BOAC;
What I think I see here and from BEA is that the THS did not move from its cruise angle until the top of the zoom climb? Given that it is supposed that PF held a nose-up demand most of the way up, why not? There must have been a good 40 seconds or more of 'demand'.
While it may be an impression on the part of some, the reference for any of this is not here but the BEA Update, and it does not state that NU SS was held most of the way up. It states that after the plane started to climb the PF made ND control inputs and alternately left hand right roll inputs.
We see a this best in the
Excel graph which A33Zab provided, (post #691) in the previous thread - He has shown, and I think accurately so, that the THS does not begin to move from its 3° position until the aircraft is almost at the apogee. The SS was not NU most of the way up but was NU briefly which initiated the pitch-up then ND which began a slight level-off though the aircraft kept climbing. The stall warning occurred @02:10:51 according to A33Zab's graph and a continuous NU SS and application of TOGA thrust is coincidental with that event, and the THS begins to roll towards NU. The aircraft actually stalls at about 02:11 as the descent begins, while the SS is continuously held in the NU position with the pitch attitude at 16deg and thrust set at TOGA. According to the graph, the THS reaches 13NU at around 35,000ft in the descent at about the same time the captain enters the cockpit.
I suspect that while the THS position moves to continuously neutralize elevator forces just as any trim does, the movement is a "follow-up", the rate of change being governed by the pitch basic control loop which has a number of discrete inputs but primarily the sidesticks and the accelerometers. A long discussion has already taken place on Nz law and trimming to 1gee. Manual control of the THS can be taken any time by rolling the trim wheel forward or back. The following is a schematic of the THS general arrangement:
I'm sure there are those here who think PF made the a/c climb, or am I imagining that? Anyone own up or can we eliminate that 'theory??
Again, the BEA Update states that the PF made "a left nose-up input". It isn't a "theory". Back-stick was later held during the stall, and for 30 seconds during the descent. Also, ND SS was briefly held after the initial pitch-up and briefly again during the descent. Knowledge of all other times will have to wait for the next Interim Report.