hello every one,
cfr this uptrim business at 400ft for b737classic in a 2 autopilot cat3 approach i think we should keep it as simple as possible: if it is not somewhere necessary on safety grounds or not required by reg's, be assured mr boeing or any other airplane manufacturer would not go over to the trouble of designing/certifying this feature on cost grounds alone.
so, i would consider the lack of uptrim at 400ft, if noticed, a failure of the integrity of the automatic gizzmo's & unwilling to be in for some unexpected nasty surprises during subsequent flare/landing when least needed(cat3 wx conditions): would call something like:"no uptrim, go-around", disconnect the autopilots, push toga & do a manual go-around as per sop's an automatic go-around would only be performed on weather considerations only: eg. not enough visual cues at dh.
but i agree, it looks a strange & mystery failure.