To me, the actions of the Horizontal Stabiliser seem very important. Why did it stop trimming when the a/c started its climb? Why did it start again just prior the Stall, and go to its stop and stay? BEA write that the simulation provided affirmation that the system worked according to its logic, what is its logic?
I wonder why in the first place it's a "Alternate law" (and all the derivatives included) in the fly logic system of Airbus
This is a lead buoy for the pilots in case of problems
Why not only "Normal law" and "Direct law" .. like for the Concorde ?
Why impose to the pilots a complicated "Alternate law" ?
More:
In addition to the laws "Normal" and "Alternate", there are on Airbus a law called "
Unusual attitudes ", which is activated in case some values very critical
are affected, especially when the incidence exceeds 30 °.
1 minute 25 after the pitot icing, the aircraft reached 447 this incidence of 30 ° and
this law "Unusual Positions" went into action, replacing the law "Alternate"
with the effect of eliminating the automatic action of the PHR.
The PHR is then to full nose and is therefore fixed in position by law
"Unusual Attitudes", as the aircraft came into stall 40 seconds earlier.
The only course of action would have been the drivers of the PHR bring in "Manual" to its normal position.
This law "unusual attitudes" has not had an adverse effect because the fate of the aircraft was
already sealed, but it is obviously disorder in the design of the Airbus and the BEA
therefore denied that she is enabled by arguing that:
"Because of the rejection of 3 ADR (Air Data Reference) by the flight control computers
(PRIM), the law of unusual attitudes could not be triggered on criteria related to
inertial parameters, which were never met "
The BEA does not provide any justification for this assertion, which one looks in vain for a trace
in the documentation of the A330.
The little credit to be given to the assertion of the BEA's report appears on page 101, which
shows that the FD (flight directors) were valid for 53 seconds at a time
where the incidence of 30 ° was reached (02h November 30).
However, for the FD run, it took at least 2 ADR in operation and in this case,
during this period of 53 seconds, we maintain that the law "unusual attitudes"
was very active and full PHR frozen pitch, prohibiting a de facto attempt to recover
the stall!
http://henrimarnetcornus.20minutes-b...2/69907446.pdf
PDF translated in english available here (as HTML page)
translate_f.zip