NDB/DME approaches

[Let'sgoflying!]

A pal is studying up on an advanced rating, out of discretion that is all I will say.
The question arises from study of the legend page of an iap book.
In it, there is a diagram of an NDB/DME.

The question is, when you dial in the vor/loc frequency to receive the DME information, what does the nav head display?

Auxillary questions would be:

-Are any of these DMEs not associated with a vor or loc? Ie is it possible that you will get no signal to the nav head? (it is realized that any info is to be ignored anyway, just wondering what the needle would do)

-Could you/should you use the flag on the nav head to decide if the dme info is reliable or not?

Here is one in Canada
http://va-transaero.ru/files/charts/CYCD.pdf
There is also one in Oxford, England....can't put my hands on the link right now.

 

[ajstoner21]

I believe you can get DME information before any navigational course deviation information is reliable (I could have those reversed?) OK, to be honest, I am not sure which one you will lose first when flying away from a station, but I think you will have either the Nav Course information or the DME information longer than the other.

EDIT: OK, I really have no idea. Both seem to be Line of Sight, so I'm not sure any more. I thought I read it somewhere....

That said, I THINK you can get DME information with a nav flag showing.

When a DME is colocated with a VOR, the DME identification is transmitted once for every three or four times the VOR identification is transmitted.

IF they are colocated, and you hear an identification about once every thirty seconds, the VOR is inoperative and the DME is still operational.


*** I am out of town, but I can check in my books when I get back. I definitely remember reading about this.

 

[Areeda]

Interesting. i found 3 of these in the NACO plates. See attached.

2 of them have the DME associated with the NDB, I wonder how you figure out how to set the DME. I guess that table in the AIM that has VOR Freq and the associated DME channel is actually good for something.

Joe

 

[Everskyward]

Interesting. i found 3 of these in the NACO plates. See attached.

2 of them have the DME associated with the NDB, I wonder how you figure out how to set the DME. I guess that table in the AIM that has VOR Freq and the associated DME channel is actually good for something.

Joe

In the Hailey example they give you the frequency in the box that says IAF (DME channel 25 108.8) and in the Ryan example you use the DME off the Tuscon VOR.

 

[chucky]

The Ryan field NDB/DME approach uses the Tuscon DME, it looks like, but the Friedman Mun. does have a DME co-located with the NDB. The Friedman one lists the pared frequency in the navaid box: DME Chan 25 (108.8). This is a cool approach, though. I think I'm going to try it in FSX, just for laughs.

 

[ajstoner21]

Whenever the VOR/LOC information (box with identifier, morse code...) has a "Chan" in it, I believe it indicates a DME is colocated. (TACAN?)

That is a way to tell if it is Tuscon VOR that the DME is off of.

 

[Areeda]

In the Hailey example they give you the frequency in the box that says IAF (DME channel 25 108.8) and in the Ryan example you use the DME off the Tuscon VOR.

that makes it easy. I should have read closer.

 

[tonycondon]

last i knew there was at least one airport in minnesota (Pipestone i think) that has a NDB and DME on the field but no VOR associated with it. from what I remember on my first solo XC the VOR indicator remains dead when the Nav radio is tuned to the frequency

 

[Areeda]

last i knew there was at least one airport in minnesota (Pipestone i think) that has a NDB and DME on the field but no VOR associated with it. from what I remember on my first solo XC the VOR indicator remains dead when the Nav radio is tuned to the frequency

Your right, but the DME is not required so it's not in the procedure name and I missed it.

You do get lower minimums with a DME.

Joe

 

[poadeleted20]

The question is, when you dial in the vor/loc frequency to receive the DME information, what does the nav head display?

Depends on the source of the DME data and how your DME frequency selection is channeled. If the channeling comes from the VOR receiver, and the DME signal comes from a TACAN or independent DME transceiver, the VOR CDI should show centered and OFF. If the channeling comes from the VOR receiver, and the DME signal comes from a VORTAC or VOR/DME, the VOR CDI should show a valid TO/FROM and needle positioning based on whatever you have dialed in on the OBS. If the channeling comes from direct input on the DME control head, the VOR CDI indications will depend on what you have in the VOR receiver, and will be unrelated to the DME settings.

-Are any of these DMEs not associated with a vor or loc? Ie is it possible that you will get no signal to the nav head? (it is realized that any info is to be ignored anyway, just wondering what the needle would do)

I've seen them that way.

-Could you/should you use the flag on the nav head to decide if the dme info is reliable or not?

No -- not in this case, and not ever. DME data are entirely independent of VOR data even for a VORTAC or VOR/DME station. The only way to know if the DME data are valid is to listen to the DME receiver audio and see if you're getting the station Morse ID at 30-second intervals (vice 10 for VOR) with a higher pitch tone than VOR.

 

[Let'sgoflying!]

very cool, thanks all.