Forum: Reliability & Maintainability Questions and Answers

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Posted by: Elizabeth M. Chappel (elizabeth_M._chappel@belcan.com )
Organization:Belcan Engineering
Date posted: Tue May 11 16:31:55 US/Eastern 1999
Subject: FMEA (CA) Definitions and Guidelines
Message:
I am establishing the guidelines and the definitions for severity (criticality), failure mode probability and detection for a System Level FMEA. The product has an aerospace application in which it is active at all times. Some vendors will be providing data (failure rates) for electronic components, while others may find it easier to provide probabilities of occurrences. However, there's the rub, how to define and correlate the two and make sense. I need to provide def'ns that make sense. The present military definition for Qualitative Probability isn't helpful, nor is the automotive. Help. What type of scale do you suggest for a product that is always active? (I have completed the Severity (Criticality) Definition, Detection won't be a problem, it's just this probability). The various sources I've viewed don't clarify it any. (old Mil-Std-1629, SAE-ARP-5580 advanced review copy). Thanks Beth

Replies: (list all replies)
FMEA Probabilities
Bruce Dudley Tue May 18 14:18:26 US/Eastern 1999
Bruce's Reply
Elizabeth M. Chappel Mon Jun 21 11:18:25 US/Eastern 1999

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Posted by: Pat Green (pgreen@grintek.com )
Organization:GRINTEK AVITRONICS
Date posted: Wed Apr 28 10:07:40 US/Eastern 1999
Subject: MIL STD 810E SAND AND DUST TEST
Message:
The company I am employed by manufactures optical equipment which is fitted to Rotary as well as fixed wing cargo aircraft. We were contracted to perform a sand and dust test on the quartz lense of the specific LRU in question in accordance with MIL STD 810E method 510.3. The lense was sandblasted to a opaque condition and the result of the test was a fail for the LRU.
Is there any method that one can equate this test to any type of operation or flying hours. Is this test a requirement for all airborne optical equipment.

Replies:
Sand And Dust Testing
Bruce Dudley Wed Apr 28 15:21:19 US/Eastern 1999

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Posted by: Ben Walters (bwalters@etec.com )
Organization:Etec Systems, Inc.
Date posted: Wed Apr 21 15:01:12 US/Eastern 1999
Subject: Case Studies of Reliability Improvement
Message:
I am looking for any case studies or examples of large reliability improvement in a product. My executive management is asking about what it would take for a 10X improvement in our product lines. We make large, complex equipment for the semiconductor industry. Any case studies or examples would be greatly appreciated.

Replies: (list all replies)
Reliability Improvement
Bruce Dudley Tue Apr 27 14:43:11 US/Eastern 1999
10X Improvement
Jerry Cartwright Fri Apr 30 15:28:02 US/Eastern 1999

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Posted by: GR Gibbons (gibbonsg@stelcos.com )
Date posted: Fri Apr 16 15:57:35 US/Eastern 1999
Subject: Reliability Modeling
Message:
Parallel reliability models described in Mil-Hdbk-338-1A refer to redundant items. What is the equation for a 5:1 model, i.e., 5 non-redundant items with the same failure rate and 1 hot spare for all five? If it is the same as the K out of N configuration model which is in terms of availability, what is the equation in terms of the failure rate?

Replies:
Redundancy Modeling
Bruce Dudley Mon Apr 19 14:09:01 US/Eastern 1999

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Posted by: Chris Wright (christopher.d.wright@lmco.com )
Organization:Sanders, A Lockheed Martin Co.
Date posted: Wed Apr 14 16:42:39 US/Eastern 1999
Subject: MIL-HDBK-217 being revised?
Message:
I heard a rumor that Mil-Hdbk-217 is being revised. Is this true?
If so, will it be incorporating the new proposed PEM model?

Replies: (list all replies)
MIL-HDBK-217 Update
Bruce Dudley Thu Apr 15 13:45:43 US/Eastern 1999
Mil 217 & IEEE 1413
Jerry Cartwright Wed Apr 21 10:18:14 US/Eastern 1999

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