Materials and Manufacturing Know-How Bests Failed Breakers Published June 15, 2010 By Daniel Adducchio Materials and Manufacturing WRIGHT-PATTERSON AIR FORCE BASE, Ohio -- Thanks to Air Force Research Laboratory's expertise in evaluating and resolving a potentially costly problem related to KC-135 circuit breaker failure, a novel routine for checking--and, as necessary, replacing--these critical components is now in place. Affecting nearly 400 aircraft, the lab-developed approach is likely to save the government nearly $5 million; expedite the delivery (or, where applicable, the resumed delivery) of critical wartime assets; and reduce the number of future missions aborted as a result of the failure scenario. Further, the sharing of AFRL's findings with a joint service working group is prompting checks for similar problems with aircraft other than the KC-135. In response to reports of failed circuit breakers causing aborted flight operations at forward operating locations, preventing timely delivery of overhauled KC-135 aircraft, and otherwise negatively impacting operational tempo, AFRL personnel leveraged a unique application of materials science, engineering, and physics of failure principles to address the problem. They developed and implemented a strategy for rapidly obtaining circuit breaker samples--whether from various maintenance bench stocks or from deployed, newly modified, or home station aircraft--in order to understand the proliferation of issues occurring in the field. Their investigation revealed that over 400 circuit breakers (specifically, MS25244-5s) per KC-135 aircraft could be defective and require replacement throughout the entire fleet--translating to literally thousands of breakers posing significant risk to operational fidelity. Working with the KC-135 depot program office, Defense Logistics Agency, and original equipment manufacturers, AFRL materials engineers devised a mitigation process and accompanying plan for imparting minimal effect on modification production lines and operational aircraft and meanwhile maintaining appropriate, fully-mission-capable rates. The method involved evaluating the circuit breakers and analyzing the results of aircraft load testing to assess both the current impact and the likelihood of subsequent damage. The engineers employed innovative problem-solving skills and substantial knowledge of electrical materials, manufacturing systems, and physics of failure tenets to evaluate OEM processes and their contributory role in the problems experienced in the field. Given the collective level of expertise in these areas, the team was able to satisfactorily discount failure modes provided by the OEM. Accordingly, this comprehensive approach effectively influenced key changes to OEM production and quality assurance techniques. Beyond identifying the root cause of failure and supplying the solution for mitigating this failure condition, AFRL also provided the KC-135 System Program Office extensive follow-up support by testing adjusted circuit breakers for compliance with the MS25244 specification used for other military aircraft. In addition, AFRL assisted the SPO in developing and negotiating a course of action establishing ongoing vendor responsibility, both in terms of testing circuit breakers and in replacing hundreds of existing, defective breakers at no cost to the government.