Originally Posted by FullWings
If you (as a controller) have sent two aircraft directly at each other and there is no further intervention (from you, pilots, TCAS, etc.) then they're going to collide.
If this really is the case, how do you explain, that not every loss of separation situation inevitably lead to a mid-air?
I understand that you - and many company's SOPs - instruct the crew to follow the TCAS RA. This will be the solution for 2 aircraft situations, which are the most probable to occur. But this threat is not only about what TCAS can do, but also about what it cannot do - and the effects the TCAS design produce.
ATC in Africa have plenty of practice at setting this up!
I imagine, there is a reason for stagger and right-of-way rules in poorly monitored areas.
But if the african ATC is so capable in producing dangerous situations, and the probablity of aircraft flying without operational TCAS is highest in poor regions like Africa, why don't we hear about more mid-air collisions over Africa in the news?
So, there is a probablity, that ATC will not solve a critical solution. But why does it sound to me, that you weight the probability of shortcomings in the TCAS system more lightly, than you weight an ATC instruction not solving a conflict situation. (Note that the scenario was not about latency in communications, preventing the crew to get the instruction.)
ATC voice instructions have a very high potential latency compared with TCAS interactions. If there are other aircraft on the frequency and one transmits for, say, 20 seconds then there is no chance to issue any avoiding instructions until too late. The situation becomes worse because if a potentially serious conflict is noticed by pilots, one of the first things that often happens is they check with ATC about the situation, thereby blocking information flow from ATC to the pilot(s); Standard VHF R/T is only half-duplex.
Latency and problems with half-duplex communication are well known problems, but what would solve this? I don't think that one can rely on technical conflict solution as much, as would be necessary for freeflight, e.g..
Perhaps the introduction of full-duplex digital communications and transmission of digitized instruction, with person-to-person communication being an exception for uncommon situations could help, but their impact on aviation safety is still unknown.