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I tell you, man. I don't want load factor demand with no envelope protection.
The FAR are very clear that there must be a positive force gradient vs speed: Starting from trim, it's REQUIRED that a push force is needed to increase speed, and that speed increase must grow with the push force applied, and the same goes for a pull force and reduction of speed. There is a very good reason for this requirement, and it's called "speed stability"
The load factor demand concept ignore this requirement. There is no force on the sidestick needed to change speed. Airbus somehow managed to get rid of that requirement, that they are clearly not fulfilling. Probably that was by arguing that the envelope protection offered an at least as effective means of preventing a dangerous speed excursion. And I agree. AS LONG AS THERE IS AN ENVELOPE PRETECTION!!!
Remove that, and the load factor demand concept just doesn't belong to an airplane. It's simply too dangerous. Figure this:
They had dozens of warnings to troubleshoot. The memory items of the unreliable airspeed were just one of many. There is the risk that they didn't notice that the A/T had reduced thrust shortly before the event. There is the risk that, as you've said, they forgot to move the T/L away from, and then back to, CLB. There is the risk that they got distracted by the other warnings, or by severe turbulence, or whatever. In a classical approach, and even in an Airbus in direct law with just a spring as the only force feedback, you need to apply increasing displacement of the yoke/stick, which also takes an increasing amount of force, to keep slowing down. No matter what you do with the throttles, the plane just won't slow down unless and until you pull up.
In normal law, on the other hand, with the load factor demand concept, the plane can slow down with no stick input: If the thrust less than needed to keep the speed, the FCCs will keep increasing the AoA to maintain 1G and won't let the nose go down (in fact it will go up), and the plane WILL slow down. But only so much. There are several layers of protections against the stall made by the FCCs, that includes adding nose down input first, then linking the stick deflection with AoA and not load factor (hence the AoA won't keep increasing unless the pilot keeps pulling up more and more), and finally the FCCs will just ignore the pilot's inputs that would stall the plane. Very much like HALL in 2001, the computer will simply not let the pilot stall the plane.
Now, remove the stall protection and the slow speed stability protection, keep the load factor demand concept, and the pilot is left with what? With no muscle feedback, be it in terms of position of the sidestick or force needed. Ok, he has some very nice screens in front of him that he can use for visual feedback. Except that they are filled with non-usual symbols and messages, some usual information is removed, and they still have to troubleshoot a few dozens of warning messages while fighting to keep the memory item pitch (and thrust) in the middle of some nasty turbulence. Ideally, that is doable. One pilot aviates, the other troubleshoots. The flying pilot might need to move some switches, look for some information, and answer some challenges from the checklists. To do that, ideally, the flying pilot would look away from the attitude indicator just 2 seconds each time, then return to the AI for a few seconds to check that things are still as he left them and check that the tendency is still that they are staying there, and only then look away for another 2 seconds.
Yes, it's doable, but it gives you no margin.
Make those 2 seconds 10, remove all feedback from the sidestick, remove envelope protections, add anxiety, turbulence, darkness and some confusion, and you are dead.
Unacceptable!
Imagine yourself driving a car where it could slowly turn with no input in, and no feedback on, the steering wheel. And that you are required to concentrate on the road 100% of the time to keep on it. Now go change the DC and I see you in the woods.
The speed stability requirement is there for something! And if the lack of speed stability becomes acceptable in lieu of other layers of safety, then it becomes instantly unacceptable the instant that these other layers of safety are removed.
As I've said, IMHO, if Airbus was working on the guarded "direct law switch" right now, I would tell them: Stop. Take these engineers. Fix this first. Then go back to the guarded switch. And that's a significant comment coming from me, a strong supporter of the need of that guarded switch.
