Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 767-300 series airplanes. This proposed AD would require replacing the frequency converters used to supply power for medical outlets with modified frequency converters, and related actions. This proposed AD is prompted by a report indicating that a hard short circuit condition between the output of certain frequency converters and their downstream circuit breakers will produce a continuous output current that could cause the undersized output wiring to overheat when the frequency converters fail to shut off. We are proposing this AD to prevent overheating of the output wiring of the frequency converters, which could result in the failure of a wire bundle and consequent adverse effects on other systems sharing the affected wire bundle.