Hello mm43,
I've noticed in your post a number of differences in the use of words, that are perhaps just semantics? There are also a number of adjustments to be called. For instance:
Originally Posted by
mm43
... Any further ND would have provided increased control as THS followed .... The whole process could be sped up by use of the Manual Trim Wheel.
Your "THS followed" .... is the THS being moved NOT MANUALLY, but under electrical control by the A/C's PRIM computer controls - which I would call - following the documentation - "autotrim".
The THS is a major control surface,.... in Normal Law it is taken care of automatically, but in Alt Law the situation changes.
In Alternate Law, the "autotrim" is still active. See page 75 of BEA Report (English version), second paragraph of Phase 3 Section, in two sentences: "
THS began a movement...
It should be noted that in Alternate Law the auto trim is still active."
As for the THS doing its 3°NU to 13.6°NU thing; it had nothing to do with 'autotrim'. It was operating in an integrated demand/time manner to neutralize the elevator input demand - nothing more.
The NU move from -3 to -13 degrees was controlled electrically, as the Autotrim was active - see the BEA Report, same section, and more.
You're using the word "neutralize", while some documentation is using the word "compensate".
As the THS's role is in stabilizing the pitch attitude that has been reached by means of the Elevators - that's why the name - perhaps "compensate" is closer to the definition of the function? although I can see how "neutralize" can be used with the same meaning in mind.
Once the THS is in a NU at a certain angle, a further Elavator NU at a certain angle is summing the NU effects of the two, while if the Elevator goes ND at a certain angle, the effect is a difference as long as the THS is at an opposite (pitch, or angle) position.
The elevator demand was wilful.
It is generally accepted that the CVR transcript shows confusion, which puts a certain doubt if such a demand was in full awareness of the situation, and with a clear defined goal.
The A310 TAROM approach
zoom climb/stall/recovery incident at Orly on 24 September 1994 provides some insight into the movements of the THS. ..... Also, the incident was marked by NO stall warning, and the reason given was that AoA SW thresh-hold had not been reached before the IAS had dropped below 60 KTS and the control logic inhibited it. Sound familiar?
I am familiar with the Tarom case, as well as some other successful Airbus Stall Recoveries, as I've read several reports, watched 3D renditions, but a while ago.... For the Tarom case, the BEA English version of the report, which you've pointed to, has the CVR transcript in a mix of French and English - with several instances of "alarme decrochage-cricket" for "Stall Warning" at page 54.
Despite their mistakes, they've shown their airmanship, and pilot talent, achieving quite a recovery from only 4100ft to 800ft (250m), 60 degree AOA and 30 knots Stall, landing shortly after.
Essentially the same logic with minor changes has been around for a long time. Unfortunately it requires incidents/accidents before everyone realizes how some of this control logic works.
That's so true...