TCAS Phraseology

[SB4200]

Did the AIP used to have "TCAS climb" and "TCAS descent" as the standard phraseology as opposed to "TCAS RA"?

Gen 3.4 para 5.1

This is more a question for me to determine if I'm losin' it than anything else...

[Capt Claret]

SB4200

You're not losing it.

I'd be interested to know the rationale behind the change. TCSA RA seems to give less useful info than TCAS Climb/Descent.

[ITCZ]

You are right. Used to. Better now.

You might be following a Preventative TCAS RA ("adjust vertical speed") instead of a Corrective RA ("climb, climb").

You just say "TCAS RA" to let the ATC know that you are following RA guidance, not his/her clearance.

From the Human Factors point of view, it also minimizes the potential for the ATC to jump in with an instruction that contradicts the RA guidance.

CHANGES TO ICAO RULES REGARDING TCAS RAs (as of 22 Nov. 07) (http://www.eurocontrol.int/ra-downlink/gallery/content/public/library/ICAO%20ACAS%20changes%2022Nov07.pdf)

[Brindabella]

It may well have changed because a 'TCAS climb' report to ATC can be potentially false information if the RA reverts to a 'Descend, Descend now' RA when multiple intruder aircraft are present.

Consequently it may then not be an option to give another TCAS report to ATC due to frequency congestion. With the new procedures ATC will not be lead into a false sense of security thinking that you are doing one thing (climbing) when the RA reverses its instruction to a descent.

[SB4200]

Interesting read, thanks for the info ITCZ :ok: