Well, I finally went back to read all the thread - and found Dozywannabe and Clandestine (thanks, guys!) quoting a longish note of my to the safety-critical systems list at York on this accident. It predates my longer paper, which I linked in my note of 17th December, by a few weeks.
If I remember rightly (and it has only been a few minutes, so there is some chance), the big issues discussed have been
* Rudder actuation design
* Whether the PF actually moved the controls
* Whether the turbulence encounter was unusual in any way
* How AAMP advocated use of rudder in recovering from upsets
* How and when to use the rudder on a large transport airplane
* Whether people knew that arbitrary control inputs could break commercial transports at less than manoeuvring speed
* How APC (Airplane-Pilot Coupling, to use the National Research Council's term for it in their decade-old report) occurs and how it can occur more easily with rudder than with other flight controls on a transport airplane
* Whether the vertical fin on AA587 was strong enough
These are all well addressed in the docket (not just the report, but significant additional material) as well as in my article.
But there is one relevant point which was not raised, concerning sensitivity of the rudder controls. It is in my paper (p13). Rudder pedal displacement measured from the FDR during the episode shows at one point 2 inches and at another 2.5 inches. This compared with a travel to the stops of only 1.3 inches. AI engineering estimated it would take 130-140 lbs of pressure to achieve this. With those kinds of forces, any rudder on any airplane with a variable-stop design would have been taken to the limits, no matter what its sensitivity in terms of break-out-force vs. full-travel force. This makes the sensitivity point moot as a causal factor. It is of course appropriate to address sensitivity in the investigation, for the point of an investigation is to illuminate any safety issues that might arise, not only those deemed to be causal to the accident.
I also took up airsupport's challenge to go back and read all his posts. He says
* Water used to get trapped in the fin of such airplanes
* This may have been (not was, but may have been) a factor in the accident
In other words, just what he has been saying this time around, plus:
* An airplane should be built such that any application of control inputs like this should not break it
Now this further point is easily answered, of course, and was, by Mad (Flt) Scientist. I shall not repeat the answer here. John Tullamarine also stepped in with some comments. airsupport responded with the by-now customary deprecations.
This time around he says
Originally Posted by airsupport
it is just not worth it trying to have a sensible professional discussion
which leads me to wonder whether we attribute the same meaning to the phrase "sensible professional discussion", just as I wondered earlier whether we attribute the same meaning to the phrase "seriously weakened".
PBL