One POTENTIAL 'gotcha' occurs in the 747-400. Trim is set relative to the load sheet MAC % and the resultant positioning of the 'green band'. Should the trim not be set correctly with respect to the 'green band', opening the throttles (sorry, thrust levers, for the pedants) will generate a warning. Similarly, that entered MAC% will be checked against the nose wheel oleo compression for gross error and should such an error be present, will generate a 'Stab green band' ADVISORY message. All seems pretty fool-proof so far, doesn't it.
However, suppose an incorrect MAC% is entered and the trim is set to the INCORRECT green band. Since the alerting message is an ADVISORY, there will be NO AURAL ALERT (and I can assure you that it is very easy to miss visual alerting messages) so off we go into the wide blue etc with an out of trim aircraft. But what about the take-off config warning? ( I hear you ask) IT WON'T WORK - because the aircraft has been trimmed to the INCORRECT green band and it is the presence of the trim in the green band logic which triggers the take-off warning!! As far as I know, it hasn't happened yet, but ........... be aware
