SRC Forum - Message Replies

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

Original Message:

Posted by: George (gpyryt@draper.com )
Organization:Draper Laboratory
Date posted: Mon Sep 9 13:21:17 US/Eastern 2002
Subject: Estimating defect density for ESS
Message:
I'd like to use MIL-HDBK-344 procedures to: 1) Estimate an equipment's defect density. I have extracted data from the reliability prediction to estimate the defect density but I am struggling with the final result because I can't make sense out of the examples in the handbook. In the MIL-HDBK-344A example on page 5-14, the part quantities of section 9 do not add up to the total # of parts in section 11. Perhaps this is why I can't determine how they arrived at the numbers in sections 2, 3 and 4. In the Litton Systems/Rome Lab document ADA245735, I tried to use the data in Figure 2.8 to arrive at the 2.95 value in Table 2.1 for the ML environment, but again I was unsuccessful. Any helpful suggestions or references that can help with the estimation of defect density would be much appreciated.

Reply:

Subject: ESS
Reply Posted by: B.W.Dudley (bdudley@alionscience.com )
Organization: RAC
Date Posted: Tue Sep 10 14:07:20 US/Eastern 2002
Message:
You are correct in that figure 5.7 of MIL-HDBK344 has erroneous data. The information presented in this figure is the same as that is shown in figure 5.5, which appears to be correct. I suspect that someone typed in the wrong information in figure 5.7. The correct number of parts for figure 5.7 is 3339 and the number of connection is 15,690. I cannot determine the remaining values for this chart.