Good evening HN39,
That's a super graph! I was going to ask you which sources you chose for the Alpha1 and Alpha2 curves, and I see that you have now averaged the two values into one curve.
However, although it doesn't affect the overall picture radically, I remain unhappy with the apparent one-second discrepancy between the time bases you and I have been using. (See also my posts of
Dec18/0021z and
Dec18/2008z.)
In the text accompanying your
first graph, you quoted the BEA as follows:
"...the report puts t=0 at 12:45:39 and states that the airplane entered alpha protection mode at 12:45:34 (t-5) at 122 kIAS and alpha=13 degrees."
Why would Alpha-Prot have engaged at an AoA of +13, i.e., 1.5 degrees early? As previously mentioned, the only reference I've found so far is as follows (1.16.1.2):
"A t - 4 s, commutation sur la loi de pilotage en incidence, la valeur de 14.5 deg ayant ete atteinte, cette loi etant ensuite conservee."
[At t - 4 s, switching into the angle-of-attack law, the value of 14.5 deg having been attained, this law being maintained thereafter.]
It also defines "t" as "GMT" 12:45:39; as you have stated. My interpretation of the DFDR print-out is that 12:45:39 is paired with an elapsed time in seconds of 335.0 - not the "334" which you state.
Referring to the first of the many lines annotated "1245", which must represent 12:45:00, the elapsed time is 296.0. So 12:45:30 would be 326.0, and 12:45:39 would be 335.0. That is the last line on each DFDR "Tome", page 8. (BTW, the elapsed times continue at the top of Page 9, but - curiously - the associated GMT times are erroneous.)
So, using your time base, where "t" (12:45:39) is 334.0, t -5 is 329.0, at which the AoA on Tome 1 is indeed +13 (and the Tome 6 values U13.1 and U12.7).
If I am right, however, the time-vs-AoA figures are as follows:
t -06 12:45:33 (329.0) +13 U13.1 U12.7 (Landing mode of Normal Law)
t -05 12:45:34 (330.0) +14 U14.4 U14.4 (Landing mode of Normal Law)
t -04 12:45:35 (331.0) +15 U15.3 U14.4 (Alpha Prot)
t -03 12:45:36 (332.0) +14 U14.3 U13.8 (Alpha Prot)
t -02 12:45:37 (333.0) +14 U13.8 U15.6 (Alpha Prot)
t -01 12:45:38 (334.0) +15 U15.1 U14.9 (Alpha Prot)
t -00 12:45:39 (335.0) +15 U15.3 D73.8 (Alpha Prot)
t +01 12:45:40 (336.0) -00 D00.2 D00.2
I suggest that the numbers annotated on your time axis need to be moved one space to the right. Also, the first two values of "AlphaCmd" need to be deleted, because Alpha Prot did not start until t -4.