Introduction to Maintainability. What is Maintainability?
The prediction of the expected number of hours that a system or device will be in an inoperative or “down state” while it is undergoing maintenance is of vital importance to the user because of the adverse effect that excessive downtime has on mission success.
Therefore, once the operational requirements of a system are fixed, it is imperative that a technique be utilized to predict its maintainability in quantitative terms as early as possible during the design phase. This prediction should be updated continuously as the design progresses.
MIL-HDBK-472, Notice 1, Maintainability Prediction
MIL-HDBK-470a, Designing and Developing Maintainable Products and Systems.
This information can be found in either MIL-HDBK-472 or MIL-HDBK-470A. This example shows the remove and replace times associated with Standard Screws and other types of fasteners.
Above is an example of remove tasks for an Elapsed Time Meter. The total time is 4.03 minutes to perform this set of tasks. This would be considered the Remove Time for this item.
Above is an example of replace tasks for an Elapsed Time Meter. The total time is 5.15 minutes to perform this set of tasks. This would be considered the Replace Time for this item. The Interchange Time is the sum of the Remove Time and the Replace Time for the item of interest.
Above is an example of a simple Maintainability Prediction that includes three replaceable items