Originally Posted by
sonicbum
The only reason the inputs are algebraically added is because there is no better solution; it is the one that makes more sense from a design point of view.......
Well, actually PM's side-stick could be designed to be ignored by the FBW unless and UNTIL the take-over button was pressed. On pressing the take-over, PM's 'stick would become active and PF's; inactive. That would exactly prevent dual inputs happening, but still allow PM to take control.
But Airbus did not engineer it that way - why ? Nor did they provide a take-over button for the tillers, and the "dual input" warning does not activate when dual tiller inputs are made. Why is that ?
.....The “Dual input” is a big no-no. It’s a warning rather than a caution like: “you are not supposed to be doing this”.
In your example of a bad gust near the ground you push the TakeOver PB and you correct. the sentence “I have control” is simultaneous to pressing the red button.
Yes but remember in your very initial PPL training, when the instructor occasionally applied pressure or even firm corrections to their yoke when you were learning and feeling how to flare for the very first times - without the "I have control" full dramatic take-over, just gentle guidance and finesse.
Completely taking over is not gently correcting, and the cadet is left feeling that they screwed-up big time rather than simply being guided.
I was often invited to "follow me through on the yoke" when learning to land my first commercial types, and deal with crosswinds etc. You cannot do this with un-linked controls, and I think Airbus engineered the arithmetical addition and keeping both 'sticks active to allow this sort of assistance, and the ability to quickly "nudge it" to avoid a prang.
Cadets are now going from a flight school Diamond 42 straight onto an A320 large jet, rather than gradually building up skills and experience via small turbo-props, larger turbo-props, small jets and then large jets. So the first flares and landings on the A320 family are going to be a huge step from what they are used to. The first few might therefore be a bit sketchy, and I suspect that Airbus designers allowed both 'sticks to be always active to allow a TRE to prevent it going bad, or gently nudge it, but without all the drama and stress of "I have control", and taking over, which would destroy confidence.
.......Trainees of any experience level have to be taught by the instructor from Day 1 that on Airbus FBW there is no room for “a little help in flare”........
Why not though ? You have that facility on every other aircraft type, why should it be denied on Airbus FBW ? The Airbus side-sticks are not mechanically linked of course, so this arithmetic addition is probably the closest way of simulating it.
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