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The Right Stuff
for Aging Electronics/Intermittence/No Fault Found
ISSN: 0148-7191, e-ISSN: 2688-3627
Published September 16, 2019 by SAE International in United States
Annotation ability available
Event: AeroTech Europe
For those in the avionics repair and maintenance business, the acronyms NFF (No Fault Found), NTF (No Trouble Found), and CND (Cannot Duplicate) are, unfortunately, all too familiar terms. After several decades of frustration with this illusive phenomenon, it continues to consume an enormous amount of test and diagnostic effort and is the source of considerable cost and discomfort within the multi-level avionics repair model.
There are undoubtedly many causes of NFF and all of them should be addressed. The question is: Where do you start and which solution will be the most beneficial?
Our particular efforts have focused on the literal or statistical analysis of NFF, recognizing that if the system’s MTBF (Mean Time Between Failure) has decreased, or if the device's NFF rate has increased with age and deterioration, a physical fault is most likely present. However, if it isn’t found during conventional testing then it probably only fails intermittently. Similarly, having an intermittent failure mode, it in all probability cannot be detected or diagnosed at testing time because of known and demonstrated limitations in the conventional measurement equipment used to perform the tests.
In this paper we will outline the problem of intermittence and its testing difficulties. More importantly, we will describe the unique equipment and process which has produced overwhelming success in Intermittence / NFF resolution and MTBF extension. Our team-developed overhaul system called IFDIS 2.0 (Intermittent Fault Detection and Isolation System 2.0) incorporates all the necessary testing procedures and technological capabilities that are proving to be critical to the resolution of the chronic intermittent / NFF problem.
CitationKnudsen, H., "The Right Stuff
- Horn, J., Kourimsky, F., Baderschneider, K., and Lutsch, H. , “Avoiding Fretting Corrosion by Design,” AMP Journal of Technology 4, June 1995.
- van Dijk, P. and van Meijl, F. , “Contact Problems due to Fretting and Their Solutions,” AMP Journal of Technology 5, June, 1996.
- Correspondence with Peter, Fussinger, Chairman AMC., On-file.
- Horn, J., Baderschneider, K., and Lippmann, B. , “A New Criterion for Dynamic Reliability of Contacts,” AMP Journal of Technology 2, November 1992.
- Gemas, G.L. , “Aircraft Avionic System Maintenance Cannot Duplicate and Retest OK Analytical Source Analysis,” Master’s thesis, Air Force Institute of Technology (DTIC), WPAFB OH, September 1983.
- Dunwoody, S., Bock, E., and Sofia, J. , “A Practical and Reliable Method for Detection of Nanosecond Intermittency,” AMP Journal of Technology 5, June, 1996.
- Shawlee, II, W. , “How Parts and Systems Age,” Avionics System Design, Avionics Magazine, November 2000.
- Sorensen, B., Kelly, G., Sajecki, A., and Sorensen, P. , “An Analyzer for Detecting Aging Faults in Electronic Devices,” IEEE, AutoTestCon, September 1994.
- Sorensen, B. , “The Achilles Heel of Modern Electronics,” Evaluation Engineering Magazine, June 2004, Feature Article.
- Tustin, W. , “Random Vibration and Shock Testing,” Equipment Reliability Institute, 2005.