Punkalouver:For the record : I am not associated with PBL (nor yourself.)
I am also not an engineer, just a simple Controller with some extra knowledge.
I however think that you should open your mind beyond what you read in the Eurocontrol ACAS bulletins. They are meant for the education of the public users , (i.e pilots and controllers) , and provide standard basic solutions to selected illustrative incidents . They are not the TCAS Bible .They do not cover the philosopy of the system , which is what we try to discuss here.
You said :
actual collisions caused by ignoring TCAS
We only have one in Europe :so let's take it as an example ( because we all know this one quite well by now) I asume you wrote this because you mean the TU154 pilot ignored TCAS ?
Now this is how I see it :
The collision was not caused ONLY because the 154 ignored TCAS.
To occur this collison needed more :
1) To have both aircraft fitted with TCAS ( because with no TCAS there would not have been a collision ) and
2) for the other aircrfat to follow his RA .
The 757 followed his own RAs more or less as the book said ,and still collided.
(so TCAS did not help/protect him at all )
Finally on this point : based on the regulations in force in July 2002 , it was not irrational for the Tu154 crew to follow the ATC instruction.
Next :
I have no technical engineering or studies to give mathematical probabilities of how much safer it is to follow the RA in the midair collision incident.
Nobody has. Therefore when I see statements like it is 4 times safer to follow RAs , I smile a bit behind my PC. In any case the numbers are far too small to deduct any useful statistics.
Remaining in Europe ,and only looking at facts : since 1970, there were only 2 high altitude collisions before Ueberlingen.( Nantes in 1973 and Zagred in 1976 ) Those 2 collisions would most probably have been prevented if TCAS would have been available then. However in the period 1976-1994 . No collision and No TCAS either. For the period 1994 -2000 a large portion of aircraft at High altitude in Europe were fitted with TCAS , but not all, especially not those of the former Soviet Union States .Again no collision during that period.
But since mandatory carriage of TCAS in Europe ( 2000) 2 years later one collision partlially caused by TCAS.
So, allow me to question the philosophical statement that " TCAS is good for you "
So when you say that ( quoting you ) :
Publications giving example after example of saves by TCAS,
I also smile a bit. We did not have a collision in 26 years despite many , many millions of flights in that period, and suddendly, we now have a system that would have saved dozens of collisons every year ?
TCAS was introduced in the USA without a proper safety case , for political reasons. It was later introduced in Europe for legal reasons (it would not have been sustainable legally for a State to have a collision in its airspace that could have been prevented by a system that was technically available then ).
Now it is its technical ( in abroad sense ) shortcomings that are being discussed.