What is happening to the RPN?


  • One of the most significant (and some will say shocking) changes to the FMEA Process is the elimination of the RPN (Risk Priority Number) and its replacement with AP (Action Priority).

Why was the change made?

  • Some quality professionals have pointed out (for many years) that using the RPN to determine the priority of potential risks to tackle is a flawed approach.
  • The RPN is determined by multiplying the “Severity x Occurrence x Detection (or S x O x D)” rankings; this methodology sorts the potential 1,000 problem descriptions (10 x 10 x 10) into 120 groupings.
  • Unfortunately, the use of only 120 possible groupings with its corresponding limitation in discrimination can distort the importance of one potential risk relative to another.
  • And additionally, when the RPN is used to determine a rank order of action plans, some “severe” potential risks (with a Severity ranking of 9 or 10) may not get the attention that they should because low Occurrence and Detection rankings may drop the RPN below an actionable level.
  • The AIAG-VDA (draft) Manual states that the RPN method overlooks “rational logic” thereby allowing some combinations of S, O and D to be overlooked when mitigation action plans should have been initiated.
  • Don Wheeler, author, statistician and well-respected legend in the Quality field wrote about the shortcomings of the RPN in Quality Digest back in 2011.

Calculating the Action Priority (AP)

  • The new (draft) standard still uses the familiar Severity, Occurrence and Detection (S-O-D) and each can still range between 1 and 10.  However, instead of multiplying those three numbers, the AP is determined using a table that lists roughly 30 different combinations of S, O and D ranges.
  • Three unique AP Tables are proposed; one each for Design-FMEAs, Process-FMEAs and FMEA-MSRs (Monitoring and System Response). This is why we say “roughly” 30 different combinations of S-O-D.  There is a different number of combinations for each of the three AP Tables.
  • Each combination is associated with an Action Priority Logic.  The benefit of this is that it standardizes action priorities across all companies regardless of their products or processes.

Prioritizing Action Plans

  • Each of the roughly 30 “S-O-D” combinations are assigned a High (H), Medium (M) or Low (L)” designation for Action Priority.
  • For “Priority High,” action to improve prevention and/or detection controls (or justification on why current controls are adequate) MUST be taken.
  • For “Priority Medium,” action to improve prevention and/or detection controls (or justification on why current controls are adequate) SHOULD be taken.
  • For “Priority Low,” action to improve prevention and/or detection controls COULD be taken.


  • Replacing the RPN with the AP effectively removes a logic issue (associated with the use of RPN) that allowed some potentially high priority risks to escape attention.

Coming Up Next Week

We thought it was important to provide some insight into the replacement of the RPN with the AP before we dive into how the FMEA process will be modified.

In the next six weeks, you will get a better understanding of the six-steps of the new FMEA process as defined by the (draft) standard.

  • Step 1:  Scope Definition and Project Planning
  • Step 2:  Structure Analysis
  • Step 3:  Function Analysis
  • Step 4:  Feature Analysis
  • Step 5:  Risk Analysis
  • Step 6:  Optimization

After that, we will dig into details on the changes in the FMEA Form followed by changes to the Ranking Scales.

Scope Definition and Project Planning

More specificity is provided in the form of the “Five T’s”

The Six Step FMEA Process

The (draft) 2018 AIAG-VDA FMEA Handbook breaks all types of FMEAs down into six steps:

  1. Scope Definition and Project Planning
  2. Structure Analysis
  3. Function Analysis
  4. Failure Analysis
  5. Risk Analysis
  6. Optimization

The first three steps are focused on System Analysis.  The second three steps deal with Failure Analysis and Risk Mitigation.

The 6-Step FMEA Process represents a systematic approach for conducting an analysis of the potential failures modes and their corresponding effects (of products or processes) using a standardized method to document the risk assessment.

We like that AIAG-VDA has defined a clear step-by-step process. In fact, if you have taken our FMEA training, you know that we have always presented FMEAs in terms of 10 steps.

This and the next five weeks we will be walking through each of the six steps.

Step 1: Scope Definition and Project Planning

Step 1 covers the scope definition, project team make-up and project planning aspects of the study.


Define what is included as well as what is excluded from the scope of the FMEA. A clear definition of the scope minimizes the probability of “scope creep.”

  • For a DFMEA, define aspects of the (product) design and its components and subassemblies that are to be included in the study and those that are to be excluded.
  • For a PFMEA, the scope defines the boundaries of the process to be studied, indicating whether the “entire” process including support utilizes should be studied or only the “base” process (without support processes) should be studied.
  • For a FMEA-MSR (Supplemental FMEA for Monitoring and System Response), the scope should define which sensors, control units and actuators with their corresponding hardware and software should be studied for safety relevance, safety goals (according to ISO 26262) and (legislative) regulatory requirements.

