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Lambda Search

Lambda Search is a method within eXpress for prioritizing the replacement of repair items in an isolated ambiguity group, based on isolated failure probability. Testability analyses often include both fault isolation metrics (based on testing only, without the use of lambda search) and fault resolution metrics (which take into consideration both testing and serial replacement prioritized using a technique like lambda search).

In any system there are many variables that contribute to risk. Among these are reliability, cost, time, maintainer capability etc.

In working with risk management it is sometimes good to consider a lesser degree of perfection to reduce the cost – time variables. This is what Lambda search does in eXpress. It provides you with a means of calculating the effects of a Lambda ratio on the cost-time factors of replacement.

It all comes down to a calculated curve for risk management that takes into account the probability of success weighted by the cost-time of success vs. the cost-time of failure. In an operational system, the optimum lambda ratio would be different for every single ambiguity set. The key is to find a ratio that optimizes the majority of ambiguity sets.

All that being said, it can readily be seen that Lambda Search requires the failure rate (λ) to determine a prioritized replacement of repair items in an isolated ambiguity group. At the present time, the FCS program has direction to use group parts count rather than Lambda to weight the repair parts replacement priority. With only using parts count, the probability for replacement selection is “1”. All parts will be equally weighted and Lambda Search will effectively be equal to “Random Search”.

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