In the UK, towers tend to have VDF (VHF direction finding), even at the “poor” places.
But triangulation is only at the military D&D unit on 121.50, AFAIK.
What about the rest of Europe?
Peter wrote:
But triangulation is only at the military D&D unit on 121.50, AFAIK.
Because for that a common frequency is required. Every airfield with VDF has it’s own frequency, some of them still “hardwired” by a single crystal on some smaller airfields and glider sites. So in order to get a position by triangulation, a pilot would have to transmit three times on three different frequencies and do the calculation himself.
Around here, more and more VDF stations get dismantled at the smaller fields. They require costly calibration every so and so many years and many airfield operators don’t think it’s worth the expenditure. Apart from some training aircraft nobody has asked for a QDM since the early 1990ies anyway when affordable GPS receivers became available.
German ATC and FIS get the sending station displayed on their radar screen via VHF triangulation. They have lots of receivers throughout their FIRs. It helps a lot to prevent the very common mistake of station B reading back and confirming an instruction for station A which sometimes remains unnoticed by all parties involved.
All Belgian controlled airports have it. As well EBBU ACC and FIC. It is superimposed on the radar display. Works very well !
what_next wrote:
Around here, more and more VDF stations get dismantled at the smaller fields. They require costly calibration every so and so many years and many airfield operators don’t think it’s worth the expenditure.
Wouldn’t numerous antique VDFs survive at club airfields at an unofficial level, uncalibrated? A VDF requires very little maintenance and even without calibration provides a relatively foolproof way to guide a clueless lost student pilot back to the airfield.
Ultranomad wrote:
Wouldn’t numerous antique VDFs survive at club airfields at an unofficial level, uncalibrated?
Yes, sure – they are still there. But I wonder how many students/pilots would dare to ask an airfield for a QDM if it doesn’t have that asterisk on the ICAO map. On the other hand, even student pilots know how to use the GPS inside their smartphone and don’t get lost so easily.
We didn’t ask for a single QDM throughout my PPL training despite visiting numerous fields which are supposed to be able to give on according to the DFS visual charts, including my home field.
MedEwok wrote:
We didn’t ask for a single QDM throughout my PPL training …
That’s probably because your instructor already belongs to a “generation” of pilots who grew up with GPS, flying-wise. Asking for a QDM is not part of his mindset. Myself I had to do it a couple of times for training purposes during my own training but never needed it in real life. And by the time I was instructing myself (early 1990ies) GPS was the thing to go for. I remember students who showed up for the flying lessons with early Garmin units which cost more than the car that I drove then… you certainly don’t teach someone like that to ask for a QDM.
My original post was really asking about whether ATC can see the bearing of a transmission, or even a triangulated location.
I don’t think anybody has flown VDF approaches in 20 years…
I am tempted to post an mp3 showing somebody reading back a clearance addressed to me and ATC responding to him normally, as well as never realising that I did not read it back 
I could see what happened but one can never be 100% sure until playing it back several times. It was in the UK which has normally very good ATC hence I am hesitant because I don’t just want to show somebody in a poor light for the fun of it. But VDF might have prevented that.
what_next wrote:
But I wonder how many students/pilots would dare to ask an airfield for a QDM if it doesn’t have that asterisk on the ICAO map. On the other hand, even student pilots know how to use the GPS inside their smartphone and don’t get lost so easily.
I meant a truly clueless and panicky species, like:
– Aaaah! I don’t know where I am and where the airfield is, I’m going to run out of fuel and craaaash! Aaaah!
– Stop whining, look at your compass, turn to heading 155, keep flying it and you’ll see the airfield in several minutes.
