Interesting stuff. Thanks M609 for your explanations. Peterh, I'm with you all the way up to the AIDS research. AIDS, Malaria etc. are still serious diseases and deserving of research and the type of fundamental research involved often produces discoveries and benefits not necessarily related to the original research subject. Now if you were to start talking about the general level of panic and hysteria surrounding AIDS, BSE, Avian 'flu, SARS, Volcanic Ash, etc., etc., and the predicted mass fatalities resulting, I would definitely be with you on that as well.
I still don't understand the claimed benefits of PRNAV though. M609, you state that, "With PRNAV procedures that are properly designed, you can IMHO shift more aircraft in a given volume of airspace with the same staff and ATM equipment." I respect your opinion as one who is apparently involved at the 'sharp end' of this but you do say that this is only your opinion. Is there any real evidence that this is the case and if so I still don't really understand how.
You also however say that, "(When it happens nowadays, the crew mostly confess to having gone into heading mode or some such, and not trusting the box. Or cancelling the procedure in the FMS, and wandering off whilst trying to put it back in, without telling ATC." So even with PRNAV there is, of course, still no guarantee that aircraft will be where the procedure says they should be. So all of the design to put tracks closer together seems simply to be a degradation of safety.
Surely, "When i have a SID that turns parallell to a STAR with say 7nm, any overshoot on that turn will mean a loss of separation, so with BRNAV you would never design them that close, or you would use vertival separation until the turn was observed to be accurate, or turn the departure onto the desired heading earlier to assure separation. Hence increase worload. " if the tracks are that close, then it would be foolhardy in any case, PRNAV or not, to not have an element of vertical separation for just the reason which you describe.
As a related remark in all this I could mention at least one airline, which while PRNAV equipped and approved, chooses not to put the "P" on the FPL as the PRNAV procedures add so much extra track mileage that it would add significantly to costs.
While we are on this type of subject and have M609's attention, perhaps you would give us your take on another of the dreams of the 'Gravy train committees,' the 'point merge' procedures? What on earth is that all about?
10W, you make exactly my point: there is no difference in separation standards and in European airspace aircraft are continuously radar monitored. So what is the benefit of PRNAV, RNP - and ADSB in Europe, come to that?
Back when I were a lad and things were simple(r), they larned I at skool, that an airway was a corridor of airspace whose limits were defined vertically and which extended five miles either side of the centreline, i.e was 10nm wide. I am still unclear as to whether this has changed or what effect all this RNP stuff actually has in practice. I still don't really see how it improves 'flight efficiency' which is another of the committees' 'metrics.' I hope you appreciate my use of all the jargon!
It is interesting that, 10W, you also state that, "In TMA airspace, even lower RNP values might be achievable, but by interpolation of guidance material, would still only offer a slightly decreased route separation value, which in any case could never come below the separation standard value of the surveillance equipment being used." So you agree that what is really important is the surveillance equipment being used, i.e. radar, not so much what is on the aircraft or what it is called. Ultimately the limits, particularly in a congested TMA, are mostly defined by physical constraints, particularly separation required due to wake turbulence requirements and no amount of mandating upgraded on-board equipment is going to change that. Only a change in aircraft design or maybe the laws of physics! As to procedural separation, I would be interested to know where, in European non-oceanic airspace, there is normally en-route procedural separation.