Hi gums,
Originally Posted by gums
One of the laws in the 'bus will crank the THS nose up if the computers think you are overspeeding. So with all the sorry data being fed the AF447 computers, I can see the plane cranking the THS all the way up.
You should read again what flight envelope protections are left under ALTERNATE LAW 2, also displayed as ALTERNATE LAW (PROT LOST).
Difference between ALT1 and ALT2 is due to loss of Air Data, it just can't work with unreliable Air Data (at least 2 reliable ADRs needed).
ALT2= no high speed protection, no high angle-of-attack protection, because no valid airspeed can be computed by the PRIMs to display VMO/MMO or Valpha-prot and Valpha-max =
Loss of the function enabling calculation of limit and characteristic speeds.
In fact, this may explain why the PF was pitching up before realising that it was not working. He was not stable due to oscillations (turbulences?) and wanted to slow down to better manoeuvering speed and to catch up Alpha-prot... which was never triggered.