Joernstu wrote :
Even without TCAS RA aircraft are allowed to deviate from their assigned flightlevel. Only if the deviation exeeds 200ft ATC can become aware of the deviation.
True for the 200 feet deviation, it's actually 299 feet. But a TCAS originated FL deviation will very soon get beyond 300 feet. I agree this has some impact on the time lapse before a controller could see the FL deviation without a TCAS RA downlink. But remember the context of my point. Because there is no attention getter related to the FL deviation, it is not very likely that the controller will see it because his attention is drawn somewhere else. What the controller needs is the attention getter in order that he can take the right measures, which normally will be to refrain from action vis-a-vis the RA affected aircraft.
As the radarsystems updates the displayed information in intervals, the timespan between begin of the deviation and recognition by ATC can be several seconds.
Yes, several seconds, but always better than the average 29. In busy areas, with multiple ground radar antennes integrating the signals for display on the controller's radar screen, the delay is only two or three seconds.
Even with all these factors for delay, technically there are two institutions trying to control during a conflict situation (ATC and TCAS). These two obviously need to be coordinated in some way.
Very well put, this is the heart of the matter. And it requires a good solution, see my further points to conclude that a good solution is achievable and is better than a do-nothing attitude, waiting for the best solution.
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ATC Watcher wrote:
First : the 29 seconds is indeed an average. That means some are sooner , but some are also taking longer or missed altogether. On the sooner ones, you say after 9 seconds max for a radar return, this is not universal . The Zurich radar return was 12 seconds in Ueberlingen for instance .
You put the 29 seconds and the 9 seconds in one basket but they apply to different magnitudes. The 29 seconds gives the average time lapse before pilots inform ATC on the radio, whereas the 9 seconds is, at least according to the Qinetiq study, the average radar return. My point was that on average there is 20 seconds to gain for getting the information where it is needed. Now on the detail, in Zurich 2002 the radar return was 12 seconds. However, the Swiss violated here the Eurocontrol standard of 8 seconds. I think this is mentioned in the investigation report but I haven't checked up yet.
Second : In doubt why not ask the pilot if he is following an RA. : Why not indeed .
As you will have read, I have my doubts myself, but it's better, or shall we say less harmful, to ask a question than a contravening and confusing instruction against TCAS.
Just that in case of imminent collision, as a controller, you are more likely to want to issue avoiding instructions instead of loosing precious seconds asking the pilot if he has a functioning TCAS and if he is following an RA.
Exactly, the instinct of a controller is to do as you describe. But the difficulty is that in the case of a TCAS RA, he should not follow his instincts any more. TCAS has taken over and the controller should act accordingly which in this case is to refrain from action, other than removing third party traffic. You will have seen my own hesitation to put up this possibility of asking the pilot. The main point is that the controller should, at the earliest possible time, be stopped from doing the wrong thing, that is to issue a contravening instruction which is so much confusing in the hectic situation of an RA.
90% of RA downlink messages are false RAs not displayed in the cockpit, but are broadcasted. .
So, connect the downlink to those RA's which are displayed in the cockpit. Problem solved.
Of the 10% that remains, a further study indicates the following percentages : in 20% the pilots actions are inappropriate, in 10% pilots are acting in the opposite direction of the RA, and only 70% are more or less followed correctly.
A remaining problem indeed. As I said before, a lot of work remains to be done. On the detail again, it is not clear to me wether the '70 % more or less correctly' is of the total population, or only of the 10% that remains. If the latter is the case, then, logically, the real problem is only for 3 % of the TCAS total?
I for one believe that downlinking RAs Mode S messages at the moment will increase controller involvement and contribute to more confusion , or Ueberlingen type scenario.
I don't think your statement is supported by the downlink simulations which were organised in Bretigny. Furthermore, how can knowledge, acquired by a downlink, be confusing. It is lack of knowledge and bad decisions taken based on a lack of knowledge, which is confusing. Not only in ATC but anywhere else. In this context but nothing to do with TCAS the Amsterdam crash of the El Al a/c flying into an appartment building springs to mind. The crew couldn't see what had happened with the engines which had fallen off, by this lack of knowledge they decided to turn in the wrong direction which caused the dramatic going down of the aircraft.
For the moment I am responsible for anti collision TCAS is only a safety net that i should not take into consideration when I work. ( I am even not sure/ aware who has a functioning one ).
STCA (short term conflict alert, the ATC safety net) is only a safety net. I'm sure all area controllers take it into consideration when they work (admittedly, provided the number of false alerts is reasonable, but if this is the case management and technical staff should urgently repair the tool). Why should TCAS, as you say equally 'only a safety net', be treated differently when this is made possible? Why wait the average 29 seconds before it is taken into consideration anyway? I am pleading for improving the controller's situational awareness, rather than impeding. Improved situational awareness will improve his decision making, and not confuse. In my previous message I called this good controllership.
immature introduction of version 6.04 ,often without training , in life traffic.
True. The first TCAS versions were introduced, pushed through even, without safety cases as to the impact on ATC. However, that's spilt milk, ATC has to live up to the situation and should embrace the improvement at hand, which brings the individual controller in a better position to apply his judgement when he gets involved in a horrifying RA situation.
The ball is in EASA and the FAA ca
I have noticed with satisfaction that you have put in bold '
for the moment'. That would seem to imply that you, and dare I say through you IFATCA, provide an opening to accept the downlinking of TCAS RA. You are right of course that the legal stuff should be solved. But the statement that the ball is elsewhere (what has the FAA to do with Europe, but that's another matter, I would think worldwide ICAO is the Ageny to address), alludes to a passive attitude from the side of IFATCA. Laxism may have been a too strong expression, but I would expect IFATCA to be active on this front. If it's only a few sentences in some documents to be changed : don't wait but go for it.