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Re:U.S. to ground Boeing 737 Max 8 by sangnoir on Wednesday March 13, 2019 @03:19PM (#19382532)
It's not the center of gravity that causes pitch-up - it's additional lift by engine nacelles at higher angles of attack; this lift increases the AoA further due to the position of the engines relative to the wing. This feedback loop leads to a stall when the angle gets high enough
Re:U.S. to ground Boeing 737 Max 8 by subhro on Wednesday March 13, 2019 @03:26PM (#19382617)
Probably not completely true. An airfoil stalls when the critical angle of attack is exceeded. For most airfoils, this sits at around 17°. For all commercial aircrafts (I think 727 onwards) there is a mechanism called stick pusher that will not allow an airfoil to go over critical AoA. I am not sure if this has been overridden somwhere in the 737 Max 8 though.
Re:U.S. to ground Boeing 737 Max 8 by sangnoir on Wednesday March 13, 2019 @11:13PM (#19386256)
I was describing the physical "bug" Boeing was solving in software: MCAS is a stick-pusher because it forces down the nose - which led to the Lion air crash because of a faulty AoA sensor made MCAS avoid an imaginary stall, forcing the nose down into a powered flight into terrain.
Re:U.S. to ground Boeing 737 Max 8 by tostr on Wednesday March 13, 2019 @03:34PM (#19382738)
Are you saying 17deg from horizontal? Let's ignore wind and other influences. A normal plane can not climb more steeply than 17deg?

I'm not implying you're wrong, just very surprised to see this low a number. I would have guessed much closer to something like 45deg, maybe even more.

Re:U.S. to ground Boeing 737 Max 8 by subhro on Wednesday March 13, 2019 @03:40PM (#19382806)
The Angle of Attack is defined as the angle between relative wind and chord of an airfoil. So if your engine has enough juice to climb at 45° (and many aerobatic aircrafts do), your relative wind is coming at 45° from ground, but almost at 0° with respect to the chord. So your wing is still flying.

Let me know if that makes sense.

Re:U.S. to ground Boeing 737 Max 8 by Gibbon1 on Wednesday March 13, 2019 @03:23PM (#19382573)
They should have put spoilers on the nacelles instead of trying to fix the planes bad aerodynamics in software.
Re:U.S. to ground Boeing 737 Max 8 by iamaelephant on Wednesday March 13, 2019 @03:39PM (#19382792)
Yeah you would know.
Re:U.S. to ground Boeing 737 Max 8 by Gibbon1 on Wednesday March 13, 2019 @04:14PM (#19383261)
How do you know that I don't know.

Please explain.