Central Maintenance Computer (CMC) Data Logging automatically stores avionics data, events/faults, exceedances, and aircraft logs. Each designated GDU allocates 8 GB of non-volatile internal memory dedicated for CMC data log storage. This feature is useful for system integration, maintenance diagnostics, maintenance scheduling, return to service, and in-flight reporting of failure status.

All CMC data logged on a specific date is stored in a file named in a format which includes the aircraft bureau number, engine serial numbers, flight date, and time. The file is created automatically each time the system is powered on. The .csv file may be viewed with Microsoft Excel or other spreadsheet applications.

The file containing CMC recorded data will appear in the format shown in the following figure. This file can be imported into most computer spreadsheet applications.

The following image is an example of how the file could be named.