TA/RA
Thread Starter
Joined: May 2008
Posts: 4
Likes: 0
From: ashamed to say
TA/RA
Hi guys,as far as you know,is it possible this situation? 2 aircrafts in proximity,one recieves a TA and the other one recieves RA? one is climbing from 340 to 360,passing through 343 recieves TA,the other traffic level flight at 350, 6NM.Thanks for your answers.
Joined: Sep 2002
Posts: 2,188
Likes: 6
From: La Belle Province
I think I can think of a circumstance: the a/c at FL350 is at the altitude above which climb or increase climb RA are inhibited, for performance reasons.
In that case, if we assume a cooperative scenario, the climbing aircraft will I believe be told to stop climbing (via an RA) and the FL350 aircraft will just hold, which may just mean a TA since no action is required? Because the only RAs that can be issued for the higher a/c are descend cases, which dont help resolve the conflict.
In that case, if we assume a cooperative scenario, the climbing aircraft will I believe be told to stop climbing (via an RA) and the FL350 aircraft will just hold, which may just mean a TA since no action is required? Because the only RAs that can be issued for the higher a/c are descend cases, which dont help resolve the conflict.
Thread Starter
Joined: May 2008
Posts: 4
Likes: 0
From: ashamed to say
well,maybe I was not clear,we were climbing,as instructed by the atc,and we`ve got a TA, but the other traffic complained to atc that they`ve got a RA. The moment ATC realised a potential conflict said our callsign ....maintain for a while...ughhh.We`ve stopped climbing,had a TA alert,then the other traffic passed over but 6 miles to the south and 4-500ft above,and they`ve been complaining to the ATC that they had RA.As far as I know we were supposed to have a RA as well,but maybe the other pilot wasn`t clear about the phraseology and TA/RA meaning.So my question actually is,shouldn`t both a/c involved in a conflict recieve RA,or TA?or one can get a RA and the other a TA? Thanks
Joined: Oct 2007
Posts: 27
Likes: 0
From: UK
It is perfectly possible for one aircraft to get only a TA while the other gets an RA. A common mechanism by which this occurs is the operation of the horizontal Miss Distance Filter in TCAS version 7.
If TCAS can reliably determine that there will be significant lateral separation then any RA that would otherwise be generated is suppressed. However if the the TCAS surveillance happens to be "noisy" then the determination is not reliable and so the RA is issued.
It is often the case that the MDF on one aircraft's TCAS suppresses an RA on that aircraft while the MDF on the other aircraft's TCAS does not supopress the RA on that aircraft.
If TCAS can reliably determine that there will be significant lateral separation then any RA that would otherwise be generated is suppressed. However if the the TCAS surveillance happens to be "noisy" then the determination is not reliable and so the RA is issued.
It is often the case that the MDF on one aircraft's TCAS suppresses an RA on that aircraft while the MDF on the other aircraft's TCAS does not supopress the RA on that aircraft.
Joined: Dec 2007
Posts: 127
Likes: 0
From: Changi
I have encountered this situation before, my aircraft being in a steeping descent than the aircraft above .... What I have gotten is an amber square on my ND, with "Traffic, Traffic" aural warning.
The other aircraft in fact encountered a TCAS RA ! He was "forced" to carry out a TCAS CLB. He was not suppose to descend until we pass his descent path but he did anyway.
The other aircraft in fact encountered a TCAS RA ! He was "forced" to carry out a TCAS CLB. He was not suppose to descend until we pass his descent path but he did anyway.
Joined: Oct 2007
Posts: 27
Likes: 0
From: UK
No - selecting "above" or "below" makes no difference to RAs. It merely determines which aircraft are displayed on the traffic display. The aircraft that are not displayed are still tracked by TCAS and RAs will still be generated against these aircraft if required (and those aircraft will be displayed as a red square whichever display mode is selected).
Joined: Nov 2004
Posts: 230
Likes: 0
From: Gangster Paradise, RSA
Joined: Dec 2007
Posts: 127
Likes: 0
From: Changi
Hi Guys,
Just to revisit this thread. Recently I heard that it's impossible to get a TA with a conflicting traffic getting an RA.
When a TA occurs with a conflicting traffic getting an RA, I was told that it was due to the interrogation rate was not "fast enough" and it keep recalculating based on the our instantaeous V/S, which we are changing, thus only "able to render" a TA on our side.
(The arguement was that both A/C having the same envelope will definitely get a similar Resolution.)
Apperently, when a TA occurs, we are not suppose to make any changes to the vertical plane so that we can allow the TCAS to do the calculation.
Sounds logical if there's more than 1 conflicting traffic.
Anyone have got more information about TCAS system ? Especially on horizontal Miss Distance Filter in TCAS ?
Thank you in advance.
Cheers,
lion-g
Just to revisit this thread. Recently I heard that it's impossible to get a TA with a conflicting traffic getting an RA.
When a TA occurs with a conflicting traffic getting an RA, I was told that it was due to the interrogation rate was not "fast enough" and it keep recalculating based on the our instantaeous V/S, which we are changing, thus only "able to render" a TA on our side.
(The arguement was that both A/C having the same envelope will definitely get a similar Resolution.)
Apperently, when a TA occurs, we are not suppose to make any changes to the vertical plane so that we can allow the TCAS to do the calculation.
Sounds logical if there's more than 1 conflicting traffic.
Anyone have got more information about TCAS system ? Especially on horizontal Miss Distance Filter in TCAS ?
Thank you in advance.
Cheers,
lion-g
Joined: Jun 2000
Posts: 4,507
Likes: 4
From: last time I looked I was still here.
Apperently, when a TA occurs, we are not suppose to make any changes to the vertical plane so that we can allow the TCAS to do the calculation.
Sounds logical if there's more than 1 conflicting traffic.
That's an interesting one. Does everyone do this? I can think of many occasions where doing something after a TA is a good idea to avoid an RA: e.g. a steep climb or descent. You see the TA, maybe the TFC even before a TA; note its reletive level and clb or desc profile, and adjust yoiur profile accordingly. Is this not common conflict preventation airmanship?
Sounds logical if there's more than 1 conflicting traffic.
That's an interesting one. Does everyone do this? I can think of many occasions where doing something after a TA is a good idea to avoid an RA: e.g. a steep climb or descent. You see the TA, maybe the TFC even before a TA; note its reletive level and clb or desc profile, and adjust yoiur profile accordingly. Is this not common conflict preventation airmanship?
Joined: Jun 2005
Posts: 5
Likes: 0
From: England
Limit rate of descent to 1500 fpm within 2000' of levelling off.
If TA triggered prob to late.
TA alert
SOPs should take over
PF directs PNF to conflicting traffic whilst preparing to 'correctly' respond to the impending RA.
Never assume the traffic out the window is actually the conflicting traffic!
If TA triggered prob to late.
TA alert
SOPs should take over
PF directs PNF to conflicting traffic whilst preparing to 'correctly' respond to the impending RA.
Never assume the traffic out the window is actually the conflicting traffic!
