ORIGINAL: starfir
...By the way, what is Mass Balancing?
This is a flutter induced failure, it is not a simple hinge failure. This would have happened even if all hinges were perfect. When an airplane demonstrates known severe tendencys toward flutter, mass balance is the only simple fix and it will work every time. No matter what.
As Tweety correctly noted mass balancing is simply is extending fixed weight forward of the hingeline to partially balance that surfaces weight behind the hingeline. It does not have to be anywhere near the weight behind and it does not have to be anywhere near 100% balanced.
As little a a half ounce of lead imbeded on those aerodynamic balances of those elevators for that airplane would have prevented this elevator flutter. There are other ways of doing simple mass balances on different kinds of surfaces too and I have posted pics many times but mostly ignored. It mostly ends up in hinge discussions that really are not the culprit.
John