Criticality Matrix

The criticality matrix provides a means of identifying and comparing each failure mode to all other failure modes with respect to severity.

The Criticality matrix plots the criticality number on a logarithmic scale along the y-axis, while the x-axis displays the severity classification.

Criticality Number (C_m)

Criticality number is a semi-quantitative measure of a failure path leading to an end effect.

The equation for C_m is expressed as: C_m = β × α × λ × t

Where:

• α is the failure mode ratio
• β is the probability of the failure mode leading to an end-effect of a given severity classification (estimated by the engineer)
• λ is the item failure rate per million hours
• t is the operating time based on the applied mission profile

Item Criticality Number (C_r)

The sum of all failure mode criticality numbers for an item.

The equation for C_r is: C_r = Σ C_m

Since item Reliability data can refer to either physical faults or functional failure modes, MADE allows the user to decide which type of data to input for the calculation of C_m.

Severity Classification

Ranking	Category	Severity Class	Description
10	Catastrophic	I	Loss of mission and aircraft, injury to pilot.
7 - 9	Critical	II	Loss of mission, extensive repairs required.
4 - 6	Marginal	III	Degraded mission, significant repairs required.
2 - 3	Minor	IV	No effect on mission, some repairs/maintenance required.
1	Minor	IV	No effect on mission, minor repair/maintenance required.

Operating Time

Operating time is taken from the Duration of Operation for the given System.

To set this value, select (right-click) an item from the Project Explorer and select the 'Advanced Properties' option. Next, modify the Duration of Operation or select a mission profile if one has been assigned.

Part Failure Rate

The Part Failure Rate is a property of a Component or Part. To change part failure rate for a model item:

• Select the 'Criticality & Reliability Editor' option from the Analysis menu
• Select the 'Reliability' from the drop-down list in the Element Selection section
• Enter values into the General Reliability fields and select a Failure Distribution Type (Exponential or Weibull)
• Enter MTTF, Part Failure Rate & Standard Deviation for the Exponential distribution type
• Enter Slope, Characteristic Life, Mean Characteristic Life, and Standard Deviation

Alternatively, part failure rate can be accessed and edited from the Properties viewer:

• Select the RAM Module from the Icon Menu
• Select an item in the System Model editor
• Select the 'Reliability' tab in the Properties viewer to enter General Reliability data, and Exponential/Weibull tabs to set values for each failure distribution type
• Use the slider bars to change values or enter digits manually in the provided numerical fields on the right.