment didn’t lock on to the more powerful/closer one).
Ibra wrote:
I think DME require continuous ident as DME suffer from max aircraft pairing
You will still hear the ident even if your receiver isn’t the “chosen one”… it could also be painful as in many aircraft the DME does not have a volume control, and the ident has an annoyingly high pitch.
Cttime wrote:
1. You shouldn’t be within range of another DME/ILS pairing (granted you’ve identified the correct LOC) and 2. If for whatever freak reason you picked up a distant DME while correctly identifying the LOC, the distance error would give it away (assuming your DME equipment didn’t lock on to the more powerful/closer one).
It is a good idea to ident, the real risk is having set the DME manually to a fequncy (for example, to fly a DME Arc around the Maasticht VOR/DME to intercept a radial from Olno LNO – there used to be a departure procedure like that at Maastricht, IIRC, and if you only have one VOR receiver, you end up “unpairing” the DME); if you then return to Maastricht later you will get a semi-plausible DME distance from MAS when you have dialled the ILS on NAV1….)
Admittedly these are very rare, especially these days where everything has gone RNAV / RNP.
Peter wrote:
I have no recollection of ever seeing the DME having a different ident to the LOC.
I believe it is an ICAO standard that paired facilities have the same ident. A good trick identifying them is to switch the intercom to listen to both NAV and DME. The two facilities transmit the ident 2x on the nav and 1x on the DME, so you just wait until you have heard the ident twice at different pitches and then swicth them off again.
the rationalization given to me was that the G1000 auto identification is identifying the LOC and not its DME pairing (ie. that you aren’t sure you are receiving the correct DME unless you hear the identifier over the DME ident on the intercom.
That is possible, because the LOC ident comes from demodulating the LOC VHF signal (and a Garmin navigator has this internally, GNS430 onwards) whereas the DME ident comes from demodulating the DME UHF signal (and no Garmin navigator has this internally). The navigator probably (I could dig through some IMs) has a digital serial output stream for tuning a DME channel (a KX radio has that, for example) but probably doesn’t have an audio input which it could use for the ident decode.
But anyway a LOC ident says nothing about the GS, which has no ident. And is the LOC ident suppressed if the monitoring equipment finds the GS has failed? I don’t think so, because when you see GS flagged you are supposed to go around and then fly the LOC approach.
A good trick identifying them is to switch the intercom to listen to both NAV and DME. The two facilities transmit the ident 2x on the nav and 1x on the DME, so you just wait until you have heard the ident twice at different pitches and then swicth them off again.
That’s clever. I knew they were spaced appropriately but didn’t realise the pitch differs.
for DME? I heard that re: ADF as yes, you have no way of ensuring that the NDB is still alive otherwise.
Could be… It is 11 years since my UK IRT.
Yes DME needs to be identified using the morse ident, usually outbound on the procedure or downwind vectors. Bournemouth picks up Stansted under some atmospheric conditions.
I have no recollection of ever seeing the DME having a different ident to the LOC.
ILS 22 at LDZA uses standalone DME LUK with LOC IZG.
ILS 13 at LDZD uses DME ZDA with LOC IZD.
