Elemental Activities are simple maintenance actions of short duration and relatively small variance that do not vary appreciably from one system to another. An example of an elemental activity is the opening and shutting of a door. The philosophy of the procedure is based on the principles of synthesis and transferability. The transferability principle embodies the concept that data applicable to one type of system can be applied to similar systems, under like conditions of use and environment, to predict system maintainability. Other useful maintainability references are Military Standard 470, which describes a maintainability program for systems and equipment, and Military Standard 471, which provides procedures for maintainability verification, demonstration, and evaluation.
Availability is a measure of the readiness of a system.
There are three categories of availability. Inherent Availability is the ideal state for analyzing availability. Inherent availability is defined as Achieved Availability includes preventive maintenance as well as corrective maintenance. Achieved availability is defined as Operational Availability includes preventive maintenance, corrective maintenance, and delay time before maintenance begins, such as waiting for parts or personnel. It is a function of the mean time between maintenance actions and the mean down time, MDT, and is defined as It is important to note that the type of availability being described is often not distinguished.