The management team is responsible for setting the scope of the study. If the team finds it necessary to go beyond the original scope, that expansion should be confirmed with, and approved by, the management team.

Project Plan

The following “Five T’s” from the draft standard should be covered in the FMEA kickoff meeting.

Team | Who needs to be on the team?

The make-up, roles and responsibilities of the team are covered in this section.
Project teams conducting FMEAs are comprised of a Core Team plus an Extended Team of subject matter experts called upon when needed.

  • The Core Team should include a group of people with multi-disciplinary, cross-functional backgrounds and experiences.  Core Team roles include an overall (FMEA) Project Manager, Technical Lead and Facilitator. The make-up of the Core Team for DFMEAs, PFMEAs and FMEA-MSRs will involve members with different disciplines and backgrounds representing applicable subject matter experience and expertise.
  • An Extended Team of subject matter experts should be available to support the Core Team on an as-needed basis.

Timing | When is this due?

Using FMEAs early in the development process can mitigate risks that may be more difficult and costly to address later. Conducting an FMEA in each of the 5 sequential phases of the APQP process is recommended.

  • APQP Phase 1: Plan and Define the Program
  • APQP Phase 2: Product Design & Development Verification
  • APQP Phase 3: Process Design & Development Verification
  • APQP Phase 4: Product & Process Validation
  • APQP Phase 5: Feedback, Assessment & Corrective Action

inTent | Why are we here?

Every FMEA Team member should have had training in the intent, purpose and methodology of the 6-Step FMEA Process. Participating in an FMEA study requires a commitment in both time and effort; team members must be aware of the time requirements and be willing and able to meet that obligation.

Tools | How do we conduct the analysis?

Commercial software packages, use of a Structure Tree or a Spreadsheet are all acceptable methods of documenting the results of the FMEA study.

Tasks | What work needs to be done?

A primary task of the FMEA Team is to complete the 6-Step Process, resulting in the following deliverables:

  • Identify and evaluate potential risks of failure.
  • Analyze the causes and subsequent effects of failures (if a failure does occur).
  • Describe and characterize existing preventive and detection controls.
  • Recommend actions to mitigate or reduce risks.

Upon completion and documentation of the FMEA study, the team will review their outcomes and recommendations with management (and customers if appropriate). Which action plans and who will be tasked with implementing them will be determined with guidance from management.

  • Items not requiring action should be marked as “No revision planned” to indicate that the risk assessment was completed.
  • Items requiring action will be marked as Open, Decision Pending, Implementation Pending. Discarded or Completed to indicate the status of the actions.

FREE DOWNLOAD | FMEA Preparedness Checklist

We recommend that a standard checklist be used at the beginning of any FMEA to make sure the organization has planned adequately for the study.  We have a new PDF version of our FMEA Preparedness Checklist for the 2018 AIAG-VDA FMEA. It will help you identify and gather the information needed to effectively and efficiently begin the FMEA study.

FMEA Step 2

Structure Analysis

Breaking down the system for a comprehensive risk analysis.
This week look at Step 2 of the new (draft) AIAG-VDA FMEA Process. But, before we jump into the details, here is some context behind what motivated the detailed analysis in Steps 2 and 3.  Bear with us; this short discussion may help you better appreciate the changes.

Background for the changes in the AIAG-VDA FMEA Steps 2 and 3

The 4th Edition of the AIAG FMEA Handbook explains what each column in the FMEA worksheet is for, but the format doesn’t “encourage” the FMEA team to dig deeply into the item or process step.  According to an AIAG presentation document highlighting “Change Points,” the methodology in the 4th Edition Handbook can lead to completing an FMEA using a “fill in the blanks” approach; we agree.
Typically, a team would start with the first column and identify an “item” for a Design-FMEA or a “process step” for a Process-FMEA.  The team would then work their way across the worksheet for that item or process step only to return back to the beginning of the worksheet to list the next item or process step and again work their way across the worksheet.

With the revised FMEA process, what was the first column in the 4th Edition FMEA Worksheet is now actually six columns – columns one through three are completed in Step 2: Structure Analysis and the fourth through sixth columns are completed in Step 3: Functional Analysis. The expectation is that this will help the FMEA Team complete a more thorough (effective) analysis. Equally important, it is anticipated that this “step analysis method” will ultimately be faster (more efficient) for FMEA teams because it clearly separates the logical, “left-brain” task of assigning Severity, Detection and Occurrence Ratings from the more creative, “right-brain” task of failure analysis.

This diagram shows that the intention of the New AIAG-VDA FMEA process is to complete data documentation for each step in its entirety before moving on to the next step.
This graphic is from AIAG’s FMEA Workshop Update on the AIAG-VDA FMEA Harmonization Project presented on September 19, 2017.


