5.8 R&M Trade-Off
System effectiveness and cost/effectiveness models provide the
best tools for performing tradeoff studies on the system level. Because of the
complexities involved, most of these models are computerized. Through the
computerized models any changes in any of the multitude of reliability,
maintainability, performance, mission profile, logistic support, and other
parameters can be immediately evaluated as to their effect on the
effectiveness and total cost of a system. Thus cost effectiveness modeling and
evaluation, besides being used for selecting a specific system design approach
from among several competing alternatives, is a very powerful tool for
performing parametric sensitivity studies and tradeoffs down to component
level when optimizing designs to provide the most effective system for a given
budgetary and life cycle cost constraint or the least costly system for a
desired effectiveness level.
At times, however, especially in the case of the more simple
systems, tradeoffs may be limited to achieving a required system availability
while meeting the specified reliability and maintainability requirements.
Comparatively simple trade-off techniques can then be used as shown in the
paragraphs below. The maintainability design trade-off aspects and the cost
oriented trade-offs are discussed further in Sections
10 and 12.