OK, we are doing this for the love of aviation. I am hoping that CENIPA will clarify all these questions.
ATC never wanted to clear Legacy, or any other plane, to FL 370 at UZ6 from Brasilia to Manaus. They never want to do that with any plane. What was ATC mistake? What was their exact word that was misunderstood? When? What makes Legacy understood to keep FL 370 after Brasilia VOR until Manaus? I suppose that was their last words to Legacy, right? What they said, we know, but what they should have said them? There is not any value judgment in this question. It is only a simple question.
My point-of-view is that communications lost was a minor issue in this case. Why? My answer: Last two-way contact was 15:51, 40 miles far from Brasilia. ATC should have said something, which I don’t know what, but I would like that you tell me, that when they have reached Brasilia VOR they would have descended to FL 360.
Then 16:02, at same time, Legacy don’t descend, and transponder has no signal. ATC thinks it is only a transponder issue and assume they are at FL 360. This (16:02) is the beginning of the incident
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ATC from São Jose, did clear the Legacy to fly 370 until Manaus. This is recorded. I have listened to it. Of course - and it couldn´t be otherwise - pilots must follow the last clearance from ATC. And this frequently happens as you can imagine. The ATC in Sao Jose could have said what the original flight plan said. But he didn´t.
The ATC in Brasilia saw in the screen that the Legacy icon was showing 370:360 and of course could have asked the pilots about this discrepancy. The transponder was ON and this lasted for
7 minutes. Why there was that secong 360? Because the original flight plan was entered in the system and called for 360. The International Association of Air Traffic Controllers questioned the software that entered 360 WITHOUT REQUIRING AN AGREEMENT BETWEEN PILOTS AND ATC (automatically). They claim that this doesn´t work like that in the rest of the word and that for that 360 to be there PILOTS AND ATC should have talked and agreed. Not in Brazil. (The Air Force denies that and defends the software)
ATC could not think that it was just a transponder issue. There was clearly in the screen that the transponder was not working and the 360Z360 reading was not reliable (that is what th Z means). The first 360 was coming from a military radar that ATC new was not reliable in terms of altitude, and the second was entered automatically by the software without requiring that ATC and PILOTS talk. So by looking at the scree for almost one hour ATC saw that the transponder was not working, that the 360Z360 was not reliable and, as you said, felt that this was the altitude... Couldn´t they have -way before communication was impaired- talked to the pilots and ask why the transponder was off and in what altitude they were flying?...
As for the pilots, yes they could have seen in their screen in small letters that the transponder was off. But they were small letters in yellow, not even red. The NTSB has issued directives for this to be changed and for the pilots to have more clear warnings when the transponder goes off. And the FAA has said that in the Legacy, placing the feet on the feet rests altered the transponder to stand-by and altered the radio frequency.
This is how I see, but of course waiting for the final report from CENIPA (the only problem with CENIPA is that it belongs to the Air Force who administers Traffic Control in Brazil in terms of softwares and equipments).
Sarava!