PPRuNe Forums - View Single Post - Ethiopian airliner down in Africa
View Single Post
Old 11th Mar 2019, 17:05
  #396 (permalink)  
gums
 
Join Date: Jun 2009
Location: florida
Age: 77
Posts: 1,141
@ Indigo A mod too far?
Salute!
For those wondering why MCAS is being discussed. A brief look.
As discussed on another forum and its references, the MCAS was implemented to cope with some aerodynamic "characteristics", as the name suggers:" Maneuvering Charteristics Augmentation System" As others have pointed out, the new engines and their mounting can provide nose up forces at higher than normal AoA. So looks to this old pilot, who has lottsa high AoA experience, the MCAS was supposed to make it harder to command more nose up.

I include a small diagram of pitch coefficient for one plane I flew. At one AoA and higher, the plane "digs in" with neutral controls, and further, it "pitches up" even with forward stick. So it is not surprising Boeing would add something to "help" keep the nose down and not enter that arena where even nose down commands would not be enough. A poster has commented that the 737 stall has plenty of warning, and I doubt it has that one area where nose down stick won't help. Nevertheless, the MCAS looks like it will make it hard to get there. We saw over 100 pounds of back force for JT610 once the trim was way nose down.



You can see the problem.

Gums sends....

Last edited by gums; 11th Mar 2019 at 18:19. Reason: typo, et l
gums is offline