While we are pernickety – it is the gravitational acceleration in vacuum near the surface of the earth, and defined as 9.80665 m/s2. As has been pointed out before, to arrive at the actual force you need to multiply it by the mass of the thing subject to gravitation.
[break, break]
The reason we can’t quite decide why it is weight and balance or mass and balance is that the way we do it, it really only works if mass and weight are interchangeable so it really does not matter at all.
There are some aspects of flying that depend on mass. For example acceleration and hence take-off and landing performance.
There are some aspects of flying that depend on weight. For example climb rates and induced drag and hence sustained speeds (e.g., cruise performance).
There are some aspects where it makes no difference. For example the centre of mass and centre of gravity (leaving alone flying aircraft several dozen miles long, or flying close to a neutron star)
All this “it is really mass” and “it is really weight” is fun from a purist physics point of view, but it is completely irrelevant when flying on Earth alone, and neither is correct.
