I find VOR’s very little help as a back up for VFR navigation partly because no airfields close to me have a VOR on site and due to decommissioning I now have to be above 2000 feet to actually pick one up.
Oddly I find the much maligned NDB/tDME to be much more useful. They are located at every airport with an instrument approach in my area and with it not being line of sight I can receive three on the ground at my home base.
None of that not FM immune utter crap either.
What nobody mentioned so far is: if GPS should really fail, you still have radar control in European mainland and may have vectors to any ILS, all based on Radar data, which is totally independent of GPS. Even without any radio signal you are able to maintain altitude and steer using headings.
So this is another net layer of safety.
But if GPS fails AND radio communications is lost AND you are flying solid IMC without “VFR exit”, all at the same time, in this case the remaining layer of safety is thinned out, leaving only a few Old Radios online to navigate with. Presumably there will be enough stations so that a signal may be received.
By the way: Using a GPS you still can navigate without GPS signal, however this requires looking outside the window and identify position and terrain in relation to the map shown on the GPS. With Skydemon etc. this is easily done, like in the old days with paper charts.
As long as you understand the limitations of NDBs they are a useful tool. Before they started to disappear in this area, I used to use them a lot for both VFR and IFR.
NCYankee wrote:
In most instances, DME is retained when VOR is shut down.
This is the case here as well.
NCYankee wrote:
US has 4086 LPV published with 1057 using LPV200.
Good news for me is my home field, EHRD, went from LNAV+VNAV to LPV on both ends. So a net win in my book.
In Germany we have areas with so many VORs and DMEs that I feel no one will ever have any problem whatsoever if a third or more were decommissioned, especially the VORs . Quite a few locator NDBs are still there too, but frankly I don´t have a clue why. Same goes for the one and only area NDB in the area. They might just be around until EASA gets rid of NDB questions in their QB. Just kidding, these should really be gone by now.
A few years ago we had a VORTAC notamed for like two years or so and everyone but the fighters flew the same SIDs and STARs using RNAV. Since that time I´ve been convinced it´s not a big deal putting many navaids offline while a few remaining ones retain conventional capabilities. For IFR flying I never use green needles unless I want to practice, as I think most of us could. Most airliners are RNP capable too nowadays, unlike a few years ago when a crew requested a GPS approach only to be embarrassed two minutes later after they had found out their jet actually featured no GPS.
For VFR, I really don´t need to have VORs at all. I will rely on GPS and if that or the antenna´s gone TU there´s still an iPad, a map, radar, radio and Mark I eyeballs. It worked 100 years ago on less equipment, we´ll cope I´m sure.
So in my view the bottom line is: ILS will be around for many more years, DME/DME will be used as RNP primary and backup especially for the airlines. Enroute VORs will be reduced to the absolute minimum for the worst contingency case you can imagine. NDBs will go away within the next decade.
Caba wrote:
DME/DME
Just wondering. In Norway I see that NDBs around airports are going away and being replaced by two DMEs, one at each end of the runway. How are these DMEs used? Do the airlines have some automatic system that use these DMEs to pinpoint the position, like a moving map GPS kind of thing?
Yes, there are DME / DME procedures. But you need to have an inertial reference unit installed (and working).
T28 wrote:
Yes, there are DME / DME procedures. But you need to have an inertial reference unit installed (and working).
OK, but how is it used, what is the system and principle of operation? and why 2 DMEs?
Is the INS the primary system and DMEs are correcting it? Then why have an INS at all, when you have two DMEs ?
LeSving wrote:
two DMEs, one at each end of the runway.
Are these really two different DMEs at each end, or one DME that is active for the runway in use?
I don’t think two DMEs that close to each other are very useful; in order to get a position fix you need at least three DMEs (well, two if you can rule out one of the points definitely) and they cannot be too close to each other, and especially not “behind” each other as seen from the aircraft;. The closer they are (and the narrower the angle as seen from the aircraft) the less precise the fix will be.
Cobalt wrote:
Are these really two different DMEs at each end, or one DME that is active for the runway in use?
I don’t know, but they certainly looks like two separate DMEs, one at each runway end. They are shown in particular on the “visual approach chart”. It’s the one we usually also use for VFR, with a couple of exception. At ENGM there are four. One at each end of each runway.
