The HS on the NG is a very powerful device. If it is grossly out of trim, the elevators are not big enought to get you out of the situation. You have to use the trim as well. Or stop it from happening in the first place.
The problem is this, we are dealing with a system that is not monitored for a runaway condition. Boeing put those big, ugly trim wheels in there, but they live their own life, spinning this way or that way depending on the trim situation. We are used to that, so it takes time to react to a runaway situation. No lady yelling STABILIZER MOTION, STABILIZER MOTION, STABILIZER MOTION on the NG.
Add Speed Trim as framer introduced a few posts ago. That system would most likely have been in full motion trimming down, as it is designed to do, during this go around.
So how are we supposed to discover a runaway trim? After 6 hours flight time, at night, ****ty weather, tired and turbulence. Very easy to miss.
Never heard about a runaway trim on the NG, though.
STS is another weird Boeing system. Most of the time I end up trimming to cancel out this system dueing take off. Why they put it in there, I have no idea.
Iceing? I don't buy that, partly because of that effective HS, and I don't know of a single incident with ice on the HS on a 737. The frozen stab on that Norwegian NG is not applicable for the conditions this FZ aircraft was in. 6 degrees on ground means a lot of any ice would have melted off during approach.
Accidently trimming by hitting the wrong switch?
A. The auto pilot will disconnect if you use stabilizer trim.
B. If you fly manually, you will feel this after a few turns of the trim wheel. It would be very weird if you continue to trim and fight the out of trim with the yoke at the same time.
Unless the PM was trimming? That would be weird too.
There has been a number of near accidents related to level off and pitch down during level off (with aircraft without any defects) as
pr the Boeing magazine somebody copied from way back in this thread.