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Analysis with the Crow Extended Model

Traditional reliability growth analysis is used to analyze data from tests where design fixes are incorporated during the observation period (the test-fix-test strategy). However, in actual practice, fixes may be delayed until after the end of the observation period (test-find-test), or you may implement some fixes during the observation period while delaying others (test-fix-find-test).

With the Crow Extended model, you can perform reliability growth projections, planning and analysis—which allows you to analyze test data from any or all of these strategies by providing additional information about the failure modes and the reliability growth management strategy (i.e., which modes are fixed and how effectively the design improvements reduce failure intensity). You can also use this model for data from fielded repairable systems in order to evaluate the improvement (i.e., the jump in MTBF) that could be achieved by rolling out a set of fixes for all systems operating in the field.

The following topics describe how to use the Crow Extended model in RGA, including:

• Data types that can be used with the model

• Classifying failure modes according to whether and when fixes will be implemented

• Setting the effectiveness factors for delayed fixes

• Using event codes to specify the type of event that each row in the data sheet represents (applies to the Multi-Systems with Event Codes data type only).

• Analysis results for Crow Extended

• QCP calculations and plots

• Two examples of analysis with the Crow Extended model, including:

• • An example of using the model with developmental test data

  • An example of using the model with operational test data (fielded data)