Maintainability-related data may be obtained from several different types of sources. Some potential sources of maintainability data include:
- Historical data from similar items
- Item design and/or manufacturing data
- Data recorded during item demonstration
- Field use data
The data may be expressed in a variety of terms. These include observed values or modified values (true, predicted, estimated, extrapolated, etc.) of the various maintainability measures. Some precautions are therefore necessary regarding the understanding and use of such data.
Historical data -The origin of the historical data (e.g., field operation, repair shop and software center) and the item on which such data are based should be described and the reasons why and how they apply to the current item should be addressed. The methods used to collect the data, together with the training and skill levels of maintenance personnel involved, should also be clearly stated. Discrepancies which might affect the applicability of historical data to the item under consideration should be specifically addressed.
Historical data is used primarily during the concept definition phase and for specification requirement generation purposes. In the later phases of the item life cycle, historical data may be considered in relation to actual data obtained for the current item. They can also serve as an additional source of information for maintainability verification.
Item design/manufacturing data - When maintainability-related data are obtained through the use of design analysis or prediction, or from data generated during the design phase or the manufacturing phase (e.g., development tests, production or assembly operations), the methodology used needs to be clearly identified. A discussion may also be needed to explain how the specific method was selected and applied. Any possible resulting limitations in data accuracy needs to be noted. Design/manufacturing data may be used as the basis for:
- Item qualification and acceptance (with regard to maintainability requirements)
- Review of the relevancy of historical data and the validity of previous maintainability assessments
Item demonstration data and/or field data-Maintainability-related data may also be obtained from formal or informal demonstration tests on mock-ups, prototypes or production equipment in either a true or a simulated environment. Data may also be generated during actual item use (e.g., support center, repair work shop, field operations, etc.). The methods for selecting specific maintenance actions, data monitoring and recording techniques thus need to be described. The skill level of maintenance personnel and the specific equipment training they have received should be noted. The feedback of item demonstration data and field data is the primary means for sustaining engineering activities during the in-service phase of the item life cycle.