You can use multiplicative and additive adjustment factors to adjust the failure rates calculated for system tree items. In the General Data pane for an assembly or part, Mult FR adjustment factor and Add FR adjustment factor specify values to multiply by, add to, or subtract from the base failure rate calculated for this item.

For more information, see:

Multiplicative adjustment factors are applied before additive adjustment factors. A multiplicative adjustment factor of zero sets the MTBF (mean time between failures) and the failure rate to zero.

The following figure shows a very simple system tree in which multiplicative and additive adjustment factors are entered.

The non-adjusted MTBF for A1 is calculated first.

Where:

MA = The multiplicative adjustment factor.

AA = The additive adjustment factor.

The MTBF for A1 is then adjusted.

MTTR (mean time to repair) and cost calculations are not affected by failure rate adjustment factors.