Mission Reliability Calculations
Operating environment, dormant environment, temperature, and duty cycle values affect the failure rates calculated by many models. For these models, you specify the operating environment, dormant environment, and temperature values in the assembly’s Calculation Data pane and in the Project’s Mission Profile file. You specify the duty cycle only in the assembly’s Calculation Data pane. For more information, see:
The following table describes the various scenarios for computing failure rate and mission failure rate for all but the 217Plus, PRISM, FIDES, IEC TR 62380, and RDF 2000 models. While the failure rate (FR) calculation does not take the values specified in the Mission Profile file into account, the mission failure rate (FR) calculation does take these values into account.
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The concept of dormant phases is supported in the Mission Profile file. For more information, see Dormant Conversion Table. When the phase is dormant, the duty cycle is set to 0 because no partially dormant phase can exist.
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Scenario
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Operating Environment
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Dormant Environment
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Duty Cycle
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Mission Profile File for Project
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Failure Rate Equation
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Mission Failure Rate Equation
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1
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Specified
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None
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Specified
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No Data
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Active FR * Duty Cycle
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None
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2
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Specified
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Specified
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Specified
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No Data
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(Active FR * Duty Cycle) + (Dormant FR * (100 − Duty Cycle))
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None
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3
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Specified
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None
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Specified
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Contains Data
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Active FR * Duty Cycle
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For active phases in the Mission Profile file:
1. Calculate Active FR of Phase(n) using operating environment and temperature from Mission Profile file.
2. Calculate Phase FR = Active FR * Duty Cycle.
3. Calculate Total FR = SUM(Phase FR(i) * Percentage in Phase (i)).
For dormant phases in the Mission Profile file:
1. Calculate Dormant FR of Phase(n) using operating environment, dormant environment, and temperature from Mission Profile file.
2. Calculate Phase FR = Dormant * 100.
3. Calculate Total FR = SUM(Phase FR(i) * Percentage in Phase (i)).
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4
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Specified
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Specified
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Specified
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Contains Data
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(Active FR * Duty Cycle) + (Dormant FR * (100 − Duty Cycle))
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For active phases in the Mission Profile file:
1. Calculate Active FR of Phase(n) using operating environment and temperature from Mission Profile file.
2. Calculate Dormant FR of Phase(n) using operating environment and temperature from Mission Profile file and dormant environment from Calculation Data pane.
3. Calculate Phase FR(n) = (Active FR * Duty Cycle from Assembly) + (Dormant FR * (100 − Duty Cycle from Assembly))
4. Calculate Total FR = SUM(Phase FR(i) * Percentage in Phase (i)).
For dormant phases in the Mission Profile file:
1. Calculate Dormant FR of Phase(n) using operating environment, dormant environment, and temperature from Mission Profile file.
2. Calculate Phase FR = Dormant FR * 100.
3. Calculate Total FR = SUM(Phase FR(i) * Percentage in Phase (i))
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