When planning fact gathering, the analyst should remember that events
occur along a time line, and that failure can occur many weeks or months
after the root cause event happens. For example, a cooling system
problem can overheat an engine for a short time, damage pistons, be
corrected, and not cause immediate failure. The operator may then run
the engine with damaged pistons for many days or weeks before piston
failure occurs. As the failure progresses performance may still be "good."
Only after failure occurs is performance "bad." If no root cause facts are
found just before failure, the analyst should begin gathering facts from the
past.ns.