B777 Alt Cg
When the CG is moved aft, the aircraft pitching moment is reduced .This results in a reduced downward tail load required to trim the aircraft.Since the required wing lift is the sum of the aircraft weight and the tail-download for trim, this aft CG reduces the required wing lift.This reduction of required wing lift manifest itselfs as reduction in speed for the same pitch attitude and weight that reduces the stall-limited speed.The wing lift reduction also reduces the takeoff attitude -limited speed ( the parameter used to set the margin to tail strike rotation). These reduction in speeds reduces the field length required for given takeoff weight;the reduction in tail down load reduces the trim drag which improves climb capability
Using the alt cg option on the B777-300 B777-300 ER allows the possibility of are Higher Assummed temp or increasing the performance TOW at the particular airfield when the Takeoff MAC is 26% or greater.
This ALT CG selection is usually available when the Boeing OPT ( optmized Performace Tool) is used via the EFB or the Laptop.
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