Alf5071h :
The safety certification should show that the probability of the collision scenario is sufficiently extreme to discount it; thence it meets an acceptable level of safety. The principle of aviation safety is that it is not absolute; it accepts that rare events can occur, but the probability of them resulting in death has to be extremely remote (10-9).
Your approach appears to take the limit case as ‘the’ hazard without qualifying (bounding) it with the probability of its occurrence. Yes it is a real hazard, but if by following TCAS it only occurs in one manoeuvre in 10 million, then the industry accepts that following TCAS is the safer option.
I remember clearly the FAA initial “ marketing” speeches when introducing TCAS in the very early 80s: No safety case as we know today was made, it was a political decision that mandated TCAS in the USA , not a rational one.
An initial independent paper showed that in 100 encounters, TCAS will solve X number of cases , would not make any difference in X number but in 4 cases it “ could induce a collision “
But the system was judged extremely beneficial and it was mandated.
If you look carefully at the official TCAS II training manual you will find in a general text mentioning something like : “in rare cases the system might induce collisions “ ( I am overseas at the moment , with no access to my archives for correct text /references )
4% is far from 1 in 10 million , but to be fair the percentages were calculated with version 5.0, since then we had 6.0, 6.04, 6.04A and now 7.0, so the percentage should be (much) lower hopefully by now, but I do not know of any scientific study with new figures on the recent versions.
Bsieker :
The only reason I can imagine for your reluctance to address it is that you feel Ueberlingen was a fluke, it is considered that low "acceptable risk", and nothing needs to be done about it
I think you are correct in your assumption.Fullwings is unfortunately not the only one who believe this.
Whereas Ueberlingen ended in a real collision , there are many more Ueberlingen –type incidents on record , both before and after 2002.
Some were heavily mediatized ( like the JAL/JAL case in Japan ) most others were not.
A very recent one is a carbon copy but with Climb RA +ATC instruction to climb to teh other. Aircraft missed mostly because one of the aircraft was powerful and outclimbed the other one . As it has been said here already, it is extremely difficult to make 2 aircraft collide , even if you intend to . (Ask any Military interception controller about it ) It is not because there is actually no accident that we can disregard the issues. Believing that the problem dramatically illustrated in Uberlingen is unique is wishful thinking.