Perhaps ewe could add those in Europe who fly IFR without DME and use GPS distance for instrument approaches to this list.
@AandC, well I will take the bait. Airways requires IFR GPS and does not require DME, and you are legal to fly RNP and ILS approaches without DME in a radar environment.
There have been fatal accidents in Europe where the crew flew a non precision approach using GPS as a diy DME substitute. These accidents were due in part to Europe not allowing overlay GPS procedures. Also poor understanding of IFR GPS amongst crews (regular MOR reports of CAT being un stabilised on RNP approaches because the crew did not understand the run in to the FAF).
If the crew in these fatal incidents had loaded and activated the relevant NPA, the relevant DME read outs would have been accurate. The crew flew DIY substitutes mis specifying the OBS waypoint for azimuth distance.
I would argue that a proper understanding of IFR GPS is a chronic problem in Europe despite endless RNP training and re validation.
DME distance vs GPS distance delta errors would range from around 0.5nm to 3nm, if one sticks to 5km visibility & 800ft ceiling they should be fine fiddling with GPS (even direct to ARP should be more than enough) bellow that one need to be a nav aids calibration expert to stay alive away from his home-base, even those dme calibration flights are done in CAVOK 
I agree with A_and_C there is just too much to watch for, besides anything that does not bring a single pilot straight to the runway threshold is really bad (whatever superior offset one applies to their mental model)
ILS/DME is safer than GPS to ARP/TRH/MAPt but I would argue GPS to TRH substitute is way safer than VOR/DME or NDB/DME, without looking at the plates my vague recollection is that VOR & NDB stations are most likely near top of the hills or middle of the forests rather than near runway thresholds, so not conceptually sound to start with, unlike ILC/LOC how DME is collocated & calibrated to show “0DME” for VOR/NDB is never clear and needs a careful look at the plates on case by case
Robert18C
I have much sympathy with your point of view having flown for a very forward thinking U.K. company who found themselves hindered a little by the CAA but at in the end common sense won out in the way the navigation system was used.
I them moved to a very forward thinking Scandinavian company overseen by an equally forward thinking airworthiness authority who understood the use of GPS technology, then for business reasons the AOC was transferred to another EASA authority and we returned to the dark ages of navigation and flight safety management.
However this does not distract from the fact that in Europe it is easy to select the wrong radio aid to get GPS distance data and for the answer to be plausible and until the multiple ident issue is resolved simple DME substitution remains hazardous.
However this does not distract from the fact that in Europe it is easy to select the wrong radio aid to get GPS distance data and for the answer to be plausible and until the multiple ident issue is resolved simple DME substitution remains hazardous.
@AandC we agree completely – simple DME substitution is hazardous! You put it more clearly than my shorthand of DIY fixes.
