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Old 24th Jul 2009, 14:26
  #3869 (permalink)  
Hyperveloce
 
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Turbulences and A/P or A/THR

So as to the A/THR (and A/P) settings & procedures about bad weather or turbulences, the Air Caraïbe crew applied the "weather deviation in oceanic controlled airspace" proc. altering their altitude to try to find better conditions ; then they applied the QRH 5.01, "severe turbulences" proc.: the crew disengaged the A/THR and fixed the N1 between 81 and 82% (for a mass of 206T and FL350). The A/P remained engaged untill its automatic disconnection (along with the ADR disagreement and the sequence of Pitots induced ECAM alarms). The AF 447 had probably not disengaged its A/THR: the AF 447 was probably not experiencing severe turbulences but only moderate ones then ? (at least before 02:10Z)
About a link between Pitots induced phenomenons & turbulences: even if the turbulences it experienced may not have been so severe, if the AF 447 had narrowed its upper aerodynamical margin (increasing its speed, due to stall alarms and maybe (?) a speed that had already been increased by the A/THR just before its disengagement), it may have been far more vulnerable to turbulences ? (even not so severe)
Jeff
PS) I have been said that if the A/THR was not disengaged, it should have been in managed speed mode ? If the measured airspeeds vary due to turbulences, the A/THR (maybe 3 or 4 sec. of reaction time) could also vary the engines regime trying to follow these sensed airspeed fluctuations as it could try to follow an airspeed rollback.
PPS) http://www.a330jam.com/documents/turbulence.pdf

Last edited by Hyperveloce; 25th Jul 2009 at 00:55.
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