Taking Aim at Hard-to-Hit, Intermittent Wiring Faults with Improved Test Equipment

Joint Intermittence Testing (JIT) Capability – Phase II


Wiring faults cost air carriers tens of millions of dollars a year, and intermittent faults―temporary and seemingly random shorts, breaks, and other failures―are especially challenging to find and fix, often being designated no-fault-found (NFF) when technicians try and fail to replicate the problem. Total failures in a wiring system are easy to recognize, but a problem that occurs sporadically, in a complex system containing thousands of potential circuits, is anything but.

NFF costs the Department of Defense (DoD) approximately $2 billion a year, with intermittent faults identified as the primary cause. To better equip the DoD to repair these faults, Copernicus Technologies, as part of an NCMS-led project team, developed an Intermittent Fault Emulator (IFE), a tool to test the capabilities of new technologies intended to pinpoint these faults within aircraft systems, and are developing a test protocol for the IFE’s use by commercial and defense aerospace companies and the U.S. military. Together, the IFE and Joint Test Protocol can ensure that aircraft repair technicians have access to reliable diagnostic equipment, greatly increasing the efficiency and quality of aircraft maintenance.

Currently, visual inspection only identifies around 25 percent of the DoD’s total weapon system wiring problems. Intermittent faults are particularly time-consuming to detect. Finding them requires significant knowledge about the system being examined, and they can only be identified after their underlying causes have led to significant deterioration. In the private sector, intermittent faults can frustrate manufacturers’ attempts to control and assure product quality, increasing inconvenience to customers and maintenance needs, decreasing consumer confidence, and creating hard-to-anticipate safety hazards. Use of the IFE to identify effective fault-detection tools allows repair technicians to more confidently conduct repairs based on need, conserving resources, improving logistics, and reducing downtime due to maintenance.


Based on inflation-adjusted estimates by the U.S. Air Transport Association (now Airlines for America),[1] NFF could cost air carriers roughly $150,000 in maintenance per aircraft in 2017; according to Ken Anderson, Vice President of Universal Synaptics, for a company operating a fleet on the scale of Delta, FedEx, or UPS, NFF-related maintenance costs could be in the ballpark of $40 million per year. One rail industry source speculates that NFF costs the entire industry roughly $1 billion annually in maintenance.

NFF is a source of significant costs for consumer industries as well. In 2011, the U.S. consumer electronics industry lost almost $17 billion owing to product returns, 68 percent of which were designated as “No Trouble Found” when tested. Accenture, a management consulting and professional services firm, concludes that even a one percent reduction in NFF-related returns “could translate to annual savings of 4 percent in return and repair costs, or $21 million for a typical large consumer electronics manufacturer and $16 million for the average consumer electronics retailer.”[2]

The exact frequency and impact of NFF is difficult to measure. In a 2015 survey by Copernicus Technology, 47 percent of responding aerospace engineers and technicians reported that their organization did not collect data on NFF’s maintenance impact, or that they did not know if it did; 61 percent responded similarly when asked about NFF’s financial impact. When asked about the frequency of NFF in system and component repairs, an overwhelming majority of respondents cited estimates in lieu of actual data.[3]

The most immediate impact of JIT Phase II is to facilitate the DoD maintenance and sustainment community’s adoption of Condition-Based Maintenance Plus (CBM+), reducing maintenance-related downtime, increasing operational availability (Ao), reducing the logistics footprint (i.e., material, waste, and disposal), and reducing overall sustainment costs.


The DoD is currently unable to detect and isolate intermittent faults in aircraft wiring bundles and Weapon Replaceable Assembly (WRA)/Line Replaceable Units (LRUs), which include opens and shorts, degraded and intermittent signals, and insulation degradation. These faults are a source of significant cost and inefficiency, with the DoD spending approximately $2 billion annually just removing and replacing WRAs/LRUs that, when tested, are determined to be NFF. Those WRA/LRUs are returned to service with underlying problems unaddressed, only to be returned to maintenance when they fail again. This cyclic process wastes man-power and resource without yielding improvements in reliability and Ao. This problem can only be expected to grow as legacy electronic components experience increasingly reduced reliability as a result of component age and usage.

Current visual inspection processes lack effectiveness, and can identify only approximately 25 percent of total weapon system wiring problems. Intermittent faults can be found using traditional test equipment to a limited extent, but this is only possible with conventional test equipment when the intermittent faults have degraded to the extent that they are closer to becoming hard faults. Additionally, inspection with conventional test equipment tends to be time-consuming, requires strong understanding of the affected system circuits, and can still overlook the root causes of intermittency.

While there were several newer technologies that allow for the identification and isolation of intermittent faults in WRAs/LRUs, there existed no Joint Test Protocol for intermittent fault emulation equipment. To properly assess the capabilities of such devices offered by industry, there needed to be a validation process for detecting and isolating intermittent faults, and set standards for an IFE. The Joint Intermittence Testing (JIT) project team guided by NCMS spearheaded the development of an IFE and a protocol for its use as part of maintenance and sustainment activities.

As part of the JIT project, a new Joint Military Performance specification (MIL-PRF-32516) was produced and a Working Integrated Product Team (WIPT) was formed to ensure that current and emerging technologies would be properly leveraged across all departments of DoD. As of August 2017, the WIPT continued meeting and hosted an “Industry Week” event evaluating industry capabilities, drafted a Joint Test Protocol Military Handbook currently under review by DoD, and established a national Joint Roadmap for Transition of Intermittent Test Equipment.

Project Partners

  • S. Navy – NAVAIR Lakehurst
  • S. Air Force – Hill Air Force Base
  • S. Navy – Fleet Readiness Center Southwest (FRC SW)
  • S. Air Force – Warner Robins
  • Eagle Systems, Inc.
  • Universal Synaptics Corporation
  • Eclypse International
  • Ridgetop Group, Inc.
  • Solavitek
  • National Center for Manufacturing Sciences (NCMS)

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[1] John Ahmet Erkoyuncu et al., “A Framework to Estimate the Cost of No-Fault Found Events,” International Journal of Production Economics 173 (March 1, 2016): 207–22, doi:10.1016/j.ijpe.2015.12.013.

[2] “U.S. Consumer Electronics Industry Faces a Projected $17 Billion Product Returns Bill This Year, Accenture Research Finds,” Accenture, December 13, 2011, https://newsroom.accenture.com/industries/electronics-high-tech/us-consumer-electronics-industry-faces-a-projected-17-billion-product-returns-bill-this-year-accenture-research-finds.htm.

[3] “No Fault Found: 2015 Aerospace Survey Results” (Copernicus Technology, 2015).