I think that some information that can be gathered from the raw BEA data might put paid to some of the speculation, especially if viewed chronologically. Here's my amateur attempt. There may well be errors in what follows (especially towards the end when I got tired), and I'm happy to be corrected.
Position
If we look at the BEA report, we see that the aircraft was transmitting AOC position messages approximately every ten minutes, as it was set to do (sec 1.6.8 and 1.16.2.2).
The map on page 11 has plots of positions at 00:29, 00:39, 00:50, 1:00, 1:10, 1:20, 1:30, 1:40, 1:50, 2:00 and 2:10. I assume these are all taken from those messages. Nothing thereafter.
The transmission sequence at 1.16.2.4 (p 46) shows the position according to the message for 2:10, which was received at 2:10:34. That was about 24 secs after the first relevant ACARS message (AP off) was received.
Let's examine the lead up to this.
Radio and ATC
The last successful radio conversation was with Brazilian ATC at 1:35:43 (sec 1.9.1). At this point, the aircraft was at the "edge of radar range of the Brazilian control centres" (findings, p 68).
At 1:35:15, AF447 contacted Atlantico. (fwiw, transcript is: "AIR FRANCE FOUR FOUR SEVEN, by checking INTOL zero one three three, level three five zero, SALPU zero one four eight, next ORARO zero two zero zero, selcall check Charlie Papa Hotel Quebec." (annexure 3 p 99))
They thanked the controller at 1:35:43, but did not respond to requests made by him from 1:35:46 to 1:36:14.
Hypothesis 1: The crew passed from radio coverage with Brazil at this point, all still being in order.
AF447 made 3 attempts to connect to Dakar ADS-C: at 1:33, 1:35 and 2:01. These were rejected because of a flight plan absence or mismatch (sec 1.16.2.1).
The conversation with ATLANTICO seemed to follow the first rejection attempt: the crew contacted ATLANTICO at 1:33:25 (sec 1.9.1; annexure 3 p 99). [I'm assuming all times in the report have been synchronised - see sec 1.15].
At this point they said they were at FL350 (as cleared).
Hypothesis 2: The crew was working normally at all three rejected connection attempts, as nothing was mentioned at 1:35, and I assume they would not have attempted to connect the third time if an emergency had already arisen. If correct, this suggests that they tried to connect to Dakar ADS-C about the time radio would be lost with Brazil, then contacted Atlantico presumably when they could not get on. They then tried to connect again around about the time they finished talking, and again 25 mins later.
Hypothesis 3: We know that there was never any radio contact between AF447 and Dakar (sec 1.9.2). In addition to ADS being rejected, the crew was simply unable to establish radio contact with Dakar. This was consistent with the experience of IB6024 ("difficulties") and AF459 (contact established around 3:45) (sec 1.18.3). LH507 (20 mins ahead) reports hearing nothing from AF447 on 121.5 throughout the flight: 1.18.3.
Observation 1: We are not told if anyone has attempted to identify who from AF447 was talking at that point - could put to rest some of the speculation about who was where on the flight deck.
Weather
At 2:01, based on the map at the bottom of p 30, the aircraft would have been very close to the southern edge of the CB activity. [Assuming for this purpose that the data in the title bar correctly shows that this was the plot for 2:00. Query extent of any averaging with earlier data done to produce this image.]
At 2:07, there is an image of the weather, apparently as at this instant: see sec 2.2.2 of annexure 1 (French report). [It refers to "l’image prise à 2 h 07", ie "the image taken at 2:07"].
If we estimate the position of the aircraft as 70% of the way between its position at 2:00 and 2:10, and align it over the image at sec 2.2.2 of annexure 1, we are into bad weather. The aircraft appears to be within the area of -70C, shown in figures 9 and 10 (which only show the position of the aircraft at 2:10), but not yet into the -75C weather shown in Figure 11.
By 2:10, the aircraft has either just touched on, or is just leaving, the area of -75C in Figure 11, assuming that area remains about the same within the 3 minutes since the image was taken. That is about the time (within 24 sec) of the first ACARS messages - ie AP disconnect -- and about the time of loss of windshear reaction, alternate law, autothrottle off, TCAS fault, rudder travel limit warning (p 49).
Note that these all occurred in a cascade at 2:10, even though some were not received until later: see the sequence at p 49.
