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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

Topic Posted by: Reliability & Maintainability Forum (src_forum@alionscience.com )
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998

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Original Message:

Posted by: Lim (limth@cet.st.com.sg )
Organization:CET Tech
Date posted: Sun Jul 29 22:17:45 US/Eastern 2001
Subject: Use of COTS equipment in Military environment
Message:
Hi, I have a question regarding the use of commercially-of-the-shelf (COTS) equipment in a military vehicle and environment. For e.g. we use a COTS equipment (say a modem)and shock mount it on the racks of the military vehicle. The vehicle is air-conditioned and the COTS is non-operating during movement to the deployment site. Once at the site, the equipment is powered on and operated. If the MTBF of the COTS modem is 13,000hrs (based on GB environment as given by the supplier), can i still use this figure in my MTBF prediction or do i need to degrade it by a certain factor. If there is a need to degrade it by a certain figure, is there any reference that provide this factor? Would appreciate it if anybody could provide some advice. Rgds.


Reply:

Subject: Use of COTS equipment in Military environment
Reply Posted by: Gary Sunada (gsunada@alionscience.com )
Organization: Reliability Analysis Center
Date Posted: Wed Aug 1 11:36:45 US/Eastern 2001
Message:
The normal conversion factor for recalculating the GB MTBF into ground mobile (GM) is 0.2 that is, for a GB MTBF of 13,000 hours, the corresponding GM MTBF is 2,600 hours. Your description of its environment is certainly that of a less taxing one than typical GM, but it is still classified as GM. Much of the consideration for the conversion factor will be dependent on: the performance of the shock mount relative to the traveling conditions; the uniformity of the cooling within the vehicle during transport and during equipment operation, as well as the conditions during vehicle storage; quality of the power source, etc. I recommend that you break down this analysis into two parts: one based on nonoperating equipment in a GM environment, and another for operating equipment in a ground fixed (GF) environment, with a conversion factor of 0.5. GB is a laboratory or an office environment, so it is unlikely that the GB MTBF will apply, even in a hard shelter with environmental controls.


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