[olliej]

The guidance and sole purpose of TCAS is "do what it says", in that respect it is no different from a stall warning.

The fact that Russian aviation failed to train (or even require training for that apparently) is absurd, the fact that the EU allowed planes to travel with TCAS but not with pilots that had the most basic understanding of TCAS is a sad example of the results of checkmark based safety.

As even this article acknowledges, TCAS as a system makes no sense of any kind if it can be countermanded by someone other than the pilot. There is no use case for TCAS that makes anything other than "do what it says, a fast as possible" have any value at all. Disobeying TCAS because of ATC is no different than ignoring a stall warning because ATC told you to climb.

[kingofpandora]

When it was introduced - and it was new at the time - not everything was as neat and clear as you state.

Quoting Wikipedia: "The [TCAS] manual described TCAS as "a backup to the ATC system", which could be wrongly interpreted to mean that ATC instructions have higher priority."

In fact, you'd do well to read the entire Wikipedia article to see that this was not the only case where pilots did not have clear guidance on which orders to follow in the case of conflicting ATC and TCAS orders.