FMECA Planning
Planning the FMECA work involves the contractor's procedures for implementing their specified requirements. Planning must include updating to reflect design changes and analysis results. Worksheet formats, assumptions, ground rules, failure definitions, recognition of the level of analysis, and recognition of coincident use of the FMECA by the contractor and other organizational elements should also be considered.
Ground Rules and Assumptions
The ground rules recognize the FMECA approach (e.g., hardware, functional or combination), the lowest level to be analyzed, & include statements of what may constitute a failure in terms of performance criteria. Every effort must be made to identify and record all ground rules & analysis assumptions prior to initiation of the analysis; though, ground rules and analysis assumptions might be adjusted as requirements change.
Variations in design complexity & available data will usually dictate the analysis approach to be utilized. There are two prime approaches for the FMECA. One is the hardware approach that lists specific hardware items & analyzes their probable failure modes. The other is the functional approach that identify that every item is designed to perform a number of outputs. The outputs are listed down and their failures analyzed. For more complicated systems, a combination of the functional & hardware approaches may be considered.
The hardware approach is normally used when hardware items can be uniquely identified from schematics, drawings, & other engineering & design data. This approach is suggested for use in a part level-up approach frequently referred to as the bottom-up approach.
The functional approach is normally utilized when hardware items cannot be uniquely identified or when system complexity needs analysis from the top down.
Level of Analysis
The level of analysis applies to the system hardware or functional level at which failures are postulated. In other terms, it is how the system being analyzed is segregated (e.g., a section of the system, sub-component, component etc.).
It is a common statement of what constitutes a failure of the item in terms of performance parameters and allowable limits for each specified output.
These reports should identify areas of marginal and state-of-the-art design and explain any design compromises and operating restraints agreed upon. This information shall aid in determining the possible & most probable failure modes & causes in the system.
Design data and drawings identify each item and the item configuration that perform each of the system functions. System design data & drawings shall usually explain the systems internal and interface functions beginning at system level and progressing to the lowest indenture level of the system. Design data shall usually include either functional block diagrams or schematics that will facilitate construction of reliability block diagrams.