Nigel
Couple of points, first, the Swiss tragedy was, in the beginning, a controller error, in that two aircraft were converging at the same level. In this case TCAS gave instructions which were tragically overridden by ATC, amongst much confusion. The scenario I am talking about is somewhat different, where there is no chance of loss of separation, I would like the chance to inform pilots of this fact so that when they recieve a nuisance RA (agreed, better terminology) they can choose to disregard it. I can give traffic info to pilots in such a case, indeed I often do, but it seems it is just a waste of time and breath. If I have screwed up and TCAS can save my butt (not to mention the lives of those on board) then naturally I will be glad to let that happen.
Now I don't know that much about the technical side of TCAS, but would I be correct in saying that different operators can calibrate theis TCAS differently? I only ask because there is one particular operator who, in my limited experience, have more RA's than others. A few weeks ago, I had two of their aircraft, one climbing, one descending, cleared levels separated by 1000 feet, opposite direction. Neither were high roc/d, both had traffic info. At 1800' separation, both had simultaneous RA's and both reacted. I have similar situations nearly every day, but never before with the same outcome. In this case it was not busy, and there was no other tfc to effect, but next time?
As I said, it is against the instinct of any controller to sit back and let a machine which is not aware of the traffic picture carry out your separation for you, but it is what we are legally obliged to do. Let me put it this way, if you were on the operating table for major heart surgery, what would you prefer, an experienced surgeon trained to deal with all scenarios, or a robot who knows only the programmed operation? Not a perfect analogy I know but you get the picture.