Originally Posted by
Lonewolf_50
Dozy, I appreciate your stubborn defense of this design decision, but do not accept from that side of the rooom, as it were, that the decision necessarily allowed for the "right" balance between man and machine in the man-machine interface.
I'm painfully aware of that, and if you think I'm being blase or somehow dismissive of tactile feedback in it's place I promise you I am not. However, when I talk about these things I am talking with my "engineer's hat" on. As I've said countless times before, there are failure modes of a backdriven system that are distinctly non-optimal, as well as the consideration of extra complexity.
The "feel" that a pilot gets back through the yoke from the Comet onwards has been mechanically interpreted. You are not "feeling" what the aircraft is doing, you are merely feeling what the artificial feel system thinks you should be feeling based on the input parameters it is getting. In the Comet up through the 767, what you were feeling was mechanically driven. The A320 and her descendants dispensed with it entirely and the 777 actually had that feedback response programmed into the computers. That was a design choice, and while a non-trivial number of pilots have reservations about the fact that Airbus dropped it, it is also true that a non-trivial number barely missed it at all. It is therefore a matter of personal preference. Dealing with the visual-only feedback channel is a matter of training.
We don't know whether the PNF spoke up about the strange attitude or not at this point, so any argument over backdriven sticks is basically irrelevant to the subject at hand. We *do* know that when whoever was in the LHS tried to take control, the PF spotted it and handed over without a fuss. In the stick-shaker regime, connected control columns did neither Birgenair nor Aeroperu's crews any good, as the cacophony of lights, sounds and warnings made problem-solving practically impossible. This was a nightmare situation that would test even the best pilots no matter what aircraft they were flying.
Originally Posted by
gonebutnotforgotten
I would still like to understand why the first two stall warnings were generated before everything went pear shaped, doubtless the full BEA description will clarify that, but it would seem that when the PF took over he put in a mighty demand for no very obvious reason
According to an earlier BEA report on a different incident (I'm still trying to track down the original research - any help much appreciated), tests indicated that in a panic situation 80% of pilots would instinctively pull back on the stick. I'm not saying that's what happened here, but it's definitely one of the possibilities.