Lazerdog, quote:
"Would full forward side-stick have caused immediate stall recovery, or would the PF have to wait until the THS auto-trim caught up with nose-down trim?"
hris Scott
Short answer is: don't know. But I think we can expect that the AoA would have started to reduce immediately. Unless the THS motor stalled, which would be unlikely at such a low airspeed (low loading), the THS would have started moving immediately.
Again the question on what ground this believe on THS authority is founded.
The aircraft was in a stall with an AOA of around 60°. If this AOA applies to the aircraft cell, it applies as well to the two airfoils of the aircraft, the wings and the THS with minor offsets.
What AOA did the THS have during the fall from FL380? Aircraft AOA of 60° minus the 13.5° noseup trim of the THS, which gives us a THS AOA of 46.5, right? (I disregard the effect of curvature of the THS, dont know how that changes my assumption).
What kind of airfoil is working at that AOA and with what kind of outcome? If we trim the THS to full ND as necessary for recovery, the THS AOA even increases to 63.5° AOA plus the profile change due to elevator deflection.
See that nice picture in post
1817 from mm43. Just move the depicted angels to the THS!
What kind of miracle airfoil is there on the THS of the Bus? To bring the nose down its not enough to produce drag at the tail, you need a functioning (unstalled) airfoil producing lift (in this case downward ).
Remember also, the liftvector of an airfoil points basically perpendicular to its chordline, not to the relative wind. So even if the THS produced any measurable amount of lift, the main part of it would not have pointed in the desired direction.
IMHO Elevator ND or trimming the THS down, after this high AOA of 60° was established, only increased the drag of the tailplane but had no permanent effect to get the nose down to the horizon and to increase the speed as necessary.
Whereas stick NU decreased the AOA on the THS below 46.5° , reducing drag and causing some feedback to the crew (noseup input brings the nose somewhat up, but nosedown input doesn´t change anything). That would also explain the noseup input in the final moments.
I might well be wrong, just tell me where!