Intermittent fault issues are an ongoing problem for electronics across the military. Those that occur in a line replaceable unit/weapon replaceable assembly (LRU/WRA) and weapon systems electrical wiring interconnect system (EWIS) are a challenge for several critical Department of Defense (DOD) platforms, especially aircraft. These intermittent faults―temporary and seemingly random shorts, breaks, and other failures―cost billions of dollars, jeopardize mission success, and reduce readiness. Over the last few years, several CTMA initiatives have introduced and demonstrated innovative intermittent fault detection technologies to the DOD, which have resulted in significant increases in weapon system availability.
Due to the critical nature of this intermittent faults issue, the Joint Intermittence Testing Working Group (JIT WG) was chartered in 2012. This joint services forum leverages current and emerging commercial industry activity for demonstration, testing, and cost analysis of intermittent fault detection technologies.
Thanks to the efforts of JIT WG, the MIL-HDBK-454, General Guidelines for Electronic Equipment, has some new guidance related to intermittent fault detection. The guide provides the technical basis for the design and construction of electronic equipment for the DOD. It captures in one document, under suitable subject heading, fundamental design guidelines for multiple general electronic specifications.
In support of the JIT Working Integrated Program Team, Ed Taylor, electrical engineer with Eagle Systems and a subject matter expert, drafted a new guideline to be included in the draft MIL-HDBK-454C. New Guideline 79, Intermittent Fault Diagnosis, was added to the draft being coordinated to address the issue of intermittent faults. The new guideline establishes criteria for diagnosing intermittent faults in electronic equipment backplane, chassis and wire harness conductive paths. Among its features, the new guideline references MIL-PRF-32516, electronic test equipment, intermittent fault detection and isolation for chassis and backplane conductive paths; defines intermittent faults; and provides general guidelines in diagnosing intermittent faults.
Draft MIL-HDBK-454C started its 30-day government/industry coordination on May 21, 2021. This coordination is a DOD standardization process for review of changes by government and industry technical personnel to ensure technical accuracy and completeness of technical requirements. Though the handbook provides guidance and lessons learned for designing electronic equipment, it is for guidance only and cannot be cited as a requirement.
The inclusion of the new intermittent fault guideline is an important step in addressing one of the most pressing wiring fault challenges in LRU/WRA and weapon systems EWIS facing the DOD today.