An overloaded aircraft may fail to become airborne, while out-of-limits centre of gravity seriously affects the stability and controllability
CENTRE OF GRAVITY
is the point at which the aircraft would balance if it were possible to suspend it at that point. It is the theoretical point at which the entire weight of the aircraft is assumed to be concentrated.
WEIGHT X ARM = MOMENT
arm = distance of the object to a reference point (or datum). moment= weight of the object multiplied by the arm. In other words, moment is a force which results from an object's weight acting at a distance. the summation of "moments" helps you determine(calculate) your airplane's balance point (or the center of gravity).
WEIGHT AND BALANCE CALCULATION, TABULAR METHOD
instead of calculating Moments they are listed in tables next to the corresponding weights
WEIGHT
A measure of the heaviness of a particular object.
ARM
horizontal distance in inches from the reference datum line to the center of gravity of an item.
The algebraic sign is plus (+) if measured aft of the datum, and minus (–) if measured forward of the datum.
MOMENT
The product of the weight of an object multiplied by its arm
Expressed in pound-inches (lb.-in).
Total moment of an aircraft is it’s weight multiplied by the distance between the datum and the CG.
DATUM
An imaginary vertical plane from which all horizontal distances are measured for balance purposes.
WEIGHT AND BALANCE CALCULATIONS, GRAPHIC METHOD
Instead of calculating by hand or using a table, the graphing method uses a graph to make the calculation for you.