Development data include built-in-test (BIT)
effectiveness information, such as fault detection and fault-isolation
performance, and repair data. Whenever failures occur during development or
demonstration testing (such as a reliability demonstration test), the results
of fault isolation, such as time to isolate, ambiguity levels, and resources
expended should be recorded. Any problems noted during troubleshooting of
failures should also be recorded. Such information should be tied to the
failure information, such as failure mode and cause, so that the effectiveness
of any diagnostic elements in correctly detecting and isolating the fault can
be determined. If the fault was a false alarm detected by system BIT, this
fact should also be recorded. If such a problem continues to exist, then an
analysis will be required to determine why the problem exists and how it can
be fixed. In addition to diagnostic data, data on repair actions should also
be collected. Once again, information on repair times, resources and any noted
problems should be collected. All data should continuously be reviewed to
determine if corrective actions are necessary to improve maintainability.
These reviews should be done in conjunction with and as part of a failure
reporting, analysis and corrective action system, or FRACAS. Although most associated with reliability programs, FRACAS is a closed-loop data reporting system for the purpose of systematically recording, Analyzing, and resolving equipment reliability AND maintainability problems and failures.
To benefit from a FRACAS, the maintainability manager must closely coordinate with the reliability manager to ensure that maintainability data are incorporated into a FRACAS data collection form. An example of a FRACAS form, showing blocks for maintainability data (highlighted) is presented as
Figure 18. In addition to collecting maintainability data resulting from actual failure occurrences, information from maintainability simulations should also be
documented. This information would include BIT coverage values derived via fault simulations and the results of simulating product repair procedures.
Figure 18 - Example FRACAS