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Old 7th May 2019, 23:55
  #5102 (permalink)  
Join Date: May 2010
Location: Boston
Age: 69
Posts: 440
Originally Posted by gums View Post

Losing credibility faith in you, Murph...... to wit:
Other than it's existence and a few things posted here I have no knowledge of sts, however does not look to be a significant factor in ET case.
Even Driver has referenced STS and that MCAS was considered a sub-mode by some folks. And due to STS rolling that trim wheel a lot, the Lion crew commented that STS was working backwards. I would also like to hear the CVR on that flight, as all we hear via the rumor mill is the jump seat guy saved the day. Until we have the trial testimony and depositions, we may not know. Maybe the CVR had some of the conversation, as the FDR had a lotta hours. My not so humble opinion is that crew lucked out and "went manual" when the trim system was not acting as they expected. I give them a lotta credit for doing all that with then shaker goingon, but their CVR shoul give us a clue if it ever becomes public.

Comes down to same thing - longitudinal pitch moments and such, not simply back stick forces per AoA unless you are flying a pure cable and pulley plaine. The 737 variants added STS after a coupla generations because it had to satisfy FAR speed stability reuqirements. And BTW, I do not like that "speed" term. It's AoA and basic aero to force the nose down/up when decreasing/increasing speed/AoA from a reference speed/AoA. It's called "trim".And most here learned all about it back when learning in the Tiger Moth or Aeronica or Cessna or.........

Big B has a lotta public relations work in store, and I am not sure they will recover for long time. Irritates this old fart, as I always liked their control authority philosophy.

Gums sends...
What I mean is that in ET case it was clear from the traces that although there was one probable STS trim it had no impact on the accident sequence.
I was attempting to answer a question about STS possible active involvement in the ET accident.
Not at all saying that STS was not of overall significance, possibly by adding confusing expectation of intermittent auto trim, although the magnitude and other behavior is much more benign than MCAS.

While MCAS is a subsystem of STS it would be confusing (to say the least) to blame "STS" for the difficulties faced by the crews.

BTW: 737 driver STS explanation is much better than mine since it also includes response to column cutout switches etc further supporting the case that it had no direct role in ET.
MurphyWasRight is offline