Originally Posted by
Smythe
On the subject of trim, I saw that the FAA/EASA information on thumb switches on the MAX, which are trim limited, and that operations at the edge of the envelope would need to be manually trimmed.
Why would there need to be a limit on the thumb switch?
I thought I saw this covered elsewhere, but here’s my understanding. First, the yoke trim switches are only limited in how far nose down they can move the stab. There is no limit on moving the trim BACK toward the “green band.” I suspect the reason for this has to due with the fact that the only time one would need to trim that far toward the forward limit would be in a certain unusual flap, airspeed and aft c.g. combinations. In generally, when an aircraft starts approaching its aft c.g. limit, the handling characteristics get a bit more sensitive about the pitch axis. I suspect that Boeing wanted to limit how quickly trim could be applied toward the nose down limit in this region.