Originally Posted by
FlightDetent
To my understanding the adverse effect is negligeable, the case is well understood and contained by ACAS II specification.
Upon closer inspection, the actual RAs caused by the hypothetical airplane slicing through busy levels from the above will not be that many. Without ATC coordination that is.
(Answering as someone who stopped teaching TCAS 7.0 vs. 6.04 in EUR RVSM airspace also 14 years ago
)
Thanks for that. It comes down to risk assessment from competing requirements. It would indeed be very unlikely (and very unlucky) if an aircraft initiating an emergency descent for any reason before coordination with ATC happened to collide with another not far below it. A delay before initiating descent might subject cabin crew and passengers to risk of hypoxia (because their masks do not supply oxygen under pressure) but might prevent a catastrophic loss of life resulting from a midair collision.