fdr;
Thanks for your input and observation. Your posts on PPRuNe may not be many but they are worth reading. I may have some B777 questions for you.
With loss of the VS, (I am imagining your scenario at high altitude, not lower down) I wasn't thinking a longitudinally stable trajectory as a scenario in a high speed descent - it isn't possible without lateral stabilization. I would expect strong roll due to yawing, loss of the engines due yaw/roll and a high speed descent of what remained of the airplane. For me, the parts that remained of the cabin structure, (from cockpit to rear galley) either indicated an intact-fuselage as described in the BEA report or a mid-air break up of the fuselage. Perhaps your scenario, (low speed descending spin after loss of the VS at high altitude, I think?) may have obtained. I don't think so, but that doesn't matter; as with every scenario, it is at this point where we must wait.
As far as AA587 goes, I know there is substantial controversy regarding the conclusions and reasons for the loss of the vertical stabilzer and that APA has provided significant input. My thinking and therefore my opinion on the design of the AI VS is unimportant as I am not an engineer and cannot validate design. I believe however that this fashion of attaching the VS to the fuselage is the way it is done throughout the industry.
Regarding use of the rudder, I can offer the following:
I have to say that I knew very early on that use of the rudder on a jet transport was discouraged except to keep the aircraft straight during an engine failure and to align the aircraft with the runway in de-crabbing during a cross-wind landing. Otherwise one kept one's feet on the floor.
In the very early 70's, "Jet Upset" did not exist as a concept or a cause of an accident and so was never discussed. In any later (post 2000 or so), jet upset literature we had access to, (we were not, and to my knowledge, still are not, taught recovery from jet upset in the simulator), use of the rudder was specifically warned against.
As a result of all this I would never have expected the use of the rudder in the manner indicated in the AA587 data, not because I thought it might break the VS but simply because one just never did that with the rudder in a jet transport...I never thought there were ever any circumstances in which it was required and while I've certainly experienced wake turbulence at low and cruise alititude, use of the rudder to control the airplane just wasn't a consideration, not from AA587 on but right from the beginning of the career. I think that I wasn't unusual in this understanding.
That said, I wasn't on the flight deck of AA587 so don't know what they faced.
I read with interest both bearfoil's and mm34's input, especially the notion of a sacrificial rudder vs the loss of the VS. The merits of such notions may already be under examination, we don't know.
In the event of a compound ADC failure, all bets are off as to control gain and FBW stability systems, and the potential in moderate severe turbulent conditions to result in a control system initiated structural failure remains possible. This is not limited to pilot only control inputs, as the FBW system would until reverting to direct law be acting in 2 channels to retain attitude. Whether this did in fact occur to 447 remains an open question, but is probably inconsistent with the BEA's observation of a failure of the VS/rudder on water impact. I personally find that opinion, and the available data inconsistent, suspect that the loss of data airborne and the preceding system degradations indicative of structural failure airborne, with VS separation a potential consequential failure following the ADC and turbulence encounter.
As has been pointed out somewhere, (can't recall), the PRIM failure on the QF A330, which did cause a violent manoeuvre (but did not break or damage the airframe) was not the same failure as was recorded in the series of ACARS messages. While I am not qualified to say that ADC failure would not behave similarly and move flight controls violently, would an ADC system failing in designed-for manner command airframe-breaking control deflections? Regarding the limitation on the actual rudder, vice the pedals, I believe the rudder itself is limited but it will take some time go go through the documents and manuals I have to determine same. I know there have been discussions on various aspects of this limitation in the other thread.
My one question, and I must emphasize that this and all comments regarding what happened after the loss of control are, for me, far less important than what caused the loss of control in the first place; I realize that structural break-up may be part of the latter point but given intact cabin material, some of it pristine, I question any high-speed scenario which also includes the loss of the VS before impact.
That is the fine thing about this forum. Informed and thoughtful participants bring their theories for others to respond to and we get to think on things we had heretofore possibly never considered.
PJ2