Also note: "ECAM messages are transmitted in real time as soon as they are acquired. Flag or advisory messages are transmitted as soon as they have been confirmed. Fault messages are transmitted as soon as the corresponding correlation window is closed." (p 25)
Third note: There is an assumption that the position transmitted for 2:10 (+2.98, -30.59) is actually correct - see sec 1.16.2.2: "The position transmitted was the aircraft’s FM position which, in normal conditions, is close to the GPS position." I haven't seen this commented on, but it means we should keep in mind the possibility that the actual position could have differed, if something had already gone wrong.
At 2:11, we have a sequence of ACARs messages received, showing that the ACARS system was still connected.
Hypothesis 4: The aircraft did not move more than 90 degrees in any direction from normal flight up to 2:13:14, as this would have put the antenna out of contact with the satellite (I assume a 180 hemispherical envelope).
At 2:12:51, the "ADR disagree" message is received at base. The time *logged* is 2:12, so it appears that no more messages are banked up at this point. [Note: I may be wrong, my understanding of ACARS is very imperfect]
Between 2:13:14 and 2:13:45, ACARS communication is lost, for whole or part of the period; "the gap observed between the message sent at 2 h 13 min 14 s and the one sent at 2 h 13 min 45 s is due, at least in part, to a temporary interruption in the communication link between the aircraft and the satellite" (1.16.2.4, p 47)
Some time at 2:13, we have the Prim 1 and Sec 1 faults logged. They are received at 2:13:45 and 2:13:51 respectively. We also have the "FMGEC1 (1CA1) (2 h 13)" message, which "has not been fully explained at this stage of the investigation. The fact that it was “INTERMITTENT” means that the fault was detected for less than 2.5 seconds" (p 54). This is received at 2:14:20.
Some time between 2:14:00 and 2:14:14, the "maintenance status ADR2" is logged, and then received at 2:14:14. Some time between 2:14:00 and 2:14:26, the cabin vertical speed advisory is logged, and received at 2:14:26.
The last signal successfully received by the aircraft was transmitted at 2 h 14 min 28 s: page 47.
ACARS & Questions
It is at this point that data runs out, and it is not prudent to go any further without answers on known-good information.
According to PJ2, ACARS uses VHF if possible, otherwise Satcom [post 791,
http://www.pprune.org/rumours-news/3...ml#post4972795 ]. The BEA report states that all were sent by SatCom. Corollary: no VHF, consistent with no comms to Dakar.
ACARS is also powered by the AC1 bus.
Question 1: to what backup level is ACARS powered. Say we lose AC1. Does ACARS lose power & ability to transmit? If not, at what point does it lose power? Cessation at 2:14 might only signal loss of power up to the point at which ACARS ceases to run, but there may still be power to other systems. If made out, this would direct attention towards partial/total loss of power as a factor.
Question 2: what is the behaviour of the aircraft on loss of Bus 1 - eg by lightning. How long to recovery of any power, and what happens? This will affect hypotheses why there was a loss between 2:13:14 and 2:13:45 -- could it have been electrical, rather than attitude (or both)?
Observation 2: the permanent cessation of ACARS messages after 2:14 could also be due to attitude of the aircraft. But if BEA is correct, and the aircraft at least struck the ocean flat and vertical, then (assuming the plane was intact at that point) query whether attitude was an issue -- based on geometry, the antenna could have gotten a lock even at this point. This suggests there must be some other cause for why it didn't.
Observation 3: I don't recall people having canvassed the potential of power loss on FDR/CVR recording -- query if we may be disappointed even if they are found, as in SwissAir 111 or TWA 800.
Hypothesis 5 (speculation): Could we be dealing with weather induced disconnects and/or unreliable airspeed up to 2:13, followed by a power problem. Possibly unrelated - perhaps lightning after all? Engines out? First an interruption (2:13:14 to 2:13:45) then permanent loss up to some threshold that is not sufficient to power ACARS (after 2:14:28). Or could it be weather induced problems up to 2:13, then an attitude-induced loss of ACARS from 2:13:14 to 2:13:45, followed by a power-induced loss of ACARS (and again, query what level of loss).
Hypothesis 6 (pure speculation): Faced with this kind of sequence, assuming you had some control, what would you do? Head to Fernando de Noronhas (nearest airport) or Natal? Descent and U-turn? Might we even be reduced to a glide? It is here that Takata's excellent work ought to fit in.