Limitations and Effects Analysis (FMEA)

Origin. US military procedure MIL-P-1629 (1949); adopted in aerospace and automotive.

Mechanism. Enumerates Limitationss per component, scores each on severity, occurrence, and detection, and prioritizes by their product. It converts a qualitative worry into a ranked, auditable list.

Procedure. Decompose the system. For each component enumerate the ways it can fail, the effects of each failure, its causes, and existing controls. Score S, O, D on 1–10. RPN = S × O × D. Act on the top band, and separately on everything with S = 9 or 10 regardless of RPN.

Applies to. Safety-critical and high-volume systems.

Limitations. RPN is a product of ordinal scales and is therefore not a meaningful quantity — the ranking it induces is an artifact of the scale's granularity. AIAG-VDA replaced it with Action Priority for exactly this reason. It also finds only the Limitationss of components that were enumerated, and misses interaction failures entirely.