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Old 14th Nov 2002, 15:45
  #106 (permalink)  
PickyPerkins
 
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Wino I can't screen capture like you can Picky, but the next reversal, before the bang and tail departed had both exceding the movment limits.
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Technically you are right, the rudder is shown in the Reconstruction video (Rv) immediately before the fin separates as being a bit outside the limits.



Above are two frames taken within the same second at 09:15:58, the top one before the fin separates and the lower after the fin has separated. The rudder is shown as being just outside the limits in the top frame, and gone in the bottom frame.

However, looking at the (unfiltered) FDR trace, I am not sure that we really know that it did go out of limits.



Here is the FDR rudder position trace during the second wake encounter. Positive (downward) deflections on this graph correspond to deflections of the rudder to the right on the a/c. The first point outside the limit is at a rudder deflection of -115º, and hence is clearly during/after the fin separation. The three later points are all at zero, presumably representing a disconnected circuit. Since the point before the -115º reading is also zero, it may also represent a disconnection and not be valid. All the other points are at or within limits.

So I don’t see any evidence that the rudder really went out of limits in this case.

Curiously, you can see above that the last points on the (unfiltered) FDR trace before the -115º point are at about 6º right and zero, whereas the last frame of the Rv before fin separates shows the rudder deflected to the right limit (or slightly more). I imagine the Rv uses estimated unfiltered rudder positions, so that to some extent the Rv rudder positions are synthetic (and of course the FDR readings are “wrong” because they are filtered).

I think that this all adds up to there being no evidence that the rudder really went out of limits in this case.

I have a question: did the process of estimating the unfiltered rudder positions ASSUME that the limiter worked?

If anyone has a transcript of the NTSB hearing, I would be interested to hear Airbus’s exact words on overpowering the rudder and/or its pedals.

BTW, I can’t screen capture video either. All these video frame illustrations are digital photos of the monitor screen.

I agree with your comments about Airbus’s attitude at the hearing. One of the most disturbing impressions I got listening to parts of the NTSB hearing was the complete satisfaction of the Airbus engineering test pilot with the present rudder system. He was completely happy with it. There was also a complete conviction expressed that anything not specifically required by the FAR’s wasn’t necessary. (Like displays if you are out-of-the-envelope in a 65º bank?) Guess he was wearing the company hat that day.

Last edited by PickyPerkins; 14th Nov 2002 at 16:34.
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