What-If and Scope

MTTR What-If

Changing repair time recomputes the cycle and availability.

highlighted = computed this step

What-If MTTR

The what-if repair time is 5 hours.

what-if MTTR=5\text{what-if MTTR} = 5
MTTR what-ifThe table recomputes the cycle and availability when repair time changes.MTTR what-ifvalueMTTR5cycle45availability8/9downtime1/9gain4/45

What-If Availability

The what-if availability is 8/9.

what-if availability=8/9\text{what-if availability} = 8/9
Maintenance availabilityThe chart compares the base cycle with the lower-MTTR what-if.maintenance availabilitycycle 50; availability 4/5; downtime 1/5caseMTBFMTTRcycleavailabilitydowntimebase4010504/51/5what-if405458/91/9baseup 40down 10cycle 50what-ifup 40down 5cycle 45what-if MTTR 5; availability gain 4/45deterministic two-number availability arithmetic only

Availability Gain

The availability gain is 4/45.

8/9−4/5=4/458/9 - 4/5 = 4/45
Maintenance availabilityThe chart compares the base cycle with the lower-MTTR what-if.maintenance availabilitycycle 50; availability 4/5; downtime 1/5caseMTBFMTTRcycleavailabilitydowntimebase4010504/51/5what-if405458/91/9baseup 40down 10cycle 50what-ifup 40down 5cycle 45what-if MTTR 5; availability gain 4/45deterministic two-number availability arithmetic only