TCAS RA
Thread Starter
Join Date: May 2010
Location: EARTH
Posts: 7
Likes: 0
Received 0 Likes
on
0 Posts
TCAS RA
One aircraft is cruising at FL 310. A reciprocal traffic at FL 320 starts descending. Is it possible the descending traffic experienced RA and the cruising traffic only TFC advisory? I mean and the cruising traffic should have RA. Or not?
Join Date: Sep 2014
Location: Canada
Posts: 1,257
Likes: 0
Received 0 Likes
on
0 Posts
Is it possible the descending traffic experienced RA and the cruising traffic only TFC advisory? I mean and the cruising traffic should have RA. Or not?
That's because the shape of the RA protection area is highly elongated (it's not a circle) so it is possible that an RA will be triggered in one aircraft but not (yet) in the other. Chances are, the aircraft first receiving the RA will respond to it, such that the other aircraft never gets an RA.
Also, it may depend on the setting in the individual aircraft. If Your TCAS is set to TA Only (as recommended in some books for final approaches to parallel runways), this might alter the TCAS callouts a bit.
I am surprised to hear that only one airplane would get the RA. My understanding is that the RA is coordinated (if both aircraft are so equipped) to ensure no further conflict - even if no maneuver is required - the RA command is keep doing what you're doing - still an
ra.
ra.
Only half a speed-brake
Toseg: Absolutely yes, in your particular scenario.
Eversince introduction of TCAS ver 7.0 for RVSM implementation, a modified logic is embedded to reduce nuisance, high V/S level-off encounters.
If such is the case, the onset of RA being triggered for the aircraft maintaining level flight is delayed by 10 seconds. This applies to "time to CPA(*)" algorithm.
Feel free to PM me for authoritative reference, though I only have one for 7,0 that has been superseeded since.
* = closest point of approach
Hi, peekay4 you are suprisingly off here, I am afraid. Comapred to your standards, that is . You cannot hit one aircraft into another without including the second one in the collision, right?[/I]
Eversince introduction of TCAS ver 7.0 for RVSM implementation, a modified logic is embedded to reduce nuisance, high V/S level-off encounters.
If such is the case, the onset of RA being triggered for the aircraft maintaining level flight is delayed by 10 seconds. This applies to "time to CPA(*)" algorithm.
Feel free to PM me for authoritative reference, though I only have one for 7,0 that has been superseeded since.
* = closest point of approach
Hi, peekay4 you are suprisingly off here, I am afraid. Comapred to your standards, that is . You cannot hit one aircraft into another without including the second one in the collision, right?[/I]
Thread Starter
Join Date: May 2010
Location: EARTH
Posts: 7
Likes: 0
Received 0 Likes
on
0 Posts
TARA
Dear colleagues the scenario is true. I had the traffic advisory and the other aircraft reported that he had resolution, but i am a bit reluctant to believe it. My transponder was in TARA mode.For this reason my question.This happened in Beira airspace. I had permission from Maputo to divert up to 40 miles right off track due to weather. After Maputo i changed to Beira and i reported that i divert right off track up to 40 miles. I was approximately 30 miles right off track.He acknowledged and he said to report abeam a point named AXIBO. After few minutes suddenly presented on the ND the traffic at FL 320 starting descent and we did not remember to hear any descent clearance from Beira. It was a Mozambique flight . He passed through our FL and very closed . To be honest i don't remember how closed he was and as i told before we had only TFC advisory. He reported RA and after this, he started to speak in Portuguese with Beira. We didn't understand what they said . The one i did not like at all was that i have been asked by Beira to confirm if i was diverting right or left off track. He pretended that he did not remember . Any way in Beira there is no any radar coverage so is very risky to accept directs or divert for weather. I have done the ASR but i have not received any answer yet. Does any body know if Beira will give the recordings? I don't think so
Last edited by toseg; 17th Dec 2016 at 02:56.
The whole point of the system is to ensure the instructions are mutually relevant. No point in giving one guy one instruction and another nothing. That defeats the purpose of the system. Unless we are talking about being on the cusp of the cone in which the system changed its mind half way, but you say you were quite close.
Last edited by MonarchOrBust; 17th Dec 2016 at 08:31.
Join Date: Aug 2000
Posts: 1,501
Likes: 0
Received 0 Likes
on
0 Posts
It depends on the situation.
I was in level flight and had a KLM descend towards our level.
He got a TCAS RA, (level off order is my guess) and we got a TA. Had he continued his descent we would have gotten a TCAS RA, but there was no need for that as he leveled off.
