The life modification factor for systems approach aISO takes into account lubrication properties and fatigue limit of the bearing and it is multiplied to the L10r life to get the modified reference life. According to ISO 281 this factor is limited to a maximum value of 50. In some cases, for example in wind turbines a smaller maximum limit of 3.8 is required.
The maximum limit for the aISO factor can be specified here. The input is only an upper limit for the aISO factor which is calculated according to (ISO 281, 2007).