2.3.4.6 Maintainability requirementsThe MTTR/MTTM (Mean Time To Repair / Mean Time To Maintain) includes the time for fault finding and fault diagnosis, replacement of faulty items, and the subsequent resetting or functionality testing. Times for transports, waiting for maintenance resources and documentation are not included, but the time for all preparatory tasks is.A Maintainability Demonstration Test (MDT) shall be required as part of the test program and shall be performed with the first article inspection (FAI) or with other test activities.