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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

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

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Original Message:

Posted by: M Boerner ( )
Date posted: Tue Sep 28 14:20:38 US/Eastern 1999
Subject: Reliability Predictions versus Actuals for electronic equipment
Looking for comparative data of MIL-217 predictions vs field actuals by equipment type (or WUC) for electronics for use as a reliability derate factor. Thanks in advance for your assistance.


Bruce Dudley Subject: Prediction Vs Actual
Reply Posted by: ( )
Organization: Reliability Analysis Center
Date Posted: Thu Sep 30 10:23:49 US/Eastern 1999
Mr. Xiangping asked a similar question back on 31 Aug 99 in this forum and several replies were received that should be of interest. Our experience and data collection with military equipment was last documented in a 1989 report called RADC-TR-89-299 Reliability and Maintainability Operational Parameters Translation. This report collected predicted reliability values and test data for a varied array of equipments. This report indicated a general ratio of 0.9 for ground fixed equipment (Actual/Predicted). Other folks are showing that Mil-Hdbk-217 predictions are very pessismistic with ratios of 2 to 1 or 3 to 1 being experienced for actual to predicted. Much of the cause of this change is related to the lack of an up-date to Mil-Hdbk-217 which is based on 1980s failure experience data. RAC is developing a new prediction technique called "PRISM" which should change the ratio back to a one to one relationship. This technique should be available sometime in the November 1999 time frame.

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