Was the autopilot an automatic disconnect, or did the pilot disconnect?
I seem to remember that the autopilot will continue to remain engaged with a reduction in speed (whether in say Alt Hold or in this case locked onto the glidepath) and continuing to trim the stabiliser for this new speed until the stall is approached when it stops trimming. No-one explained on the course whether the autopilot cuts out as a function of speed or due to the "out of trim situation".
Flying manually is exactly the same, the stabiliser can be trimmed until approaching the stall when further trimming is inhibited. Thereafter the fly by wire restricts (but can be overridden with excessive force) further rearward movement of the control column.
With regard to the fuel system and the possibility of any ice in the centre tank melting during the descent (and being scavenged to the wing tanks) my question to the fuel/liquid property experts is....
How would a small amount of water (now just above zero centigrade) react with being introduced into a wing tank containing about 6000kgs of fuel still well below zero. Could/would it form small ice pellets.