This new process is expected to speed up conducting FMEAs.  Of course, this is yet to be proven in practice, but we believe that your FMEAs will be more valuable, they will be easier for teams to work through and will reduce the chance of your teams getting off-track from the task at hand.

So, with this background, here is a summary of Step 2 of the new AIAG-VDA FMEA Process: Structure Analysis.

Step 2: Structure Analysis

Structure Analysis is used to identify and breakdown the system (design or process) into the system, subsystems and component elements so that a comprehensive risk assessment can be conducted.

Regardless of the type of FMEA (design, process or MSR), tools such as block diagrams and structure trees are used to create a visualization of the design or process.  This helps the team stay focused on the task at hand without ignoring downstream and upstream impacts the item or process step has on performance.

The Structure Analysis is the basis for Step 3: Function Analysis

Because of the unique differences between Design, Process and FMEA-MSRs, we will handle each type separately as it is done in the draft handbook. Depending on your job responsibilities, you may not need  to know how all three work, so feel free to skip ahead to the information relevant to your work.
A DFMEA Structure Analysis uses the boundaries set by the Scope Definition (Step 1) to identify the overall (design) system, subsystem(s), assemblies and/or components to be studied for a (System or Component) DFMEA.

  • It is important that the DFMEA Team understand the chain of customers to effectively identify the various functions, requirements and specification of the design elements so that potential effects of failure modes can be correctly categorized.  Customers include:
    • The chain of (internal or external) manufacturing or assembly operations using the design
    • The eventual End User
  • A Block (or Boundary) Diagram or a Structure Tree (or Tree Diagram) is useful to provide a visual representation of the design.  Editorial note: We suggest a detailed blueprint can also be used.
    • A Block Diagram delivers a visual depiction of the entire system or design, showing the boundaries of the FMEA (i.e. what is and is not included) and noting every interface between the system elements.
    • A Structure Tree shows the hierarchy of a structure (system) in a graphical form.
    • Editorial note: A spreadsheet can be used to represent the system structure. A detailed blueprint or drawing of the design (system, subsystem or component) noting all interfaces can provide another valuable perspective for the team.
  • All interfaces, interactions and other relationships between system elements must be noted including:
    • Physical connections, energy transfers, supporting or conditioning features and data exchanges should all be noted.
    • It is vital to study interfaces because they can often account for a significant portion of failure modes.  Don’t forget to investigate the interfaces between subsystems, assemblies and components in addition to those that are part of the system elements themselves.
This diagram shows how the “Item” column for DFMEAs from the AIAG 4th Edition FMEA will become three columns under the heading of Structure Analysis. This graphic is from AIAG’s FMEA Workshop Update on the AIAG-VDA FMEA Harmonization Projectpresented on September 19, 2017.
A PFMEA Structure Analyses uses the boundaries set by the Scope Definition (Step 1) to identify and breakdown the process flow into Process Items, Process Steps and Work Elements.

  • A Process Flow Diagram or a Structure Tree (or Tree Diagram) provide a visual representation of the process.  Editorial note: A detailed “traveler” (work instructions) may also be used to document the process flow.
  • A Process Flow Diagram depicts all the process operations that are required to produce the manufactured or assembled product that fall within the scope of the PFMEA study.
  • Editorial note: We find it useful to use a Top-Down Process Flowcharting approach where each major step of the Top-Down Flowchart represents a Process Item.  Transactional (i.e. office or service) processes can also be effectively analyzed with Top-Down Process Flowcharts. 
  • Process Flow Diagrams, Structure Trees and Travelers can be used as the input for a spreadsheet representing the system structure.
This diagram shows how the “Process Step” column for PFMEAs from the AIAG 4th Edition FMEA will become three columns under the heading of Structure Analysis. This graphic is from AIAG’s FMEA Workshop Update on the AIAG-VDA FMEA Harmonization Projectpresented on September 19, 2017.
The structure of an FMEA-MSR (FMEA for Monitoring and System Response) is typically comprised of both hardware and software elements . The FMEA-MSR is a new addition to the types of FMEAs making its debut in the 2018 AIAG-VDA FMEA Handbook. Here is a concise article describing exactly what an FMEA-MSR is.

  • Two methods are generally used to visualize a MSR System Structure:
    • Block (or Boundary) Diagrams defne the scope of the design typically from a sensor to a control unit to the source of engagement (i.e. a motor).
    • A Structure Tree can be at the fully assembled level (i.e. a vehicle) or it can be at an interface (i.e. limiting the analysis to a subsystem or component).
    • Editorial note: A spreadsheet can be used to represent the system structure.
  • Many FMEA-MSR analyses involve “mechatronics,” a multidisciplinary field that combines traditional mechanical and electronics systems with computer, telecommunications, and control technologies as applicable.
new FMEA process : AIAG and VDA converge: New process, RPN gone and new FMEA – MSR is required

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