Songbird :
Your English is far better that mine, aso you explain this shorter an better. (I indeed beleived Mr Aviatornovado was refereing to FLAS in his questions)
No disagreement anymore with your reasoning.
From what we have learned in Brazil , it would appear that the semi circular is used as a form of FLAS in the known-to-them non-radar areas, but remember this whole airspace is declared full radar everywhere by the military. So for the outside world , radar procedures apply ( and any non-Brazilian pilot would not be alarmed to keep its last assigned altitude ,even if it contradicted the published semi-circular )
This is for me one of the contributing factors of this collision , among many others of course.
Rob 21 :
Yes indeed , introducing dual tracks in what most of us are doing in busy airspace. Not only safer , but far easier to control the traffic. And today with RNP5 it is dead easy to do so. I would not be surprised if either the CENIPA/NTSB report do not mention this in their recommendations, or if quietly, the Brazilians did not introduce this in the meantime.