How do you find out the max take off weight of an airliner?
In our company FCOM Limitation section it lists the Max take weight as 74,990 (at the top of the paragraph it has our company identifier which means the info has been changed from the original Boeing master copy in some way.
Else where on this site it lists it as a high gross weight max take-off 79,015kg and on the Boeing site it is listed as 79,010 kg.
What are the reasons behind an airline choosing a lower Max weight, does it affect maintenance/charges for using the aircraft like a car tax?
In relation to this, when we press TOGA on a G/A the bug speed drives to a flap speed for the aircraft at the max take-off weight so if it gets all the way to flaps up before ALT ACQ the speed window will open at 222 knots, now will this be the up speed for the weight that Boeing has or the one the company has chosen? Would that sort of change affect the flight instrumentation software?