6.2.3 Time Measure or Mission
Time is vital to the quantitative description of reliability. It
is the independent variable in the reliability function. The system usage from
a time standpoint, in large measure, determines the form of the reliability
expression of which time is an integral part. The types of mission times
commonly encountered are given in Figure 6.2-3. For those cases where a system
is not designed for continuous operation, a total anticipated time profile or
time sequences of operation should be defined, either in terms of duty cycles
or profile charts.
The mission reliability for an airborne fire control system
shall be at least 0.9 for a six-hour mission having the typical operational
sequence illustrated in Figure 6.2-3.