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Name as eXpress FMECA Column Header
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Name on Options Dialog
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Description
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Attribute Name
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(none)
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ID
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The numbered cells appearing in the left margin (or, when exported, in the first column).
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Item
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Item
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The name of the eXpress item associated with the given failure.
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Item / Functional Identification (Nomenclature)
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Failure
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Failure
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The name of an object failure effect associated with an eXpress item. This is treated as the “failure mode” for the given level of indenture.
(Note: An object effect on an assembly, although it constitutes the effect of a lower-level failure mode, can also be considered to be a failure mode of that assembly)
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Failure Modes
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Root Failure Mode Causes
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Root Failure Mode Causes
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The lowest-level failure modes that could result in the given failure.
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Failure Effects
Local Next Higher End Item
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Effects (Local + Next Higher
+ End Item)
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A trio of columns containing the eXpress design effects that include the given failure as a cause at:
1) the same level as the failure
2) one level above the failure
3) the top level
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Failure Effects
Local Effects Next Higher End Effects Level
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Compensating Provisions
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Compensating Provisions
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The compensating provisions included for each design failure effect in eXpress.
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Compensating
Provisions
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Severity Class
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Severity Class
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The greatest (most severe) of the severity settings associated with the given failure’s end item effects.
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Failure Ratio
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Failure Ratio
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For each given failure, its percentage of the associated item’s failure rate.
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Failure Mode Ratio
(alpha)
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Failure Rate
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Failure Rate
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The failure rate credited to the give failure. This can be computed by multiplying the Failure Ratio times the Item Failure Rate.
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Failure Detected
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Failure Detected
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“Yes” if all associated root failure mode causes can be detected by the strategy in the linked diagnostic study;
“No” if none of the root causes can be detected; and “Partially” if some, but not all, can be detected.
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Failure Detected
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Fault Group Sizes
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Fault Group Sizes
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The sizes of the various fault groups that can be isolated for the different Root FM Causes that could result in the given Failure. The size of an isolated fault group is the number of repair items in that group.
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Fault Group Sizes (Number of Items)
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Fault Groups Sizes
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Relative Criticality
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Relative Criticality (Modal)
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A number derived by multiplying the Failure Rate of the given failure by a percentage derived from the numeric equivalent of the associated severity class (for the most severe, 100%). This is similar to the RPN calculation, but 1) does not take Detection into consideration, and 2) is based on real, rather than integer, factors.
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Uniquely Isolated
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Uniquely Isolated
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This calculation looks at the lowest-level failure modes isolated for the given failure (different sets of failure modes may be isolated for different root causes). If each isolation contains no failure modes that are not root causes of the failure (if the fault groups all unambiguously point to the given failure), then “Yes” will be reported in this cell; otherwise, the cell will contain “No”.
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Number of Root FMs in Fault Groups
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Number of FMs Isolated
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The total number of lowest-level failure modes (not limited to the root causes of the given failure) that can be isolated to fault groups associated with that failure.
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Fault Groups
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Fault Groups
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The labels of the various fault groups that can be isolated for the different Root Failure Mode Causes of the given failure.
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Fault Groups Name
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Severity Rating S
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Severity Rating (for RPN)
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An integer from 1 to 10 (with 10 being the most severe) indicating the most severe end effect that could result from the given failure. This integer is derived by scaling the numeric Test limits assigned to the different severity classes into scale of 1 to 10.
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Occurrence Rating
O
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Occurrence Rating (for RPN)
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An integer from 1 to 10 (with 10 being the most frequent) indicating the frequency of occurrence of the given failure. This integer is derived by mapping the failure rates in eXpress to a predefined set of occurrence categories (with 10 being failures that occur more than 1/10 hours and 1 to failures that occur fewer than 1/10,000 hours).
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Overall Pctg. of Failure Detected
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Pctg. Detected (Overall)
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The percentage of the given failure’s failure rate that can be detected by tests in the specified diagnostic strategy.
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Detection Rating
D
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Detection Rating (for RPN)
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An integer from 1 to 10 (with 10 being the least detected) indicating the likelihood that given failure, when it occurs, will not be detected by the specified diagnostic strategy. This integer is derived by mapping the inverse of the detection pctg. for the given failure into a scale of 1 to 10.
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RPN (Risk Priority Number)
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An integer Test limit from 1 to 1000 reflecting the qualitative risk for a given failure (with 1000 being the highest possible risk). This Test limit is calculated by multiplying the Severity, Occurrence and Detection Ratings for the given failure. The highest RPNs in the chart will reflect the most severe, most frequent, yet least detectable failures. Conversely, lower RPNs will be assigned to failures that are less severe, less frequent and/or more detectable.
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End Item Effects
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End Item Effects
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The top level eXpress design effects that include the given failure among their lower-level causes.
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Detection Test(s)
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Detection Test(s)
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The test(s) in the specified diagnostic strategy that can be used to detect the given failure.
