Originally Posted by
LarryJ
On larger airplanes, the weight of the carry-on bags are included in the "average" passenger weight used to calculate the airplane's weight and balance. The smaller airplanes can't fit nearly as much carry-on baggage on board so they use a lower average passenger weight and each valet gate-checked bag in counted as additional weight. Since the weight and balance program is not allowing for that extra weight in the cabin, they have to restrict the amount of baggage each passenger brings on board or their lower average passenger weight will result in under-estimating the weight of the airplane which has safety implications.
Ding!
Weight and balance issues become even more critical on foul weather days because they are more likely to load extra fuel to handle potential diversions (or the non-availability of en route airports that could have been used by diversions).
At some point it's a pilot or Ops decision to direct bags to cargo and then passengers are to do as instructed.