PPRuNe Forums - View Single Post - AF 447 Thread no. 4
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Old 22nd Jun 2011, 16:21
  #273 (permalink)  
Chris Scott
 
Join Date: Jan 2008
Location: Blighty (Nth. Downs)
Age: 77
Posts: 2,107
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Quote from PJ2:
"The BEA states that the pitch-up was caused by a side-stick being pulled back. We have good reason to take that at face value until the next Interim Report because at some point we're going to have some actual data to examine and the BEA know it."
[my emphasis]

Quote from PJ2:
"I think we need to re-focus on why the side stick was pulled back after a stall warning and why it was held fully back for thirty seconds while the aircraft was on the way down at >10,000fpm."

Quote from BEA Update (2011-05-27):
"The altitude was then about 35000ft, the angle of attack exceeded 40 degrees... [...] The aeroplane's pitch attitude did not exceed 15 degrees... [...] The airplane was subject to roll oscillations that sometimes reached 40 degrees. The PF made an input on the sidestick to the left and nose-up stops, which lasted about 30 seconds."
[my emphasis]

That last sentence, taken at face value (noting PJ2's first comment quoted above) is almost incredible. The beginning of the 30-second period seems roughly to coincide with the THS reaching full-travel (13NU).

It will be interesting to see what change in AoA took place during the 30 seconds, and what change(s) of bank. One would expect both to be considerable, yet there is little to suggest that is what happened.

My proposal is that the EFCS (FBW system) had already applied considerable up-elevator to try and regain 1G (in Pitch-Alternate Law without protections).

However, full aileron and roll-spoilers being required (in Roll-Direct Law) for 30 seconds, to level the wing, is a different matter.
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