RetiredF4:
Well, last try. It works both ways, also in IMC and dark night and especially there. Your words, ....."You rely on the instruments to tell you what the aircraft is doing"..... and i fully agree and never ever said anything else. But flying does not stop there. A pilot will be and has to be in constant monitoring modus to compare the "what is the aircraft doing" to the "what should the aircraft be doing, which i call the expectation state. To be able to get this comparison you need the input value into the system . If you are flying manual in your 152 and you didnīt deflect any flight controls, because you didnīt want any change of the flightpath, but you observe a sudden bank, you know it is not your input, because you have your hands on the yoke and didnīt move any control surface. There must be another reason causing the input and that again might cause a diferent action from yourself.
Same if you are flying as PF, wether you made the flightcontrols change by manual input or by programming the automatics, you will know that it was your input. Will the PNF know ? He observes the change on the instruments and in a yoke aircraft observes the yoke movement in his lap, but in a non interconected SS aircraft? He has to guess.
Well, that works most of the time, because transport aircraft are and should be operated in a safe and preplanned mannor, so due to CRM it is common knowledge when something should happen in regard to flightpath or performance parameters change, because it is announced by PF, briefed before, or ordered by ATC. Therefore the expectation (we will now start descent, climb, turn..... ) shows as reality on the instruments.
When the sh**t hits the fan really bad like in AF447, the reality on the instruments is no longer nearing the expectation, the aircraft does not behave like expected (iīm in TOGA hehe..........I pulled back for quite a while....) and even both PF and PNF have now different understandig of things and the awareness, what the other guy is doing is lost. The corelation of the aircraft behaviour to the flight control inputs is lost, no valid feedback loop any more and therefore complete loss of situational awareness.
By the way, as far as i understand FBW systems it would be the same. If the system would loose the ability to recognize and measure its own input into the system, it would not be able to maintain normal control, like the dampers then counteracting the flightcontrol deflections.
I totally agree with you RetiredF4.
Further to the need of an AoA display unit, I believe this would be better than nothing but, unfortunately, that feature only addresses the stall issue. The question is wider than that IMHO. It has to do with the need (or not) for the PNF to "know" exactly what the other pilot is doing in all phases of flight and circumstances. How can I "see" if my copilot is over-controlling the aircraft? (Especially in the final stages of the approach?) How can I confirm that he is using all available performance of the aircraft to (lets say) perform an EGPWS terrain avoidance maneuver?
The actual (side-stick) system seems to leave one of the pilots out of the loop, throwing him into a situation in-which he is just watching the unfolding of events, once he can only take part, after his (delayed) interpretation of what was already "done" by PF. How can we interpret a
"reaction" without knowing the
"action" that led to it? What we "see" on instruments is the reaction of the aircraft to certain actions/inputs (whether done manually or via automation) but, as you say, there is an expectation created upon those inputs. We manage expectations along our flights. Long term (strategic/FMC/FMGC), medium term (FG/FCU) and short term (manual). Just like the 3 levels of automation... And when in doubt: click click...click click.