1. A method of making a decision on a status of a mechanical system, comprising: selecting a mechanical system responsive to at least one operating input load so as to have an operating response to said at least one operating input load; collecting first data representing said at least one operating input load; collecting second data representing said operating response; generating an in-situ representation of said mechanical system as a function of said first data and said second data; assessing said in-situ representation so as to make a decision regarding the status of said mechanical system.