Originally Posted by Spuds McKenzie
Fact is, if TCAS had not existed on 1 July 2002, there wouldn't have been a collision
Yes. I am very glad to see that this straightforward observation is now becoming common currency.
Fact is that, had TCAS been available since 1950, it would have helped avoid four collisions in 36 years (Grand Canyon, Zagreb, San Diego, Cerritos). Since it was mandated (a matter of some 16 years in the U.S., less elswhere), use of TCAS has almost caused two collisions (Albany, NY, 1998, another three-aircraft situation; 28 June 1999 in Chinese airspace between BA027 and KE507) and been a contributory factor in one accident (Überlingen, as you point out). And that's just what I know about. Interestingly, the potential outcome at Albany was ameliorated through intervention of a controller, just the opposite of what is "supposed" to happen.
So, 4 in 36 years against 3 in 16 years. These figures are too sparse to draw any statistical conclusions. But they should suffice to indicate that the risk analysis is not at all obvious.
PBL