PPRuNe Forums - View Single Post - AF 447 Thread No. 11
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Old 9th Nov 2013, 14:13
  #713 (permalink)  
vilas
 
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DozyWannabe

"It used to be that to cancelAoA protection - in which the nose comes up - one had to push the nose backdown, which seems reasonably intuitive to me. The change meant that leaving thestick in neutral for a certain period of time would also return you to NormalLaw - again, not exactly rocket science".
I am sorry but it appears that you have completely misunderstood normal law and protections. Normal side stick fore and aft movement is a load factor demand and computers position elevator and stab to give you that. Pitch control through load factor demand has an advantage in that aircraft response remains same at all speeds. High angle of attack protection which begins at Valpha prot the pitch control is changed to directly achieve through AOA change and not through load factor demand. Valpha Max is maximum AOA aircraft can be pitched upto. When the angle of attack increases deliberately as in case of wind shear and GPWS issues or through atmospheric disturbance the pitch control is changed to AOA mode since that is more appropriate for the situation, this does not mean aircraft pitches to alpha max, rather it tries to pitch down to alpha prot which is the first low speed threshold and pilot has to overcome it by backward pressure if he wants more pitch up.. If you release the stick aircraft will pitch down and maintain that AOA (Valpha prot). If the contingecy is over and you want return to normal speed you push the stick forward as you would do in any aircraft and the pitch control changes back to load factor demand. You have to remember that only method of pitch control is changed aircraft doesn't pitch up on its own. During all this aircraft remains in normal law. In the incident we are discssing the protection mode had no negative impact whatsoever. It is definitely not rocket science but you have not understood it at all.
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