PPRuNe Forums - View Single Post - AF 447 Thread No. 9
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Old 15th Aug 2012, 02:56
  #1299 (permalink)  
Turbine D
 
Join Date: Dec 2010
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My understanding as a fully paid up SLF with bus driver friends, is that the THS movement is not commanded in automatic operation, but operates to reduce the stress on the elevator hinges so it motors to the position that requires no further elevator deflection to maintain the 1g flight path. As has been said earlier if you reduce the power the THS will try to keep the nose high enough to maintain the 1g flight path all the way into the stall.
I would really hope you didn't get the THS movement idea from an Airbus driver. The sidestick controls the elevators. On the A-330, the elevator deflections are 30º nose up and 15º nose down. THS deflections are 14º nose up and 2º nose down. So if a pilot flying level at 350 and Mach 0.80 with a thrust setting of ~85% N1 decides to pull back the sidestick and hold it for a prolonged period of time, some time being all the way back, the elevators will accommodate his command. They will deflect all the way to 30º nose up which it did on AF447. then the THS will begin movement (trimming), as calculated by a computer, to neutralize the pressure on the elevators and also moving up to near the maximum of 14º nose up which it did on AF447. So simply said, the THS didn't lead to the stall, the elevators did based on sidestick positioning determined and held by the PF. Once in the stall, the elevators held the aircraft in the stall, not the THS.
I would very strongly urge you to go to R&N, AF447 report out to PJ2's post #811. Read what he has to say and click on the underlined post #457 to learn about the THS from an expert.

Last edited by Turbine D; 15th Aug 2012 at 03:02. Reason: added thread identity
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