Summary
We propose to adopt a new airworthiness directive (AD) for the products listed above. This proposed AD results from mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as:
Some operators have reported occurrences of loss of the AC BUS 1 with subsequent loss of the AC ESS BUS and DC ESS BUS, resulting in the loss of 5 upper Display Units and the loss of integral lighting. In this situation, flight crew[s] have reported concerns in reading the standby instruments when the DOME lights were selected to OFF. This situation, if not corrected, could increase the workload of the flight crew * * *.
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The unsafe condition is reduced ability of the flightcrew to maintain the safe flight and landing of the airplane in adverse operating conditions. The proposed AD would require actions that are intended to address the unsafe condition described in the MCAI.