The configuration of a test facility that exists at the time when a correlation is being carried out should be "base lined" as a condition of correlation approval acceptance, and, be maintained during the time period that the respective correlation approval lasts. This defines test facility configuration control. This is due to the fact that a change in configuration may have the potential to change the established correlation factors and measured engine performance. If such a change occurs then this should be judged by the respective OEM's or designated correlation approval authorities Subject Matter Expert (SME). In some cases, this may involve consultation with the engine project customer or airworthiness authorities. This paper can be considered applicable to all types and standards of test facilies in the aero, marine and industrial gas turbine engine businesses.