I was in level flight and had a KLM descend towards our level.
He got a TCAS RA, (level off order is my guess) and we got a TA. Had he continued his descent we would have gotten a TCAS RA, but there was no need for that as he leveled off.
Join Date: Feb 2007
Location: Central Scotland
Posts: 61
Likes: 0
Received 0 Likes
on
0 Posts
You might get a "Monotor Vertical Speed" and the VSI green band being 0 fpm. Its still an RA though, and you must comply with it. ( Disclaimer:-my Company Ops, and type)
Join Date: Sep 2014
Location: Canada
Posts: 1,257
Likes: 0
Received 0 Likes
on
0 Posts
Hi, peekay4 you are suprisingly off here, I am afraid. Comapred to your standards, that is . You cannot hit one aircraft into another without including the second one in the collision, right?
No, I am not off, as both toseg and ManaAdaSystem have confirmed exactly what I wrote through their actual experiences.
As mentioned previously, it's not unusual at all for only one aircraft to receive an RA. In fact, it is the norm, due to the elongated shape of the protection area. TCAS II facilitates RA coordination between aircraft, but does not require both aircraft to receive RAs.
Here's a typical TCAS II protection area diagram (2D view):
Notice that the area is asymmetric front & back. Since the protection area is not a circle (sphere in 3D), one can easily construct a scenario where the intruder aircraft is within the other aircraft's RA zone, but not the other way around.
With TCAS II, the first aircraft that generates an RA will transmit its maneuvering intention (e.g., climb, descend) to the other aircraft, but this transmission in itself does not force an RA on the 2nd aircraft.
If (and only if) the 2nd aircraft also generates an RA some time later, the first aircraft's intention will be taken into account by the 2nd aircraft in issuing a coordinating RA, subject to whatever inhibits are active at that time.
Join Date: Sep 2008
Location: Paris
Age: 39
Posts: 5
Likes: 0
Received 0 Likes
on
0 Posts
Dear all,
I was querying some information about TCAS RA and found that thread (sorry for coming back to a rather old discussion).
Last week, flying an A220 level at FL320 within German Airspace, we received a TCAS RA Descend order which we obviously followed promptly.
Once clear of conflict, we returned to FL320 and asked the ATC about the other aircraft.
It was apparently flying level as well at FL330, a northern-american B767 which reported no RA but also no TA.
We were quite surprised to ear that the conflicting traffic could have no RA or TA while we were manoeuvring away.
This thread suggests that it could be possible.
Anyone experienced something similar recently?
Thank you for your feed back.
Regards.
I was querying some information about TCAS RA and found that thread (sorry for coming back to a rather old discussion).
Last week, flying an A220 level at FL320 within German Airspace, we received a TCAS RA Descend order which we obviously followed promptly.
Once clear of conflict, we returned to FL320 and asked the ATC about the other aircraft.
It was apparently flying level as well at FL330, a northern-american B767 which reported no RA but also no TA.
We were quite surprised to ear that the conflicting traffic could have no RA or TA while we were manoeuvring away.
This thread suggests that it could be possible.
Anyone experienced something similar recently?
Thank you for your feed back.
Regards.
Dear all,
I was querying some information about TCAS RA and found that thread (sorry for coming back to a rather old discussion).
Last week, flying an A220 level at FL320 within German Airspace, we received a TCAS RA Descend order which we obviously followed promptly.
Once clear of conflict, we returned to FL320 and asked the ATC about the other aircraft.
It was apparently flying level as well at FL330, a northern-american B767 which reported no RA but also no TA.
We were quite surprised to ear that the conflicting traffic could have no RA or TA while we were manoeuvring away.
This thread suggests that it could be possible.
Anyone experienced something similar recently?
Thank you for your feed back.
Regards.
I was querying some information about TCAS RA and found that thread (sorry for coming back to a rather old discussion).
Last week, flying an A220 level at FL320 within German Airspace, we received a TCAS RA Descend order which we obviously followed promptly.
Once clear of conflict, we returned to FL320 and asked the ATC about the other aircraft.
It was apparently flying level as well at FL330, a northern-american B767 which reported no RA but also no TA.
We were quite surprised to ear that the conflicting traffic could have no RA or TA while we were manoeuvring away.
This thread suggests that it could be possible.
Anyone experienced something similar recently?
Thank you for your feed back.
Regards.
In your case it seems to be a problem with your TCAS as with both of you at level with a 1000' between it should have given neither a TA nor an RA.