Hi Dozy, thanks for your replies. Points made and understood. It's complex, no?!
Machinbird, interesting thoughts. I wonder about the notion that the stick was there in one's hand and so one had to 'do something' with it. It is an extremely powerful extension of the hand as you know. It takes time, a bit of experimentation, discussion and particularly paying attention in class to learn what the stick actually does and as a result, how to use the stick well.
Stirring the stick was a well-known action. I recall many years ago, (early 90's), examining some data of an Airbus aircraft on approach in gusting conditions. The autopilot was on and the aileron parameters showed small, sometimes slightly larger deflections as the bank angle was held as commanded, (level, on an ILS approach, not turning). The autoflight system has roll information more accurately and quicker than pilots are able to perceive through the PFD and their human sensory equipment; the autoflight anticipates more quickly and makes smaller adjustments. ....(Even when disconnected, the Airbus remains in what Boeing drivers today would call CWS, control-wheel-steering; within certain limits, the airplane stays in its last-commanded pitch-and-bank attitudes. This is because lateral movement of the stick is a roll-rate request and longitudinal movement is a 'g' request - many here will know this from the extensive discussions on the autoflight system's design to maintain 1g flight, but what may not be appreciated is the implications for manual flight.)
When the autopilot was disconnected just prior to touchdown, one could see the difference immediately, (different, not bad, not good, just different) - the aileron deflections using stick control were notably greater in amplitude. I did not note any PIO by the way but it seems to me that that would have been an ideal circumstance in which PIO was "in-forming" the airplane-pilot combination.
The important understanding in use of the stick here is of course, neither bank nor pitch change unless commanded, ergo, in gusting conditions, leave the airplane alone and it will return to it's last-known-and-commanded attitude.
Very difficult though for a pilot to "leave the stick alone" when in hand, and watching the rocking-and-rolling in turbulent conditions; one must by virtue of being a pilot "do something" to make the machine do as one wants. The notion that it will if one just leaves it alone has not been "exorcised" either in training or in the industry; stirring the pot is endemic because, (the subtle thought or 'the psychology' goes), "when one has one's hand on the stick, one does things, for why is the hand there if not to move the stick?"
I know the notion seems simplistic; the vast majority of pilots are keenly purpose-driven and will quite legitimately state that unless one "controlled the airplane" it wouldn't do as one wanted in manual flight. I think that is largely true, but not exclusively - I tried "leaving the stick alone", (holding, not moving) and it is a challenge.
One could leave the stick alone in a gusting approach to wait to see what the autoflight (not the autopilot) system was going to do when a wing dropped momentarily on short final..., or one can do what comes naturally to any pilot and use the available control (column or stick) to pick the wing up and settle the airplane.
FWIW, I think the stick arrangement is more condusive to PIO than the wheel/column arrangement which is why it is important to learn how to fly the stick. When one makes inputs, one must make small movements, (move the hand nearer to the base of the stick, use only thumb-and-forefinger and move from the wrist...those kinds of things).
In doing so, one must learn when to leave it alone, even while it is in-hand. It is old, old hat for Airbus pilots now, but one can rotate the airplane on takeoff to 15deg and just let go of the stick until the next requirment for attitude change arrives. The airplane maintains the attitudes, despite gusts.
In practise one doesn't do this because one is "in command" of the airplane; the subtlety is that one must move things to "be in control", but knowing when to "do nothing", (different than the AF447 "do nothing - that entreaty would apply to all airplanes, not just the Airbus), is as important an understanding with such a system.
Of course in Alternate Law, it is just an airplane, and (essentially, though not wholly) WYSIWYG, and the discussions on AltB and gain have been had.
In the vast debates regarding stick-or-column one wonders how a stick-as-column, (like a fighter) would fare in the "visibility-of-the-other-pilot's-input" discussion. I'm sure Airbus considered it. To me it is a non-sequitur because the PFD certainly says sufficient to know what needs doing to correct whatever the other pilot may be doing incorrectly, and there is always the take-over button which one can either take over momentarily using the Priority button or take over permanently by holding the button in for, (IIRC), 15 seconds.
I hope this little input is helpful. I'm sure you know most of this but there are some subtleties from an Airbus guy's p.o.v.
Last edited by PJ2; 28th Sep 2014 at 16:33.