Originally Posted by
Loose rivets
Avionista #4661
We know why it's there, and more or less what it does, but I have to agree with this part of the above post. It's been nagging at me since November.
Why is such a powerful tool used to simply stop the PF heaving back too easily at a high AoA?
Boeing chose not to use conventional stall protection but instead devise a system that changes the aircraft's overall handling at a critical time. For a few moments, they are trying to make the MAX be something it's not. The necessary certifiable handling characteristics are synthesised by moving over 47 feet of flying surface - it's as though the design of the entire aircraft was being momentarily tweaked to cover one issue.
This vast surface is altered to give this synthetic nose down just at a time there's presumably a danger of the wings stalling. If it was capable of a lightning fast return to normal datums, it would just about be acceptable, but any return has to be done by the cranking of that jack. On that dark and stormy night, a last minute change of runway and a moment's inattention. Is that extra weight on the pole going to save the day? If it doesn't, even with a fully serviceable aircraft, it seems to me that the problem of an embarrassing stick shake could be turned into something orders of magnitude worse.
It has been said time and time again:
MCAS is not for stall protection.
MCAS is only there to provide the correct elevator feel at high angles of attack to meet the FAA certification requirements. You can still stall the aircraft, the only difference is how the elevator feels. With MCAS the elevator feels like every other aircraft you have flown. Without MCAS the elevator feels light at high angles of attack.
In my opinion, the original MCAS design was really not that big a deal. Boeing and FAA probably decided one Angle of Attack sensor was enough because it still flies just fine without MCAS. It just feels different. If the Angle of Attack sensor fails and MCAS operates incorrectly, you just trim it away with the thumb switches. (Lowering the flaps for landing also deactivates MCAS) If you get tired of playing with the trim switches to keep the nose up, then just turn off the Electric Stab switches and trim manually. No big deal right?
WRONG.... It seems that there are pilots who will have difficulty with this simple concept of FLY THE AIRCRAFT so now Boeing has refined MCAS to make it less likely to confuse these pilots. Now it takes 2 Angle of Attack sensors to agree before MCAS activates, AND it will not apply nose down trim repeatedly. That should make it safe for all pilots.
YES?
But, for some reason, people are still not satisfied. It seems these people have a real hate-on for Boeing and the FAA. I think this is all an over reaction to a simple design underestimation that has an easy solution.