FMECA Plus: “Extending the Relevance and Utility of the Traditional FMECA”

 

The most notable and valuable enhancement to eXpress is the FMECA Plus. FMECA Plus provides any of the needs and expectations of Traditional FMEAs and FMECAs (e.g. 1629A, SAE J1739, etc.), but most importantly, transcends the limitations of other commercially available tools and independent, single-purpose practices.

FMECA Plus offers a revolutionary and powerful capability that is able to quickly associate Diagnostic Information with Reliability and Maintainability information at any time during the product or Integrated Systems’ Life Cycle.

FMECA Plus provides a multi-purpose solution from the leveraging of data from various traditional resources or data products typically used for independent purposes. Then, FMECA Plus will leverage eXpress’ ability to repeatedly capture, (re)structure and (re)organize data at will. Since the data in FMECA Plus is mapped to the eXpress Diagnostic capability of the design, it also provides a flexible environment that can assess and represent any “actual” or future modification(s) of the design(s) – thus exhaustively mapping any new data source into a form that seamlessly, consistently and immediately represents the fielded state of the design – today and tomorrow.   

 

New Relevance

  • A collaborative instrument between all design and support activities
  • Easily developed, re-propagated and restructured, all automatically through eXpress
  • Reflects current status as determined by multidisciplinary project activity through integrated system development and support
  • Considers Operation and Maintenance, including PHM, objectives and constraints versus FTA static Failure Probabilities
  • Captures and interrelates design knowledge across wide selection of alternative configurations
  • Integrates maintenance requirements and capabilities from LSA with test requirements and capabilities from Test Engineering

New Utility
  • Unites, updates and leverages a central and shared data base
  • Captures data from existing data sources including various Reliability Tools
  • Effectively supports the integration of a myriad of design and support “processes” as well as providing requirements traceability
  • Provides dynamic interoperability and extends the useful life of the static FMECA
  • Facilitates FMECA consistency, repeatability and traceability across the multi-disciplined projects


Predefined FMECA Plus Configurations

The FMECA Plus engine in eXpress provides the analyst with nine predefined configurations—six categorized as “eXpress Charts” and three categorized as “Traditional Worksheets.” It must be remembered that analysis is in no way limited to these nine configurations (which should be thought of as useful demonstrations of the FMECA Plus capability, rather than as definitive “outputs” of eXpress). Analysts can customize these charts not only by reorganizing, re-labeling and regrouping columns, but also by inserting additional calculated or attribute-based columns to support their specific needs. Customized chart configurations can then be saved for later reuse.

eXpress Chart Configurations

FMECA Plus provides the following six predefined “eXpress Chart” configurations:

  • eXpress Diagnostic FMEA Chart
  • eXpress Critical Failure Diagnosis Chart
  • eXpress Risk Priority Assessment Chart (Brief)
  • eXpress Risk Priority Assessment Chart (Detailed)
  • eXpress Fault Signature Analysis Chart
  • eXpress Diagnostic Coverage and Remediation Chart


The columns in each of these six charts are based solely on data contained within the specified eXpress model or diagnostic study—there is no need for analyst-supplied attributes other than the failure rates and severities that are already used for diagnostic analysis.

  


Traditional Worksheet Configurations

The following three “Traditional Worksheets” are also provided among the predefined FMECA Plus configurations:

  • Traditional FMEA Worksheet
  • Traditional Criticality Analysis Worksheet
  • Traditional FMECA Worksheet with Maintainability Info

The three predefined “Traditional Worksheet” configurations are based on FMECA and Criticality Analysis worksheet formats defined within MIL-STD-1629A (Procedures for Performing a Failure Mode, Effects and Criticality Analysis).

Configuration Descriptions

eXpress Diagnostic FMEA Chart

The eXpress Diagnostic FMEA Chart—the default configuration within FMECA Plus—takes an abbreviated FMEA chart and adds columns describing the frequency of occurrence (Failure Rate and Failure Ratio) and the diagnostic coverage (Failure Detected and Fault Group Sizes) for each failure.

By linking standard FMEA data to analysis results in an eXpress Diagnostic Study, this chart allows the efforts of both Reliability Analysts and Diagnostic Engineers to be presented in a manner that not only extends the activities within both disciplines, but also satisfies contemporary contract requirements that actual (rather than speculative) diagnostic design characteristics be referenced within the FMEA.

The analyst can easily customize eXpress Diagnostic FMEA Chart by adding additional diagnostic or attribute-based columns.

 

eXpress Critical Failure Diagnosis Chart

The chart produced by this configuration provides analysts with an excellent tool for determining how well critical failures are handled by system diagnostics. When standard FMECA activities examine the diagnosis of a critical failure, they usually consider it sufficient to indicate whether or not that failure can be detected by the diagnostics. Although useful for minimizing the likelihood that a non-detected fault will result in a catastrophic system failure, standard FMECA analysis techniques offer very little to help analysts identify and eliminate other consequences of poorly-developed diagnostics, such as inflated False Alarm rates or large numbers of unnecessary System or Mission Aborts.

