Introduction to FMECA What is a FMECA? An Analysis technique which facilitates the identification of potential design problems by examining the effects of lower level failures on system operation. “Obviously, a major malfunction.” - Stephen A Nesbitt NASA Public Affairs Officer

Why is it Important? Provides a basis for identifying root failure causes and developing effective corrective actions Identifies reliability/safety critical components Facilitates investigation of design alternatives at all stages of the design Provides a foundation for other maintainability, safety, testability, and logistics analyses

Definitions FMECA - Failure Mode, Effects, and Criticality Analysis. FMEA - Failure Mode and Effects Analysis. COMPENSATING PROVISIONS - Actions available or that can be taken to lessen or eliminate the effect of a failure on a system. NEXT HIGHER EFFECT - The consequence a failure mode has upon the operation, function, or status at the next higher level of assembly. END EFFECT - The consequence a failure mode has upon the operation, function, or status at the highest level of indenture.

How is it Done? Note: This is a bottoms up example. What are the effects of box failures on the system? What are the effects of board failures on the box? What are the effects of part failures on the board? Note: This is a bottoms up example. Top down examples are possible.

Simple Example: Flashlight This flashlight is for use by special operations forces involved in close combat missions (especially hostage rescue) during low visibility conditions in urban areas. The light is to mounted coaxially with the individual's personal weapon to momentarily illuminate and positively identify targets before they are engaged. The exterior casing including the transparent light aperture are from an existing ruggidized design and can be considered immune to failure.

Simple Example: Flashlight (cont.) How can it fail? What is the effect? Note that Next Higher Effect = End Effect in this case. Part

Severity SEVERITY classifies the degree of injury, property damage, system damage, and mission loss that could occur as the worst possible consequence of a failure. For a FMECA these are typically graded from I to IV in decreasing severity. The standard severities defined in MIL-STD1682 may be used or equipment specific severities may be defined with customer concurrence (recommended).

Simple Example: Flashlight (cont.) Severity Severity I Light stuck in the “on” condition Severity II Light will not turn on Severity III Degraded operation Severity IV No effect

Simple Example: Flashlight (cont.)

Criticality CRITICALITY is a measure of the frequency of occurrence of an effect. May be based on qualitative judgement or May be based on failure rate data

Simple Example: Flashlight (cont.)

Simple Example: Flashlight (cont.) Can circled items be designed out or mitigated? (There may be others that need to addressed also.)

Integrated FMECA FMECAs are often used by other functions such as Maintainability, Safety, Testability, and Logistics. Coordinate your effort with other functions up front Integrate as many other tasks into the FMECA as possible and as make sense (Testability, Safety, Maintainability, etc.) Integrating in this way can save considerable cost over doing the efforts separately and will usually produce a better product. If possible, use the same analyst to accomplish these tasks for the same piece of hardware. This can be a huge cost saver.

FMECA Facts and Tips FMECAs should begin as early as possible This allows the analyst to affect the design before it is set in stone. If you start early (as you should) expect to have to redo portions as the design is modified. FMECAs take a lot of time to complete. FMECAs require considerable knowledge of system operation necessitating extensive discussions with software/hardware Design Engineering and System Engineering. Spend time developing groundrules with your customer up front.