ATC watcher, it was still on my to-do-list to react to your statements about TCAS downlinking to ATC.
A recent QinetiQ study show that the average delay for controllers to be aware of an RA via Mode S is about 9 seconds and to get a verbal report from a pilot after an RA is currently about 29 seconds.
The main problem is what happens during those 20 seconds.According to the current ICAO documentation the controller is still responsible and could/should issue instructions as long as the aircraft /pilot do not manoeuvre. The chances to have controllers intervene in those 20 seconds is higher than without RA downlink.
First, there may be an average of 29 seconds before a pilot informs ATC. But that does not mean that ATC is unable to become aware much earlier, when an aircraft deviates from its assigned level. At the most 9 seconds after the pilot's following the RA instruction, the climb or descent will become visible in the data block on the controller's screen. Visible, but the controller will only observe height readout if he happens to look to that particular spot on his radar screen. And in the case of a TCAS RA, chances are high that ATC has missed to see the development of a close encounter and consequently will not look to the spot where collision risk exists (because he is too busy elsewhere or because it's an unknown military or GA), unless a simple message from the TCAS RA downlink mechanism through Mode S draws his attention to it.
Second, in case of doubt wether the pilot follows the RA, ATC might ask.
Might ask, because I am not sure the question is welcome at the flightdeck during those hectic and critical 29 nine seconds before the average pilot comes to informing ATC himself. But, to all intents and purposes, a simple question is much better than a contravening instruction from ATC which cannot be other then confusing.
Third, either ATC trust that pilots act in accordance with their SOP's and adhere to the RA, or we take it for granted that pilots ignore a potentially life-saving warning. Shouldn't we just agree that it is bad airmanship when pilots play around a TCAS RA. Ok, we know it happens, 10 % according to the study you quote. That means that there is still work to do at this front. But bad controllership also exists and I maintain that it is bad controllership if ATC prefer to ignore knowledge of RA's which affect the progress of a flight. Politique de l'autruche, the ostrich putting its head in the sand.
should we decide to downlink one day, there is a strong debate about displaying or not to controllers the sense of the RA. Seen the mode S delay to display the information, a risk exits that the displayed information will be different of the actual RA ( especially in case of sense reversal )
I'd think this debate is academic and by extension false argumentation. In the case of an RA, the provision of separation by ATC has failed (in the neutral sense of the word) and is replaced by the pilot taking ultimate responsibility for the safety of flight. The only action to be taken by controllers is... to refrain from any action, to shut up except for advising other aircraft in the vicinity which might be affected by the evasive action.
Finally, I must say that I have never understood the lax attitude of the controllers' international organisation IFATCA vis-a-vis the possibility of getting technical life-saving improvements, which could to a high degree prevent a collision from happening.
In the aftermath of the Uberlingen accident technical improvements remained limited to some improvent of procedures and airborne TCAS upgrades. This was necessary and useful, but we are still waiting to see ATC improvements that preclude ambiguity with RA instructions through downlinking of the RA. ATC administrations and airlines who have to pay the bill were wary of the financial implications. Uberlingen was quickly put back in their minds in favour of the rise in traffic figures, resultant capacity problems and cost reduction.
But the controllers had to get through the assassination of one of their colleagues. His recent acquittal by a Swiss court could not bring him back. Every TCAS RA event happening in their sectors reminds them of the shortcomings of the system. Yet, their representative body IFATCA, instead of putting pressure on their administrations to provide them with the best possible technical information about TCAS RA's, kept pressing on legalistic argumentation about responsibilities and accountabilities.