FRACAS: An Essential Element In The TAAF Process
A disciplined and aggressive closed-loop FRACAS must be a part of the TAAF process. The essence of a closed-loop FRACAS is that:
- failures and faults of both hardware and software are formally reported,
- analysis is performed to determine the failure cause, and
- positive corrective actions are identified, implemented, and verified to prevent further recurrence.
All failures must be analyzed to the extent necessary to determine their root causes. In many cases the cause of the failure will be readily apparent, as with test procedure errors, wrong parts, overstressed parts, workmanship errors, etc. Corrective actions for many of these types of failures will also be relatively straightforward and easily implemented.
Determining the root cause of more complex failures and developing corrective actions early in the development process are crucial, even though the effort may be costly and time consuming. The dollars spent and time expended will still be greatly less than waiting until later in the acquisition process to correct the failure. And, corrective action options are more numerous early in the design evolution, when even major design changes can be considered in order to eliminate or significantly reduce susceptibility to known failure models.
If reliability growth tests are to be interpreted correctly, all test conditions and occurrences must be recorded accurately and completely. Temporary repairs/replacements are usually permitted so that testing may continue while permanent fixes are being explored. The implications of failure differ both qualitatively and quantitatively between repairs and fixes - a repeat failure after repair simply provides more data on the same phenomenon, while a repeat after a "fix" may invalidate the corrective action. An accurate test log can prevent misinterpretation of results.
Limits to the resources in time, money and engineering manpower to expend on an analysis of a particularly complex failure mode or the implementation of corrective actions must be determined by management by assessing:
- item priority,
- program urgency,
- available technology, and
- engineering ingenuity.