Vor/dme

[van der vart]

are all VOR and DME co-located?

if VOR/DME is unserviceable, what methods can pilots use to track to that unserviceable VOR/DME?

[Spitoon]

you can have a vor without a dme - or a dme without a vor. speaking as a controller, i've never known of an aircraft having a problem navigating to a fix that is normally defined by a vor. there are plenty of other ways to navigate using bearings from other navaids - or more normally these days letting the rnav equipment point towards wherever the pilot wants to go.

[van der vart]

spitoon, as a controller what would you tell pilot if the VOR is unserviceable? "use RNAV to XXXX VOR"?

[Tinstaafl]

VOR & DME are two independent & unrelated systems except for the frequency pairing tables ie if a VOR of xxx.x MHz frequency has an associated DME, the DME will use yyy.y Mhz.

This pairing of frequencies enables a single selector in the cockpit to handle tuning both aids. Select the VOR frequency & any associated DME will automatically be tuned in.

Bearing in mind that they're independent navaids then the failure of one doesn't cause the failure of the other (erm..... Hollywood-esque explosion in the electronics room, anyone?).

If the DME fails then one navigates to the VOR as normal sans the DME function.

If the VOR fails then you would need an alternate navigation source although DME would still be available. One method of navigating to the VOR/DME (the original question) would be to use DME Homing techniques. Not often taught now though... :sad: That would work if no other navaid is useable for the task eg not in range, lack of a/c receiving equipment etc.

If another navaid is in range then you could:

1. Use an alternative azimuth aid to fly a bearing (NDB/ADF) or radial (VOR) to the failed VOR. DME will show when over the aid (if the failed VOR & DME are co-located) or use another azimuth aid to obtain the fix.

2. Use a separately located DME that is within range of the failed VOR & fly a DME arc until over the failed VOR/DME. Find the fix over the failed VOR as above.

3. Navigate visually (gasp!) to the VOR.

Alternatively you might have the option of GPS, INS or even a radar vector.

[*Lancer*]

And to answer your first question... they're often co-located, but not always. The maps have a combined symbol for co-located aids, not the be confused with a VOR symbol overlayed (or very close to) the DME symbol. EFIS systems also have a symbol for co-located VOR/DME.

ILS/LOC approaches often use DMEs that aren't 'co-located' (joint frequency) to the threshold of the approach. It's sometimes necessary to tune the DME (or a VOR/DME) seperately for the approach.

[Spitoon]

sorry van, wasn't ignoing you, just been a bit busy! A few years ago this a consideration but it seems far less so in practice these days.

First, in the UK, many VORs have a co-located NDB mainly to provide back-up if the VOR is oos or u/s. Even if there's no NDB, if the vor failure is unexpected I'll advise the pilot of the VOR failure and watch the aircraft carry on as normal.

I guess the situation might be a bit different if position reports were needed over the VOR - not because the pilots of modern aircraft will have much trouble doing it but because it sounds daft to say ABC is broken report passing ABC!

If, on the other hand, it's Air Antique I'd be ready to offer more assistance if required.