FMEA explained: Failure Mode and Effects Analysis
How Failure Mode and Effects Analysis (FMEA) works: the difference between DFMEA and PFMEA, the severity, occurrence and detection ratings, and how RPN and Action Priority prioritize risk.
Failure Mode and Effects Analysis (FMEA) is a structured, proactive method for finding the ways a design or process can fail, judging how serious and how likely each failure is, and deciding where to act before failures reach the customer. It is a core tool in automotive and aerospace quality, and a common requirement inside a broader approval process. This guide covers the types of FMEA, the ratings that drive it, and how risk is prioritized.
DFMEA vs PFMEA
The two most common forms differ by what they analyze. A Design FMEA (DFMEA) examines how a product’s design could fail to meet its intent: a dimension, a material, an interface. A Process FMEA (PFMEA) examines how a manufacturing or assembly process could produce a non-conforming result: a missed operation, a wrong setting, a handling error. Both use the same rating logic; they differ in scope and in who owns them.
Severity, occurrence and detection
For each potential failure mode, an FMEA rates three factors, typically on a 1–10 scale:
| Rating | Question it answers |
|---|---|
| Severity (S) | How serious is the effect of the failure? |
| Occurrence (O) | How likely is the cause to happen? |
| Detection (D) | How likely are current controls to catch it first? |
The traditional score is the Risk Priority Number: RPN = S × O × D. A higher RPN flags a failure mode for action. The current AIAG-VDA FMEA handbook replaces a single RPN threshold with an Action Priority (High / Medium / Low) that combines the same S, O, and D more carefully. The aim is the same: focus effort where the risk is greatest.
RPN is a prioritization aid, not a verdict. A failure mode with a modest RPN but a severity of 9–10 (a safety effect) can still demand action regardless of the product, which is exactly why Action Priority weights severity first.
How FMEA fits the wider quality toolkit
FMEA rarely stands alone. A PFMEA feeds directly into a control plan, which defines the checks that catch the high-risk failure modes on the line, and real failures captured in non-conformance reports feed back to update the FMEA. In automotive, the FMEA and control plan are both elements of the PPAP submission. Because an FMEA is a living, controlled document that is revisited whenever the design or process changes, it benefits from a structured, version-controlled format. DataSheets Pro provides a structured starting point; the analysis and rating scales remain your responsibility.
Start from the templateFMEA template: free & editable
Analyze how a product or process can fail, rank the risks and drive actions, then export a print-ready FMEA as a PDF, free to start.
Open the template →Standardize this in DataSheets Pro
Turn what you just read into a repeatable, on-brand template, with no design tools required.