[kayfox]

Its possible and I think it was demonstrated in one of Mentour Pilot's videos that both pilots can work together to manually trim. Boeing put notes in the manual that this may be needed and it would not break the manual trim system to apply that much force to the trim wheels.

[proctor]

the fact that the combined strength of two humans would not be enough to _break_ the manual trim system does not tell us whether that combined strength would be enough to _turn_ the trim wheels at all.

https://news.ycombinator.com/item?id=19575318 "option 2)" (on this same page) refers to a situation where a "dive" could be executed in a situation where manual strength is not enough to trim the aircraft.

[cjbprime]

Recall that at the same time it's taking the strength of both pilots on the yoke to keep the plane approximately level. You're saying they should both let go at low altitude and see if they can crank a trim wheel together?