Effective Failure Rate of Two Active Redundant Units, with Different Failure Rates, without Repair

This tool calculates the effective failure rate of two active on-line units, where "1 of 2" units are required for success. Each unit may have a different failure rate. The calculation implements Equation 5 shown on page 90 of the United States Air Force Rome Laboratory Reliability Engineer's Toolkit (1993).

Reliability Block Diagram:

Calculation Inputs:

Unit A failure rate, failures per million hours (FPMH): Unit A MTBF, hours:

Unit B failure rate, failures per million hours (FPMH): Unit B MTBF, hours:

Decimal places: 2 0 1 2 3 4 5 6 7 8 9 10 15 20

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References:

1. United States Air Force Rome Laboratory Reliability Engineer's Toolkit (1993).
2. MIL-HDBK-338, Electronic Reliability Design Handbook.
3. Klion, Jerome, A Redundancy Notebook, Rome Air Development Center, RADC-TR-77-287, December 1987.
4. Reliability Modeling and Prediction, MIL-STD-756B, November 1981.

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