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DME - any point in having one?

Timothy wrote:

While huv is kind enough to agree with me, I’ll agree with him. It’s appallingly unintuitive. I don’t fly G1000 that often (there might be several weeks between times) and when I do, I really struggle to remember this bit of the interface.
My G1000 aircraft has a completely separate DME installation. Only the DME audio is connected to the G1000. I have been annoyed by that but maybe I should be happy instead?

ESKC (Uppsala/Sundbro), Sweden

I have just fitted a KN64 DME to my UK RV that’s cleared for IFR. The biggest problem I had was positioning the Antenna, it requires “Avoid mounting the antenna within three (3) feet of any COMM antenna and six (6) feet from a transponder antenna, with a max cable length of (10) feet.” I managed the 3 feet from both Comms but only 5 feet from the transponder and about 7 feet total length, but it works really well.

Another vote for OnLineGar – it’s one of those tools that very neatly takes care of an annoying problem.

United Kingdom

I agree that a DME is great, for all the reasons given above. It’s really a pity that the market for them (the USA ) has collapsed and the ones out there are bulky and expensive. A DME should cost about the same as a GTX330 to make (parts cost about $300) and the installation is basically the same.

Shoreham EGKA, United Kingdom


I have. King DME indicator that would be suitable for your GTN650 / KN 63 installation the unit comes with a conector and an EASA form one.

In this post Timothy wrote:

There was no RNAV approach at the time, so PN09 wouldn’t have existed.

I probably did not get the right waypoint name. Maybe it should be RWY09.

I was referring to the way the threshold would be coded in the GPS overlay for the conventional approach.

As stated in the PPL/IR PBN manual:
GNSS database procedures are coded so that the Runway Threshold waypoint is always the Missed Approach Way Point ‘MAWP’.

So the runway threshold is coded, hence it is easy to get a GPS distance from it.

I have not looked at how this particular approach is coded in the database but I am pretty sure the pilot would have gotten other clues as to his position had he used an overlay approach. The FAF/FAP is normally indicated.

I am not really advocating flying ILS without DME, especially if the approach is explicitely labeled “DME required”. I am just saying that giving a little thought to how to identify the stepdown fixes without DME, it can be done. Using distance from the NDB was not smart.

There are ways to screw up with a DME too. Like remote channeling from the wrong source for example. Someone (may have been an instructor) referred to the RMT switch on some well known DME receivers as the “suicide” button. Or tuning in the wrong DME. Using an overlay should enable you to catch such things.

Last Edited by Aviathor at 11 Oct 17:22

I have said all I can usefully say on why you should have a DME. Personal choice is a wonderful thing.

EGKB Biggin Hill

So the runway threshold is coded, hence it is easy to get a GPS distance from it.

Until you get an IAP where DME=0 is elsewhere, and not read the plate properly.

Not many people will kill themselves using GPS in place of DME by doing a DCT [airport name] if DME=0 is at the MAP.

Shoreham EGKA, United Kingdom

I would say DME substitution on a published approach (and using an overlay approach) is safer than

  • DIY approaches
  • Descending to 500’ (or lower) over the sea.

both of which have been advocated here.

Last Edited by Aviathor at 11 Oct 21:07

Because one thing is safer than another, that does not make it either safe or a good idea.

Getting an approved LPV put into your strip is either very expensive or impossible depending where you live. An alternative is to do a DIY approach to the highest standards of safety available. Some consider that excessively dangerous, others differ.

Putting a DME into your panel, or keeping an existing one, is generally considerably more accessible and affordable, by orders of magnitude, and brings a considerable safety benefit.

Chacun, as they say, à son goût.

EGKB Biggin Hill

DME is there for a reason. If it wasn’t, we would have just binned markers and carried on with ILS only. There are places where I have flown where a GPS DCT(airport) distance would give me a range inaccuracy of 2nm compared to the IL synched DME. So what’s it to be – follow the ‘GPS DME’ or trust your ILS GP, implicitly?

Last Edited by Dave_Phillips at 11 Oct 22:02
Fly safely
Various UK. Operate throughout Europe and Middle East, United Kingdom
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