I went to a Eurocontrol nav workshop recently.
There are all kinds of "plans" going around, some less bizzare than others.
NDBs are a bit of a special case because they are manifestly not needed for anything, and IMHO they will go within 10-20 years.
The UK is almost unique in requiring the carriage of an ADF for all IFR in all classes of CAS. Switzerland was the other one but it allows IFR GPS substitution, USA-style. This requirement will disappear, I am sure, within the next few years.
As regards other navaids, some must remain. Airliners (CAT) have INS but this requires DME-DME fixes for reasonable accuracy. Eurocontrol have one plan under which all navaids except DME are dismantled and most ATC radar too (because airlines want lower enroute charges) but hundreds of new DMEs are installed to provide a uniform DME coverage for CAT.
VORs are quite expensive and they may go within say 20 years.
The practical reality is that the IFR world is wholly RNAV (INS+DME, or GPS) with all flight using virtual waypoints (which occassionally are real VORs etc but almost nobody tunes in the actual navaids) and VORs/NDBs are an irrelevance except on instrument approaches.
But there remains the perpetual chestnut of what will happen if GPS fails.
"The Plan" is that CAT will use a combination of INS+DME+ATC radar, while non-INS traffic (GA, up to light jets) will use ATC radar to get back down. One perceived problem with this is that if airlines get their way and most ATC radar coverage has been dismantled and replaced with ADS-B (hey, this is Brussels) then there won't be enough ATC+radar capability for the thousands of VLJs (yes, Brussels have not yet realised that Eclipse has gone bust, the air taxi model is dead and always was, etc, etc, etc) to get back down.
Yet anybody actually working in IFR ATC will say that the chance of ATC radar disappearing is nil, which IMHO is bang on. Radar will always be needed for national security reasons.
So I don't see much changing, but I can see non-approach NDBs (e.g. WCO) disappearing, with the IFR ADF carriage requirement.
There was some subtle reason why the CAA didn't want to remove this requirement but I cannot remember what it was.
Last edited by IO540; 18th Apr 2009 at 08:22.