DME / ADF substitution by GPS is not allowed in any EASA member state. I thought you didn’t want to discuss the legal aspects?
Maybe that makes sense, but it’s a little beyond me to have an RNAV/GPS approach that requires an ADF. They trust the GPS to get you down …, but not for the MA?
I guess I have a long way to go to understand some things, or the deeper meaning at least.
@ Achim
I know it now. Thank you. (how much can the fine be? Please say again)
I think we can all agree that use of NDBs for missed approach procedures on RNAV approaches is complete nonsense. But that is just how it is in the UK.
With regard to DME “non zero offset”, how can GPS-for-DME substitution not have a problem with this in the US, but potentially have a problem with it in Europe? Where is the difference in implementation? Is this just a hypothetical issue or are there real world known instances of it?
Surely any IFR certified GPS nav database will always have coordinates for an ILS DME that correspond to its zero distance location. The physical location of the DME has no relevance to a GPS database, if different from its “virtual” location.
The US has a lot of approaches with markers, ILS/DME is nowhere near as universal as it is in Europe.
And if you don’t care about any interim altitude checks on the ILS, you don’t need it at all. The ILS procedure in the GPS has the FAF in the database so you can use that to do the gross error check when intercepting the glideslope, and after that you should be quite safe.
You will really miss the DME on a localiser approach, though.
I have to say the predilection for having ILS only without DME in many German airports is a major bug ear of mine. Some avionics set ups will let you “hold” the DME from another station which can also kill you on a LOC approach if you are descending based on the wrong DME.
GPS makes life easier but if a plate says DME or ADF required, there is no way around EASA!
ortac wrote:
Surely any IFR certified GPS nav database will always have coordinates for an ILS DME that correspond to its zero distance location. The physical location of the DME has no relevance to a GPS database, if different from its “virtual” location.
That’s not possible. There is no “virtual location” for an offset DME. It will show zero distance in a circle. One reason an offset DME is used is to make the same DME show zero at both runway thresholds.
Yes but the circle will intersect the two opposite ILS courses at two different points. And each ILS has its own ident so the two different points can be coded into the GPS nav database as different waypoints using these two identifiers. All other points on the circle are redundant. So I still don’t understand what the issue is here.
But is it always done that way? Do you have any sources for this stuff, I’d love to learn more about it.
All other points on the circle are redundant
That’s unless the DME is also used for other parts of a procedure, not in line with the runway.
But is it always done that way?
It has to be like that (with a fake DME offset) with any runway which has an IAP to both ends of a runway. Otherwise you would need two DMEs, each located abeam the TDZ.
