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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: Sheila Prather (sheila_s_prather@mail.northgrum.com )
Organization:Northrop Grumman Corporation
Date posted: Wed Sep 20 14:25:14 US/Eastern 2000
Subject: Operational Parameter Translation - Question #2
Message:
This is a followup to my question posted on 9/11/00 regarding the TR-89-299. I've noted the caution that should be exercised when using this document...this question addresses the examples that are published in the "Reliability Toolkit: Commercial Practices Edition". I see where example #1 has been corrected from the previous 4/93 version of the toolkit; but, my question rests with example #2. Looking at Section 5.4.1.1 of TR-89-299, in example #2 why was the field number for flight hour determination based on 1,672 hours versus 1,000 hours (50% of 2,000)?


Reply:

Subject: Operational Parameter Translation
Reply Posted by: Bruce Dudley (bdudley@alionscience.com )
Organization: Reliability Analysis Center
Date Posted: Wed Sep 20 14:59:37 US/Eastern 2000
Message:
The example #2, as shown in the Reliability Toolkit; Commercial Practices Edition, is in error. Your comment is correct, the default value should be used for this approximation. Therefore, the MTBF(f) is equal to 2000/2 which equals 1000 hours between failure not the 1,672 shown. If flight hours are considered, the number is 1000/1.2 which equals 833.3 flight hours between failure. If the toolkit is ever updated this correction will be entered.


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