+/** Models weight, balance and moment of inertia information. Maintains a vector
+ of point masses. Sums the contribution of all, and provides this to FGPropagate.
+ Loads the \<mass_balance> section of the aircraft configuration file. There
+ can be any number of <pointmasses>. Each can also have a shape which - if
+ present - causes an associated moment of inertia to be calculated based on
+ the shape. Note that a cylinder is solid, a tube is hollow, a ball is solid
+ and a sphere is hollow.
+
+ <h3>Configuration File Format:</h3>
+@code
+ <mass_balance>
+ <ixx unit="{SLUG*FT2 | KG*M2}"> {number} </ixx>
+ <iyy unit="{SLUG*FT2 | KG*M2}"> {number} </iyy>
+ <izz unit="{SLUG*FT2 | KG*M2}"> {number} </izz>
+ <ixy unit="{SLUG*FT2 | KG*M2}"> {number} </ixy>
+ <ixz unit="{SLUG*FT2 | KG*M2}"> {number} </ixz>
+ <iyz unit="{SLUG*FT2 | KG*M2}"> {number} </iyz>
+ <emptywt unit="{LBS | KG"> {number} </emptywt>
+ <location name="CG" unit="{IN | FT | M}">
+ <x> {number} </x>
+ <y> {number} </y>
+ <z> {number} </z>
+ </location>
+ [<pointmass name="{string}">
+ <form shape="{tube | cylinder | sphere | ball}">
+ <radius unit="{IN | FT | M}"> {number} </radius>
+ <length unit="{IN | FT | M}"> {number} </length>
+ </form>
+ <weight unit="{LBS | KG}"> {number} </weight>
+ <location name="{string}" unit="{IN | FT | M}">
+ <x> {number} </x>
+ <y> {number} </y>
+ <z> {number} </z>
+ </location>
+ </pointmass>
+ ... other point masses ...]
+ </mass_balance>
+@endcode