Quote:
Originally Posted by
Loose rivets 
A stick nudger is totally different and not at all what was required to solve the aerodynamic problem.
Well . . . but what, exactly, is the aerodynamic problem? We've been told that it's a pitch-up tendency in some corners of the envelope and that MCAS was required to create linear stick forces to help keep the airplane out of those corners. OK, but using the H-stab for that job is pretty radical. Also, as Grebe and others have pointed out, stab trimming is inherently slower than the elevator movement controlled by the yoke, so it seems like an odd choice for that reason.
I think most of us are still trying to figure out how any of this makes good engineering sense -- even if the system design hadn't been so truly awful.
"A pitch-up tendency" is probably technically okay but if I understand it correctly, Boeing like to define the issue as a lightening of stick loads in circumstances that might lead the pilot flying into a trap. We know this means being shepherded into a dark corridor and stalling the aircraft, but it's all about words and the way we use them.
I missused the word eloquent for the MCAS logic. People steal that word a lot these days, but I imagined MCAS working as it was intended, a scenario of say, a last minute runway change and four eyes staring into the blackness for the new centreline. A child of the Magenta Line and an auto-throttle forgotten, so much would depend on the feel of the controls. (shudder)
I suppose that's typical of why that particular certification criteria was put in place. Indeed, the smooth re-datumising of the aircraft's pitch, I begrudgingly concede is best done with the horizontal stabilizer. That jack-screw is perfect for the job: easily electronically controlled and perfectly smooth in operation . . . and ultimately powerful. And there's the rub, just one short period in Boeing's history of design and a ghastly cluster of mistakes allows, what did I call it, the
uncensored use of that ultimate power. One faulty, possibly 'bogus' part and there was nothing but the operating aircrew to override the nightmare. Boeing's faith in the crews to catch a runaway situation is touching, or would be, if on the other hand they hadn't blamed said crews for failing to be that firewall.