TCAS RA - preventive RA, basic question
 

Hello everyone

I understand MAINTAIN VERTICAL SPEED MAINTAIN , MONITOR VERTICAL SPEED are preventive RAs

My FCOM states this means Maintain the vertical speed indicated on the green area of the PFD and Ensure that the vertical speed remains outside the red area
respectively .
But I am not able to figure out the difference between these two and and in what conditions will these trigger , since one says maintain vertical speed on green area and other says maintain vertical speed outside the red area, which basically means the same

I appreciate you taking time to help me out with this
Thank you

Does it matter ?

Stay in the green and out of the red, pretty simple

Maybe this helps: https://ad.easa.europa.eu/blob/SIB_2.../SIB_2009-16_1

As far as I understand one expects a specific rate while the other prescribes rates that must be avoided.

From the linked document:

"Monitor Vertical Speed” RA always requires that the
vertical speeds prohibited on the RA display are adhered
too. Typically, a “Monitor Vertical Speed” RA does not
require a change in vertical speed.

“Maintain Vertical Speed, Maintain” RA always requires
the climb or descent to be maintained in accordance with
the indications on the RA display

“Adjust Vertical Speed, Adjust” has been replaced by "level off" in TCAS Standard 7.1 (if I remember correctly).

As far as daily workings as a pilot are concerned, I am with Stilton: KISS (keep it simple stupid). Stay in the green and out of the red - which is a lighter way of saying what the official TCAS standards say: "never manoeuver against a TCASRA".

Thank you so much for your help
This makes sense

I am glad you helped !

Very good explanations given by Stilton and 1201 alarm . Just a minor correction on your statement , there is no such thing as "preventive RAs" , there are just TAs ( alerting ) and RAs ( vertical guidance.) All RAs are to be followed.

or alternatively, all RAs are preventative. Preventative of metal on metal contact.

Re the term "preventive RA". I also know the terms "increase RA" and "reverse RA".

Both only occur after a "normal" RA. What sets them apart from the "normal" RA is the time you have to react. While you have 5sec to react to a "normal" RA, for "increase RA" and "reverse RA".you only have 2.5sec to react. This is also obvious, since the original manoeuver was not sufficient, you then have to react even faster.

The EASA linked SIL sounds like pre-TCAS 7.1, when there were identified issues.

Maintain V/S is a RA.
Monitor V/S is a TA

right?

No, both are RA's, meaning you have to follow the orders of the system, and tell the controller you are doing so.

Correct, I stand re-educated.

n.b. what we are discussing are the aural warnings over the actual system RA commands. Interesting, quite varied.

Cheers everyone.
https://cimg8.ibsrv.net/gimg/pprune....ed18f4fc61.png


And the overlaying audio warnings:
https://cimg9.ibsrv.net/gimg/pprune....8ece7b92f5.png

Great table, FlightDetent. Could you may be specify the source?

The table also has the "preventive RA", the "increase RA" and the "reversal RA". So everything fits now nicely together.

Just for clarity, only for RA in defiance of actual clearance is the call mandated. This has some implications for the nuisance HVR case.
https://cimg6.ibsrv.net/gimg/pprune....360137a8f8.png

My pleasure, it's the ultimate go-to on this matter: https://www.faa.gov/documentlibrary/...%20booklet.pdf.

Notably, the recently updated FAA AC 90-120 is also a great resource, the list of referenced materials is priceless. https://www.faa.gov/regulations_poli...mentID/1043337

Great, thank you.

Re which RAs have to be reported to ATC: I had a look again at my company manuals and indeed it also contains that you don't need to report a TCAS RA which does not require a deviation from the clearance.

However in daily pilot life, is there any harm in doing so anyways? The chance seems high to me that most probably in such situations the controller might eventually interfere and try to solve the conflict, so instead of waiting for that to happen and saying "unable - TCAS RA", is there any harm in announcing the RA from the very beginning?

And what do you mean by "nuisance HVR case"?