Why Finding Fault is A Good Thing

Identifying, repairing electronic intermittencies lowers costs, saves lives

7 Ratings

Imagine you are piloting a B-52, an aircraft that has been in the skies for more than 50 years. A warning light appears on your dashboard. Imagine your annoyance–and possible distraction–if this is the second or third time this same problem has occurred. Ridgetop Group's expert troubleshooting and repair system (ETRS) prevents this scenario because circuit card assemblies (CCAs) exhibiting this type of fault are identified and repaired before they find their way back into operation.


The Air Force reports that “bad actor” CCAs, which are reported as bad in the field but pass all tests at the repair depot, cost up to $2 million per year per CCA type. There are hundreds of types of CCAs. These electronic boards may fail during operation in an aircraft, causing premature termination of a mission or even loss of life, but are coded as “no fault found” when tested using existing instrumentation. Intermittencies can result from multiple causes, including marginalities introduced by aging and degrading components, and existing test programs are frequently unable to identify the root cause of intermittent problems. Without effective means to isolate what causes bad actors to fail, CCAs are marked as usable and eventually returned to service, only to fail again and repeat the cycle. This is wasteful and expensive for the Air Force, and dangerous to personnel. The ETRS system identifies the root cause of failures and determines how to repair the CCA.


The Air Force needs to break the expensive and wasteful bad actor cycle of CCAs, which fail in the field and are later returned to operation, only to fail again later. The negative results without ETRS are quite plain: (1) the wasted time and expense of trained depot electronics technicians repeatedly and unsuccessfully trying to troubleshoot bad actor CCAs, (2) decreased fleet readiness because of excessive maintenance events that could have been avoided with ETRS, and (3) possible loss of life if a critical system chooses the wrong time to fail due to an intermittency ETRS could have fixed. The test program set (TPS) developed CCAs were created over many years and for several different test systems. These TPSs were not created to isolate the failure mechanisms that have become prominent as aircrafts age and wear out. Subtle timing and voltage shifts may cause failures, appearing only under specific stress conditions that existing TPSs are not able to replicate and observe. ETRS uses advanced algorithms to create the upgrades necessary for the TPSs to identify the problems.


The Air Force awarded Ridgetop parallel Phase I SBIR programs in 2009 and both continued to Phase II in 2010. One program was focused on developing a method to identify and troubleshoot failing digital components in bad actor CCAs, and the other was focused on the same for analog/mixed-signal CCAs. Ridgetop applied techniques developed for prognostics and health management systems, along with other methods Ridgetop has since developed. The additional Phase II and CRP awards have allowed Ridgetop to continue the development for the Air Force’s VDATS platform, and Ridgetop is now applying ETRS to select CCAs as the initial proving ground for this program.

"ETRS provides powerful tools for Air Force repair depots to identify, isolate, and repair bad actor CCAs, eliminating wasteful, expensive maintenance operations and improving aircraft readiness." — Doug Goodman


ETRS improves speed and accuracy of fault isolation via advanced anomaly detection methods and fault tree analysis, leveraging Lean Depot Management System data as well as other historical repair information. Besides the substantial savings realized by reducing “no fault found,” “could not duplicate," “retest OK,” and similar codes, ETRS software extends the life and power of existing ATE systems without hardware upgrades. ETRS employs advanced algorithms that address off-nominal performance of modules due to aging and wear-out mechanisms. ETRS improves the fault and test coverage of existing TPSs. Based on historical data, the design of the CCA, and anomaly detection algorithms, ETRS generates a prioritized troubleshooting procedure. This enhanced soft fault detection procedure is used to improve the existing TPS, and the new TPS is placed into the repository for future application. The improved TPS is loaded into the VDATS or other ATE system to provide enhanced troubleshooting and repair guidance for each CCA type. This guidance includes visualization aids to help the operator probe the CCA and interpret results.


ETRS provides depot-level repairs for previously elusive problems that aircraft crew members have reported, thus improving morale and confidence that the aircraft is in top operational condition and readiness. Similarly, maintenance depot personnel are able to provide support to their aircraft and crew members, which had been extremely time-consuming or impossible prior to ETRS.

Ridgetop has helped address the need to reduce aircraft maintenance costs and improve fleet readiness, and is bringing similar technology to the commercial marketplace. Ridgetop has begun working with a satellite set-top box manufacturer and its partners to develop an ETRS-based system to reduce the incidence rate of bounces (bad actors). The SBIR and CRP supported research and development for ETRS and the platform by which Ridgetop can supply this technology to commercial vendors.

As ETRS reduces maintenance time and costs by addressing intermittent problems, U.S. organizations and companies can apply precious resources to other issues.

Organizational productivity and fitness also increase with the improvement in readiness and availability of systems supported by ETRS technology. ETRS is based in part on Ridgetop’s patented technology and we expect other patents will be derived from this program, further increasing U.S. competitiveness on the international stage.

Ridgetop Group, Inc.


Tucson, AZ

Ridgetop Group, Inc. is a world leader in advanced electronic prognostics and health management solutions, semiconductor IP blocks, and built-in self-test solutions. Ridgetop Group has a library of IP cores and board-level solutions for optimized integrated subsystems and systems.

David Robillard David Robillard

David Robillard

Principal Electrical Engineer

Robert  Wagoner Robert  Wagoner

Robert Wagoner

VP Product Develoment

James Hofmeister James Hofmeister

James Hofmeister

Distinguished Engineer


Failure Prognostics Based on Existing Data [AF093-207]; Expert Troubleshooting Technology for Rapidly Diagnosing Failures in Complex Systems [AF093-208]


AF093-207 & AF093-208



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