TCAS RA - preventive RA, basic question
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From: not in database
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
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
Joined: Apr 2004
Posts: 2,166
Likes: 86
From: Planet Earth
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
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
Joined: Oct 2015
Posts: 155
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From: above Tranquility Base coming long
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".
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".
Thread Starter
Joined: Mar 2018
Posts: 22
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From: not in database
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".
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 !
Pegase Driver
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From: Europe
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From: London
or alternatively, all RAs are preventative. Preventative of metal on metal contact.
Joined: Oct 2015
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From: above Tranquility Base coming long
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.
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.
Only half a speed-brake
Joined: Apr 2003
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From: Commuting not home
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.
And the overlaying audio warnings:
n.b. what we are discussing are the aural warnings over the actual system RA commands. Interesting, quite varied.
Cheers everyone.
And the overlaying audio warnings:
Last edited by FlightDetent; 13th June 2025 at 11:46.
Joined: Oct 2015
Posts: 155
Likes: 38
From: above Tranquility Base coming long
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.
The table also has the "preventive RA", the "increase RA" and the "reversal RA". So everything fits now nicely together.
Only half a speed-brake
Joined: Apr 2003
Posts: 4,459
Likes: 136
From: Commuting not home
Only half a speed-brake
Joined: Apr 2003
Posts: 4,459
Likes: 136
From: Commuting not home
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
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
Joined: Oct 2015
Posts: 155
Likes: 38
From: above Tranquility Base coming long
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"?
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"?
