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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: Ken Burgess (burgessfk@raytheon.com )
Organization:Raytheon AIS
Date posted: Wed Mar 7 13:52:28 US/Eastern 2001
Subject: Humidity Effects on Reliability
Message:
I am trying to ascertain the effects of humidity on component reliability. The purpose is to determine if dehumidifying an aircraft and its installed systems while on the ground is cost effective from a reliability perspective. The aircraft will be stationed in the UK where relatively high humidity is present in a relatively cool environment. This is contrary to where higher temperatures are usually associated with higher humidity. Does anyone know where I can find any data on humidity and the effects on reliability of airborne electronic systems? I am particularly interested in the time period that the systems are not operating.


Reply:

Subject: Humidity Effects on Components
Reply Posted by: B.W.Dudley (bdudley@alionscience.com )
Organization: Reliability Analysis Center
Date Posted: Tue Mar 27 10:23:02 US/Eastern 2001
Message:
Humidity is always a concern during non-operating periods as the corrosion failure mechanism may take place causing component failures or degraded performance. Another concern with humidity is exposure to hydroscopic dust which when combined, can become electrically conductive due to the salts. This combination can result in two different failure mechanisms, electrical overstress and the formation of leakage paths or sneak current paths. From a reliability modeling perspective, the failure rate impact is small. The RAC PRISM model was exercised and the relative change in failure rate is only one percent or less improvement when the humidity is increased from 0 percent to 100 percent.


Reply:

Subject: Humidity Effects on Reliability
Reply Posted by: Tony Harris
Date Posted: Wed Apr 11 4:41:35 US/Eastern 2001
Message:
Ken. I know that the Royal Air Force and the Norwegian Air Force have done some DH studies and trials so you might want to approach those two organisations. If I recollect correctly, any potential value was somewhat outweighed by the practicalities of applying the DH, ie the cost of totally dehumidified accommodation or the problems associated with where to pump the DH air in to the aircraft - and the equipment required. Anyway, you might find some information there regarding actual equipment reliability if they measured it.


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