What is the steady state availability of a module with an MTTF of 50 years and MTTR of 10 hours?

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To determine the steady state availability of a module, the formula used is:

Availability (A) = MTTF / (MTTF + MTTR)

In this case, MTTF (Mean Time To Failure) is given as 50 years, and MTTR (Mean Time To Repair) is provided as 10 hours.

First, convert MTTF into hours for consistency in units:

50 years = 50 * 365 days/year * 24 hours/day = 438,000 hours.

Now, substituting the values into the availability formula:

A = 438,000 hours / (438,000 hours + 10 hours)

= 438,000 / 438,010.

Calculating this gives:

A ≈ 0.999977.

This result indicates that the module has a very high level of availability, reflecting minimal downtime compared to operational time.

Thus, the correct choice is the option that corresponds to this calculated value, highlighting that the module is expected to be operational almost all the time, with only a very small fraction of time spent in repair.