The accuracy of the approximate calculation methods of the antiaircraft emplacement electronics instantaneous availability by elements reliability indexes is study. Their addition to overhaul-period renewal problem solution, specified life and others are considered. Exploitation of Armament and military technique in modern terms requires the decision of tasks of decision of the appointed resources (terms of work), extension of resources after completion of the appointed terms of work. The decisions of these tasks are related to the calculations of non-stationary coefficient of readiness and non-stationary coefficient of operative readiness.
non-stationary availability factor, service lifeprolongation