ILS Question

[Lefty]

I think your slightly confused on the NAVAIDS we are talking about. So I am going to reference some of your posts above as well.

An interesting thing that you should be able to do is, at any tacan only station you should be able to get dme off of it if you know what frequency is paired to the channel the vortac operates on.

You mention Tacan only station and a VORTAC. Tacan only means when you tune up the applicable Tacan channel your aircrafts Tacan reciever automatically pulls the DME info to display on your Tacan equipment in the cockpit. A VORTAC is designed for military and civil use, so there is a VOR and a Tacan co-located. The DME equipment picks up the signal from the carrier frequency associated with the VOR's VHF frequency.

No, if you have the channel the tacan is operating on, say 57, then if you knew the paired frequency, in this case 112.0, you could put 112.0 in your dme and should be able to get dme off it. Another example would be you run across a tacan on channel 37. If you put 110.0 into your dme, you should get distance.

What you're saying here is much more complex than what you're saying. For the above to be feasible, you would have to find out what Tacan channels are associated with what specific UHF carrier frequencies. Then find out what specific VHF frequencies are paired with those UHF carried frequencies to input into your civil DME equipment. So essentially you would have to research Tacan = UHF = Associated VHF frequency that carries the same UHF freq as a specific Tacan channel.

An no, no DME info is broadcast on 112.0. I don't know if I'm misreading you. The paired frequencies does not mean it is also broadcast on, rather the DME knows where to look because 57 is paired to 112.0. And of course the channels correspond to a frequency.

Yes you are misreading me, I did not say that 112.0 broadcasts the DME info. However with civil use DME equipment you can only input a VHF freq. Therefore for all intents and purposes, 112.0 is where you will get your DME info (because your DME equipment will automatically pull the DME data from the appropriate carrier frequency.)

Using your post as an example, Channel 57 in this specific example is associated with this Tacan only station, for civil use. However I think you will be hard pressed to find a CFII that would teach their students to look up the UHF frequencies associated with a Tacan channel so that they could pair them with a VHF frequency to use the DME. It really has no practical use. All you would be doing is flying around the saying "Well I am 33.5 DME from ABC tacan."



This is getting way beyond the scope of a civilian pilot, because unless s/he work for Flight Check, s/he will most likely never use Tacan equipment.

 

[Lefty]

I think that more or less we are talking about the same thing. :crazy:

In theory yes you could do it, is it practical not so much. :beer:

 

[Ollie]

A quick google search even turned this up. To deduce the channel from tacan to it's VHF pair you add 1063 up to channel 57 and add 1053 if it is 70 or above. Nothing was mentioned in between those, but it seems to work with the tacans and vortac's I looked up on a sectional.
channel 57 + 1063 = 1120 channel 37 + 1063 = 1110
And here is a list of the pairings: http://braun-home.net/michael/info/radio_navigation/TACAN-channels.xls

Now you can go around and get DME off of all those tacans, lol.

That's some pretty convoluted mathematical sorcery just to get DME information from random TACAN stations. I'm sure it works perfectly well but I don't see any purpose for it whatsoever. For all I know there's some equation to derive frequency pairings to get DME information from the local Pizza Hut but it does me no good whatsoever.

I think we're all on the same page on this issue we're just agreeing with each other using different words. Between the three or four of us actively posting in this thread we've absolutely answered the OP's question. :beer:

 

[z987k]

I edited my last post so I don't know if you caught the last part. You don't have to do tacan channel = uhf = vhf. The DME equipment onboard your airplane already knows the uhv to vhf pairing. All you have to know is the channel to vhf pairing. I posted a chart that lists such pairings, and a formula to do it on the fly.
Yes, this probably has no practical use, we are purely into the academic at this point.
However, I also noticed while looking at an L chart that all the tacan only stations also have their vhf pair listed. I would presume this is to get DME off of it. It may not commonly be of use, but maybe there is a time where it would be helpful to know your distance from a tacan, and if you have dme, you always can. If nothing else maybe in some cases it would help out with your SA.
I don't think it's commonly known that you can get dme off of a plain tacan, and I don't think that's a bad thing to know. Just in case some crazy situation happens. Or just better understanding a tacan.

 

[Lefty]

I edited my last post so I don't know if you caught the last part. You don't have to do tacan channel = uhf = vhf. The DME equipment onboard your airplane already knows the uhv to vhf pairing. All you have to know is the channel to vhf pairing. I posted a chart that lists such pairings, and a formula to do it on the fly.
Yes, this probably has no practical use, we are purely into the academic at this point.
However, I also noticed while looking at an L chart that all the tacan only stations also have their vhf pair listed. I would presume this is to get DME off of it. It may not commonly be of use, but maybe there is a time where it would be helpful to know your distance from a tacan, and if you have dme, you always can. If nothing else maybe in some cases it would help out with your SA.
I don't think it's commonly known that you can get dme off of a plain tacan, and I don't think that's a bad thing to know. Just in case some crazy situation happens. Or just better understanding a tacan.

Completely agree!

 

[z987k]

That's some pretty convoluted mathematical sorcery just to get DME information from random TACAN stations. I'm sure it works perfectly well but I don't see any purpose for it whatsoever. For all I know there's some equation to derive frequency pairings to get DME information from the local Pizza Hut but it does me no good whatsoever.

I think we're all on the same page on this issue we're just agreeing with each other using different words. Between the three or four of us actively posting in this thread we've absolutely answered the OP's question. :beer:

I've got a scenario. Say you are VFR and /A around OKC. You want stay clear of C under the shelves. You can use the dme off of the tacan at tinker to stay clear of their C, at least as a backup to your visual. Giving you one less task - ensuring visually you are not busting C.

 

[Ollie]

I've got a scenario. Say you are VFR and /A around OKC. You want stay clear of C under the shelves. You can use the dme off of the tacan at tinker to stay clear of their C, at least as a backup to your visual. Giving you one less task - ensuring visually you are not busting C.

I didn't catch your edit in time to prevent my mind from being blown by that first forumla. Your scenario is definitely legit.

When I was instructing at OUN I used to fly directly over Tinker multiple times a day and loved watching the AWACS/TACAMOs doing practice approaches. Oke City Approach was usually cool about it and didn't even start issuing an overflight altitude restriction until the post-9/11 days. You're making me homesick now...

 

[z987k]

I've got a real scenario where knowing that I can get DME off a tacan is useful that I'll be using tomorrow.
Beale AFB has a TFR up from the top of their C to 18k tomorrow. I'll be dropping jumpers about 3nm south of their airspace. Norcal approach likes us to climb north of the field once we get above 4100 so that we're over top of them but clear of the arrivals into SMF since their arrival goes right over or slightly to the south of our dz. So now I can use DME off the TACAN to help make sure I stay clear of the TFR while also staying out of the approach path for Sacramento.