When you are audited to AS9100C by a certification body auditor, they follow AS9101D which specifies the use of the PEAR to determine if your processes are effective. It is their way of determining if you have met element 8.2.3.
A PEAR (process effectiveness evaluation report) is used for each product realization process identified in your interaction of processes description. An interaction of processes description is a requirement for what needs to be included in your quality manual.
On the PEAR, after describing the process, it asks for your method of determining process effectiveness. That seems to usually be from tracking a KPI metric. Then the auditor evaluates if you are effectively monitoring that process. Next he grades you on how well you monitor that process. Any process that is not effectively monitored generates a major nonconformance. Any process that is monitored, is under goal, and you have not taken action to get on goal earns a nonconformance that can be either a major or minor depending on circumstances (auditor's judgement). Any process that is monitored and does not meet goal but you are doing something about it is OK. Then the ideal is when the process is monitored and you are meeting your goals.
I hope that helps.