Thread: Lion Air 737 Max Accident
View Single Post
Old 11-13-2018 | 04:54 PM
  #58  
Adlerdriver's Avatar
Adlerdriver
Gets Weekends Off
 
Joined: Jul 2007
Posts: 4,064
Likes: 37
From: 767 Captain
Default
Originally Posted by 1wife2airlines
I was under that assumption, not having flown it, that the ability to stop the stabilizer from trimming by moving the elevator opposite it was the same mechanical system as is on the B727. Is it? If not was it an electrical system that Boeing then removed.


I’m pretty sure that’s how I remember it working. Moving the control column in the opposite direction of undesired trim motion, automatically cuts out those trim inputs. Does that constitute a “mechanical brake” in your view?

757/767, 777 all have the same STAB cutout switches that remove hydraulic power from the stabilizer (never flown 747 or 787 but they look to be the same as well). Those are memory items switches if we receive warning of uncommanded/unscheduled stab movement. Once they're off, hydraulic power is removed from the stabilizer trim control module. I don't believe it's possible for the stab to move due to air loads (because of the actuator design).
Reply
0