Abstract: A method of diagnosis and prognosis for various operative systems is provided so that maintenance can be efficiently and effectively scheduled and provided. The invention is applicable to a broad range of systems, but particularly to aircraft brake systems and tires. An aircraft brake may be modeled by attributing brake wear factor values to various parameters associated with the aircraft brake that impact wear. Over the course of time and during braking events, the brake wear factor values are summed and a running total of that sum is kept over the life of the brake. At a point in time when the sum of weighted factors exceeds a preset threshold, an indicia is generated that service is required.