Forum: Reliability & Maintainability Questions and Answers
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
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.
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.
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?
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?
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