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Allocation Method
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Required Inputs
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Base, Non-normalized
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A failure rate or MTBF goal must be entered. Additionally, a weight factor of any numeric value can be entered.
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Base, Normalized
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A failure rate or MTBF goal and a weight factor must be entered. The weight factor can be any numeric value in the range of 0 to 1.
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Equal Apportionment by Components
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A failure rate or MTBF goal must be entered for the top-level assembly. No weight factor is entered. The weight factor is computed as:
100 / Number of Parts in Entire System
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Equal Apportionment by Subsystems
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A failure rate or MTBF goal must be entered. No weight factor is entered. The weight factor is computed as:
100 / Number of Parts in Subassembly
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ARINC
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A failure rate or MTBF goal must be entered. No weight factors are entered. Prediction calculation results are used to generate weight factors. According to this method, which was proposed by Aeronautical Research Inc., weighting factors derived from the present allocation of the system are used to improve subsystem failure rates.
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AGREE
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A reliability goal and an importance factor must be entered. No weight factors are entered. According to this method, which was developed by the Advisory Group on Reliability Equipment, Office of the Assistant Secretary of Defense, USA, a system based on reliability of subsystems (as a measure of complexity), an importance factor, and mission time are used to compute the allocated failure rate.
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Feasibility of Objectives
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A failure rate or MTBF goal must be entered. No weight factors are entered. Weight factors are computed based on values that you enter on a scale of 1 to 10 for four rank factors:
• Intricacy
• State-of-the Art
• Time
• Environment
The four rating values are multiplied together for an overall value between 0 and 10000. The weight factor is computed as the total of all ratings added up and then normalized.
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Repairable System
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A required availability goal must be entered and MTTR values must be available for MTTR in the System Tree Items table. No weight factors are entered. Failure rates are computed based on the required availability and MTTR values. Equal availabilities are allocated to all subsystems.
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