PPRuNe Forums - View Single Post - 737MAX Stab Trim architecture
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Old 16th Dec 2018, 01:13
  #76 (permalink)  
gums
 
Join Date: Jun 2009
Location: florida
Age: 81
Posts: 1,609
Received 52 Likes on 15 Posts
Salute!

No need to "read between the lines", Climber.
I shall assert that without MCAS, the doggone plane would not have met the FAR 25 requirements for longitudinal stability, as well as the approach to stall, or even control in the stall.
One phase appears several times.
....average gradient of the stable slope of the stick force versus speed curve
It may be that as the Max approaches a critical AoA, not speed, that the stick forces lighten to the point that the plane eventually continues nose up with zero control input. Same as my VooDoo did 50 years ago ( but we didn't need Part 25 cert, and our control forces were way lower per gee and trim speed changes that I see in the Part 25 tables, e.g. about 4 pounds per gee, and this was same years later in the Viper, as our max force for 9 gees was about 35 pounds).

I suggest most here read the relevant FAR paragraphs, which are :
Parts 25.173, 25.175, 25.201, 25.203
I like "25.203 Stall characteristics", as it may provide a clue why MCAS was incorporated. The first paragraph requires:
No abnormal nose-up pitching may occur. The longitudinal control force must be positive up
to and throughout the stall.
.
All for tonight, but this should keep discussion going another week or so, huh?

Gums sends...

Last edited by gums; 16th Dec 2018 at 01:19. Reason: grammar, mainly
gums is online now