NCY didn’t mean you can’t fly ground based radio nav approaches without an IFR database – just that if you are using the GPS to substitute a ground station you should load the relevant approach.
I am not able to match your 32 year pre GPS experience, but I can still recall the four range approaches – although didn’t take the time to fly to Northern BC to fly one when they were still around.
I’ll try and see if the search engines might still have an old plate and a primer on how to fly it.
…Wikipedia has a nice entry on LF Range approaches and navigation, including an old approach plate
RobertL18C wrote:
NCY didn’t mean you can’t fly ground based radio nav approaches without an IFR database – just that if you are using the GPS to substitute a ground station you should load the relevant approach.
Robert,
My point is that GPS substitution for DME is not premised on loading the relevant approach. For many GPS systems, example the KLN90B, they don’t have the ILS procedures in their database. If you have one of the later GPS systems that include the ground based procedures, then it is usually a good idea to load the approach using the database, but not always. There are some procedures that don’t have the DME waypoints, particularly on the final approach segment, and one might have difficulty determining these waypoints and simultaneously loading the approach. So I don’t agree with the blanket advise “should load the relevant approach”.
@Guillaume – sorry for the delay in responding, this thread has moved fast:
I understand your point. However I would rather put it this way :
“The DME bias gives more altitude for obstacle clearance (and not safety) if not implemented in the GPS, as it reports you as further than charted and hence you will be too high.”
Being too high (~200 / 300 ft) on an approach is not necessary a good thing for safety as it leads to non-stabilized approach.
Obviously, being too high on a long runway with a SEP in good weather will not lead to an accident.
But I’m not convinced that approaching too high is good for safety in general.
I agree, being too high on an approach is not ideal. But not really dangerous either, if the pilot is aware of this effect. If everyone could accept that the above is the only technical issue associated with GPS-for-DME-substitution in Europe (i.e. ignoring human factors and training issues), then we can debate how much of an issue and how dangerous it is. But right now, most people seem to be sticking with “substituting GPS for DME is just stupid and dangerous, period”, without saying why.
For reference, on a 2000m runway, 3deg glideslope, assuming DME in the centre of the field (1000m or 3,300ft DME bias), GPS-for-DME substitution puts you at 1,128ft at 3 miles vs 955ft using the “proper” DME distance, so 173ft too high (3/4 deflection on the glideslope indicator). At 1 mile it becomes 491ft vs 318ft so proportionally more significant. But you are at a constant 173ft too-high throughout the approach, if you fly to the DME/altitude profile but using GPS distances.
ortac wrote:
But right now, most people seem to be sticking with “substituting GPS for DME is just stupid and dangerous, period”, without saying why.
WHAT I’VE BEEN SAYING FOR THE LAST 9 PAGES
And American pilots seem to be coping with the human aspects quite well, 18 years on now …
Thanks ortac for stating the OBVIOUS 
Well done Michael !
You fail to quote the whole of Ortac’s post and miss the " ignoring human factors & training issues " as you seem to be only looking at what is technical posable and not if it is wise to do.
There are very few accidents that are mechanical problems, a few mishandled aircraft but most IFR GA accidents are CFIT and can be considered human factors as the navigation kit is usually working correctly.
There is not currently any training in Europe for this being it is not approved, so pilots like you are making your own procedures……. some may not have been well reasoned to avoid errors.
A large number of airports have the same IDENT for a number of navigation aids that are not co-located and so would invite errors.
Most GA pilots are on their own when flying so there is no-one to check the data that has been selected in the data base is correct.
Add to this the attitude of infallibly with modern avionics that I find with the children of the magenta line and we have too many bits of Swiss cheese with the holes lining up and not much to catch the errors.
Until procedures are put in place to train pilots to use the GPS equipment for DME substitution with emphasis on trapping prograning errors, multiple identical NAV aid indents are removed and ATC become are briefed about DME substitution then this should not take place.
We have seen an accident happen with a relitivly simple IFR approach, problems are much more likely with complicated approaches and high workload situations, there is no doubt that the GPS system is technically sound but as yet there are not enough measures put in place to mitigate for human errors.
Over confidence and disregarding established procedures are classic human factors problems that we see in accident reports, I see this in some posts above, by all means pressure the authority’s to consider GPS substitution for DME but let’s not have another person killed because of flying an untrained,half baked home made procedure.
So can we all finally agree that there are no safety issues with GPS-for-DME in Europe, bar being slightly high on the approach, given adequate training and following of appropriate procedures?
Let’s say you commence a VOR/DME approach and then lose the DME. Should you continue with the “no DME” alternative procedure and higher minima because it’s “safer” or should you use the training you have (hopefully) received to safely make use of GPS instead?
A_and_C wrote:
You fail to quote the whole of Ortac’s post and miss the " ignoring human factors & training issues " as you seem to be only looking at what is technical posable and not if it is wise to do.
And you obviously choose to ignore the simple fact that US based pilots have handled ALL aspects of using GPS for DME fixes, including human factors, without coming to grief 18 years on now.
Errrr no
I have not said it is technically unsafe provided the correct training & procedures are in place and the traps like multiple identical navaid intents are removed ………. as of yet this is not the case in Europe.
When Europe has accepted the procedure I will be more than happy to fly GPS substitution for DME but until then I will not.
I don’t see any reason to cheapskate for the price of a DME unit, my life is simply worth more than that.
I don’t see any reason to cheapskate for the price of a DME unit.
But what action would you take in the event of a DME failure prior to an approach that used DME? Assuming no RNAV alternative. Would you use GPS or not?
Personally: I would happily fly any ILS/DME approach (regardless of what the zero-range is) using the FAF in the GPS database as the only glidepath altitude check.
I would happily fly any VOR/DME or NDB/DME approach, provided the approach is in the GPS database and EITHER the DME is co-located OR all step-down fixes are in the GPS procedure.
I would NOT fly a LOC/DME approach unless all step-down fixes are in the database.
Basically I would not want to make anything up in the air that is not trivial.
