PPRuNe Forums - View Single Post - AF 447 Thread No. 10
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Old 4th Mar 2013, 17:49
  #824 (permalink)  
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Join Date: Jun 2009
Location: florida
Age: 81
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Salute!

TNX, Doze for confirming my understanding of the THS.

However, the big point I have trying to make for 2 years is that the flight control laws for the 'bus use the basic gee command, but corrected for the pitch attitude.

Releasing the stick effectively commands attitude in Normal Law and all modes of Alternate. Releasing at a given pitch attitude will cause the flight control logic to gradually release the elevator demand used to acquire that pitch attitude as the trim takes up the slack.
The biggie is "effectively commands attitude". In other words, it will use 0.87 Nz at a pitch attitude of 30 degrees. So without increasing power, the speed/AoA changes and the THS keeps on keeping on to maintain the 30 deg pitch attitude until the jet reaches the AoA protections - HANDS OFF!!. This has an insidious effect, as "normal" jets would require more and more back-stick to maintain the attitude due to increasing AoA as it slows down. Again, I must remind all that our first FBW system was a blend of AoA and Nz. So we noticed that we had full back stick and nothing was happening with the nose once we hit the AoA limit for that gee. At max AoA, we were one Nz gee command.
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