Originally Posted by
RedBaron007
Does anyone know why changing to a -200 spar would change the ZFW? I would think that spar would be beefier than the -100 spar since it strengthens the wing to hold -300 engines and go faster. Maybe I'm just too tired and not seeing something obvious with the airframe strength relating to ZFW?
It's the MAX ZFW that is the issue. The wing has to carry the load of the fuselage and this leads to bending stresses in the wing, especially at the wing attach points. By strengthening the wing it can handle an increase in these stresses. Since the fuel is carried in the wing its weight does not add to this flexing at the attach point and thus can be carried in excess of the max ZFW.
Having said this - I doubt that swapping a Q200 wing spar would be much of an option. The spars are (usually two spars - front and rear) an integral part of the wing and the wing would probably have to be disassemble to replace the spars. A major undertaking to get only 500 lbs more allowable ZFW. A more likely scenario would be to add to the existing spar to beef it up a bit - still, a costly solution but a bit more doable.