Maintainability testing and demonstration
The primary function of maintainability testing and demonstration is verifying the maintainability-related features that have designed and built into a system/product [1, 2]. Maintainability testing and demonstration also provide the customers with confidence, prior to making any production commitments, that the system/equipment design under consideration meets the maintainability-related requirements. Prior to the testing and demonstration phase, the maintainability program tasks have been basically analytical. The main drawback of the analytical evaluations is that they do not reflect practical experience with the actual hardware.
Thus, it is quite essential to add realistic evaluations to analytical evaluations by performing real maintainability tests and demonstrations with the equipment/system in its operational environment.
This chapter presents various important aspects of maintainability testing and demonstration.
Maintainability testing and demonstration planning and control requirements
In order to gain maximum benefits from maintainability, tests and demonstrations require good planning and control. Thus, maintainability testing and demonstration planning and control requirements may be categorized under six classifications, as shown in Fig. 10.1 [2, 3].
All the six classifications shown in Fig. 10.1 are described as follows.
10.2.1 Creating a demonstration model
This is basically concerned with developing/creating a mock-up model representing the final product to demonstrate maintainability features. A mock-up model serves the following two basic functions :
Figure 10.1 Classifications of maintainability testing and demonstration planning and control requirements.
- • Providing a basic mechanism to demonstrate the product's/system's proposed quantitative parameters and qualitative design features for maintainability.
- • Providing a designer's tool for visibility, packaging limitation, experimentation, and planning, prior to release of the final design/ drawing.
- 10.2.2 Developing a demonstration plan
A good demonstration plan should cover areas such as test planning, administration, and control; test conditions; and test documentation, analysis, and report. Also, it should conform to the specifics described in Ref. .
During the early manufacturer/contractor participation in a program such as the validation phase, the first step is conceiving, proposing, and negotiating the demonstration test planning subject. As the program progresses, the mutually agreed-upon test plans are updated in regard to items such as schedules, demonstration model designation, personnel selection, and identification of logistic support resource-related requirements. The key factor in accomplishing the demonstration on schedule and within budget is the demonstration's administration and control. Some elements of administration and control are as follows:
- • Method of organization.
- • Test monitoring.
- • Test event scheduling.
- • A team approach, if desired.
- • Assignment of responsibilities.
- • Cost control.
- • Organizational interfaces.
- • Test data collection, reporting, and analysis.
It is to be noted that the complexity and type of the equipment/system under consideration plays a key role in shaping the requirements for test documentation. Documentation requirements generally include items such as failure reports, demonstration task data sheets, demonstration work sheets, task selection work sheets, demonstration analysis work sheets, frequency and distribution work sheets, interim demonstration reports, and final reports.
10.2.3 Following MIL-STD-471 guidelines
This document developed by the U.S. Department of Defense lays out guidelines that equipment/system manufacturers should consider in the planning and control of maintainability demonstrations . The document covers the following topics :
- • Administration, control, reporting, evaluation, and analysis procedures for the demonstration.
- • The pre-demonstration, formal demonstration, and phases.
- • Test conditions, selecting a test method, establishing test teams, and suggested test support materials.
- • Data collection.
- • Selection, performance, and sampling of corrective and preventive maintenance tasks.
Finally, it is added that this document (i.e., MIL-STD-471) guidelines are considered essential for an effective maintainability demonstration.
10.2.4 Providing appropriate manpower
The personnel who conduct maintainability demonstrations will be essential to their success. Thus, it is very important that they possess backgrounds and skill levels similar to those of the system's/product's final user, operating, and maintenance personnel. One way to do this is to have such individuals from the client organization to conduct the test.
Useful guidelines for selecting demonstrators are available in Ref. .
10.2.5 Specifying parameters
The basic purpose of a formal maintainability demonstration process is to verify compliance with stated parameters. Thus, the specifications for demonstration parameters should be stated in quantitative terms. Some examples of measurable time parameters are mean preventive maintenance time (MPMT), mean corrective maintenance time (MCMT), and mean time to repair (MTTR).
10.2.6 Taking environment into account
Past experiences over the years have shown clearly that system/equipment downtime may vary quite significantly between laboratory-controlled conditions and actual operational conditions. Thus, environment is an important factor in testing, and those responsible must carefully consider factors such as support resource needs, test facilities, and limitations simulations.