Originally Posted by
silverstrata
The STS normally trims nose down after take-off.
It is safer that way....
Silver
From you posts it is obvious you know more about the 737 than I, so apologies for going on about this, but I feel it is an important point:
The main reason for the STS is to make the airplane more speed stable, so it artificially flies the airplane back to a reference speed with trim inputs. If the STS trims AND after T/O your speed must have been below the reference speed, and the STS trims to get the nose in the direction of the speed change back to reference speed.
It does not trim AND just because it is safer, it is flying the aircraft with the trim to get the aircraft back to reference speed. Most pilots seem to blip the trims to set a new reference speed, and stop the STS from trimming in that direction. As the pilot starts to accelerate the STS will try to keep the reference speed so it will trim ANU, while the pilot wants to accelerate and trims AND.
What I think happened with the write-up is that after they raised the flaps and were accelerating the MCAS kept trimming AND and that is the unexpected trim direction the previous captain was referring to, because the STS would still be trying to trim ANU normally. I am inclined to believe he knew what the expected trim direction was in this situation based on the fact he was able to continue without crashing.
Again, all just based on an A pilot reading about B planes, so if I am incorrect about the technology please correct me.