> Interesting that MCAS wasn't like cruise control where any significant input deactivates the automated controls.
It would disengage... but then would immediately re-engage if the bad sensor readings were still there. And would, in the meanwhile, have reset its control limiter so it would push even harder than the first time.
Also thanks to "zero training delta" commitment pilots probably didn't even know it exists or in a high-stress situation like imminent stall probably just forgot about it all.
It's worse: the pilots are supposed to "jump in" instead of the software when the plane is typically already in the critical state and then to control the plane which behaves exactly differently from the way they are trained. Only when the MCAS operates "properly" the plane behaves as they were trained!
That "omission" was intentional as the Boeing selling point was "it is the same old, no new pilot training needed." That's how they have "sold" the worth of 600 billion dollars of the MAX planes!
The probable strategy for Boeing was "we will blame the pilots" and had the two crashes not happened so fast one after another they would have probably got away with it!
They're supposed to jump in and resolve the problem within forty seconds apparently. Otherwise they're screwed[1].
Those involved in the testing hadn’t fully understood just how powerful the system was until they flew the plane on a 737 Max simulator, according to the two people.
The 40 seconds is misleading. The MCAS system could in the worst case run the trim full nose down in 40 seconds (it's active for 10 seconds with a 5 second delay between cycles) if the pilot does nothing to counter it.
It's like if you are driving and the road starts to curve. If you do nothing, yes you will get to a point where a crash is unavoidable. But you know that when your car is not following the road, you turn the steering wheel. Pilots know that when they have to pull the yoke to keep the plane level, they need to trim.
The problem is that if you do the intuitive thing (which is what pilots are trained to do for most trim overruns - pull on the stick to counter the trim), the MCAS goes through the increasing cycle to full nose-down. It's 40 seconds to realize that your usual strategy isn't working, figure out what to actually do, and then turn off the exact right system.
It would disengage... but then would immediately re-engage if the bad sensor readings were still there. And would, in the meanwhile, have reset its control limiter so it would push even harder than the first time.