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Detection Tests Test Name
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Fault Signature
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Candidate Tests
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All of the tests (in specified test sets) that would fail if the given failure were to occur. For example, If the specified test sets contain individual Fault Codes, then this cell would contain the set of Fault Codes that would be reported when the given failure occurs.
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Fault Group Items
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Fault Group Items
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The eXpress items in the fault groups isolated for the different Root FM Causes that could result in the given Failure. (Note: if the failure can be isolated to multiple fault groups—due to different root causes of the failure— then this cell will contain the union of the items in all fault
groups that can be isolated for that failure.)
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Fault Groups Items
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Detection Tests Pctg. Detected
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Pctg. Detected by Test
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The percentage of the given failure’s failure rate that can be detected by a particular test in the specified diagnostic strategy.
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Identification Number
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Identification Number
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An eXpress text attribute (associated with Failure Effects) that typically contains the unique identification number associated with the given failure.
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Function
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Function
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An eXpress text attribute (associated with Objects) that typically contains a brief description of the function performed by the associated item.
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Causes
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Causes
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An eXpress text attribute (associated with Failure Modes) that typically contains a brief description of the failure mode (as a cause of higher-level effects or modes). The cause attributes for all root failure mode causes of the given failure will be appended within this cell.
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Mission Phase / Operational Mode
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Mission Phase/Operating Mode
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An eXpress text attribute (associated with Failure Effects) naming the mission phase and operational mode in which the given failure may occur.
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Failure Detection Method
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Failure Detection Method
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An eXpress text attribute (associated with Failure Effects) that typically contains a description of the methods by which the occurrence of the given failure is to be detected by the operator.
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Remarks
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Remarks
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An eXpress text attribute (associated with Failure Effects) that typically contains any pertinent remarks pertaining to and clarifying any other column in the worksheet for the given failure.
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Failure Rate Data Source
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Failure Rate Data Source
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An eXpress text attribute (associated with Objects) that typically contains a brief description of the source of the failure rates included in the worksheet.
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Failure Effect Probability (beta)
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Failure Effect Probability (beta)
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An eXpress real attribute (associated with Failure Effects) that typically contains the conditional probability that, if the given failure were to occur, it would result in an end item effect of the indicated severity.
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Item Failure Rate
(lambda)
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Item Failure Rate
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The total failure rate for the item associated with the given failure.
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Operating Time (t)
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Operating Time (t)
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An eXpress time attribute (associated with Objects) that typically contains the operating time per mission for the associated item.
(Note: although this Test limit may be entered using various units within eXpress—minutes, hours, days, etc.—these Test limits will all be converted into hours when calculating the Criticality of an item or failure mode.)
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Failure Mode Criticality
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Criticality (Modal)
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A real Test limit calculated as the product of a given failure’s
failure effect probability (beta), failure mode ratio (alpha), item failure rate (lambda) and operating time (t).
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Item Criticality
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Criticality (Item)
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A real Test limit calculated by summing the Failure Mode Criticality for each failure associated with a given item
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Failure Predictability
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Failure Predictability
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An eXpress text attribute (associated with Failure Effects) that typically contains a description of known incipient failure indications that might permit prognosis of the given failure.
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Failure Detection Means
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Failure Detection Means
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An eXpress text attribute (associated with Failure Effects) that typically contains a description of how the given failure will be detected by the organizational level maintenance technician and to what indenture level the failure will be localized.
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Basic Maintenance Actions
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Basic Maintenance Actions
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An eXpress text attribute (associated with Failure Effects) that typically contains a brief description of the basic
actions which, in the analyst’s judgment, must be taken by the maintenance technician to correct the failure.
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Affected Functions
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Affected Functions
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A list of the eXpress output functions that are directly affected by the given failure.
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Average Fault Group Size
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Avg. Fault Group Size
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The average size of the fault groups that can be isolated for the different Root Failure Mode Causes of the given failure. The size of an isolated fault group is the number of repair items in that group.
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Detection Test Set
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Detection Test Set
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The name of the eXpress test set(s) containing the test(s) that, in the specified diagnostic strategy, will be used to detect the given failure.
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Local Effects
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Local Effects
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The eXpress design effects—at the same level as the given failure—that list that failure as a cause.
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Maximum Fault Group Size
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Max. Fault Group Size
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The maximum size fault group that can be isolated for the different Root Failure Mode Causes of the given Failure. The size of an isolated fault group is the number of repair items in that group.
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Next Higher Effects
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Next Higher Effects
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The eXpress design effects—one level above the given failure—that include that failure as a lower-level cause.
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Object
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Object
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When an item is comprised of multiple objects at the same level, this cell will contain the label of the specific eXpress item associated with the given failure.
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Relative Item Criticality
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Relative Criticality (Item)
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A number derived for a given item by summing the Relative Criticality Test limits calculated for each failure mode
of that item.
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