Introduction to FMECA n What is a FMECA

Introduction to FMECA n 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 Slide 1 REL 103; 01202004

Why is it Important? n n 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 Slide 2 REL 103; 01202004

Definitions n FMECA - Failure Mode, Effects, and Criticality Analysis. n FMEA - Failure Mode and Effects Analysis. n COMPENSATING PROVISIONS - Actions available or that can be taken to lessen or eliminate the effect of a failure on a system. n NEXT HIGHER EFFECT - The consequence a failure mode has upon the operation, function, or status at the next higher level of assembly. n END EFFECT - The consequence a failure mode has upon the operation, function, or status at the highest level of indenture. Slide 3 REL 103; 01202004

How is it Done? 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. Slide 4 REL 103; 01202004

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. Slide 5 REL 103; 01202004

Simple Example: Flashlight (cont. ) How can it fail? What is the effect? Note Part that Next Higher Effect = End Effect in this case. Slide 6 REL 103; 01202004

Severity n 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. n The standard severities defined in MIL-STD 1682 may be used or equipment specific severities may be defined with customer concurrence (recommended). Slide 7 REL 103; 01202004

Simple Example: Flashlight (cont. ) n Severity – Severity I Light stuck in the “on” condition – Severity II Light will not turn on – Severity III Degraded operation – Severity IV No effect Slide 8 REL 103; 01202004

Simple Example: Flashlight (cont. ) Slide 9 REL 103; 01202004

Criticality n 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 Slide 10 REL 103; 01202004

Simple Example: Flashlight (cont. ) Slide 11 REL 103; 01202004

Simple Example: Flashlight (cont. ) Can circled items be designed out or mitigated? (There may be others that need to addressed also. ) Slide 12 REL 103; 01202004

Integrated FMECA n 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. ) l Integrating in this way can save considerable cost over doing the efforts separately and will usually produce a better product. l If possible, use the same analyst to accomplish these tasks for the same piece of hardware. This can be a huge cost saver. Slide 13 REL 103; 01202004

FMECA Facts and Tips n 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. n FMECAs take a lot of time to complete. n FMECAs require considerable knowledge of system operation necessitating extensive discussions with software/hardware Design Engineering and System Engineering. n Spend time developing groundrules with your customer up front. Slide 14 REL 103; 01202004