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:
Three (3) events have occurred where the Air-Driven Generator (ADG) failed to provide power on CL-600-2B19 (CRJ) aeroplanes during their regularly scheduled operational/functional checks. An investigation revealed that in all cases, the silver-plated copper wires within the ADG power feeder cables were damaged due to galvanic corrosion. It was subsequently determined that the silver- plating is inadequate for this application.
In the event of damage to the power feeder cable wires, the ADG may not be able to provide emergency electrical power to the aeroplane.
Although there have been no reported failures to date on any CL- 600-2B16 (604 Variant) aeroplanes, a sampling program carried out on these aeroplanes showed signs of microscopic galvanic corrosion on the ADG power feeder cable wires.
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The proposed AD would require actions that are intended to address the unsafe condition described in the MCAI.