PPRuNe Forums - View Single Post - Air Asia Indonesia Lost Contact from Surabaya to Singapore
Old 11th Dec 2015, 14:28
  #3772 (permalink)  
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Join Date: Jun 2009
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For those not familiar with the FBW systems, once outta neutral you are commanding a "change"

So as Vila points out for the 'bus, pulling back on the stick in NORMAL you have a blend of AoA and gee when slow, but mainly gee when not slow. This means you can increase pitch to steep angles with only a slight amount of back stick as you are not commanding elevator position - the computer is!. In DIRECT, you do command position, but in either of the ALTERNATE laws you do not.

We discovered this aspect of FBW in the Viper after the first deep stalls. Just a tiny amount of back stick kept increasing pitch and we got too slow too quicky for the AoA protection to take effect. AF447 did the same thing but at a much lower pitch attitude, and the elevator/THS had little to no command authority for getting the nose down, although some sim tests showed it was possible using manual THS trim and nose down command.
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