Originally Posted by
Uplinker
I have always wondered about this. Why do Airbus side-sticks arithmetically add if they are never supposed to be operated together ? I think the intention is so that a TRE can grab the situation and pick up a wing in the event of a bad gust near the ground, or a missed flare, or a bounce, that a trainee does not react appropriately to, to avert a prang. If they also press the red button, fine, but even if they don't, they can still save the situation. I suspect that the "Dual Input" warning was provided for the trainee to be aware that their instructor was correcting on the non linked side-sticks.
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.
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.
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”. So if needed the instructor/cpt/FO (incapacitation) will takeover and no hard feelings. It’s absolutely normal.