The “Uniquely Isolated” column, for instance, indicates whether or not the set of failure modes that are indicted (called into suspicion) by the diagnostics when this failure occurs are all possible root causes of this failure. If the fault group associated with this failure contains any failure modes that are not a root cause of that failure, then the failure is not uniquely isolated by diagnostics. The non-unique isolation of critical failures is a primary driver of false alarms and unnecessary system or mission aborts.

  



 

eXpress Fault Signature Analysis Chart

This configuration reinterprets the basic concept of failure-mode-and-effects to mean failure-mode-and reported-fault-signature. For each possible failure, this chart will list all tests within specified test sets that would fail if the given fault were to occur.

The eXpress Fault Signature Analysis Chart—by showing how each failure will manifest itself as a set of reported fault codes—allows the development of embedded diagnostics to be coordinated with diagnostic analysis efforts. As a result, fault signatures will be produced for each specific failure/cause pairing (to correctly represent the different fault signatures that will be reported when a failure results from different causes).

  



 

eXpress Diagnostic Coverage and Remediation Chart

The final “eXpress chart” configuration produces a detailed analysis of how well each failure can be detected and isolated by the diagnostics. When generated for a diagnostic study that represents the operational diagnostics for a system or device, then this chart can be used to supplement information presented in the eXpress Fault Signature Analysis Chart. When generated using a diagnostic study representing maintenance or “troubleshooting” diagnostics, however, this chart becomes a valuable indication of which failures will be effectively diagnosed during maintenance.

Traditional FMEA Worksheet

The Traditional FMEA Worksheet is based on the “Failure Modes and Effects Analysis” worksheet format defined in MIL-STD-1629A and contains all columns shown on page 101-11 (Figure 101.3) of the standard. Several of the columns in this chart (Item, Failure Modes, Failure Effects, Compensating Provisions and Severity Class) can be easily derived from standard elements within an eXpress model. There are also, however, columns that contain special IDs (Identification Number) or narrative descriptions (Function, Causes, Mission Phase/Operational Mode, Failure Detection Method, Remarks) that are drawn from user-defined attributes within the eXpress model. These attributes can be quickly and easily added to the model by subscribing to the “Traditional FMECA Worksheet Columns.ext” design template. Specific attribute values can then be imported into eXpress from the appropriate Reliability resources.

Note that, in this chart, data is derived from an eXpress design, but not from a diagnostic study. The one diagnostics-related column—Failure Detection Method (a narrative description of how the failure will be detected by the operator)—is filled using a special attribute associated with object failure effects. If the analyst wishes to tie their FMEA to their diagnostic analysis in eXpress, they can replace the Failure Detection Method column with the Detection Test(s) column or add columns based on user-defined attributes associated with the tests in the eXpress design that are actually used to detect the failure.

  



 

Traditional Criticality Analysis Worksheet

The Traditional Criticality Analysis Worksheet is based on the “Criticality Analysis” worksheet format
defined in MIL-STD-1629A and contains all columns shown on page 102-6 (Figure 102.1) of the standard. Several columns in this chart (Item, Failure Modes, Severity Class, Failure Mode Ratio, Item Failure Rate) can be derived from standard elements within an eXpress model. There are also columns that contain IDs (Identification Number), narrative descriptions (Function, Causes, Mission Phase/Operational Mode, Failure Rate Data Source, Remarks), and numeric values (Failure Effect Probability, Operating Time) that are drawn from special attributes that must be added to the eXpress model. The specific attributes required by this worksheet can be easily added to the eXpress model by subscribing to the “Traditional FMECA Worksheet Columns.ext” design template. Specific attribute values can then be imported into eXpress from the appropriate Reliability resources.

Traditional FMECA Worksheet with Maintainability Info

The Traditional FMEA Worksheet with Maintainability Info is based on the “Failure Mode Effects and Criticality Analysis—Maintainability Information” worksheet format defined in MIL-STD-1629A and contains all columns shown on page 103-3 (Figure 103.1) of the standard.

Several of the columns in this chart (Item, Failure Modes, Failure Effects, Severity Class) can be derived from standard elements within an eXpress model. There are also, however, columns that contain IDs (Identification Number) or narrative descriptions (Function, Causes, Failure Predictability, Failure Detection Means, Basic Maintenance Actions, Remarks) that are drawn from special user-defined attributes within the eXpress model. The specific attributes used by this worksheet can be easily added to an eXpress design by subscribing to the “Traditional FMECA Worksheet Columns.ext” design template. Specific attribute values can then be imported into eXpress from the appropriate Reliability resources.

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