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Old 14th Apr 2013, 00:09
  #17 (permalink)  
Join Date: Jun 2011
Location: France
Age: 39
Posts: 17
That said Full Nose Down command in an Nz law should correspond to a G Load Factor significantly below 1g even if the reference Speed is pretty low. This should result in a Nose Down Elevator response finally. Taking into consideration that average G Load in a developped stall will be close to 1g an Nz law should still allow ND Elevator. As there are G Load fluctuations in the dynamic evolution of the stall they might have been unlucky that during these 2s of ND input the temporary G load was on the low end of the range. Unfortunately I don't have the traces in front of me atm. I don't see why Full sustained ND input should not lead to a significant ND Elevator deflection in an Nz Law !?
It should, but from the data on the leaked report, when the copilot puts the stick full nose down for two seconds, the elevator goes from 30 degrees pitch up to 20 degrees pitch up. How fast is the elevator supposed to move? If it is 5 degrees per second then ok they had some authority.

I think this alternate law is a big problem anyway. They should revert to direct law in case of event like this: if you are stall, with the stick at neutral, then the plane will demand 1g and will keep the stall.

On an related note, the report says that
"En cas de perte d'au moins deux ADR, la stabilité basse vitesse est perdue, il est surprenant que le trim automatique ne soit pas désactivé au voisinage de a PROT, alors que c 'est le cas en loi ALT1"

The experts are surprised that the auto trim doesn't stop trimming the plane up once alpha prot is reached, as it is the case in ALT1. I am too.
predictorM9 is offline