Originally Posted by FullWings
I'm all for academic arguments and theories as that is the way we progress science but in many cases there has to be a set way of doing something until we build up enough evidence to justify changing it.
I don't think that this is an "academic argument" any more. Perhaps it was an "academic argument" when the impact of TCAS on RVSM was analysed using airtraffic data for 2 days.
There are very real problems, in which TCAS has plays a role, as two mid-air collisions since 2002 demonstrate.
If you look for more evidence you will find complains of ATC on a device that manipulate the outcome of their instructions, leaving them without a coherent image of the situation in the air.
Another problem with TCAS is that the manufacturer (and following him many other organisations) present TCAS as a technical solution in a conflict situation where every other means to avoid a collision have failed. In the Ueberlingen mid-air TCAS gave an RA when both a/c were at 7.11 NM seperation. The limit for seperation in this airspace at this night was 7 NM, usually 5 NM. This demonstrates that TCAS can act at points in time, where other means have not yet failed, rebuting the claim that TCAS only acts when everything else has already failed.
More theoretical arguments are multiple aircraft situations (for which it can be proved that TCAS cannot give advice solving the collision threat) and aircraft without transponders.
Based on these problem (some of them real, some of them more theoretical) I get the picture, that TCAS is not the silver-bullet some want it to be. Of course TCAS is better than noting (at least I hope that this is the case as it was certified for use in aviation), but I also get the image, that it is still far from optimal. The problem is, that some of the problems with TCAS can only be solved by spending lots of money and/or replacing existing TCAS units against newer models.