TCAS - ATC uncertainty
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Ohcirrej
Joined: Feb 2003
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From: This is the internet FFS.........
TCAS - ATC uncertainty
Hey all,
I realise this probably should go in the "Questions" forum, but I have posted it here in an attempt to get more input, and if it gets moved there, so be it.
As ATC's in the UK, we have all had out TCAS briefs and seen the videos. Over the past couple of months a couple of uncertainties have come up from discussion and reviews of some incidents, especially the tragic recent mid-air over Germany.
Avoiding action given by ATC obviously can be provided by a turn or a climb/descent instruction. Over a few beers last night, a work mate of mine mentioned he has had a situation where jet in controlled airspace received a TA on traffic just outside controlled airspace below him, and wouldn't take a turn. He then went on to recount there have been several very similar situations seen in TC where drivers haven't taken an instructed turn, with a preference to "keeping the wings level" during a TA/potential RA.
It is this keeping the wings level I would like to have a healthy chat with you drivers about. Is this a standard procedure that we don't know about, or is it a "pilot perogative" in an attempt to visually aquire the traffic?
(The next bit isn't a fatalistic attempt to stir anything, or provide a journo with a great "what if" or "this is going to happen in the near future" to be splashed everywhere! Can we use it in a mature way please.)
If I could use a hypothetical situation for discussion, let's take case of a full hold at Heathrow (LAMbourne for instance). Due to it's proximity to the southbound DVR SID from EGSS that climbs to Min Stack level (with us holding traffic at Min Stack +1000ft). Hypothetically, take a full stack with every jet almost exactly on top of each other. For what ever reason, climbing EGSS DVR outbound busts his level, climbing straight at the stack. This is where the fun is going to start. Outbound causes RA between him and bottom aircraft in stack. One goes up, and one goes down. Now, I realise vertical climb profiles are monitored, and it not a case of "Oh !!!!!!" and pulling back on the stick going for as much vert as possible. However, bottom aircraft in hold RA's and climbs. What happens next? We know TCAS II talks between each other........will everybody in the hold get a RA?
As the poor controller sitting there watching this evolve, first thoughts are going to be "I can't go against a TCAS RA, I'm gonna start turning jets and passing traffic!" What are the responses from the flight deck going to be? Will the turns be taken? Another point raised was increasing speed in a attempt just to pull them apart?
Sorry if all this is a little deep. I'm not trying to be over the top.
Thanks.
J.
I realise this probably should go in the "Questions" forum, but I have posted it here in an attempt to get more input, and if it gets moved there, so be it.
As ATC's in the UK, we have all had out TCAS briefs and seen the videos. Over the past couple of months a couple of uncertainties have come up from discussion and reviews of some incidents, especially the tragic recent mid-air over Germany.
Avoiding action given by ATC obviously can be provided by a turn or a climb/descent instruction. Over a few beers last night, a work mate of mine mentioned he has had a situation where jet in controlled airspace received a TA on traffic just outside controlled airspace below him, and wouldn't take a turn. He then went on to recount there have been several very similar situations seen in TC where drivers haven't taken an instructed turn, with a preference to "keeping the wings level" during a TA/potential RA.
It is this keeping the wings level I would like to have a healthy chat with you drivers about. Is this a standard procedure that we don't know about, or is it a "pilot perogative" in an attempt to visually aquire the traffic?
(The next bit isn't a fatalistic attempt to stir anything, or provide a journo with a great "what if" or "this is going to happen in the near future" to be splashed everywhere! Can we use it in a mature way please.)
If I could use a hypothetical situation for discussion, let's take case of a full hold at Heathrow (LAMbourne for instance). Due to it's proximity to the southbound DVR SID from EGSS that climbs to Min Stack level (with us holding traffic at Min Stack +1000ft). Hypothetically, take a full stack with every jet almost exactly on top of each other. For what ever reason, climbing EGSS DVR outbound busts his level, climbing straight at the stack. This is where the fun is going to start. Outbound causes RA between him and bottom aircraft in stack. One goes up, and one goes down. Now, I realise vertical climb profiles are monitored, and it not a case of "Oh !!!!!!" and pulling back on the stick going for as much vert as possible. However, bottom aircraft in hold RA's and climbs. What happens next? We know TCAS II talks between each other........will everybody in the hold get a RA?
As the poor controller sitting there watching this evolve, first thoughts are going to be "I can't go against a TCAS RA, I'm gonna start turning jets and passing traffic!" What are the responses from the flight deck going to be? Will the turns be taken? Another point raised was increasing speed in a attempt just to pull them apart?
