PPRuNe Forums - View Single Post - Ethiopian airliner down in Africa
View Single Post
Old 3rd Apr 2019, 16:48
  #2987 (permalink)  
TachyonID
 
Join Date: Jul 2013
Location: SoCal
Age: 61
Posts: 7
Youtube videos now being pulled?

Originally Posted by safetypee View Post

Also see the video (via SteinerN)...
Whilst it appears easier to set nose down trim, it is less so to recover back to a trimmed condition. The nose down direction might be aided by the aerodynamic forces, whilst nose up the trim wheel has to overcome them.
Also, MCAS could run the trim nose down after flap retraction - lower stab trim loads, but if speed increases due to descending flight, then back trim at a higher speed is less achievable, having to overcome much higher stab trim loads.

This is a dynamic, escalating situation. And for those following the ‘40secs time to react’ theme, consider that recognition might take two MCAS cycles 10sec trim, 5 sec pause / back trim, 15 x 2 = 30 sec, only leaves 10secs for action - select trim inhibit, then apply back trim wheel. See the video, move seat back, pull the handle out, then wind - how much, how long, if able.


'
Now, it's worrisome to note that Mentour Pilot's very-illuminating videos on Youtube are being suppressed. Without being too paranoid, it would appear Boeing's PR department is now working overtime to "damage control" the revelation that the ET pilots HAD followed procedure.

It's inconceivable that, having followed the Procedure to disable TRIM, that the pilots would have re-enabled TRIM unless they found the trim wheels insufficient to overcome the nose-down attitude MCAS-HAL gave them. It's a large number of revolutions to make much impact, especially with the all the back pressure PF and PNF were likely applying via the column, and with only limited time to recover the pilots may have wished to re-enable electric trims in order to expedite matters. Perhaps the first thing MCAS-HAL does, since he'd be out of the loop on the physical disconnection of the electrical circuit, might actually be to "catch up" with a full Down Cycle when the motors are turned back on? No matter how you view it, this appears like Boeing didn't "think the realities of the situation through thoroughly".
TachyonID is offline