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During the last several years there has been an increasing tendency to include a significant element of Commercial Off The Shelf items in proposed system solutions. There is also an increasing tendency in Industry to make the statement 'It's COTS so we do not need to do ILS'. We need to dispel that rumour here! |
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When attempting to apply ILS to a COTS-based system solution it is true to say that ILS is unlikely to make a contribution to the LRU design. The LRU will be offered 'off the shelf'; although one would hope that ILS principles had been applied during the LRU design process. However, in formulating a system solution the role of ILS is to influence the integration of the COTS items into the system - and this is very important. |
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There is a well-known example regarding the manufacturer of Generating Sets. Whilst fulfilling a contract for a customer, this manufacturer integrated a range of COTS items to meet the Generator requirement. However, during the integration design little attempt was made to apply ILS principles. |
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During acceptance trials of the Generator one of the COTS LRUs kept failing. Indeed, later perusal of the R&M information on this LRU showed that it was less reliable than other system LRUs. However, the design team had integrated this LRU in the Generator such that a significant amount of other LRUs had to be removed before access could be gained to the faulty one. The result of this design error was that MTTR requirement figures could not be met and a number of maintenance failures were induced in the erstwhile serviceable LRUs. |
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Whilst this anecdote may seem minor, the reality was that the Generator had to undergo a complete re-design, which almost bankrupted the Company. The way in which LRUs are integrated into a system can have a profound effect on the performance and the support of equipment. |
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Each of the COTS manufacturers will have a suggested support solution - normally Forward to Deep; however, the system design team must not be fooled into thinking that the COTS support solution is the only one available. The overall support solution must pass the operational availability and cost-effectiveness test. Simply, the holistic support solution must be selected based on the effective use of supportability trade off analyses. |
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last update: December 27, 2004 |
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