Originally Posted by
edmundronald
Gums,
Math jargon Sri’s , “may exhibit non-linear feedback” is the engineer’s equivalent of saying may become EXTREMELY unpredictable.
- one wants a system to be controllable - ie can be brought/forced to a desired eg. nice stable state starting from any state inside the envelope.
- if the system is “linear” then a branch of engineering maths called LINEAR control theory applies, the domain where it is controllable is known, and eveything is “copacetic”, automation can be easily used, and the system may be approved on the virtues of its design.
- if the system is “non-linear” and even worse if it exhibits non-linear feedback, then can as they say in the US it can “go postal”, and standard school maths can’t describe it nor control it. An auditor won’t certify such a system unless it is extensively tested -if the auditor be honest. And automation can be very unhappy about the surprises baked into such a unpredictable system.
The suspicion is that MCAS is there to keep the MAX centered in an envelope where it appears linear, but that without MCAS it might get into states where it would be really hard to control (except for Chuck Yeager and you). The unfortunate joke is that the extant MCAS took several airframes into states where they were hard to control. Of course one could argue one can always deviate into a non-linear behaviour eg. stall, but the suspicion here is that the volume of linearity is more limited than it should be, and that really ugly things happen in places where certified airframes should still be acting nice.
I’m sorry if the above is erroneous or unclear, my opinions are usually worth exactly what people are paying for them.
Merry Xmas
If you are saying that MCAS was a brute force way of stopping the Max getting into a [secret] corner of the envelope that was nasty but ended up, through some failure, putting the poor souls into a different nasty situation, I agree entirely.