AF447 Thread No. 3

[rudderrudderrat]

Abnormal Attitude Law

Hi Check Airman,

I tend to agree. In just 46 seconds (between 2h 10 min 05 and 2 h 10 min 51) the aircraft climbed with ROC up to 7,000 ft/min from 35,000ft to “37,500 ft and the recorded angle of attack was around 4 degrees.” (which is a sensible angle of attack).

They must have ridden in the updraught of a CB to climb that rapidly and still have flying speed. Subsequently, they encounter the downdraught, their instruments don't make sense, stall warnings come and go, and I think they have mistakenly gone for Wind Shear QRH attitude 17 degs with TOGA power.

Edit. Once they were in Abnormal Attitude Law, the Stab Trim remained where it was last. (In this case full nose up)

"The system applies an abnormal-attitude law in pitch and roll if the aircraft exceeds any of these limits in flight.......

Angle of attack > 30° or < - 10° (- 15° for A319 and A321 (??? for A330))
Speed > 440 knots or < 60 knots

The law in pitch is the alternate law with no protection except load-factor protection and without auto trim. In roll it is a full-authority direct law with a yaw mechanical.

When the aircraft has recovered from its abnormal attitude, the flight control laws in effect are :
in pitch : alternate law without protection with autotrim.
in roll : full authority direct law with yaw alternate law."