Sorry if all this is a little deep. I'm not trying to be over the top.
Thanks.
J.
Joined: Sep 1999
Posts: 139
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From: uk
Jerricho
I'm not sure I can answer all you questions but from a pilots point of view we are legally bound to follow TCAS RA instructions even if this conflicts with instructions from ATC. As TCAS does not act in the lateral plane these instructions will be to climb or descend. Our airlines proceedure when receiving a TCAS RA would be to level the wings if in a turn, disconnect the autopilot and auto throttle and smoothly rotate the aircraft to the requested rate of climb/descent. Therefore if ATC give us a command to turn whilst we are in the middle of a TCAS RA we would not be in a position to comply with that request.
If an aircraft was climbing towards the base of a holding stack I would expect the climbing aircraft to receive a command "adjust vertical speed adjust" command and the other aircraft to receive a "monitor vertical speed" command. The holding aircraft should not be asked to climb . If the aircraft climbing into the stack ignored the RA and continued to climb. The holding aircraft may very well be asked to increase climb or even change to a descend command. Interaction with the aircraft higher in the stack should be very limited as TCAS can usually sort out the problem with small climb and descend imputs. Hope this helps??
I'm not sure I can answer all you questions but from a pilots point of view we are legally bound to follow TCAS RA instructions even if this conflicts with instructions from ATC. As TCAS does not act in the lateral plane these instructions will be to climb or descend. Our airlines proceedure when receiving a TCAS RA would be to level the wings if in a turn, disconnect the autopilot and auto throttle and smoothly rotate the aircraft to the requested rate of climb/descent. Therefore if ATC give us a command to turn whilst we are in the middle of a TCAS RA we would not be in a position to comply with that request.
If an aircraft was climbing towards the base of a holding stack I would expect the climbing aircraft to receive a command "adjust vertical speed adjust" command and the other aircraft to receive a "monitor vertical speed" command. The holding aircraft should not be asked to climb . If the aircraft climbing into the stack ignored the RA and continued to climb. The holding aircraft may very well be asked to increase climb or even change to a descend command. Interaction with the aircraft higher in the stack should be very limited as TCAS can usually sort out the problem with small climb and descend imputs. Hope this helps??
Joined: Dec 2003
Posts: 214
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From: UK
The flying manual for the 757/767s that I fly states that TCAS assumes an angle of bank of 15 degrees or less for climb performance purposes. This may influence a pilot's decision when given a turn by ATC during a climb RA.
I think that the TC training section have an interesting radar replay of multiple RAs in a stack. It occurs at BIG, I think.
G W-H
I think that the TC training section have an interesting radar replay of multiple RAs in a stack. It occurs at BIG, I think.
G W-H
Joined: Apr 1999
Posts: 39
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From: UK
I don't know of anything that tells me not to except a turn just because I've had an TA! If this TA becomes an RA then I will do what the magic box tells me to do.
So if the magic box shows just an TA then I will definately do what ATC tells me to do. Our manual even states that if an RA is given in a turn then the turn me be continued!
In other words, I would completely disagree with someone not following an ATC instruction on the bases of an TA! (not RA).
So if the magic box shows just an TA then I will definately do what ATC tells me to do. Our manual even states that if an RA is given in a turn then the turn me be continued!
In other words, I would completely disagree with someone not following an ATC instruction on the bases of an TA! (not RA).
Thread Starter
Ohcirrej
Joined: Feb 2003
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From: This is the internet FFS.........
Thanks for the replies so far guys.
Us ATCOs do know that you are legally bound to follow an RA (which are only given in the vertical plane), and we have our bits in the book about what to do (ie pass traffic and a request to advise when you are under our control again), but it was the turn thingy that caught my interest. GWH's input about the 15 degrees of bank is interesting to know (and thanks mate! I've seen the "double-bump" BIG video a couple of times). And Waldo has highlightes something I'm sure quite a few of us weren't aware of (and I'll contact our TRUCE people to make sure they know!)
Any other thoughts?
Us ATCOs do know that you are legally bound to follow an RA (which are only given in the vertical plane), and we have our bits in the book about what to do (ie pass traffic and a request to advise when you are under our control again), but it was the turn thingy that caught my interest. GWH's input about the 15 degrees of bank is interesting to know (and thanks mate! I've seen the "double-bump" BIG video a couple of times). And Waldo has highlightes something I'm sure quite a few of us weren't aware of (and I'll contact our TRUCE people to make sure they know!)
Any other thoughts?
