scope:

This International Standard specifies techniques for availability performance testing of frequently maintained items when the availability performance measure used is either steady-state availability or steady-state unavailability. It is applicable to compliance testing of the steady-state availability of items attaining only two states, up-state and down-state, under the following conditions:

1) One single repaired item.

2) All up times have the same exponential distribution.

NOTE - This usually implies the need for operation to reach the constant failure intensity period before the compliance test is begun.

3) Preventive maintenance time is not included in down time although it is recognized as having possible impact on availability performance.

4) All contributors to down time need to be explicitly stated in the requirement or test specification.

5) Very reliable items may require an extremely long test time to determine compliance.

NOTE - With a highly reliable item, few or even zero failures may occur within a designated period of time. In such a case, there will be little or (possibly) zero quantitative information on the availability performance since there may be no repair actions. Parties (supplier and customer) applying this standard should agree on the decision to be made in such an eventuality. In general it is recommended that before the parties invoke this standard in a contract they calculate, or simulate, the results to be obtained from the compliance test. In this way both pa rties will be knowledgeable regarding the risks they are facing.

6) The compliance test procedures use the complementary measure steady-state unavailability.